publicationDate stringlengths 10 10 | abstract stringlengths 0 37.3k | title stringlengths 1 5.74k | doi stringlengths 11 47 ⌀ |
|---|---|---|---|
2022-10-01 | This study investigates the efficacy of using an artificial neural network (ANN) to predict the seismic response of a single degree of freedom (SDOF) system comprising a reinforced concrete (RC) column supporting a mass and equipped with a superelastic shape memory alloy (SMA) damper. Nonlinear time history simulations are first conducted to build the training dataset for the ANN by analyzing the structural response under 200 ground motion (GM) records. Properties of the column, the SMA damper, and the GM records are considered as input parameters while the maximum mass displacement is the output parameter. The neural network is then trained and used to make predictions on the structural response under different GM records. The results show that using only 200 records, the root-mean-square error (RMSE) and the average error of the prediction can be as low as 0.1012 and 6.55%, respectively. Parametric studies are conducted next using the developed ANN to investigate the accuracy of the network’s predictions and its ability to capture the impact of a wide range of structural, SMA, and ground motion parameters on the structural response. The results show that the network can predict the structural response under different ambient temperatures and predict the area of the SMA damper needed to achieve a target structural drift. The results of this study demonstrate the potential of using ANNs to predict the seismic behavior of concrete structural systems with superelastic SMA dampers. | Using Machine Learning to Predict the Seismic Response of an SDOF RC Structure with Superelastic Dampers | 10.1007/s40999-022-00724-1 |
2022-10-01 | Studying wave propagation in phononic crystals (PCs) in the presence of energy dissipation is a crucial step toward the precise dynamic modeling of periodic structures. Fractional calculus is an appropriate tool to reach a more perceptive idea of energy dissipation compared to other damping models. Therefore, in this work, we aim to provide a semi-analytical model for wave propagation in fractionally damped nonlinear PCs. For this purpose, the method of multiple scales is used to solve the governing equations of PCs, and the nonlinear dispersion relations of fractionally damped monoatomic chains and lattices are obtained. The Caputo definition of fractional derivatives is used to model damping. Besides providing new insight into the energy dissipation in PCs, the results of this research emphasize the importance of considering nonlinearities in modeling periodic materials, especially because the propagation frequency in nonlinear crystals is amplitude-dependent. The obtained results are validated with numerical modeling of fractionally damped PCs. | Wave propagation in fractionally damped nonlinear phononic crystals | 10.1007/s11071-022-07704-z |
2022-10-01 | Purpose Chatter can damage parts. It must hence be avoided and/or suppressed. This paper discusses the use of active vibration control to suppress chatter in a milling process. To apply only as much force as is necessary to stabilize the process, a novel adaptive and model-free gain tuning method is proposed in which gains are adapted to the level of unstable vibrations detected during machining. Methods Vibrations during the cutting process are monitored using an accelerometer. If/when instabilities are detected, an active damper that is mounted on a flexure is supplied an appropriate control signal based on a velocity feedback control law. The actuator then applies a suitable compensatory force on the flexure to damp the vibrations. Since the amount of force to be applied is governed by the actuator type and by the level of instability detected, efficacy of proposed adaptive gain tuning scheme is tested for its dependence on the time required to update the gain and for its dependence on the levels of gain increments. Results For slot milling of steel, active damping of unstable vibrations is shown to stabilize the process and improve productivity by up to ~ 300%. With the adaptive gain tuning scheme, higher gain increments with shorter updating times are observed to result in the process being stabilized quicker. Conclusions Since the proposed scheme is model-free and much simpler to implement than other previous adaptive gain updating schemes found in the literature, and efficacy of the scheme is demonstrated experimentally, it has great potential for industrial use. | Adaptive Model-Free Gain Tuning for Active Damping of Machine Tool Vibrations | 10.1007/s42417-022-00520-0 |
2022-10-01 | The fluid characteristics of the MR damper have a notable impact on its design and overall conduct of the damper application devices. First, the hydraulic circuit design features of the MR damper are introduced and then the detailed testing scheme of the damper was proposed. The damping characteristics of fluid were tested under the triangular displacement excitation to study the performance and know the accurate amount of damping force. The test data were recorded at various piston velocities ( V _p) maintaining constant damper coil input current. The input current will produce the magnetic field and influence the nano-magnetorheological fluid (NMRF) flow across the gaps to achieve maximum damping performance. The experimental outcomes show that the fluid in MR damper has a typical feature of linearity and symmetry. The theoretical data were calculated using quasi-static model to validate the efficacy of the experimental data. The theoretical results are in good agreement with the experimental data. | Experimental Investigation of Nickel Ferrite (NiFe_2O_4)-Based Nano-magnetorheological Fluid Characteristics Using MR Damper Under Triangular Displacement Excitation | 10.1007/s42417-022-00522-y |
2022-10-01 | Vehicle vibration control must be implemented to fulfill the aims of sustainable environmental development and minimize human health risks. This article concentrates on the minimization of driver’s body vibrations by improving ride comfort and vehicle stability. The hybrid semi-active vibration control system with the combination of Magneto-rheological (MR) fluid and MR elastomer is presented to mitigate the biodynamic response to the vibration. The proposed hybrid model possesses the characteristics of controllable damping and stiffness. Additionally, fuzzy logic and PID controller are combined to regulate the current supplied to the damper. A quarter car model with a driver is considered to analyze the whole-body vibrations. The proposed model has been simulated for sinusoidal bump road excitation to test the ride comfort and vehicle stability. The results reveal that the seat suspension system with the proposed damper and controller outperforms the passive suspension system by reducing the RMS acceleration values below the ISO suggested values for comfort ride. | Improvement in Ride Comfort and Vehicle Stability using Hybrid Semi-Active Suspension System | 10.1007/s40032-022-00855-3 |
2022-10-01 | This work presents an investigation on the morphology, mechanical, viscoelastic and transport properties of acrylonitrile–butadiene–styrene (ABS) nanocomposites reinforced with nanosilica (NS) and multiwalled carbon nanotubes (MWCNTs). The nanofillers content was varied from 1 to 5 wt%. Morphological and mechanical investigations revealed a better dispersion and effective stress transfer in carboxyl-treated MWCNT composites with respect to silane-treated NS. The highest values of tensile strength and Young’s modulus were reached for 5 wt% of MWCNT. Theoretical modelling of elastic modulus of the composites with carbon nanotubes (CNT) was in good agreement with experimental data. On the other hand, in the case of composites with NS an interfacial modulus of 2.5 GPa was assumed in the model to approach the experimental data. The highest value of storage modulus was reported at a MWCNT content of 5 wt% followed by 3 wt% which discloses the stiffening effect of long curly CNTs in comparison with NS. The damping behaviour indicated a lowering and broadening of tan δ peak induced by CNT. The storage modulus and damping behaviour of the nanocomposites were analysed using theoretical models in which aspect ratio, stiffening effect, adhesion and entanglement phenomena were included. The lowest solvent diffusivity and permeability was exhibited by composite with MWCNT at 5 wt% owing to the tortuosity, higher adhesion and aspect ratio of the filler and revealed a decrement in permeability by 62% with regard to neat ABS. | Mechanical, viscoelastic and sorption behaviour of acrylonitrile–butadiene–styrene composites with 0D and 1D nanofillers | 10.1007/s00289-021-03896-3 |
2022-10-01 | Considering that the fluid-conveying pipes made of fractional-order viscoelastic material such as polymeric materials with pulsatile flow are widely applied in engineering, we focus on the stability and bifurcation behaviors in parametric resonance of a viscoelastic pipe resting on an elastic foundation. The Riemann–Liouville fractional-order constitutive equation is used to accurately describe the viscoelastic property. Based on this, the nonlinear governing equations are established according to the Euler–Bernoulli beam theory and von Karman’s nonlinearity, with using the generalized Hamilton’s principle. The stability boundaries and steady-state responses undergoing parametric excitations are determined with the aid of the direct multiple-scale method. Some numerical examples are carried out to show the effects of fractional order and viscoelastic coefficient on the stability region and nonlinear bifurcation behaviors. It is noticeable that the fractional-order viscoelastic property can effectively reconstruct the dynamic behaviors, indicating that the stability of the pipes can be conspicuously enhanced by designing and tuning the fractional order of viscoelastic materials. | Nonlinear Fractional-Order Dynamic Stability of Fluid-Conveying Pipes Constituted by the Viscoelastic Materials with Time-Dependent Velocity | 10.1007/s10338-022-00328-1 |
2022-10-01 | Currently the basis for the seismic design of most modern structures is to use a mechanism of the sacrificial members. Consequently, damage to structures under a strong ground shaking is inevitable. This article introduces a new self-centered damping device that can be used in slotted concrete connections. The purpose of the device is to avoid damage and reduce permanent deformation in the connection. Its components include a High Force to Volume (HF2V) lead damper and two sets of disc spring assemblies with precompression option, all arranged in parallel. The device is tested using Quasi-static method. The test results show that the system has repeatable, stable and almost symmetrical cyclic behavior and can reduce or eliminate permanent deformations. In addition, evaluation of the cyclic behavior of the device against different loading speeds shows that the system works with minor dependency on the velocity. Then, the derived equations for cyclic behavior of the device are compared and validated with experimental results. The maximum deviation in peak force prediction was less than 3%. | Development and experimental validation of a new self-centering HF2V damper with disc springs | 10.1007/s10518-022-01495-9 |
2022-10-01 | A study was conducted to develop a high damping elastomeric nanocomposite for constrained layer damping (CLD) arrangement to reduce structural vibration at a low weight penalty. Hence, an organically modified montmorillonite (OMMT) clay was used as reinforcement at loadings of 2, 5, 10 and 20 phr in nitrile rubber/polyvinyl chloride (NBR-PVC) 70/30 (w/w) blend to obtain a series of nanocomposites. Montmorillonite clay was selected since it is a natural mineral and hence environmentally friendly. The nanocomposites were evaluated for morphology, dynamic viscoelastic properties in frequency scale and vibration damping efficacy as a CLD on an aluminum strip (Oberst Beam) by modal response. The experimental damping was compared to two theories by Nakra and Torvik, and found to be in better agreement with that by Torvik in general between 300 and 600 Hz. There are deviations from both theories below and above this range. The dynamic viscoelasticity and vibration damping were related to the uniformity of dispersion and extent of intercalation/exfoliation of OMMT. The nanocomposite with 5phr OMMT showed best filler distribution and less agglomeration. The average CLD loss factor increased from 0.08 for unfilled vulcanizate to about 0.135 with 5 phr OMMT and 0.145 for 20 phr OMMT. The enhancement of damping at such low OMMT content compared to the unfilled vulcanizate is possibly due to additional frictional damping by the plate type nanoclay under dynamic strain similar to the Rayleigh or Coulomb damping. There was no direct correlation between loss modulus of the material and structural damping (CLD loss factor). Graphical abstract | Effect of nanoclay reinforcing filler in nitrile rubber/polyvinyl chloride blend: frequency response of dynamic viscoelasticity and vibration damping | 10.1007/s13726-022-01074-4 |
2022-10-01 | This paper introduces the F $$_3$$ 3 ORNITS non-iterative co-simulation algorithm in which F $$_3$$ 3 stands for the 3 flexible aspects of the method: flexible polynomial order representation of coupling variables, flexible time-stepper applying variable co-simulation step size rules on subsystems allowing it, and flexible scheduler orchestrating the meeting times among the subsystems and capable of asynchronousness when subsystems’ constraints require it. The motivation of the F $$_3$$ 3 ORNITS method is to accept any kind of co-simulation model as far as they represent circuits (0D models, such as ODE or DAE), including any kind of subsystem (open circuits), regardless on their available capabilities. Indeed, one of the major problems in industry is that the subsystems usually have constraints or lack of advanced capabilities making it impossible to implement most of the advanced co-simulation algorithms on them. The method makes it possible to preserve the dynamics of the coupling constraints when necessary as well as to avoid breaking $$C^1$$ C 1 smoothness at communication times, and also to adapt the co-simulation step size in a way that is robust both to zero-crossing variables (contrary to classical relative error-based criteria) and to jumps. Five test cases are presented to illustrate the robustness of the F $$_3$$ 3 ORNITS method as well as its higher accuracy than the non-iterative Jacobi coupling algorithm (the most commonly used method in industry) for a smaller number of co-simulation steps. | F
$$_3$$
3
ORNITS : a flexible variable step size non-iterative co-simulation method handling subsystems with hybrid advanced capabilities | 10.1007/s00366-022-01610-z |
2022-10-01 | Parametric excitation in the pitch/roll degrees of freedom (DoFs) can induce dynamic instability in floating cylinder-type structures such as spar buoys, floating offshore wind or wave energy converters. At certain frequency and amplitude ranges of the input waves, parametric coupling between the heave and pitch/roll DoFs results in undesirable large amplitude rotational motion. One possible remedy to mitigate the existence of parametric resonance is the use of dynamic vibration absorbers. Two prominent types of dynamic vibration absorbers are tuned mass dampers (TMDs) and nonlinear energy sinks (NESs), which have contrasting properties with regard to their amplitude and frequency dependencies when absorbing kinetic energy from oscillating bodies. This paper investigates the suppression of parametric resonance in floating bodies utilizing dynamic vibration absorbers, comparing the performance of TMDs against NESs for a test case considering a floating vertical cylinder. In addition to the type of dynamic vibration absorber utilized, the paper also examines the DoF which it acts on, comparing the benefits between attaching the vibration absorber to the primary (heave) DoF or the secondary (pitch) DoF. The results show that the TMD outperforms the NES and that it is more effective to attach the vibration absorber to the heave DoF when eliminating parametric resonance in the pitch DoF. | Parametric excitation suppression in a floating cylinder via dynamic vibration absorbers: a comparative analysis | 10.1007/s11071-022-07710-1 |
