publicationDate stringlengths 10 10 | abstract stringlengths 0 37.3k | title stringlengths 1 5.74k | doi stringlengths 11 47 ⌀ |
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2020-06-01 | In this study, a new type of steel block slit dampers (BSD) has been investigated. This type of damper not only provides good seismic performance but can be easily repaired and replaced after a strong earthquake. The stability of these dampers under periodic loading and the hysteresis behavior was also investigated in this study. It should be noted that energy dissipations and plastic deformation are concentrated only in steel slit dampers (SSDs) and plastic behavior of the beam and column, and they are both more energy-absorbing and more economical than SSDs. Therefore, in this study, effort has been made to optimize and increase the energy absorption of these dampers. Therefore, in this study, eight samples with different geometric dimensions have been simulated to develop and increase energy absorption of the steel BSD, and the results indicate that the slit dampers have more ductility and stiffness than those of previous studies, which considerably increased the energy absorption in hysteresis cycles in all specimens. | Study of the Effect of Geometric Parameters of Steel Block Slit Dampers on Energy Absorption | 10.1007/s13296-020-00343-3 |
2020-06-01 | This paper addresses the problem of determining the optimal parameters of a sky-hook damper type suspension in the control of the stationary response of half car vehicle models traversing a rough road. The optimal values of the sky-hook damper suspension parameters are obtained by equating the active suspension control force using linear quadratic regulator (LQR) with that of the sky-hook damper suspension force. Results show that the performance of half car model with optimal sky-hook damper suspension is almost close to the performance of half car model with LQR control. | Optimal response of half car vehicle model with sky-hook damper based on LQR control | 10.1007/s40435-019-00588-9 |
2020-06-01 | Integration of semi-active devices in Automotive Seating System (ASS) with intelligent control policies help attenuation of the vibration transmitted to the occupant. The current work investigates the effectiveness of a semi-active magnetorheological (MR) damper with ASS for a quarter car model with the application of suitable control algorithms. The system controller calculates the desired damping force using proportional integral derivative (PID), skyhook on/off, PID tuned using genetic algorithm (GA), skyhook continuous and modified skyhook controllers. The signum function damper controller estimates the command voltage required for tracking the desired damping force. The displacement and acceleration of the passive seat system was compared with the semi-active seat suspension system in time and frequency domains. The results from the frequency domain shows that the lowest resonance peaks for the seat system can be achieved using the modified skyhook control policy. The effectiveness of the modified skyhook controller is evaluated in terms of peak to peak (PTP) acceleration, root mean square (RMS) acceleration, frequency weighted RMS acceleration, seat effective amplitude transmissibility (SEAT), vibration dose value (VDV) and crest factor (CF) for enhancing the ride quality. The modified skyhook controller can dissipate the energy better than the passive system. The modified skyhook controller increased the occupant ride quality of SEAT, VDV and CF by 30.41%, 52.84% and 11.62% on account of small bump excitation and 31.76%, 53.27% and 11.02% on account of large bump excitation compared with passive system. The modified skyhook control policy attenuates the vibration better than other control policies addressed in this paper. | Response characteristics of car seat suspension using intelligent control policies under small and large bump excitations | 10.1007/s40435-019-00569-y |
2020-06-01 | Seismic control of cable-stayed bridges is of paramount importance due to their complex dynamic behavior, high flexibility, and low structural damping. In the present study, several semi-active Fuzzy Control Algorithms (FCAs) for vibration mitigation of Lali Cable-Stayed Bridge are devised. To demonstrate the efficiency of the algorithms, a comprehensive nonlinear 3-D model of the bridge is created using OpenSees. An efficient method for connecting MATLAB and OpenSees is devised for applying FCAs to the structural model of the bridge. Two innovative fuzzy rule-bases are introduced. A total of six different fuzzy rule-bases are utilized. The efficiency of the FCAs is evaluated in a comparative manner. The performance of fuzzy control systems is also compared with a sky-hook and a passive-on system. Moreover, the sensitivity of efficiency of control systems to the peak ground acceleration is evaluated qualitatively. In addition, the effect of time lag is also investigated. This study thoroughly examines the efficiency of the FCAs in different aspects. Therefore, the results can be regarded as a general guide to design semi-active fuzzy control systems for vibration mitigation of cable-stayed bridges. | Semi-active fuzzy control of Lali Cable-Stayed Bridge using MR dampers under seismic excitation | 10.1007/s11709-020-0612-9 |