2022-10-01 | Excessive tool wear can shorten tool life and cause low machining surface quality and efficiency in the milling of Ti-6AI-4 V thin-walled workpieces. The influence mechanism between the tool flank wear and stability predication is of significant for its further development in milling Ti-6Al-4 V. However, the relationship between tool flank wear and stability predication needs to be further investigated as the effect of time-varying tool flank wear is ignored in conventional methods. In this work, a system stability prediction model considering time-varying tool flank wear effect in milling of Ti-6AI-4 V thin-walled workpiece is proposed. The tool flank wear region is discretized into differential elements, and then, the friction effect and process damping effect caused by extruding function between tool and workpiece are analyzed, and a time-varying milling force model is established. In this process, the relationship of cutting tool flank wear band width VB and section radius difference NB is determined, and the indentation volume between tool and workpiece is iteratively calculated, which is used to investigate process damping. After, the time-varying milling force coefficients are derived considering different tool flank wear status. Then, in modal space, the evolutionary process of stability lobe diagrams considering tool flank wear effect is determined. Subsequently, to effectively predict system stability, tool flank wear curves and dynamic cutting force coefficients are calibrated by slot milling, and the average errors between cutting force prediction values considering tool flank wear effect and experimental values in feed direction and normal direction are 7.3% and 12.1%, respectively. Finally, a series of machining tests are conducted to verify the effectiveness of tool flank wear on the machining stability in the milling of Ti-6AI-4 V thin-walled workpieces to some extent, and the experimental results show that the system stability prediction accuracy of the proposed method is improved by 23.8% compared with that using conventional method. | Investigation of tool flank wear effect on system stability prediction in the milling of Ti-6AI-4 V thin-walled workpiece | 10.1007/s00170-022-10136-z |
2022-10-01 | Investigation on particle synchronization behavior and different kinds of stochastic resonance mechanism is reported in a fractional-order stochastic coupled system, which endures an external periodic excitation and polynomial asymmetric dichotomous noise damping disturbance. An extending of the method of stochastic averaging, the fractional Shapiro–Loginov formula and fractional Laplace transformation law are utilized, to determine the synchronization behavior between two coupled oscillators. The first moment of steady-state response and the output signal amplitude of the system are obtained in an analytical way, along with the stability condition. The crucial role of damping order and intrinsic frequency in stochastic resonance induced by noise intensity is explored, confirming the necessity of studying damping order falling in (1, 2). Due to the presence of nonlinear dichotomous colored noise, fresh phenomena of stochastic resonance and hypersensitive response induced by variation of external excitation frequency are found, where much more novel dynamical behaviors emerge than the non-disturbance case. It is confirmed that bimodal stochastic resonance only occurs for slow switching noise, with the damping order close to the parameter region of 0 or 2. For parameter-induced generalized stochastic resonance, explicit expressions of the critical damping strength corresponding to the optimal peak point of output amplitude are derived for the first time. By which different stochastic resonance patterns of the system under slow and fast switching noise perturbation are predicted successfully. In addition, the parametric effect and action mechanism of damping order on stochastic resonance are discussed in detail. | Analysis of stochastic resonance in coupled oscillator with fractional damping disturbed by polynomial dichotomous noise | 10.1007/s11071-022-07688-w |
2022-10-01 | Double-column bridge piers are prone to local damage during earthquakes, leading to the destruction of bridges. To improve the earthquake resistance of double-column bridge piers, a novel swing column device (SCD), consisting of a magnetorheological (MR) damper, a current controller, and a swing column, was designed for the present work. To verify the seismic energy dissipation ability of the SCD, a lumped mass model for a double-column bridge pier with the SCD was established according to the low-order modeling method proposed by Steo. Furthermore, the motion equation of the double-column bridge pier with the SCD was established based on the D’Alembert principle and solved with the use of computational programming. It was found that the displacement response of the double-column bridge pier was effectively controlled by the SCD. However, due to rough current selection and a time delay, there is a significant overshoot of the bridge acceleration using SCD. Hence, to solve the overshoot phenomenon, a current controller was designed based on fuzzy logic theory. It was found that the SCD design based on fuzzy control provided an ideal shock absorption effect, while reducing the displacement and acceleration of the bridge pier by 36.43%–40.63% and 30.06%–33.6%, respectively. | Simulation research on the energy dissipation and shock absorption performance of a swing column device based on fuzzy control | 10.1007/s11803-022-2131-2 |
2022-10-01 | Abstract For the turbine system of an aircraft, an electric-drive damper is proposed that is designed to completely block and throttle the cooling air flow in the radial-clearance control system. The valve consists of a regulating body (throttling device of flap type) and an electromechanism. Such a system provides a reduction in specific fuel consumption and an increase in the efficiency of the turbine system of the aircraft in transient modes, as well as an additional increase in the reliability and safety of the operation of the turbine system in full load mode. A mathematical model of the electric-damper drive is proposed in the MATLAB/Simulink software package that is designed to develop an algorithm for controlling the electric drive and configuring the drive controller. | Electric-Drive Damper of an Active Radial-Clearance Control System for an Aircraft Gas Turbine Engine | 10.3103/S1068371222100091 |
2022-10-01 | The optimum tuning frequency ratio and damping of the tuned mass damper inerter (TMDI) used in damped single-degree-of-freedom (SDOF) structure subjected to stationary white-noise earthquake excitation is obtained with the help of numerical searching technique. Minimization of the mean-square absolute acceleration and relative displacement of the SDOF structure, as well as maximization of the energy dissipation index, are chosen as the criteria for optimal design. A curve-fitting method is used then to derive closed-form expressions for TMDI damping, tuning frequency, and optimized response which can easily be used for practical applications. The deviation of the optimal values obtained using proposed closed-form expressions is found to be negligible and therefore these expressions are convenient for the optimal effective design of TMDI for various structures. The usefulness of the proposed expressions of the TMDI parameters is then applied to multi-degree-of-freedom (MDOF) framed structures and a comparative study of the seismic response with and without TMDI (tuned for optimization of various objective functions) is done under real earthquake ground excitations. It is seen that an optimally designed TMDI is able to reduce the acceleration and displacement response of the MDOF structures. | Optimum parameters of tuned mass damper-inerter for damped structure under seismic excitation | 10.1007/s40435-022-00911-x |
2022-10-01 | The dynamic responses of the buildings and the optimum parameters of tuned mass damper inerter (TMDI) may change significantly when soil-structure interaction (SSI) is considered. Thus, it is necessary to consider the effect of the SSI in the optimization of TMDI. The study aims at proposing a methodology for optimization of TMDI parameters in reducing maximum structural responses of a high-rise building under earthquake considering the SSI effects. The equations of motion for time-domain analysis are derived for obtaining seismic-induced vibrations of a multi-story shear building with TMDI when the SSI is considered. An improved particle swarm optimization (IPSO) is used to obtain the optimum parameters. The aim of the optimization is to reduce the amplitude of the acceleration transfer function (ATF). The effectiveness of the optimally designed TMDI is assessed for twelve earthquake records with different frequency contents. The effect of the different mass ratios ( µ ), inertance ratios ( β ) and support conditions on control performance of the TMDI are investigated in detail. Numerical results proved that the SSI effect and the inertance ratio have a significant impact on the optimal design and effectiveness of the TMDI. From the seismic analysis results, it is seen that the controlled displacement response usually increases with the increase in the inertia ratio for both the fixed and flexible foundation, and a lower seismic response is obtained in the building controlled by TMD compared with the TMDI with different inertance ratios. | Optimization of tuned mass damper inerter for a high-rise building considering soil-structure interaction | 10.1007/s00419-022-02217-y |
2022-10-01 | Background The present study insights the development of magneto rheological (MR) damper and its comparison with existing viscous damper. The advantage of a magneto rheological damper over an existing viscous damper or passive damper is that they offer semi-active control of the system. The magneto rheological damper with a little power produces a very quick response to the applied current in Ampere. Purpose As the existing viscous damper produces damping force proportional to the velocity of vibration, damping force is less at the low velocity of vibration. Semi-active suspensions provide the advantage of generating the required damping force at low velocities. To apply the theory of semi-active suspension, an MR damper was selected to generate the required damping force. Methods Both dampers are tested on a quarter car test rig and vibration amplitudes are obtained at different frequencies. A magneto rheological damper performance is compared with the existing conventional viscous damper by obtaining acceleration and displacement plots. Results It is observed that the passive damper generates a high acceleration of 5.492 m/s^2 at 20 kg load and 1.33 Hz frequency. Whereas, with the help of MR damper, output acceleration of a passenger car can be reduced from 2.981 to 2.051 m/s^2 at the same frequency. The output acceleration for a passenger car with MR damper is reduced by 46% as compared to a passive damper, thus resulting in better ride comfort. Conclusion From the experimental data, it is observed that the damping force of MR damper increases with the increase in the current and magnetic field. By changing the magnetic field, acceleration is significantly reduced at any applied excitation frequency of the system. | Improvement of Ride Comfort in a Passenger Car Using Magneto Rheological (MR) Damper | 10.1007/s42417-022-00512-0 |
2022-09-27 | This paper provides a systematic analysis of the large scale PMSG (permanent magnet synchronous generator)-based WECS (wind energy conversion system) torsional vibration problem under MPPT (maximum power point tracking) control and constant power control. This is from the perspective of SSO (sub-synchronous oscillation), SSH (sub-synchronous harmonics) and forced torsional vibration. The cause of SSO is the negative total system damping, weakened by the constant power control. The system is susceptible to inducing SSH in the grid current and voltage in the under-damped condition. To effectively suppress the torsional vibration of PMSG-based WECS, a stiffness compensation control strategy based on adaptive damping is proposed. The results show that SSO, SSH and the forced torsional vibration can be suppressed at the source using the proposed suppression strategy. | Drive-train torsional vibration suppression of large scale PMSG-based WECS | 10.1186/s41601-022-00257-8 |
2022-09-24 | This study addresses the innovative integration of free-free resonant column measurements (FFRC) of body wave velocities in rock specimens with the X-ray microcomputer tomography (micro-CT or μ-CT) imaging. FFRC seismic measurements combined with μ-CT scanning is a novelty manner to execute and interpret dynamic rock core characterization in laboratory. FFRC measurements covers unconstrained compression and shear wave velocities (Vc and Vs) as well as quality factors (Qc and Qs), which were evaluated in the ranges of frequency from ~ 3 to ~ 10 kHz for Berea sandstone specimens and from ~ 10 to ~ 20 kHz for Indiana limestone samples. In addition, the propagation velocity of constrained compression waves, V _ p , were measured for all the specimens using direct-travel times. The μ-CT scanning provided micro-structural rock parameters such as porosity, profiles of coefficients of attenuation, as well as pore-size and grain-size distributions. Also, resonance testing allowed us to evaluate the integrity of the rock cores, which could be independently confirmed by using μ-CT scanning along the specimens. Finally, FFRC combined with μ-CT might provide quantitative information to clarify atypical seismic results of rock cores. We studied and presented the novel integration of unconfined free-free resonant column (FFRC) testing with X-ray micro tomography imaging (μ-CT) for characterizing rock samples in laboratory. FFRC testing on rocks involved measurements of unconstrained compression and shear wave velocities (Vc and Vs) as well as quality factors (Qc and Qs). Wave velocities and quality factors were determined in the range of frequency from ~ 3 to ~ 10 kHz for Berea sandstone specimens, while a range of frequency from ~10 to ~20 kHz corresponded to Indiana limestone specimens. The ranges of resonant frequencies measured are near to the conventional frequency range of field well-logging information (~10 kHz). This fact could be valuable since dynamic rock properties are frequency-dependent, particularly if FFRC is compared with high frequency ultrasonic measurements (~ 1 MHz) that are extensively used in laboratory. The combination of FFRC and μ-CT results might permit to interpret quantitatively atypical seismic results of rock specimens. We found that for a specific Berea sandstone specimen, the wave velocities were up to 40% slower than rest of the sandstone samples and also had the lowest Qc of 44. The abnormal behavior might be explained by the lower density and bigger porosity of the specimen, which was confirmed by obtaining a peak intensity (number of voxels) of about 2.6 times smaller than the peak for a typical rock sample and the μ-CT analyses permitted to estimated global porosity of about 30% greater than the typical values . The rock specimens were determined to be integral and homogeneous through the FFRC testing and μ-CT analyses, since response curves of the rock specimens exhibited one well defined peak, while the profiles of coefficient of attenuation were constant along the specimens. | Rock characterization integrating free-free resonant column measurements and X-ray computed tomography imaging | 10.1007/s40948-022-00476-1 |
2022-09-17 | This work aims at exploring an antagonistic actinobacterial strain isolated from the roots of Ziziphus lotus in bioformulation processes and the biocontrol of Rhizoctonia solani damping-off of tomato seedlings. The strain Streptomyces caeruleatus ZL-2 was investigated for the principal in vitro biocontrol mechanisms and then formulated in three different biofungicides: wettable talcum powder (WTP), sodium alginate propagules (SAP) and clay sodium alginate propagules (CAP). Compared to a marketed control products (Serenade® and Acil 060FS®), the formulated biofungicides were investigated against the R . solani damping-off of tomato cv . Aïcha seedlings. The strain ZL-2 produced chitinases, cellulases, β-1,3-glucanases, cyanhydric acid and siderophores. It also showed strong antagonistic effect on the mycelial growth of R . solani . Bioautographic and HPLC analysis revealed the production of a single or several co-migrating antifungal compounds. The biofungicide WTP presented an attractive biocontrol effect by significantly reducing the disease severity index (DSI) compared to untreated seeds. No significant differences were obtained compared to the chemical treatment with Acil 060FS®. The viability of spores and biocontrol efficacy of the WTP were confirmed after 1-year storage. Strain ZL-2 has never been reported in the bioformulation of active biofungicides against Rhizoctonia solani damping-off and this work opens up very attractive prospects in the fields of biocontrol and crop improvement. | Formulation of biofungicides based on Streptomyces caeruleatus strain ZL-2 spores and efficacy against Rhizoctonia solani damping-off of tomato seedlings | 10.1007/s00203-022-03251-8 |
2022-09-15 | This paper deals with the existence of bursting, mixed-mode oscillations (MMOs) and horseshoe chaos in a mixed Rayleigh–Liénard oscillator with asymmetric double well potential driven by parametric periodic damping and external excitations. The dynamical behaviours of the considered model, when the exciting frequency is much smaller than the natural frequency, are studied using bifurcation diagrams, Lyapunov exponent diagrams, time histories and phase portraits. It is found that our model displays various bursting and mixed-mode oscillations. Moreover, various mixed-mode oscillation routes to chaos occur in the system. It is also found that the system exhibits two or three coexisting behaviours of attractors when the parametric damping coefficient evolves. On the other hand, the analytical criterion for the appearance of horseshoes chaos is derived using the Melnikov method. A convenient demonstration of the accuracy of the method is obtained from the fractal basin boundary. It is noted that the increase of the impure quadratic damping coefficient, cubic damping coefficient, asymmetric term and the amplitude of the external excitation accentuates the chaotic behaviour of the system. However, the behaviour of the system becomes regular as the parametric damping coefficient increases. | Bursting, mixed-mode oscillations and homoclinic bifurcation in a parametrically and self-excited mixed Rayleigh–Liénard oscillator with asymmetric double well potential | 10.1007/s12043-022-02412-0 |
2022-09-13 | The paper investigates the well-posedness and the regularity of the solutions, the existence and the continuity of the strong attractors for the structurally damped Kirchhoff wave models with subcritical-critical nonlinearities: $$u_{tt}-(1+\epsilon \Vert \nabla u\Vert ^2)\Delta u+(-\Delta )^{\alpha } u_t+h(u_t)+g(u)=f(x)$$ u tt - ( 1 + ϵ ‖ ∇ u ‖ 2 ) Δ u + ( - Δ ) α u t + h ( u t ) + g ( u ) = f ( x ) , where $$\epsilon \in [0,1]$$ ϵ ∈ [ 0 , 1 ] is a perturbed extensibility parameter, $$\alpha \in [1/2,1)$$ α ∈ [ 1 / 2 , 1 ) is a dissipative index. We show that when the nonlinearity g ( u ) is of either critical growth as $$\alpha \in (1/2,1)$$ α ∈ ( 1 / 2 , 1 ) or subcritical growth as $$\alpha =1/2$$ α = 1 / 2 , while $$h(u_t)$$ h ( u t ) is of critical growth depending on $$\alpha $$ α , the model is well-posed and its weak solution is exactly the strong one; the related solution semigroup $$S^\epsilon (t)$$ S ϵ ( t ) has a strong ( X , Y )-global attractor and a strong ( X , Y )-exponential attractor, which are also the standard global and exponential attractor of optimal regularity of $$S^\epsilon (t)$$ S ϵ ( t ) in X , respectively, where X is the energy space and Y is the strong solution space; these global attractors are upper semicontinuous and these exponential attractors are Hölder continuous with respect to perturbed parameter $$\epsilon $$ ϵ in the sense of Y -topology, respectively. | Strong Attractors for the Structurally Damped Kirchhoff Wave Models with Subcritical-Critical Nonlinearities | 10.1007/s00245-022-09894-9 |
2022-09-10 | To determine whether damping induced by stirring granular materials can be adopted as passive damping, the efficiency of damping upon stirring granular materials was investigated experimentally and numerically. In the experimental approach, a cylindrical mixer with a flat blade was used. As the rotating axis of the blade was driven by a stepping motor through a four-bar linkage mechanism, the blade rotated sinusoidally. The rotational angle of the blade and the torque exerted on the axial shaft by the blade were measured using two types of sensors. The energy dissipated per cycle was determined by calculating the area surrounded by the loop in the plot of the torque versus the rotational angle. The effects of packing ratio, particle diameter, particle material and blade frequency on the energy dissipated were examined. In the numerical approach, the torque exerted on the axial shaft was calculated by the discrete element method. The predicted relationship between the torque and the rotational angle of the blade was compared with the relationship obtained from the experimental results. Moreover, the effect of the frequency of the blade on the energy dissipated per cycle was investigated on the basis of numerical results. Graphical abstract | Analysis of granular damping induced by mechanical stirring | 10.1007/s10035-022-01272-0 |
2022-09-08 | Small strain dynamic properties of soil are the primary input parameter in seismic ground response analysis studies. This study examines the small strain shear modulus ( G _max) and damping ratio ( ξ ) using bender element (BE) tests on subsoil samples along with evaluation of liquefaction potential (sandy soil) using well-accepted cyclic resistance ratio relationship collected from a railway construction site at Agartala, North Eastern (NE) state of India. The objective of this study is to develop a database and empirical relationship on dynamic properties of Agartala soil which may help to carry out future site-specific seismic hazard studies of Agartala city and other regions with similar soil properties. Experimental results indicate that shear wave velocity ( V _ s ), G _max, and ξ vary within a wide range such as 60.61 to 234.64 m/s, 5.3 to 104.6 MPa, and 8.9 to 22.1% .respectively depending upon the type of soil and a closed form empirical equations are proposed to calculate G _max for different types of soil. Besides, a validation study also highlights well agreement of results on V _ s obtained through experimental measurement and field in situ-based relationship. Finally, higher liquefaction susceptibility of the study area is reported based on calculated liquefaction potential index ( LPI ). | Assessment of small strain dynamic soil properties of railway site Agartala, India, by bender element tests | 10.1007/s12517-022-10749-4 |
2022-09-05 | We studied experimentally and numerically the compaction and subsequent expansion dynamics of a granular bed composed of cylindrical repelling magnets contained in a two-dimensional cell. The particles are firstly compressed vertically with a piston at a given strain rate until a maximum force is reached. The piston is then removed at the same strain rate while the bed expands due to the magnetic repulsion of the particles. In the experiments, two different initial configurations were generated, a standard and a loose packing bed. The standard packing bed was simulated, and modelling the dry friction between the magnetic particles and the walls of the cell was crucial for the correct description of the compression and expansion dynamics. We found that the force acting on the piston increases continuously and exponentially with the piston stroke during compression, being very sensitive to the initial packing conditions of the bed. In contrast, a history-independent exponential decrease of this force was found during the expansion phase. The hysteresis in the system was quantified in terms of the average displacement of the particles. The continuous compression contrasts with the sudden force drops observed during the compaction of granular materials with direct particle-particle contacts, where stick-slip motion is induced by friction and force chain breakage. Moreover, we found that the short range of magnetic interaction induces density inversion and crystallization of the system. Our results can be useful to develop a new kind of magnetic granular dampers. Graphical abstract | Experimental and numerical investigation of the compression and expansion of a granular bed of repelling magnetic disks | 10.1007/s10035-022-01268-w |
2022-09-01 | In this paper we investigate the effect of nonlinear damping on the Lugiato–Lefever equation $$\mathrm {i}\partial _t a = -(\mathrm {i}-\zeta ) a - da_{xx} -(1+\mathrm {i}\kappa )|a|^2a +\mathrm {i}f$$ i ∂ t a = - ( i - ζ ) a - d a xx - ( 1 + i κ ) | a | 2 a + i f on the torus or the real line. For the case of the torus it is shown that for small nonlinear damping $$\kappa >0$$ κ > 0 stationary spatially periodic solutions exist on branches that bifurcate from constant solutions whereas all nonconstant stationary $$2\pi $$ 2 π -periodic solutions disappear when the damping parameter $$\kappa $$ κ exceeds a critical value. These results apply both for normal ( $$d<0$$ d < 0 ) and anomalous ( $$d>0$$ d > 0 ) dispersion. For the case of the real line we show by the Implicit Function Theorem that for small nonlinear damping $$\kappa >0$$ κ > 0 and large detuning $$\zeta \gg 1$$ ζ ≫ 1 and large forcing $$f\gg 1$$ f ≫ 1 strongly localized, bright solitary stationary solutions exist in the case of anomalous dispersion $$d>0$$ d > 0 . These results are achieved by using techniques from bifurcation and continuation theory and by proving a convergence result for solutions of the time-dependent Lugiato–Lefever equation. | The Lugiato–Lefever Equation with Nonlinear Damping Caused by Two Photon Absorption | 10.1007/s10884-021-09943-x |
2022-09-01 | The knowledge of the added mass and damping characteristics induced by the vibration of the propeller in water is important to predict the hydroelastic behavior of the propulsion system. A three-dimensional panel method combined with the finite element method is conducted to analyze the properties of wet modes and added dampings of marine propellers by imposing three different non-penetration boundary conditions. One is imposed on the blade surface of the equilibrium position. The other is named a partly non-penetration boundary condition, which is imposed on the blade surface of real-time vibration position. Only the corrections of the flow velocities that are exerted on the blade surface by the real-time vibration and the equilibrium positions are considered. The third one takes both the correction of the normal vectors and the flow velocities enforced on the blade surface of the real-time vibration and the equilibrium positions into account, and is termed as a completely non-penetration boundary condition. It is observed that the third boundary condition must be applied for analyzing the wet mode frequencies of lightweight propellers, especially for those which have a small blade number. In addition, the added damping is overestimated by applying the first and second boundary conditions. | Hydroelastic analysis of underwater rotating propellers based on different boundary conditions | 10.1007/s00773-022-00895-5 |
2022-09-01 | In this paper, the authors consider the asymptotic synchronization of a linear dissipative system with multiple feedback dampings. They first show that under the observability of a scalar equation, Kalman’s rank condition is sufficient for the uniqueness of solution to a complex system of elliptic equations with mixed observations. The authors then establish a general theory on the asymptotic stability and the asymptotic synchronization for the corresponding evolutional system subjected to mixed dampings of various natures. Some classic models are presented to illustrate the field of applications of the abstract theory. | Uniqueness of Solution to Systems of Elliptic Operators and Application to Asymptotic Synchronization of Linear Dissipative Systems II: Case of Multiple Feedback Dampings | 10.1007/s11401-022-0352-3 |
2022-09-01 | A multi-objective optimization approach for optimal smart damping treatment of functionally graded magneto-electro-elastic plate (FGMEE) structures is investigated in the present study. The finite element method is employed to analyze the vibration responses of the FGMEE plate with active constrained layer damping (ACLD) treatment patches consisting of 1-3 piezoelectric composite (1-3 PZC) and a viscoelastic layer. An optimization solving process based on the nondominated sorting genetic algorithm II (NSGA-II) is employed to obtain Pareto-optimum solutions, which show the trade-off relationship between the peak vibration response of the first vibration mode and the structural weight. The design variables include the number and location of ACLD patches, as well as the fiber orientation angles of 1-3 PZC on the surface of the FGMEE plate, in which the piezoelectric fiber orientation angles are taken as discrete variables with the constraint on the manufacturing process. Several plate structures with various shapes are investigated through two numerical examples to demonstrate the effectiveness and reliability of the proposed approach. | Multi-objective optimization of the active constrained layer damping for smart damping treatment in magneto-electro-elastic plate structures | 10.1007/s10999-022-09596-8 |
2022-09-01 | Purpose Due to the use of brittle materials and special structure, the porcelain column electrical equipment is easy to be damaged in the earthquake, so it is necessary to carry out the research on the damping control of this kind of equipment. Methods In this study, the damping control test and finite-element analysis of T-shaped circuit breaker model were implemented using shape memory alloy cables. First, based on the similarity theory, an experimental model with a scale of 1/4.5 is designed and made, and the seismic response control study on the circuit breaker model with the shape memory alloy (SMA) is implemented under different peak ground acceleration (PGA) of earthquake motion. Then, the inertia and springs/dashpots in the special setting module of ABAQUS are selected to simulate the SMA control, and the finite-element analysis of seismic response of circuit breaker model is carried out and compared with the test results. Finally, the study discussed the influence of the effective length and dip angle of the SMA cables on the damping performance for circuit breaker. Results The results show that the SMA passive cable damping system can effectively reduce the top seismic response of T-shaped porcelain column circuit breaker. When PGA is 8 m/s^2 at El Centro wave, the reduction rates of displacement and acceleration response are 38.1% and 21.1%, respectively. Meanwhile, the finite-element analysis results of dynamic response of circuit breaker model are in good agreement with experiment results, which verifies the validity of the established finite-element model. Moreover, the SMA lasso damping device can effectively reduce the porcelain bushing root stress of the circuit breaker in the earthquake, when the length of SMA wire is 200 mm, the dip angle is 60°, the SMA cable system has the best damping effect on the circuit breaker model. Conclusion The research results are of great significance to ensure the safe operation of the power system under the earthquake action. | Seismic Response Control of T-Shaped Porcelain Column Circuit Breaker Based on Shape Memory Alloy Cables | 10.1007/s42417-022-00568-y |
2022-09-01 | This paper is devoted the study of a generalized hybrid dynamical system, which consists of a history-dependent hemivariational inequality of parabolic type and a nonlinear evolution equation. The unique solvability for the system is established via applying surjectivity of multivalued pseudomonotone operators, fixed point theorem, and properties of the Clarke generalized gradient. As an illustrative application, a dynamic frictional contact problem for viscoelastic materials with history-dependent and adhesion is investigated, in which the friction condition is described by the Clarke generalized gradient of a nonconvex and nonsmooth function involving adhesion, and the normal damped response condition is expressed by a given nonnegative function depending on the normal velocity and adhesion. | Dynamic History-Dependent Hemivariational Inequalities Controlled by Evolution Equations with Application to Contact Mechanics | 10.1007/s10884-021-10088-0 |
2022-09-01 | In seismic design methods, the damping modification factors (DMFs) are the important parameter considerations in structure design. This paper investigates the effect of closest distance, site conditions, earthquake magnitude, peak ground acceleration (PGA), and damping ratios ( ξ ) on DMFs to the vertical response spectrums. 195 sets of vertical ground motions earthquakes recorded were selected from the PEER strong motion database. These earthquakes recorded are selected to cover a wide range of site distance classifications, specific average shear wave velocity intervals, earthquake moment magnitudes, and three seismic levels of PGA. The vertical response spectra for each earthquake in different damping ratios are calculated. The DMFs for damping ratio that equals 1%, 10%, 15%, 20%, 30%, and 40% are calculated using the 5%-damped vertical response spectra as standards. The results show that the soil classes, earthquake site distance, and seismic levels of PGA have little effect on the DMF, while the moment magnitude of earthquake events has a high effect on the DMF. In addition, simplified empirical formulations are presented to compute the DMF and they are compared to those found in the literature and seismic design codes. | Damping modification factor of the vertical response spectrum | 10.1007/s42107-022-00465-5 |
2022-09-01 | Micro and millimeter-scaled cantilever beams are commonly used to apply and measure microforce and manipulate micro-objects, biological cells, and tissues. In manipulating micro-objects and actuating micro-devices by cantilever beams, sudden application and release of forces are typical, and subject to static and dynamic modes of operation. Therefore, the cantilever’s mechanical behavior and vibration characteristics are vital since they are also used in force sensors and probes. The dynamic behavior of the double beam cantilever (DBC) in micro and millimeter-scaled is explored by varying the length without changing the stiffness and compared with the single beam cantilever (SBC). The dynamic attributes such as mode shape, natural frequency, resonance, and response under the impulse force and Coulomb friction are evaluated numerically. This study will assist in selecting the appropriate type and length of cantilevers in micro and millimeter-scale to manipulate micro-objects, biological cells and tissues, and use in MEMS sensors. | Mechanical and dynamic characteristics of double and single beam cantilevers for MEMS manipulation | 10.1007/s12206-022-0825-z |