2020-05-24 | In this paper, we study the indirect stabilization of a system of plate equations which are weakly coupled and locally damped. By virtue of the general results due to Burq in the study of asymptotic behavior of solutions, we prove that the semigroup associated to the system is logarithmically stable under some assumptions on the damping and the coupling terms. For this purpose, we adopt an approach based on the growth of the resolvent on the imaginary axis, which can be obtained by some Carleman estimates. | Stabilization of the weakly coupled plate equations with a locally distributed damping | 10.1186/s13662-020-02677-y |
2020-05-15 | This paper is concerned with the asymptotic behavior of solutions to a non-autonomous stochastic wave equation with additive white noise, for which the nonlinear damping has a critical cubic growth rate. By showing the pullback asymptotic compactness of the stochastic dynamic systems, we prove the existence of a random attractor in H 0 1 × L 2 $H_{0}^{1}\times L^{2}$ . | Random attractors for non-autonomous stochastic wave equations with nonlinear damping and white noise | 10.1186/s13662-020-02664-3 |
2020-05-14 | Improving the gait of transfemoral amputees and making it biomimetic and stable has always been a major effort. A dynamic model of the prosthetic device can predict the kinetic and kinematic performances, when incorporated with a musculoskeletal model. In this regard, a dynamic model of a recent trend of variable damping technology will help a great deal in evaluating the performance of the prosthetic device and also in studying the effect of various parameters on the prostheses. The current paper presents the dynamic model of a single axis two segmental prosthetic knee implemented with a magneto-rheological (MR) damper as a variable damping element. The MR damper is modeled mathematically using Bouc–Wen model with model parameters evaluated by minimizing the error norms for time, displacement and velocity between the experimental and the model-generated results using a genetic algorithm. Two different experimental data sets are used, one for mathematical modeling and other to assess the accuracy of the fit model. A Proportional Derivative plus Controlled Torque controller is employed, and the parameters are tuned to minimize the error between the desired and control input torques. Further, an inverse dynamic model using Bouc–Wen model variables is assumed and validated later. This model predicts the current directly and avoids the necessity of solving any quadratic equation, which is required in the case of inverse models based on modified Bouc–Wen. The dynamic model of the prosthesis is analyzed for the swing phase alone, and the results show that the model traces the desired knee angle and also the shank reaches full knee extension at the end of this phase with terminal velocity small enough to be handled by an extension stop. | Semi-active control of a swing phase dynamic model of transfemoral prosthetic device based on inverse dynamic model | 10.1007/s40430-020-02387-2 |
2020-05-08 | In this paper, a new transmission form of a planetary gear transmission coupled with a torsional vibration damper (PGT-D) is proposed where the torsional vibration damper is used to replace the conventional manner a certain member in planetary gear fixed with a box. The advantages of the PGT-D are investigated under complex conditions including start-up, load saltation, and load fluctuations. A dynamic model of the motor and PGT-D connection was established. The dynamic model combines a dynamic asynchronous motor model and a PGT-D model for a variable speed process, wherein the motor electromagnetic characteristics, PGT-D torsional deformation, and time-varying meshing stiffness under variable speed conditions are considered. Then, the simulation results are compared to those of a traditional motor and planetary gear transmission. The torsional vibration damper can reduce resonance points of the system in the common speed range. The PGT-D can effectively reduce the fluctuation level of motor speed and output acceleration, so that the speed of the system can rise smoothly while reducing the amplitude of torque fluctuation on the shaft during the start-up process. Moreover, the influence of time-varying stiffness on the system is analyzed during the load saltation process. Furthermore, the PGT-D can reduce the interference of the fluctuating load on the motor and gear parts. | Dynamic characteristics of a new coupled planetary transmission under unsteady conditions | 10.1007/s40430-020-02371-w |