2022-09-01 | Although self-centering rocking walls have shown acceptable performance in decreasing downtime, repair cost, and continuous serviceability, their energy dissipation capacity is relatively low. This research introduces a supplementary rebar system (SRS) to improve the energy dissipation capacity of rocking walls. The advantages of this system are its high efficiency, applicability, simplicity of the installation, and easy replacement after yielding/failure. In this research, the efficiency of the proposed SRS was assessed by conducting a parametric study by considering the cross-sectional area, number, and location of the proposed SRSs as the study variables via seven numerical models. To this end, validated nonlinear finite element models were utilized. The results demonstrated that the models with the SRSs installed at the edge had higher load-carrying capacity, stiffness, and energy dissipation capacity. All the models under cyclic loading had stable flag-shaped hysteretic behavior up to a drift of 3% without significant strength loss. Employing SRSs increases the stiffness of the walls; however, by increasing ductility, the wall stiffness declines. Increasing the studied walls’ energy dissipation capacity and reaching the equivalent viscous damping of up to 17.36% demonstrate the efficiency of the proposed SRS. Moreover, as the first moment of area of the SRS increases, the models’ maximum base shear increases, and the ductility ratio and displacement amplification factor decrease. The response modification and displacement amplification factors were recommended to be 5.50 and 3.55, respectively, for rocking walls with the proposed SRS. | Evaluating the efficiency of supplementary rebar system in improving hysteretic damping of self-centering rocking walls | 10.1007/s10518-022-01421-z |
2022-09-01 | Ultrasonic probes for high-temperature applications are provided with metallic wedges, which can withstand the contact with the high temperature of the inspected structure. The ultrasonic signal travels within the wedge and gets reflected from its boundaries, causing interference signals called “ghost echoes”. The current work presents an investigation of the additional damping effect provided by porous sintered metal plates applied onto the surface of the wedge. In particular, the study evaluates the effect of damping plate thickness on the interference signal level at different transmission frequencies. Damping plates made of sintered metal SIKA-R 15 AX were attached to a wedge prototype made of steel 1.4301. The study revealed, that the most effective thickness of damping plates in the selected frequency interval of 1 to 4 MHz is equal to 4 mm. The evaluation of the interference signal has shown that the application of such damping plates to the wedge surface contributes to an additional attenuation of an interference signal of 10 to 30 dB after 500 µs of signal propagation. | External Acoustical Damping on a Metallic Angle Wedge in a High Temperature Resistant Ultrasonic Probe | 10.1007/s40857-022-00270-9 |
2022-09-01 | Background Using dry friction damper is a very common solution to avoid resonance in turbine blade. Dry friction dampers insert non-linearity to the vibration analysis of the blade disk. To predict nonlinear frequency response of turbine blade, accurate contact simulation is necessary. Purpose To accurately simulation of contact force in this work, coupling between normal force and tangential displacement in nonlinear interface forces is considered. Method For this purpose using a model that consider lift-up phenomena (coupling effect) and using experimental set-up, effect of tangential displacement on normal force variation on response of turbine blade is investigated. To solve nonlinear equation, multi-harmonic balance method along with continuation method is used. To transfer nonlinear equation, alternative time–frequency domain is used. Parameters of contact model are identified by experimental set-up that investigated coupling effect between two aluminum surfaces. With these identified parameters of the contact model, frequency response of turbine blade of two previous models of blade is investigated. Results It is shown that considering coupling effect to predict amplitude and frequency of resonance is necessary and ignore this effect in contact force calculation which cause an error in determining parameters of dry friction damper and also its efficiency. Conclusion Effect of lift-up phenomena that is physical properties of contact surface on frequency response function of turbine blade is investigated and is shown its effect on vibration response of turbine blade. | Coupling Between the Tangential and Normal Direction in Turbine Blade Forced Vibration Analysis | 10.1007/s42417-022-00540-w |
2022-09-01 | The existing aerostatic spindle dynamic model only analyses the effects of mass imbalance and external load, ignoring the influence of cutting system on the spindle dynamic characteristics under cutting conditions. In this paper, a 5-DOFs aerostatic spindle dynamic model is established considering the influence of the micro-scale non-linear dynamic performance of the aerostatic spindle and cutting process damping. First, an analytical identification model of process damping with blunt circular cutter is established. Then, the micro-scale dynamic characteristics of the aerostatic spindle are analyzed and a 5-DOFs aerostatic spindle dynamic model is established considering the influence of process damping. Finally, the model is simulated and the influence of process damping on the dynamic characteristics of aerostatic spindle is analyzed. The simulation results show that the process damping of the cutting system has a significant influence on the dynamic characteristics of the aerostatic spindle. This study can provide theoretical guidance for coupling research of cutting system and spindle system. | A novel 5-DOFs dynamic model of aerostatic spindle considering the effect of process damping in ultra-precision machining | 10.1007/s12206-022-0801-7 |
2022-09-01 | One of the effective methods of vibration isolation of the equipment of biogas treatment plants is the use of vibration supports. Technologies for semi-active vibration damping, the main advantage of which is their stability and adaptability to the operating conditions of process equipment, are actively developing. The paper presents the design of a semi-active vibration support with magnetic fluid, the distinguishing feature of which is an extended range of operating characteristics and reduced wear rate of the components. An analysis of the damping characteristics of a semi-active vibration support with permanent magnets is presented. A simulation model of the considered vibration support has been developed. The simulation results indicate a decrease in the influence of vibration on control points. | Magneto-Liquid Vibration Support for Equipment of Biomethane Production Plant | 10.1007/s10556-022-01105-0 |
2022-09-01 | The periodic lattice structure has obvious advantages in lightweight and multi-functional design. With the development of manufacturing technology, especially the development of selective laser melting, the periodic lattice structure has been more extensively used, and attracts more attention in studying its structural behavior. According to the characteristics of periodic lattice structure, ABAQUS is used to establish its geometric model, and the mechanical properties are simulated and analyzed under compression. Considering three kinds of cantilever beams with solid, periodic lattice and rubber-filled periodic lattice as examples, and comparing with the theoretical results of modal frequencies, the simulation method of the periodic lattice structure is improved. The simulation analysis method is used to analyze the change of mechanical parameters and the change of the damping characteristics of the three types of cantilever beams caused by the dimension difference in different directions. The simulation results can provide a basis for the performance test of the periodic lattice structure and provide a reference for the design of the periodic lattice structure which meets the performance requirements. | Property Analysis of Periodic Lattice Structure with Considering its Size Effect | 10.1007/s42423-022-00112-w |
2022-09-01 | Abstract— Reductive perturbation technique is employed to obtain damped forced Korteweg–de Vries (DFKdV) equation in a dusty plasma containing non-thermally distributed electrons in presence of solitary-pulse-type and Gaussian-shaped external forces. To study the behavior of dust–ion acoustic solitary waves (DIASWs), an approximate analytical solitary wave solution of DFKdV equation is found for small values of damping and external forces considering momentum conservation law of Korteweg–de Vries (KdV) equation. By assigning different values of the plasma parameters and strength of the external forces, approximate analytical solitary wave solutions of DFKdV equation are plotted to show the variation of width and amplitude of DIASWs. The results show that the non-thermal parameter $$(b)$$ , damping parameter, i.e., dust–ion collisional frequency ( $${{\nu }_{{i{\text{d}}0}}}$$ ) and the strength of the external force play a very important role in the amplitude and width of the DIASWs. The investigated results can be helpful to study the characteristics of nonlinear waves in laboratory plasma and space plasma where external forces arise due to motion of charged space pollutants. | Influences of External Excitations on Solitary Waves in Nonthermal Dusty Plasma | 10.1134/S1063780X22100063 |
2022-09-01 | Purpose The idea is based on the usage of dynamic vibration absorber for simultaneous reduction of oscillations and energy recovery. The analyzed system consists of two main components: an oscillator (damped part) and a pendulum (tuned mass damper). The rotatory harvester device is mounted in the pendulum’s hanging. The main goal of this investigation is to achieve simultaneous mitigation of vibration and energy harvesting. To improve the effectiveness of the vibration suppression and harvesting effects, an adaptive suspension is proposed. It consists of a combination of semiactive damper (magnetorheological) together with a nonlinear spring made from a shape memory alloy. Methods This paper presents a numerical and experimental analysis of a vibration absorber/harvester system. The continuation and Runge–Kutta methods have been utilized to gain the numerical solutions. The experimental tests were performed on an specially prepared experimental rig. The effects of amplitudes, frequencies, recovered power, and semiactive suspension were studied. Results The obtained results showed that the recovered energy in the vibration mitigation conditions is about 7 mW, while in the unstable region is three times greater. The adaptive suspension can also be applied to reduce unstable regions which occur close to the main resonance and are usually unwanted. Conclusions The study gives an answer to the effectiveness of energy harvesting from the pendulum vibration absorber and suggests that the proposed concept can be useful in practice. | Nonlinear Dynamics and Energy Recovery of a Vibration Absorber/Harvester System with an Adaptive Suspension | 10.1007/s42417-022-00536-6 |
2022-09-01 | Due to the inaccurate injury assessment model of human body impact, it is hard to reasonably determine the motion speed limit of a collaborative robot in human-robot collaborative operations. In this paper, to achieve a more accurate injury assessment, an improved human-robot impact model is proposed based on equivalent mass-spring-damper model. A damper-spring structure is added between the striker and the object corresponding to ribs with mass, and human heights and weights are introduced to the model to further improve the accuracy and universality. The parameters related to mass were set to be compatible with body heights and weights, and the other parameters were identified through the particle swarm optimization algorithm. The results of the simulation show that the first segment of the improved model response is almost coincident with the test response, and almost the whole interval is improved. This study will benefit the determination of robot motion speed limit and improve the human-robot cooperation efficiency under the premise of safety in the future. | An Improved Equivalent Impact Model of Human Thorax for Human-Robot Collaboration | 10.1007/s41315-021-00213-z |
2022-08-30 | In this paper we study the global (in time) existence of small data Sobolev solutions to the Cauchy problem for semilinear $$\sigma $$ σ -evolution models with friction and visco-elastic damping and with a power nonlinearity, namely, $$\begin{aligned} \left\{ \begin{array}{ll} u_{tt}+ (-\Delta )^\sigma u + u_t +(- \Delta )^\sigma u_t=\big ||D|^au\big |^p,\\ u(0,x)=0,\quad u_{t}(0,x)=u_1(x),\end{array} \right. \end{aligned}$$ u tt + ( - Δ ) σ u + u t + ( - Δ ) σ u t = | | D | a u | p , u ( 0 , x ) = 0 , u t ( 0 , x ) = u 1 ( x ) , where $$\sigma \ge 1$$ σ ≥ 1 , $$p>1$$ p > 1 , and the data $$u_1\in L^m(\mathbb {R}^n) \cap H^{s-2\sigma }_q(\mathbb {R}^n) $$ u 1 ∈ L m ( R n ) ∩ H q s - 2 σ ( R n ) with $$s\ge 2\sigma $$ s ≥ 2 σ , $$q\in (1,\infty )$$ q ∈ ( 1 , ∞ ) and $$m\in [1,q)$$ m ∈ [ 1 , q ) . In the power nonlinearity we suppose $$a\in [0,2\sigma )$$ a ∈ [ 0 , 2 σ ) . We are interested in connections between regularity assumptions for the data and the admissible range of exponents p in the power nonlinearity. | Semilinear
$$\sigma $$
σ
-evolution models with friction and visco-elastic type damping | 10.1007/s00030-022-00795-y |
2022-08-30 | The analysis of vibration over coated sample is required to investigate the vibration and noise damping behaviors of coatings. In this research work, conventional gun spray method is used to coat oxime modified titanium (IV) isopropoxide on steel to find out damping behaviour of coating. The most conventional method modal analysis is used to measure vibration and noise damping of bare and titania coated samples. During vibration test it was observed that a thin coating has improved the vibration and noise damping when compare with bare sample. The surface morphology of coated samples analysis by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX) and Atomic Force Microscopy (AFM) revealed that the coating thickness and composition of coating. The results shows that the modified TiO_2 coating deposited over steel alloy by gun spry method is uniform, homogenous, crack free, and having high vibration damping behavior. | Vibration and noise analysis of acetoxime modified TiO_2 coating over steel alloy | 10.1007/s12008-022-01023-8 |
2022-08-26 | A container partially filled with loose plastic granules was attached to the shovel of the snowboard to suppress large-amplitude lateral vibrations by dissipating energy through non-conservative multi-granule interactions. A custom laboratory stand allowed to evaluate the performance using a full-scale snowboard deck. The response of the system with a prototype granular dissipator was measured for free lateral vibrations of the initially deflected board and under prescribed sinusoidal base motion. The damping characteristics for different fill ratios of the container were obtained using a direct method of nonparametric identification. The applied Hilbert–Huang transform-based vibration analysis method gave more insight into the board’s damping performance than the logarithmic decrement analysis. The results show that using the granular dissipator with a predestined number of granules increases the damping capacity at large amplitudes but is less effective at small amplitudes. At best, the damping factor was 70% higher when the granular dissipator was used than when the board was damped only intrinsically. | Evaluation of instantaneous vibration parameters of a snowboard with a prototype granular dissipator | 10.1007/s12283-022-00382-5 |
2022-08-24 | Over the past decades, many vibration control devices have been invented to enhance the integrity of structures and improve their safety when subjected to seismic actions. A review of viscoelastic dampers (VD) has been presented in this paper. These dampers are considered to be one of the most effective and economic passive damping devices that have been widely used in the vibration control of many structures. The review provides detailed information and references regarding viscoelastic materials and their essential mechanical parameters. Different types of VD are presented, and studies on the optimal design of VDs are discussed. The numerical models for simulating the dynamic response of VDs are explained. The paper also includes different configurations, used for the installation of VDs, and discusses the areas in which VDs need further development. | Viscoelastic dampers for protection of structures against seismic actions | 10.1007/s41062-022-00905-w |
2022-08-20 | In this paper, we consider a wave equation with frictional damping and viscoelastic damping acting simultaneously and complementarily in the domain, and study the effect of such competition between the two types of damping on the asymptotic behavior of the energy function. Under nonrestrictive assumptions, we combine both the generality and optimality in one explicit formula for the decay rates of this system. | Optimal Decay Result for Wave Equations with Frictional Versus Viscoelastic Damping | 10.1007/s12591-022-00611-0 |
2022-08-02 | This paper is devoted to investigating the initial boundary value problem for a semilinear wave equation with strong damping and scattering damping on an exterior domain. By introducing suitable multipliers and applying the test-function technique together with an iteration method, we derive the blow-up dynamics and an upper-bound lifespan estimate of the solution to the problem with power-type nonlinearity | u | p $|u|^{p}$ , derivative-type nonlinearity | u t | p $|u_{t}|^{p}$ , and combined type nonlinearities | u t | p + | u | q $|u_{t}|^{p}+|u|^{q}$ in the scattering case, respectively. The novelty of the present paper is that we establish the upper-bound lifespan estimate of the solution to the problem with strong damping and scattering damping, which are associated with the well-known Strauss exponent and Glassey exponent. | Blow-up of solution to semilinear wave equations with strong damping and scattering damping | 10.1186/s13661-022-01634-w |
2022-08-01 | This paper proposes a novel constant force tracking control scheme based on an impedance controller with online stiffness and reverse damping force (OSRDF) to track desired force. An interaction contact force between the robot end-effector and its environment was represented and analyzed using the full mechanical second-order system and individual spring model. A position-based impedance controller is used to receive a contact force signal to track the constant desired force. The proposed approach tracks the desired contact force and reference trajectory based on reference position and velocity. This OSRDF controller is implemented by adjusting the online stiffness parameter and merging the inverse damping force with the force tracking error to compensate for the unknown environment and reduce the force error to zero. A Lyapunov function is applied to investigate the stability of the OSRDF impedance controller during implementation. Simulation studies and experimental tests on a seven degree of freedom (7DOF) robot manipulator are performed to evaluate the efficiency of the proposed method compared to the traditional constant impedance controller. The results showed the validity and effectiveness of the OSRDF method and revealed a relationship between the end-effector velocity and force tracking error. The proposed approach improves force tracking accuracy with simpler computational processes in simulation and practice. | Constant force tracking using online stiffness and reverse damping force of variable impedance controller for robotic polishing | 10.1007/s00170-022-09599-x |
2022-08-01 | The steady-state dynamic response of a single-degree-of-freedom system comprising both a hysteretic element and a spring is considered. The Hertz–Cattaneo–Mindlin theoretical framework for modeling of local tangential contact with friction is applied in conjunction with the Masing model of hysteresis to describe the hysteretic behavior of the multiple localized frictional contact interface. The steady-state tangential displacement amplitude of a rigid body under harmonic tangential force excitation is approximately determined by means of the equivalent linearization technique, based on the harmonic balance principle. A special attention is paid to the evaluation of the frictional damping and the determination of the backbone curve of the Masing model from the dissipation-amplitude relation. | A hysteretic model of localized frictional contacts with instrumental stiffness | 10.1007/s11012-022-01549-x |
2022-08-01 | This study concerns the response of a spherical drop, attached to a sinusoidally vibrating wall. Given that the drop is spherical, the model is more realistic than that of a 2D drop described in [1], with which the results are compared. As in that study, the moving contact line is modelled by a Navier-type wall boundary condition and a prescribed contact angle, $$\overline{\theta }$$ θ ¯ , which can take any of the values $$0 < \overline{\theta } < \pi$$ 0 < θ ¯ < π . Assuming small vibration amplitude, the problem is linearized. In general, wall vibration has components both normal and tangential to the wall. Linearity means that the general response is the sum of decoupled components corresponding to purely normal and purely tangential vibration. The former is axisymmetric, while the latter has either $$\cos \phi$$ cos ϕ or $$\sin \phi$$ sin ϕ dependence on the azimuthal angle, $$\phi$$ ϕ , depending on the direction of vibration. Analysis of the small Ohnesorge number limit, $${\text{Oh}} \to 0$$ Oh → 0 , brings out two distinct viscous damping mechanisms. One arises from dissipation near the contact line and is characterized by a parameter $$\beta$$ β . The other comes from a boundary layer at the wall and is of order $${\text{Oh}}^{1/2}$$ Oh 1 / 2 . Numerical results follow from implementation of the small- $${\text{Oh}}$$ Oh problem. Overall, and perhaps surprisingly, these results show strong qualitative similarity with the 2D case studied in [1], though they of course differ quantitatively. Since the 2D problem is not realisable experimentally, we hope that the results and methodology described here will lead to quantitative comparisons between theory and experiment. | The response of a spherical droplet on a wall executing small sinusoidal vibrations | 10.1007/s11012-022-01545-1 |
2022-08-01 | The vibration and damping characteristics of carbon nanotubes reinforced (CNTR) skewed shell structure under a hygrothermal environment have been investigated using the finite element method. CNT as reinforcing phase and polymer as matrix phase are considered for the nanocomposites (NCs) based viscoelastic skewed shell structure. Dynamic mechanical analysis is used to conduct the creep test for NCs samples which were fabricated, as per ASTM-D4065 standard, and obtained the viscoelastic properties in the frequency domain under different hygrothermal conditions. The shell geometry is defined by considering an arbitrary coordinate system for the skewed shell structure. Finite element modelling has been done with Serendipity element with five degrees of freedom in all eight nodes. The present formulation is based on Koiter’s shell theory and first-order shear deformation theory is considered to incorporate the transverse shear effect based on Mindlin’s hypothesis. The frequency dependant viscoelastic properties are directly used to obtain the frequency responses of the skewed shell panel using fast Fourier transform (FFT) whereas the transient responses are determined using inverse fast Fourier transform (IFFT). An in-house MATLAB code is developed for the numerical simulation and the accuracy of the proposed formulation is validated with available results in literatures and using ANSYS software. A parametric study has been carried out for the skewing angle and CNT volume fraction on the vibration behaviour of different thin and thick NC skewed shell structures under various hygrothermal conditions. | Vibration and damping characteristics of CNTR viscoelastic skewed shell structures under the influence of hygrothermal conditions | 10.1007/s00366-021-01411-w |
2022-08-01 | Although the complex structure-preserving method presented in our previous studies can be used to investigate the orbit–attitude–vibration coupled dynamic behaviors of the spatial flexible damping beam, the simulation speed still needs to be improved. In this paper, the infinite-dimensional dynamic model describing the orbit–attitude–vibration coupled dynamic problem of the spatial flexible damping beam is pretreated by the method of separation of variables, and the second-level fourth-order symplectic Runge–Kutta scheme is constructed to investigate the coupling dynamic behaviors of the spatial flexible damping beam quickly. Compared with the simulation speed of the complex structure-preserving method, the simulation speed of the symplectic Runge–Kutta method is faster, which benefits from the pretreatment step. The effect of the initial radial velocity on the transverse vibration as well as on the attitude evolution of the spatial flexible damping beam is presented in the numerical examples. From the numerical results about the effect of the initial radial velocity, it can be found that the appearance of the initial radial velocity can decrease the vibration frequency of the spatial beam and shorten the evolution interval for the attitude angle to tend towards a stable value significantly. In addition, the validity of the numerical results reported in this paper is verified by comparing with some numerical results presented in our previous studies. | Symplectic Analysis on Coupling Behaviors of Spatial Flexible Damping Beam | 10.1007/s10338-021-00297-x |
2022-08-01 | We present a method, named the variable damping factor selecting method, to select reliable Euler solutions. Our method considers the influence of small perturbations on the movement of Euler solutions as a selection criterion. Small perturbations have little influence on the least-squares solution generated from a stable matrix with large eigenvalues and in the projection area of the source position in the observational data. It is found that the matrix is stable and the solutions are reliable. By using the damped least square method to calculate the Euler solutions, our method can automatically estimate whether a solution can be saved. The saved solution, which is considered to be reliable, is not sensitive to any changes of the damping factor and is usually generated within a sliding window located in the projection area. In our work, the damping factor is chosen from the eigenvalue of the sliding window. Tests on synthetic and real data showed that our method is simple and easy to conduct, and can successfully outline causative bodies and singular point sources. | Euler solution selecting method based on the damping factor | 10.1007/s11600-022-00804-9 |
2022-08-01 | Under-platform dampers (UPDs) are commonly used to adapt turbine blade vibration characteristics by friction. However, acquiring their effect on the forced vibration of high-speed rotating blades is difficult. In this paper, the blade vibration experiments with atomised liquid-jet excitation in high-speed rotation were designed to compare the effects of different UPDs on blade vibration. Also, the damping ratios of different UPDS were obtained by numerical calculation methods. The experimental and computational results showed that when the mass of the dampers was within the appropriate range, the maximum vibration responses decreased significantly, and optimum mass of UPDs reduced the vibration by 28 % compared with the vibration responses without dampers. Moreover, the frequencies of the maximum blade response increased with the mass of the UPDs by up to 4.3 %. Meanwhile, the blade vibration response had multiple amplitude peaks due to the dry friction damping with installed UPDs. | Effect of under-platform dampers on the forced vibration of high-speed rotating blades | 10.1007/s12206-022-0707-4 |
2022-08-01 | In this article, Al/SiC composites with varying reinforcement of 5, 10 and 15 % by weight were produced using powder metallurgy route. The samples were sintered at 550 °C ± 5 °C in a microwave furnace. Damping capacity (tanδ) and storage modulus (E’) of the fabricated samples were measured using dynamic mechanical analyzer at frequencies such as 0.1, 1 and 10 Hz using 3-point bending mode at constant strain amplitude and 10 N as dynamic load. The microstructural analysis is effectively studied using FESEM. Results confirmed that the tanδ and E’ increases with the increase in the percentage of SiC particulates. E’ was found to increase by a maximum of 44.7 % whereas tanδ increased by 2.48 times when compared with pure aluminium. Related mechanisms responsible for this behavior are analyzed and presented. | Damping Behavior of Al/SiC Composites Fabricated by Powder Metallurgy | 10.1007/s12633-021-01497-3 |
2022-08-01 | The dynamics of brushless DC motor (BLDCM) is studied in detail from the viscous damping coefficient, a mechanical parameter. While this parameter intervenes in determining the dissipativity of the system; it shows the high complexity of the brushless DC motor. The pitchfork bifurcation is revealed. The Hopf bifurcation is identified twice in the road towards and from chaotic dynamics regions. Rigorous methods such as the center manifold theorem and the normal form theory confirm Hopf bifurcation. The different theoretical scenarios and motor parameters are also illustrated. Real positive parameters of the coefficient are only considered to keep the physical meaning from the analysis. With some special conditions around Hopf bifurcation, the transient chaotic behaviors of the BLDCM are detected. Bifurcation diagrams and Lyapunov exponents are used to support the theoretical findings. | Local bifurcation of brushless DC motor through a mechanical parameter: the viscous damping coefficient | 10.1007/s40435-021-00883-4 |
2022-08-01 | Stochastic resonance (SR) phenomenon for a fractional linear oscillator with memory-inertia and memory-damping kernels subject to multiplicative noise and additive noise is investigated. The correlation intensity between the two noises is modeled as a time-modulated one. The amplitude gains for the input signal and that for the time-modulated correlation signal are derived. Analysis results show that SR phenomenon occurs when the two amplitude gains vary with the fractional exponent, vary with the intensity of the multiplicative noise, as well as vary with the frequency of the input signal and with that of the time-modulated correlation signal. | Stochastic resonance for a fractional linear oscillator with memory-inertia and memory-damping kernels subject to dichotomous time-modulated noise | 10.1007/s12648-021-02226-7 |
2022-08-01 | Brake squeal in friction brakes is a typical audible noise phenomenon in vehicles leading to high development and sometimes warranty costs for the suppliers. The friction forces generated during braking are responsible for self-excited vibrations in the audible frequency range starting from $$1\hbox { kHz}$$ 1 kHz . In the past countermeasures against friction-induced vibrations are mostly investigated for disk brakes while the present study focuses on drum brakes. Damping is in the context of self-excited vibrations often one of the key measures. Nowadays recuperative braking in electric vehicles relieves the conventional friction brake. Due to safety reasons, electric vehicles need to possess at least a second independent brake system. Therefore, simpler drum brakes are on the rise again when developing brake systems. Compared to brake disks, where damping elements can hardly be implemented, the freely accessible drum surface and the brake shoes offer so far unused potential for applying passive damping measures. The present paper focuses on how damping measures influence the noise behavior of drum brakes. Industrial and non-industrial brake components are investigated in detail. Experimental as well as numerical procedures are used to assess damping and noise characteristics. | Friction-induced noise in drum brakes: finite-element modeling and experiments with special focus on damping | 10.1007/s00419-022-02189-z |
2022-08-01 | The stiffness and damping of the fluid pivot journal bearing (FPJB) which has been selected as the subject of study in this paper are systematically investigated. Based on the FPJB structure and principle of operation, geometrical models have been established and numerical methods (FDM) are used to determine the floating conditions of the pads and the dynamic coefficients of the bearings. Initially, the floating conditions of the pads according to the preload factor are indicated. On this basis, the equilibrium position of the shaft and bearing system is determined according to the bearing parameters: preload, gap size, recess area. Finally, the effects of these parameters on the stiffness and damping coefficients are shown. | Effect of Structural Parameters on Dynamic Characteristic of Fluid Pivot Journal Bearing | 10.1007/s40032-022-00842-8 |
2022-08-01 | Magnetorheological (MR) fluid properties are essential in analyzing the performance of any MR fluid system. The fluid properties are dependent on shape, size, and magnetic saturation of the magnetic particles. Preliminary characteristics with SEM, particle size analysis (PSA), and vibration sample magnetometer (VSM) on carbonyl iron particles were performed to verify the particle’s feasibility to synthesize the MR fluid in a laboratory. Synthesis and characterization of MR fluids with particle concentrations (PC) of 10% (PC_10), 15% (PC_15), 20% (PC_20), 30% (PC_30), and 35% (PC_35) by volume are carried out. To show the inherent nonlinearity of the MR fluid, Herschel–Bulkley model is used. The relationship between sedimentation velocity, yield stress, and thermal conductivity is established as a function of particle concentration with experimental uncertainty of 6.15, 5, and 8.96%, respectively. Functional testing of PC_15 and PC_30 was carried out on an MR damper fabricated on dimensions obtained from the literature for the required size. The results indicate that damping force is 42% more in PC_30 than PC_15 at higher loading parameters. Finally, the saturation magnetization of the MR fluid depends not only on applied current but also on loading parameters when operating in the system. | Impact of increased particle concentration on magnetorheological fluid properties and their damping performance | 10.1007/s13367-022-00029-8 |