2020-05-01 | A mesoscale modeling of magneto-rheological damper is performed by using dissipative particle dynamics method. Bounce-back and periodic boundary conditions are used, and the model is validated by Couette flow, Poiseuille flow and flow through a micro-tube. Shear stress and damping behavior are probed with considering hysteresis condition. Three electrical coils are placed inside MR damper, control damping force by applying magnetic strength distribution as step function pattern. Results show that by increasing both of average strength of magnetic field and shear rate, shear stress increases. The effects of different parameters such as frequency and amplitude of piston velocity, magnetic field strength, diameter of magnetic particles and strength of dissipative forces on damping force and hysteresis condition are investigated by using Bouc–Wen model. Results show by increasing frequency and decreasing amplitude and magnetic field strength, hysteresis range and strength of damping force reduce. Sensitivity analysis performed on MR fluid parameters reveals that the weight of magnetic particles and the dissipative force have the most effect on strength of damping force so that, by increasing dissipative force, damping force increases linearly, but enhancement in the weight of magnetic particles leads to damping force firstly increases and then reduces. | Magneto-rheological damper modeling by using dissipative particle dynamics method | 10.1007/s40571-019-00280-x |
2020-05-01 | Dynamics in fractional order systems has been discussed extensively for presenting a possible guidance in the field of applied mathematics and interdisciplinary science. Within hundreds and thousands of reviews, regular papers and drafts, many fractional differential equations are presented for enjoying mathematical proof without clarifying the scientific background and physical principles. It seems that all nonlinear problems on integer order systems even networks can be confirmed as fractional order systems. This mini-review gives an appropriate clarification on fractional dynamical systems from the physical viewpoint, thereby presenting sufficient evidences for further study on fractional calculus. We argued that non-uniform diffusion, boundary effect and elastic deformation account for the calculation and estimation with fractional order on some physical variables, which can be mapped into dimensionless variables in the dynamical systems. In addition, some similar definitions for energy, wave propagation and diffusion are suggested to find reliable confirmation in the application of fractional calculus. | Clarify the physical process for fractional dynamical systems | 10.1007/s11071-020-05637-z |
2020-05-01 | This paper discusses the effect of multi-objective function in angle stability improvement for a single machine connected to an infinite bus system (SMIB). Minimum damping ratio, ξ _ min and maximum damping factor, σ _ max which are commonly used to indicate oscillatory stability condition in power system are merge in certain ratio to produce a multi-objective function, F _ MO . This new index brings the advantages of the two indices without compromising the weakness of the index involved. In this study, F _ MO is applied to tune parameters of static var compensator with proportional-integral-derivative controller (SVC-PID) to improve damping efficiency in SMIB. The result is compared with a system connected to power system stabilizer attached with lead lag controller (PSS-LL). The parameters of SVC-PID and PSS-LL are optimized by particle swarm optimization method. Validation based on speed response, phase plane and determination of eigenvalues confirms that the proposed F _ MO is more effective for solving angle stability problems compared to single objective function. | Swarm Intelligence Approach for Angle Stability Improvement of PSS and SVC-Based SMIB | 10.1007/s42835-020-00386-w |
2020-05-01 | The influences of cold-rolling deformation and annealing on the damping capacity of Fe–19Mn–8Cr alloy were investigated. It was observed that the cold-rolled Fe–19Mn–8Cr alloy with a reduction of 10% showed the relatively excellent damping capacity because of the relatively more ε-martensite and lower dislocation density, and the reduction of slopes of different damping curves increased along with increasing the cold-rolling reduction. Besides, the subsequent annealing process can further enhance the damping capacity. After 70% cold-rolling deformation, the austenite grain would grow up with the increase in the annealing temperature, which resulted in a significant change in the content and morphology of ε-martensite influencing the damping capacity of the experimental steel. The damping capacity was optimum when annealed at 800 °C for 30 min, displaying that the size of ε-martensite has a vital influence on the damping capacity of the experimental alloy. This study may enrich the fundamental knowledge about how to ameliorate the damping capacity of Fe–Mn–Cr damping steels. | Significant impact of cold-rolling deformation and annealing on damping capacity of Fe–Mn–Cr alloy | 10.1007/s42243-020-00386-0 |