2022-08-01 | Blast polishing offers an operator-friendly solution to many of the previously encountered polishing difficulties. However, the process lacks studies into the control of key parameters, one of which is viscoelasticity (particularly present in biological-based abrasive medias). Together with analytical-empirical models, a vibrational spring-dashpot model is presented, which characterizes the impact force, contact time, and damping ratio/coefficient of polishing media upon impact; as well as the effects of damping on contact parameters: stress, deformation, and area of contact. These are compared to experimentally gathered results for verification of the model. Impact force is shown to decrease dramatically with increasing hydration while increasing linearly with an increase in kinetic energy. Experimental findings reveal that 50% wet contact exhibits a 340% reduction in force magnitude compared to dry contact. Contact time results show an exponential increase with an increase in hydration. Research findings also show that higher hydration levels result in lower damping ratios and that higher kinetic energies (related to higher hydration levels) tend toward a decrease in damping ratio. Similarly, media damping coefficients decrease with both hydrational increases and kinetic energy increases. Results show that contact stress is reduced at higher hydration levels, which is mainly due to higher contact areas, and hence it was noticed that an increase in hydration prevents occurrence of chipping and brittle failure on the workpiece surface. Contact stress is shown to reduce by 325% from a 10% wet contact to a 50% wet contact. A high hydration of 30 to 50%, a high impinging velocity of value 31.4 m/s and above, a low stand-off distance of value 20 mm and below, a 45° polishing angle, and a polishing time of 20 to 40 min provide the most optimal parameters for efficient polishing to achieve a mirror finish on an additive manufactured Ti-6Al-4V component. The findings stipulated provide a base on which to further characterize the process and aim to promote further development and optimization of the blast polishing process. | Spring-dashpot vibrational model for the investigation of viscoelasticity in gelatinous abrasive media and subsequent control of parameters for the blast polishing of Ti-6Al-4 V alloy | 10.1007/s00170-022-09863-0 |
2022-08-01 | The main motivation of the present study is to propose a new framework of multi-objective brain emotional learning-based intelligent controller (MOBELBIC) for tuning the command voltage of MR dampers in real-time for smart base-isolated structures. To address the main goal of the seismic control of such structures i.e. creating a suitable trade-off between the conflicting cost functions in terms of the maximum base displacement and superstructure acceleration, a multi-objective particle swarm optimization (MOPSO) algorithm is also utilized. Moreover, a multi-objective proportional–integral–derivative controller (MOPIDC) is proposed for comparison purposes. Then, the validation of both proposed controllers is compared with those given by the passive-off and passive-on statues of the MR damper for a benchmark base-isolated structure subjected to different earthquake excitations. Poor efficacy of the passive-off case is found especially for overcoming the drawbacks of large base displacement during near-field earthquakes. Besides, the passive-on case is significantly able to reduce the maximum and RMS values of the base displacement at the cost of a remarkable increase in the maximum and RMS values of the superstructure inter-story and acceleration, which shows that it cannot meet the main control objectives. The simulation result during different earthquake excitations indicates that the MOBELBIC performs much better than the MOPIDC in the simultaneous reduction of the maximum and RMS of the seismic responses of the studied structure especially in terms of base displacement, inter-story drift, and superstructure acceleration. | A new framework of multi-objective BELBIC for seismic control of smart base-isolated structures equipped with MR dampers | 10.1007/s00366-021-01414-7 |
2022-08-01 | Lossless positive-real systems have been widely studied in the literature. They are systems in which the energy is entirely transferred between input and output. In this paper, new aspects related to the linear quadratic gaussian (LQG) control of lossless positive-real systems are reported including both the continuous-time and the discrete-time cases. Direct formulas for the calculation of the optimal gains will be introduced and the properties of the different structures of the LQG compensator obtained for the continuous-time and the discrete-time cases will be emphasized, also in view of designing positive-real LQG compensators. Numerical examples related to low-damped structures are also discussed to verify the possibility to design the LQG compensator on the basis of a lossless approximation. | LQG control of linear lossless positive-real systems: the continuous-time and discrete-time cases | 10.1007/s40435-021-00857-6 |
2022-07-30 | In this paper, we consider the general decay of solutions for the weak viscoelastic equation of Kirchhoff type containing Balakrishnan–Taylor damping with nonlinear delay and acoustic boundary conditions. By using suitable energy and Lyapunov functionals, we prove the general decay for the energy, which depends on the behavior of both σ and k . | General decay for weak viscoelastic equation of Kirchhoff type containing Balakrishnan–Taylor damping with nonlinear delay and acoustic boundary conditions | 10.1186/s13661-022-01633-x |
2022-07-28 | Nowadays, thin-walled structures are used as energy dampers in various industries to increase energy absorption. This study aims to improve the crashworthy performance and ductility of the simple thin-walled aluminum foil square tube structure and reduce its weight by making different slot shapes. Various slots have been proposed for the simple thin-walled square tube to create slotted square tubes. The explicit finite element method, ABAQUS software, has been used to analyze the crush behavior of slotted square tubes under axial quasi-static loading. Then, the numerical responses were compared with the experimental data. Comparing the results to the simple model, it was found that the proposed slotted square tubes have a good energy absorption. Different parameters, including energy absorption, initial peak load, crush force efficiency, and specific energy absorption, have been investigated, and it was observed that all specimens had a relatively suitable performance. | Numerical and experimental investigation of energy absorption capacity in slotted thin-walled square tube structures | 10.1007/s40430-022-03677-7 |
2022-07-23 | Abstract This research work proposes an equivalent approach modelling the peculiar hysteretic behavior of passive variable friction damper, for engineers who call for a simplified way to simulate such damper in anti-earthquake engineering practice with acceptable accuracy. This approach models the special nonlinear behavior of the damper via paralleling 3 basic link elements that commonly built-in commercially available structural analysis software, instead of developing direct hysteretic model that demands for both post development functionality on software side and programming skill on engineer side. The mathematical derivation and analytical geometric equating work are comprehensively conducted. The numerical accuracy of analysis output yielded using equivalent model is digitally verified against the one yielded using generic FEM simulation of the same damper subject to several loading cases. Code-automated optimization workflow for yielding product-wise modelling parameters is developed that is convenient and straightforward for application by engineers without requirement of high expertise, which is demonstrated by generating optimized parameters to equivalently model tested specimen. Article highlights Passive variable friction damper can be modelled by assembling friction spring, elastic spring and wen model into parallel. Code-automated optimization process can locate the most ideal modelling parameters combination in predefined numeral fields. Hysteretic behaviors yielded from equivalent modelling approach match well corresponding ones from generic FEA simulation. | An equivalent approach for modelling butterfly-hysteresis passive variable friction damper | 10.1007/s42452-022-05098-6 |
2022-07-22 | In this paper, we consider a one-dimensional coupled Timoshenko type system in the light of the second spectrum of frequency (no blow-up on second wave speed) with a single weakly nonlinear feedback acting only on the angular rotation. Without imposing any restrictive growth assumption near the origin on the damping term, we establish an explicit and general decay rate using a multiplier method and some properties of convex functions. This is made without classical equal wave speeds assumption. Before, we proved the well-posedness by using the Faedo-Galerkin method. Our results are new and considerable improve earlier results where the equal wave speeds played the role for getting the stability properties. In addition, in the conclusions section, we consider the same truncated version but with non-linear damping acting on the transversal displacement and we describe how the known mathematical techniques do not apply in order to obtain the exponential decay. | Impact of the Damaging Consequences of the Second Spectrum on the Stabilization of Nonlinear Timoshenko Systems | 10.1007/s10440-022-00516-8 |
2022-07-18 | This paper studies the long-time behavior of solutions for a transmission problem of Timoshenko beam with memory. We show that the stability of the system holds for a much larger class of relaxation functions and get better decay rate than the ones existing in the literature. We also give some numerical tests to validate the theoretical results. | Uniform energy decay rates for a transmission problem of Timoshenko system with two memories | 10.1007/s00033-022-01799-5 |
2022-07-15 | Bentonites have good application in solid walls, waterproof materials, and landfill cushions, but the cushions of landfills in seasonal frozen regions are susceptible to the effects of freeze–thaw cycles, overhead dynamic loads, and landfill leachate, which can lead to strength change and structural instability. In this paper, the cations in bentonite were exchanged by electrochemical method, and then a series of low-temperature triaxial tests were carried out on the original and modified bentonite. The study evaluated the dynamic characteristics of the different exchange ions under the factors of confining pressures, freeze–thaw cycles, and loading frequencies. The results showed that (1) the electrochemical cation exchange method can effectively replace Na^+ in the Na^+-bentonite; (2) under cyclic loading, with increasing shear strain, the shear modulus ratio decreased, and the damping ratio was gradually increased; (3) the dynamic shear modulus ratio increases with the increase of confining pressures and frequencies, and the number of freeze–thaw cycles had little effect on the dynamic shear modulus ratio; and (4) the dynamic parameters of modified bentonite were less affected by external factors and soil’s structure were more stable. | Effect of freeze–thaw cycles on the dynamic parameters of modified Na^+-bentonite by different cations | 10.1007/s10064-022-02812-x |
2022-07-11 | In this paper, we study the direct/indirect stability of locally coupled wave equations with local Kelvin-Voigt dampings/damping, where we assume that the supports of the dampings and the coupling coefficients are disjoint. First, we prove the well-posedness, strong stability, and polynomial stability for some one dimensional coupled systems. Moreover, under some geometric control conditions, we prove the well-posedness and strong stability in the multi-dimensional case. | Stability results of locally coupled wave equations with local Kelvin-Voigt damping: Cases when the supports of damping and coupling coefficients are disjoint | 10.1007/s40314-022-01956-6 |
2022-07-06 | We study the effect of heating–cooling imbalance on slow magnetohydrodynamic waves in solar coronal loops with time-varying background temperature in the presence of thermal conduction, optically thin radiation and heating. The MHD equations governing the plasma motion are solved numerically to examine the effects of heating–cooling imbalance on slow waves in the presence of thermal conduction and radiation. It is found that the amplitude of perturbed velocity decreases in the case of increasing background temperature, whereas the perturbed velocity amplitude increases in the case of decaying background temperature. The heating–cooling imbalance influences the damping of slow waves. Damping of waves is stronger for characteristic time $$\tau =1000$$ τ = 1000 s than the damping for $$\tau =3000$$ τ = 3000 s in both time-varying background temperature plasmas. | Effect of heating–cooling imbalance on slow mode with time-dependent background temperature | 10.1007/s12036-022-09824-9 |
2022-07-06 | Non-linear fluid viscous dampers have found widespread applications in engineering practice for seismic mitigation of civil structures. Topology optimization has emerged as an appealing means to achieve the optimal design of non-linear viscous dampers in terms of both layouts and parameters. However, the conventional methodologies are mainly restricted to deterministic dynamic excitations. This research is devoted to the topology optimization of non-linear viscous dampers for energy-dissipating structures with consideration of non-stationary random seismic excitation. On the basis of the equivalent linearization—explicit time-domain method (EL-ETDM), which has been recently proposed for non-stationary stochastic response analysis of non-linear systems, an adjoint variable method-based (AVM-based) EL-ETDM is further proposed for non-stationary stochastic sensitivity analysis of energy-dissipating structures with non-linear viscous dampers. The stochastic response and sensitivity results obtained by EL-ETDM with high efficiency are utilized for topology optimization of non-linear viscous dampers with the gradient-based method of moving asymptotes. The optimization problem is formulated as the minimization of the maximum standard deviation of a critical response subjected to a specified maximum number of viscous dampers, and the p -norm function is employed for approximation of the non-smooth objective function. The existence information of each potential viscous damper as well as the damper parameters are characterized by continuous design variables, and the solid isotropic material with penalization technique is utilized to achieve clear existences of viscous dampers. Two numerical examples are presented to illustrate the feasibility of the proposed topology optimization framework. | Topology optimization of non-linear viscous dampers for energy-dissipating structures subjected to non-stationary random seismic excitation | 10.1007/s00158-022-03281-2 |
2022-07-05 | Compacted clay-aggregate composites are extensively utilized or found in various geotechnical engineering projects such as the core of earth embankment dams, the pile foundation of offshore structures, or the impervious blankets in waste disposal landfills. In this study, data from resonant column tests at small shear strains are exploited to examine the dynamic shear modulus and energy dissipation characteristics of compacted clay-sand mixtures and develop empirical expressions for their small-strain dynamic properties. The models incorporate the influences of confining pressure ( p' ), void ratio ( e ), aggregate content ( AC ) and clay plasticity index ( PI ). Moreover, the application of the equivalent plasticity index ( PI* ) in the estimation of small-strain dynamic properties is rigorously examined. The level of accuracy of the developed models is inspected with simple comparisons against the experimental data. The proposed empirical correlations can be utilized in geotechnical earthquake engineering problems for the seismic stability analysis of geo-structures containing compacted clay-sand mixtures. These empirical models also comprise a basis to discuss the mechanical behavior of composite granular systems at multi-scales. In this regard, the involved micromechanisms, particularly the contact response of sand-clay systems, are discussed integrating the macroscopic results from the present work with micromechanical-based data previously published in the literature. This analysis highlighted the important role of the formed coating of microparticles on the constitutive behavior of sand grains at their contacts, which in turn, provided some additional insights to explain the macroscopic behavior of clay-sand mixtures as obtained from the element-size experiments. | Analysis of the stiffness and damping characteristics of compacted sand-in-fines granular composites: a multiscale investigation | 10.1007/s10035-022-01247-1 |
2022-07-01 | Background Magneto-Rheological (MR) fluids are made—up of iron particles suspended in carrier liquid containing additives in proportion to make reversible changes to the whole suspension rheological properties (apparent viscosity, shear stress). MR dampers have generated a lot of interest amongst researchers in the last few decades because of their fast response and mechanical simplicity as compared to active dampers. Aim The work presents a systematic approach to the design and development of a low-cost optimal MR damper, wherein the focus is on optimizing geometrical features of the annular valve along with the electric current of the MR damper by using the Taguchi approach. Method The MR damper was manufactured and experimentally tested to observe its effect on damping performance. Force transmissibility and damping ratio are important parameters for road handling and ride comfort. Results It was found that implementing in-house prepared low-cost MR fluid in MR damper application results in damping force and damping coefficient increase as current intensity increases. It has been also observed that the resultant force transmissibility magnitude at 1.5A is less compared to the passive damper due to the high damping coefficient. Conclusions Hence, concluding that MR damper based on low-cost MR fluid in the present study has better damping force performances as compared to passive dampers. It might also assist to improve the handling and comfort of passenger vehicles. The experimental results have been compared with Nagler’s fresh modified Bingham model (analytic approximation) formulation (apparent viscosity and shear stress) and literature references. A qualitative and quantitative agreement was found between Nagler—Bingham generalized model (analytic approximation) and experimental results for the examined rheological parameters (apparent viscosity and the developed shear stress). Also, a full-scale qualitative agreement was found between the experimental and analytic results (shear stress, apparent viscosity, damping force, damping coefficient, etc.) and the various distinguished literature references. | Development of Low-Cost Optimal Magneto-rheological Damper for Automotive Application | 10.1007/s42417-022-00486-z |
2022-07-01 | Synthetic Aperture Radar (SAR) plays a major role in identifying oil spills on the sea surface. However, obtaining information of oil spill thickness (volume) is still a challenge. Emulsification is an important process affecting the thickness and normalized radar cross section (NRCS) of oil film. Experiments of crude oil emulsification with C-band fully-polarized scatterometer were conducted combining airborne hyperspectral imaging spectrometer and 3D laser scanner observation data, to provide experimental parameters and method to support accurate remote sensing monitoring on marine oil spill. It is further proved that through quantitative homogeneous emulsified oil spill experiments, to a certain extent, the NRCS of oil film increased during the emulsification process of crude oil. The backscattering mechanism of crude oil emulsification was explored using a semi-empirical model (SEM); the change of oil film NRCS was modulated by its dielectric constant and surface roughness, in which the dielectric constant showed a dominant effect. The relationship between thickness and NRCS of oil film was studied under two experimental conditions. The differences of NRCS between oil film and adjacent seawater (Δ σ ^0) and the damping ratio (DR) were found to have a linear relationship with oil thickness, which were best in the vertical polarization mode (VV) at 45° incident angle during the quantitative crude oil homogeneous emulsification process. In the natural emulsification process of continuous oil spill in which oil film was mixed with both crude oil and emulsified oil, an empirical equation of oil film thickness is preliminarily established. The Δ σ ^0, DR, and the empirical equation of oil film thickness were applied to the marine continuous oil spill incident on a 19–3 oil platform with spaceborne SAR image and successfully explained the distribution of the relative thickness of the oil film. | Experimental research on oil film thickness and its microwave scattering during emulsification | 10.1007/s00343-021-1183-x |
2022-07-01 | In this paper, the analytical blowup solutions of the N-dimensional radial symmetric compressible Euler equations are constructed. Some previous results of the blowup solutions for the compressible Euler equations with constant damping are generalized to the time-depending damping case. The generalization is untrivial because that the damp coefficient is a nonlinear function of time t . | Analytical Blowup Solutions to the Compressible Euler Equations with Time-depending Damping | 10.1007/s10255-022-1100-x |
2022-07-01 | This paper proposes a novel current feedback-free speed regulation method for servo systems subject to system parameter and load uncertainties. The proposed solution has two features. First, the position measurement from the rotary encoder constitutes the speed and acceleration estimates for control loops through a position filter with nonlinearly-structured design parameters and without dependence on the system parameters. Second, the proposed controller only requires nominal system parameter information, and stabilizes both the speed and acceleration loops using only position measurements by injecting active damping terms, which leads to pole-zero cancellation. A prototype servo system was built using a 500 W brushless DC-motor-based dynamo. The prototype experimentally validates the effectiveness of the proposed solution in terms of speed tracking and regulation tasks. | Nonlinear output-feedback speed servo systems through active damping injection and position filtering approaches without current feedback | 10.1007/s43236-022-00451-9 |
2022-07-01 | Direct modal analysis of second-order systems with damping is generally not possible unless the damping and stiffness matrices commute, thereby admitting simultaneous diagonalization. When these matrices do not commute, the so-called complex-stiffness damping method has been employed to great effect, but the existing formalism provides only an indirect means of damped modal analysis. Borrowing ideas from quantum gravity physics, this paper introduces a new approach to studying damped oscillators that greatly expands the complex-stiffness concept, enabling for the first time direct (complex) modal analysis of damped systems without simultaneous diagonalization. Mathematically, this is achieved by considering the fourth-order system dynamics and writing each fourth-order equation as a system of two second-order equations, which are interpreted as two coupled oscillators. In effect, the damping terms are eliminated from the analysis at the expense of doubling the degrees of freedom. This dual-oscillator approach extends well-beyond linear systems to a large class of nonlinear oscillators with linear viscous damping and power-law hardening. Additionally, the fourth-order equations on which the dual-oscillator approach is based are shown to have interesting properties, such as a natural variational formulation based on the time average of Gauss’s constraint function, and the apparent ability to single out desirable values of the model parameters. It is hoped that the present method will facilitate modal analysis of both linear and nonlinear systems alike. | A dual-oscillator approach to complex-stiffness damping based on fourth-order dynamics | 10.1007/s11071-022-07597-y |
2022-07-01 | This study is aimed at investigating the effects of anisotropic supports on the stability of slender rotors parametrically excited by external loads. An axisymmetric shaft described by scaling a spinning Timoshenko beam on anisotropic supports is studied, loaded by oscillating axial end thrust and twisting moment, with the possibility of carrying additional inertial elements like discs, which represents a model including all the general features of slender rotors which are relevant for this kind of stability analysis, gyroscopic effects comprised. Stability is studied after discretization of the equations of motion into a set of coupled ordinary differential Mathieu-Hill equations. The influence on stability of angular speed combined with anisotropy in the supports (including principal stiffness, principal damping and cross-elements) is analysed with respect to frequency and amplitude of the external loads on stability charts in the form of Ince-Strutt diagrams. The occurrence of different kinds of critical solutions, simple and combination, is investigated, highlighting their dependency on both the degree of anisotropy in the supports and angular speed. | Effects of anisotropic supports on the stability of parametrically excited slender rotors | 10.1007/s11071-022-07487-3 |
2022-07-01 | An investigation on seismic response characteristics and modal parameters of a cable-stayed bridge with movable bearings using vibration records obtained from a seismic monitoring system is presented in this paper. The object of this study is the Tokachi cable-stayed bridge, a single plane prestressed cable-stayed bridge that is equipped with moveable spherical frictional plate (SFP). The bridge seismic responses subjected to various levels of earthquake including the 2003 Tokachi Great earthquake were obtained from a permanent seismic monitoring system. The bridge dynamic characteristics that include frequency and damping were estimated by both the time-invariant and time-variant recursive subspace identification methods. The identification results reveal that damping ratios of the low order modes estimated during the largest earthquake can reach more than 10% of the critical damping, which is higher than what usually assumed in the seismic design code. Supplementary damping caused by friction force at the movable SFP bearings was identified as the main source of the large damping, and it was quantified by a modal-based inverse analysis using the sparse regularization method. Results of the analyses confirm the influence of moveable SFP bearings performance with its Coulomb-friction type stick–slip behavior on the dynamic characteristics of the bridge. The bearings remain stuck at smaller excitation causing higher stiffness of the structure and slip during a larger excitation resulting in stiffness reduction. The sliding process induces friction force between contacting surfaces of the SFP bearings which results in the increase of damping as the excitation level increases. The damping, however, does not increase continuously, but becomes steadier after a certain level of excitation. | Influence of movable bearings performance on the dynamic characteristics of a cable-stayed bridge : insights from seismic monitoring records | 10.1007/s10518-021-01282-y |
2022-07-01 | Equations and relations have been obtained for describing one-dimensional filtration waves in a homogeneous isotropic porous medium in plane, radial, and spherical cases. To this end, use was made of the equation of motion of a liquid phase with account taken of frictional forces, which in the case of stationary filtration with parallel streamlines coincides with Darcy′s filtration law. The equations of motion and continuity reduced to an equation of telegraphy permitted constructing relations for the wave number, the absorption coefficient, and the damping factor, and also for the velocity of filtration waves. The developed theory of filtration-wave pressure fields refines the ideas of propagation of filtration wave perturbations in a porous medium. It has been shown that the obtained expressions for the wave field in a wave approximation when the wave velocity tends to infinity are consistent with the existing solutions of the piezoconductivity equation. | Filtration Waves | 10.1007/s10891-022-02559-y |
2022-07-01 | This paper presents a single-degree-of-freedom (SDOF) constitutive model for assessing the performance of freestanding block contents of buildings. The model incorporates a bespoke damper to account for energy dissipation associated with rocking. It is advantageous in its direct correlation, via energy conservation, to the restitution coefficient for impact during rocking. A comparative study with the existing SDOF rocking models shows that the proposed model significantly improves the accuracy of free-rocking simulations, in which inherent damping predominantly affects response. It provides a promising and efficient tool for computationally intensive performance evaluation of nonstructural components. | A discretely damped SDOF model for the rocking response of freestanding blocks | 10.1007/s11803-022-2085-4 |
2022-07-01 | This work formulates a comprehensive model of a nonlinear aeroelastic system developed for the analysis of complex aeroelastic phenomena related to structural and aerodynamic nonlinearities. The system is formulated as a two-dimensional cantilevered elastica with a rigid airfoil section firmly attached at its tip undergoing large displacements in the crosswind conditions. The system can demonstrate a wide range of domain specific as well as coupled nonlinear phenomena. The structural model is developed by means of the Rayleigh–Ritz approach, with shape functions discretizing both vertical and horizontal displacements and Lagrangian multipliers enforcing inextensibility. Damping is modeled based on a non-local strain-based mechanism in the Kelvin–Voigt arrangement. The resulting structural model is examined through studying the behavior under a follower load and with a tip-attached tendon under tension to study the shape convergence properties and the alignment of the results with known characteristics in the literature. The ONERA dynamic stall model is used to model the aerodynamics of the problem to accurately capture post-stall behavior at large deformations. The LCO responses of the aeroelastic problem are evaluated through time-marched simulations, and the combined airspeed–damping interactions are studied in this manner. | Nonlinear aeroelastic analysis of a damped elastica-aerofoil system | 10.1007/s11071-022-07479-3 |
2022-07-01 | The damping properties of fluorinated polyacrylate (FPA) composites with expanded graphite (EG) partially substituted for mica as fillers have been studied. EG was prepared by a rapid expansion method by microwave (MW) irradiation. The effects of the EG and natural graphite (NG) as partial substitutions for mica and the blending of epoxy (EP) resin with the polyacrylate emulsion on the damping performance of the composites was investigated with dynamic mechanical analysis (DMA). The results showed that adding EG as a partial substitute for the mica improved the intensity of the loss peak of the DMA tanδ and broadened the corresponding high loss factor (tanδ > 0.3) temperature range of the PA/EP composites. In comparison with NG or the mica, EG was more efficient in improving the damping properties of the composites. When the weight content of EP was 4% and EG was 6%, tanδ reached the maximum value of 2.16, and the corresponding temperature range with tanδ > 0.3 was about 80 °C. | Damping properties of expanded graphite filled fluorinated polyacrylate composites | 10.1007/s00289-021-03711-z |
2022-07-01 | The Mg- x Zn- y Ga ( x + y = 1 at.%) alloys are prepared by high strain rate rolling at 300 °C with the rolling strain rate of 9.1 s^−1. The effects of the Zn/Ga ratio on microstructure, mechanical, damping and thermal properties of the as-rolled alloys are investigated by x-ray diffraction, tensile testing, dynamic mechanical analyzer and laser-flash method. The as-rolled alloy exhibits the dynamic recrystallization (DRX) volume fraction above 90%. The DRX volume fraction and the grain size increase with the lower Zn/Ga ratio. With the lower Zn/Ga ratio, the elongation and the damping capacity increase gradually. The Mg-1at.%Ga alloy exhibits the highest elongation (31.1%) and the biggest damping capacity, with Q ^−1 of 0.019 at the strain amplitude of 0.1%. However, the room temperature thermal conductivity decreases with the lower Zn/Ga ratio, and the Mg-1at.%Zn alloy exhibits the highest value (143 W/(m K)). The Mg-0.75at.%Zn-0.25at.%Ga alloy has the best comprehensive performance. | Effect of Zn/Ga Ratio on Damping and Thermal Behaviors of Fine-Grained Mg-Zn-Ga Sheets | 10.1007/s11665-022-06605-x |
2022-07-01 | Gas turbine generator sets are widely used in IGCC system, gas-steam combine cycle, distributed energy system et al. for its advantages of low pollution, high efficiency, quick start and stop. The structure of gas turbine rotor can be divided into integral rotor and rod-fastened rotor. Experimental study shows that the vibration signal, especially the displacement signal, of the rod-fastened rotor will increase/decrease greatly in a small interval of rotating speed. The reason for this phenomenon is the unique structure of the rod-fastened rotor, namely the interfaces between discs. In this paper, based on the Lagrange equation, the equation of motion of a rod-fastened rotor-bearing system considering the damping of the contact interface is established. The bistable behaviour and hysteretic cycle, also called the jumping phenomenon in engineering, are revealed. In addition, a test bench of the rod-fastened rotor-bearing system is built. The bistable behaviour and hysteretic cycle are experimentally proven, and the effect of the eccentric distance of the rotor on the bistable behaviour is experimentally explored. | Study on the bistable vibration behaviour of a rod-fastened rotor-bearing system | 10.1007/s11071-022-07501-8 |