2020-05-01 | A typical quasi-zero stiffness (QZS) vibration isolator composed of two lateral springs and a vertical spring has been widely studied previously, aiming to widen the frequency range of isolation without increasing the static displacement. However, there is still a gap between the previous dynamic model and the practical application, due to the neglection of some factors that may exist in practical situations. In this paper, a more accurate dynamic model is established with consideration of these practical factors. The dynamic behavior and dynamic characteristics of this typical QZS isolator are analyzed based upon the accurate dynamic model. The biggest difference between the newly proposed dynamic model and the previous one lies in the damping characteristics. Therefore, we specially investigate the damping effects, from which it is found that the vibration isolation performance can be further enhanced by proper design of the damping parameters. | Accurate modeling and analysis of a typical nonlinear vibration isolator with quasi-zero stiffness | 10.1007/s11071-020-05642-2 |
2020-05-01 | A friction-type tensioner is widely used in a belt drive system for maintaining belt tension constantly and reducing vibration. Owing to friction dampings, the curve of the reaction torque and the imposed angle of tensioner arm is a hysteretic loop. Here, the hysteretic behavior of tensioner is considered in dynamic analysis of a belt drive system. A hysteretic model for describing the applied torque versus the imposed angle of tensioner arm is established. And an iterative algorithm is proposed for estimating the nonlinear equivalent viscous damping of tensioner under a varying excitation frequency. A timing belt drive system is taken as an example. Based on the existing research, the dynamic models for a belt, an automatic tensioner and rotational pulleys of system are also given. The vibration responses of a belt system, such as the oscillation angle of tensioner arm, the transmission error between pulleys and the hub load applied on pulley, are calculated and compared with the measurements, which are validated the presented method. The influence of damping ratio of tensioner on dynamic responses of system is investigated, and the influence of iteration parameters on the iterative efficiency is discussed. The presented method is beneficial to modifying the existing method for calculating the vibration responses of a belt drive system. | Method for estimating vibration responses of belt drive systems with a nonlinear tensioner | 10.1007/s11071-020-05617-3 |
2020-05-01 | The classical methods of surface damping of bending vibrations of thin-walled structures and a promising integrated version with a damping coating consisting of two layers of a material with pronounced viscoelastic properties and an intermediate thin reinforcing layer of a high-modulus material are discussed. A four-layer finite element for an elongate plate with an integral damping coating is developed taking into account the lateral compression of the damping layers. A system of governing equations of the finite-element method is constructed for analyzing the dynamic response of the plate during its resonant vibrations. Iterative algorithms have been developed to take into account the amplitude dependence of the logarithmic decrements of vibrations of material of the damping layers when determining the damping properties of the plate and determining its vibration eigenmodes and eigenfrequencies with consideration of frequency dependence of the dynamic elastic moduli of the material. Numerical experiments were carried out to test the finite element developed and the iterative algorithms mentioned. The influence of aerodynamic resistance forces on the overall damping level of a cantilever plate with an integral damping coating is assessed. | Numerical Modeling of Resonant Vibrations of an Elongate Plate with an Integral Damping Coating | 10.1007/s11029-020-09869-3 |
2020-05-01 | In this paper, we study the asymptotic behavior of solutions for the porous thermoelastic system with temperatures and microtemperatures effects. Our main result is to prove the exponential stability in case of zero thermal conductivity and without any condition on the coefficients of the system. This result is new and improve some recent results in the literature. | On the stabilization of linear porous elastic materials by microtemperature effect and porous damping | 10.1007/s11565-019-00333-2 |
2020-05-01 | Two condensed electron-beam copper coatings, one consisting of copper and the other of Hf/Ag/Ni/Cr microlayers, were deposited onto a titanium alloy (Ti−6Al−4V) substrate to study the energy dissipation and fatigue resistance in the uncoated and coated samples under nonbreaking and breaking cyclic stresses. The microlayer coating is peculiar in that a material with a higher elastic modulus is used in each subsequent layer (from the substrate to the outer layer) and the coating layers and submicron twins in the binder sublayer have a columnar microstructure peculiar to electron-beam evaporation and vacuum condensation. Having layered macro- and microstructure, the coating absorbs the energy of vibrations through both internal friction (between the coating layers and between the coating and substrate) and dissipation of vibration energy on numerous defects in the columnar structure (intercolumnar porosity). Resonant first- and secondmode vibrations were excited in cantilevered samples to determine how the vibration decrement depended on their maximum stresses