2022-07-01 | Background The architected mechanical metastructures have garnered significant research attention for various engineering applications due to their remarkable mechanical properties and unique deformation behavior. The lattice-based micro-structured materials have shown enhanced mechanical properties and the ability to control wave propagation, making them ideal for multifunctional applications. Objective We report the family of lattice-based hourglass metastructures within the optimal design scope and its geometrical parameter selection. The lattice-based energy absorption performance and their damping characteristics have been classified based on different constitutive lattices. Methods Herein, the uniaxial compressive response and lattice-based energy absorption capacity of a novel hybrid configuration, hourglass-shaped, consists of auxetic and honeycomb-based lattice, are systematically investigated through theoretical, finite element simulation and experimental methods. The proposed hourglass-shaped unit cell is a combination of two oppositely oriented coaxial domes that give more flexibility to control dynamic response and enhance lattice functionality passively. An additive manufacturing route has fabricated a series of hourglass-shaped lattice metastructures with nylon-based material. Results It was found from the experimental data that the Ideal energy absorption efficiency parameter ( $$E_{i}$$ E i ) is highest for the case of the auxetic-based hourglass with the increment of 22% and 35% than the solid shell and honeycomb lattice-based metastructure, respectively. The specific energy absorption parameters data have also been evaluated and compared with the numerical computational results. Conclusion The combination of numerical simulation, additive layer manufacturing (3D printing), and experimental testing are implemented to quantitatively determine the lattice-based energy absorption properties and justify their evaluation. This study suggests the utilization of novel hourglass lattice-based metastructure for multifunctional engineering applications. | Energy Absorption of Hourglass Shaped Lattice Metastructures | 10.1007/s11340-022-00840-y |
2022-07-01 | This paper mainly focus on the global existence of the strong solutions for the generalized Navier-Stokes equations with damping. We obtain the global existence and uniqueness when $$\alpha \ge {5 \over 4}$$ α ≥ 5 4 for β ≥ 1 and when $${1 \over 2} + {2 \over \beta} \le \alpha \le {5 \over 4}\,{\rm{for}}\,\,{8 \over 3} \le \beta < + \infty $$ 1 2 + 2 β ≤ α ≤ 5 4 f o r 8 3 ≤ β < + ∞ . | Global Existence of Strong Solutions for the Generalized Navier-Stokes Equations with Damping | 10.1007/s10255-022-1106-4 |
2022-07-01 | Aerospace thin-walled parts vibrates during the process of milling due to their characteristics of low rigidity, which influences the machining quality of the workpiece. Based on the characteristics of magnetorheological fluid excitation solidification, a magnetorheological damping fixture is designed to semi-actively suppress the vibration generated during the machining process. This paper simplifies the multi-characteristic structure of aerospace thin-walled parts into rectangular thin plates. In accordance with Kirchhoff G.’s small deflection bending theory of elastic thin-plates and Daramberg’s principle, the differential equations for the transverse vibration of the thin-walled parts are established, which aims to obtain the natural frequency as well as vibration mode function of the thin-walled parts. In consideration of damping characteristics and the external dynamic milling force after the magnetorheological fluid excitation solidification, this paper uses the mode superposition method and an improved dynamic response mathematical model of the magnetorheological damping fixture thin-walled parts system of the linear multiple degrees of freedom, which has different volumes of magnetorheological fluids under forced vibration, was established. The maximum error between the predicted and measured values of the fixture-workpiece system dynamic response of displacement and acceleration is 16.2% and 15.5%, respectively. Finally, this paper verifies the feasibility as well as the effectiveness of the model through dynamics experiment and milling machining experiment. | An improved dynamics modeling during milling of the thin-walled parts based on magnetorheological damping fixture | 10.1007/s00170-022-09489-2 |
2022-07-01 | Nonlinearity can take an important and critical role in engineering systems, and thus cannot be simply ignored in structural design, dynamic response analysis, and parameter selection. A key issue is how to analyze and design potential nonlinearities introduced to or inherent in a system under study. This is a must-do task in many practical applications involving vibration control, energy harvesting, sensor systems, robotic technology, etc. This paper presents an up-to-date review on a cutting-edge method for nonlinearity manipulation and employment developed in recent several years, named as the X-structure/mechanism approach. The method is inspired from animal leg/limb skeletons, and can provide passive low-cost high-efficiency adjustable and beneficial nonlinear stiffness (high static & ultra-low dynamic), nonlinear damping (dependent on resonant frequency and/or relative vibration displacement), and nonlinear inertia (low static & high dynamic) individually or simultaneously. The X-structure/mechanism is a generic and basic structure/mechanism, representing a class of structures/mechanisms which can achieve beneficial geometric nonlinearity during structural deflection or mechanism motion, can be flexibly realized through commonly-used mechanical components, and have many different forms (with a basic unit taking a shape like X/K/Z/S/V, quadrilateral, diamond, polygon, etc.). Importantly, all variant structures/mechanisms may share similar geometric nonlinearities and thus exhibit similar nonlinear stiffness/damping properties in vibration. Moreover, they are generally flexible in design and easy to implement. This paper systematically reviews the research background, motivation, essential bio-inspired ideas, advantages of this novel method, the beneficial nonlinear properties in stiffness, damping, and inertia, and the potential applications, and ends with some remarks and conclusions. | The X-structure/mechanism approach to beneficial nonlinear design in engineering | 10.1007/s10483-022-2862-6 |
2022-07-01 | The article considers theoretical and experimental aspects of determining the dynamic characteristics of a water rotary pump with an adjustable wide-frequency platelike damper of dynamic vibrations (DDV). To solve this problem, a computational model of the mechanical oscillatory system pump–DDV was developed, and the actual parameters of its model were determined. Several experiments of a water rotary pump with a platelike dynamic vibration damper were carried out, which allowed us to identify the required number of relevant parameters, in particular the amplitude, frequency, and coefficients of stiffness and viscous damping of the DDV, and determine their specific optimal values to reduce the oscillations of the rotary pump in general. The following algorithm for optimizing the parameters of the system water rotary pump-platelike dynamic vibration damper is proposed: theoretical and experimental determination of the most critical parameters of the main structure of the water rotary pump and the platelike DDV; preliminary determination of the optimal parameters of the platelike DDV, in particular, its natural frequency and damping parameters based on random search methods, in particular, the genetic method; study of oscillation waveforms of the main structure of the water rotary pump and the DDV; calculation of the amplitude-frequency characteristics of a water rotary pump with a lamellar DDV to identify its optimal parameters. This allows one to determine the optimal modes of operation, avoid resonance modes, and increase the durability and reliability of the pump design. | Calculation-and-Experimental Determination of the Dynamic Characteristics of a Rotary Pump with a Platelike Dynamic Vibration Damper | 10.1007/s11223-022-00434-y |
2022-07-01 | Purpose Track irregularities and wheel-track interaction in rail vehicles travelling at high speeds cause excessive vibrations in the train body, which affect travellers by declining ride comfort. Suspension systems play an essential role in mitigating vibration and enhancing ride comfort. In this context, secondary lateral passive dampers were replaced with magneto-rheological (MR) dampers to mitigate vibrations and enhance ride performance. Methods A seventeen degrees of freedom (DoF) rail vehicle model equipped with MR dampers is formulated, and a modified Bouc-Wen model is used to evaluate the functionality of the MR damper. Herein, two distinct controllers: disturbance refusal and damper force tracking control algorithms, are employed to control the entire suspension system. Afterwards, ride indices are computed using Sperling criteria to assess the ride quality and comfort at different train speeds, which are validated with experimental results. Results Output responses of the train body in lateral, yaw and roll directions are compared for both passive and semi-active suspension systems at speeds of 80, 120, 160, and 200 km/h. In terms of RMS acceleration, the semi-active suspension with the controllers attains better vibration reduction. Percentage reduction was found to be 23.80–27.49%, 18.75–21.23%, and 17.86–20.32% for lateral, yaw, and roll acceleration, respectively, at different train speeds. Moreover, ride quality and ride comfort were improved by 13.66–16.24% and 14.27–17.18%, respectively. Conclusions The findings reveal that semi-active suspension outperforms passive suspension in terms of vibration abatement and significantly enhances the ride quality and comfort. | Modelling and Analysis of a Passenger Train for Enhancing the Ride Performance Using MR-Based Semi-active Suspension | 10.1007/s42417-022-00479-y |
2022-07-01 | Purpose The novel metallic damper device for passive vibration control of structures, which is designed primarily for seismic protection of buildings, is described in this paper. It consists of the base plate, fixed into foundation, with two concentric cycles of vertical components and a middle steel activating plate anchored to the isolated structure. During an earthquake, the middle steel activating plate moves together with main structure causing bending of vertical components. Seismic energy is absorbed due to plastic deformation of the vertical components of the damper. The performance of various vertical components, the key elements of the novel damper is studied in this paper. The advantages of this type of damper reflect in its ability to adapt its own features depending on the intensity of the earthquake and that it has equivalent characteristics in every horizontal direction due to rotational symmetry. Methods Sixteen experimental tests of the vertical components of the damper, were conducted to obtain their hysteretic behaviour. Numerical models using the finite element method and the Abaqus/Standard software were developed, validated and verified with experimentally obtained results. Results The experimental results show significant energy absorption of the vertical components of the novel damper. Numerical models can be used in further research instead of expensive experimental tests. Conclusions The vertical components of the novel damper possess extraordinary hysteretic performance. If the components of the energy dissipation device are properly designed for maximum displacements, the device is not expected to suffer heavy damage or total failure during earthquakes. | Experimental and Numerical Study of Energy Dissipation Components of a New Metallic Damper Device | 10.1007/s42417-022-00485-0 |
2022-06-30 | We introduce the new concepts of pseudo numerical range for operator functions and families of sesquilinear forms as well as the pseudo block numerical range for $$n\!\times \! n$$ n × n operator matrix functions. While these notions are new even in the bounded case, we cover operator polynomials with unbounded coefficients, unbounded holomorphic form families of type (a) and associated operator families of type (B). Our main results include spectral inclusion properties of pseudo numerical ranges and pseudo block numerical ranges. For diagonally dominant and off-diagonally dominant operator matrices they allow us to prove spectral enclosures in terms of the pseudo numerical ranges of Schur complements that no longer require dominance order 0 and not even $$<\!1$$ < 1 . As an application, we establish a new type of spectral bounds for linearly damped wave equations with possibly unbounded and/or singular damping. | Pseudo Numerical Ranges and Spectral Enclosures | 10.1007/s11785-022-01232-9 |
2022-06-28 | This paper is concerned with the Cauchy problem for semilinear wave equation with space-dependent scattering damping and combined nonlinearities. The blowup results of solution are established by introducing proper test functions. Moreover, upper bound lifespan estimates of a solution to the Cauchy problem with small initial values are derived. To the best of our knowledge, the results in Theorems 1.1 – 1.2 are new. | Blowup for semilinear wave equation with space-dependent damping and combined nonlinearities | 10.1186/s13662-022-03719-3 |
2022-06-23 | We present a generalised Lindblad equation (GLE) for position-dependent mass (PDM). Using the GLE, we obtain the probability density, Fisher information (FI), Von Neumann entropy and the quantum Fisher information (QFI) in two different generalised Jang and Dekker cases. The behaviours of the above measures are analysed with the position, time and friction. We find that the dominance of either FI or QFI depends on fulfilling the fundamental uncertainty relation on diffusion parameters. | Jang and Dekker oscillators in position-dependent mass formalism | 10.1007/s12043-022-02366-3 |
2022-06-20 | In this paper, we consider the global existence and blow up mechanism of classical solutions for one dimensional isentropic compressible Euler equations with over damping term like $$\mu (1+t)^{\lambda } v$$ μ ( 1 + t ) λ v , where $$\mu >0$$ μ > 0 and $$\lambda >0$$ λ > 0 are physical parameters. Using wave decomposition method and energy functional, we show that for any given time $$T>0$$ T > 0 , the classical solutions of system (3) exist globally under some suitable conditions on initial data and give singularity formation of classical solutions under the assumptions that the derivatives of initial data are sufficiently negative. | Classical Solutions for 1D Compressible Euler Equations with Over Damping | 10.1007/s00021-022-00709-z |
2022-06-16 | Perpendicular magnetic anisotropy-based magnetic tunnel junctions (p-MTJs) with low Gilbert damping constant (α) are of particular interest for fast and low-power consumption magnetic random-access memory (MRAM). However, obtaining a faster switching speed and lower power consumption is still a big challenge. Herein, we report a Mo-based perpendicular double free layer structure with a low Gilbert damping constant of 0.02 relative to W-based films, as measured by time-resolved magneto-optical Kerr effect equipment. To show the influence of different film structures on the Gilbert damping constant, we measured the Mo-based single free layer. Thereafter, we deposited the full stacks with the Mo-based double free layer and obtained a high tunneling magnetoresistance of 136.3% and high thermal stability. The results of high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDS) showed that the Mo-based films had better crystallinity, sharper interfaces, and weaker diffusion than the W-based films and thus produced a weaker external contribution of the Gilbert damping constant. As a result of the weak spin-orbit coupling in the Mo-based structure, the intrinsic contribution of the Gilbert damping constant was also weak, thereby leading to the small Gilbert damping constant of the Mo-based stacks. In addition, the macro-spin simulation results demonstrated that the magnetization switching by the spin transfer torque of the Mo-based MTJs was faster than that of the W-based MTJs. These findings help to understand the mechanism behind the good performance of Mo-based p-MTJ films and show the great promise of these structures in low-power consumption MRAM or other spintronic devices. | Mo-based perpendicularly magnetized thin films with low damping for fast and low-power consumption magnetic memory | 10.1007/s11433-021-1875-6 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.