and the breaking fatigue stresses on the number of load cycles. In addition, vibration transmission coefficients for cyclic stresses and vibration energy were experimentally defined and justified for use. One coefficient is equal to the ratio of difference in stresses between the uncoated and coated samples to stresses in the uncoated sample, relative machine power being the same in various tests. The other coefficient is equal to the ratio of difference in energy between the uncoated and coated samples to the energy of vibrations induced in the uncoated sample, relative machine power being the same in various tests. The Hf/Ag/Ni/Cr coating is shown to provide greater energy dissipation but lower fatigue properties than the Cu coating and substrate. The vibration transmission coefficients are more sensitive to energy dissipation than the vibration decrement is. | Effective Reduction of Cyclic Stresses in Coated Samples | 10.1007/s11106-020-00139-4 |
2020-05-01 | In the past few decades, many efforts have been carried out to investigate and improve the cyclic performance of the precast structure joints using high-strength steel bars and plates. However, the utilization of high-damping rubber (HDR) is mainly limited as the bearing pad below the structural components to dissipate the cyclic energy. Hence, a new hook-end connection precast beam–column joint embedded with U-shaped HDR is developed in this study to investigate energy dissipation capacity and equivalent viscous damping ratio in a precast frame. The horizontal cyclic performance of the new connection is experimentally tested, numerically analyzed, and evaluated by comparing to precast reinforced concrete frame specimens built with monolithic and conventional pinned dowel connections. The experimental results showed that the precast frame with newly developed connection exhibited fatter hysteretic curves, approximately 15% and 13% higher cumulative energy dissipation capacity, and equivalent viscous damping ratio than the control specimen with conventional pinned dowel connection, respectively. Besides, it also attained similar yield force and approximately 6% lower maximum force compared to the monolithic specimen. The force–displacement backbone curves obtained from the numerical analysis also showed satisfactory matching in yield force, maximum force and maximum displacement when compared to the experimental results. | Horizontal Cyclic Performances of Hook-End U-Shaped High-Damping Rubber Jointed Precast Frame | 10.1007/s40999-019-00486-3 |
2020-05-01 | Abstract — The article presents an algorithm for and results from studying the motion of a rotor involving its simultaneous rubbing against the stator elements in the turbine set span and supports. The aim of the study was to develop the mathematical model describing vibration of the rotor resting in a few supports and to select the main assumptions regarding the contact interaction between the rotor and stator that will make it possible to model a real vibrational process that involves rubbing. An abrupt loss of balancing in the rotor’s second span section at the angular rotation speed is taken as the initial disturbance upsetting the turbine set’s normal operation. The case of a constant rotor rotation speed with loss of balancing followed by development of contact interaction between the rotor and stator elements is considered. This scenario seems to be the most plausible because the interaction persists for a short period of time during which the safety system still remains silent in producing the command to disconnect the steam supply to the turbine, and the torque on its shaft remains constant. It is shown that with the adopted clearances in the turbine set span and supports, with the loss of balancing corresponding to detachment of the mass of one turbine blade, and with increased damping in the supports, the rotor motion is accompanied by rubbing in the turbine set supports and span. If the damping coefficient in the supports does not exceed the value of this parameter in the plain bearing oil film, asynchronous reverse whirl of the rotor develops, which is characterized by self-excited vibration caused by the effect of contact interaction forces between the rotor and stator. Owing to consideration of the rotor design features, its frequency characteristics, including the change in the frequency characteristics of the rotor–supports system due to additional reactions arising at the moments in which the rotor comes into contact with the stator, it becomes possible to model the vibration development process not only during strong (when whirl is excited) but also during weak (possible excitation of low-frequency vibration) interactions between the rotor and stator and to analyze the influence of detuning from resonances and other factors on the development of self-excitation processes in systems closer to real ones. | Turbine Generator Rotor Vibrations with Rubbing in the Span and Supports | 10.1134/S0040601520050092 |
2020-05-01 | Abstract The solution to the problem of oscillations of a circular cylinder in fluid of finite depth beneath an ice cover in the neighborhood of a vertical wall is obtained. The ice cover is simulated by a thin elastic semi-infinite plate of constant thickness. Different boundary conditions at the plate edge are considered, namely, the free and clamped edges. The added mass and damping coefficients, the deflection and strain amplitudes of the ice cover, and the forces exerted on the wall are investigated depending on the oscillation frequency and input parameters of the problem. | Oscillations of a Cylinder beneath an Ice Cover in the Neighborhood of a Vertical Wall | 10.1134/S0015462820030131 |
2020-05-01 | Transporting an object during locomotion is one of the most common activities humans perform. Previous studies have shown that continuous and predictive control of grip force, along with the inertial load force of the object, is required to complete this task successfully. Another possible CNS strategy to ensure the dynamic stability of the upper limb is to modify the apparent stiffness and damping via altered muscle activation patterns. In this study, the term damping was used to describe a reduction in upper limb vertical oscillation amplitude to maintain the orientation of the hand-held object. The goal of this study was to identify the neuromuscular strategy for controlling the upper limb during object transport while walking. Three-dimensional kinematic and surface electromyography (EMG) data were recorded from eight, right-handed, healthy young adults who were instructed to walk on a treadmill while carrying an object in their dominant/non-dominant hand, with dominant/non-dominant arm positioning but without an object, and without any object or instructed arm-positioning. EMG recordings from the dominant and non-dominant arms were decomposed separately into underlying muscle synergies using non-negative matrix factorization (NNMF). Results revealed that the dominant arm showed higher damping compared to the non-dominant arm. All muscles showed higher mean levels of activation during object transport except for posterior deltoid (PD), with activation peaks occurring around or slightly before heel contact. The muscle synergy analysis revealed an anticipatory stabilization of the shoulder and elbow joints through a proximal-to-distal muscle activation pattern. These activations appear to play an essential role in maintaining the stability of the carried object in addition to the adjustment of grip force against the perturbations caused by heel contact during walking. | Muscle synergy for upper limb damping behavior during object transport while walking in healthy young individuals | 10.1007/s00221-020-05800-3 |
2020-05-01 | Abstract Theoretical studies and design studies have been conducted to demonstrate the possibility of using a long hydrodynamic damper in the supports of a hydrogen pump rotor was shown. The complex problem of rotor dynamics and design synthesis of a hydrodynamic damper for a turbopump assembly (TPA) was solved. The geometric parameters of the hydrodynamic damper are determined that ensure the necessary damping level, d = 3 × 10^3 N s/m. It is shown that at such a damping level, the amplitude of rotor oscillations does not exceed the value of clearances in supports and on blade shoulders. | Development of Damping Support for a Turbine Pump Assembly of a Cryogenic Fuel Aviation Gas Turbine Engine | 10.3103/S1068366620030034 |
2020-05-01 | Abstract —The dependence of the impact strength and damping characteristics of сBN–Al composite materials on the specific surface (grain size) of cubic boron nitride powders has been investigated. The correlation between the damping characteristics of the composite material and its phase composition has been established. The dependence of the phase composition of the material on the specific surface of the powdered cBN component has been demonstrated. Composite materials with a biphasic structure and the highest density and hardness possible for this structure had the maximal impact strength. | The Effect of Charge Grit on Impact Strength and Damping Characteristics of BN–Al Composite Materials | 10.3103/S1063457620030041 |
2020-04-23 | Titanium nitride (TiN) thin films are deposited on titanium (Ti) substrates by pulsed laser deposition and radio frequency magnetron sputtering. The main goal of this research is to improve the corrosion resistance and the vibration damping performance of the Ti substrates by surface modification of the substrates with TiN thin film coatings. Electrochemical results indicate that TiN films bring about a significant improvement in the corrosion resistance of the Ti disks in phosphate buffer saline solution. It is also observed that TiN deposited at room temperature has the best corrosion efficiency in terms of lower corrosion current density and more positive corrosion potential. From the damping measurements, it is observed that the damping ratios of the TiN-coated beams are one to two orders of magnitude greater than those of uncoated ones. Additionally, the damping amplitudes of the TiN coated beams have been observed to return to zero position faster than the uncoated beam. The energy dissipation due to internal friction at the beam-coating interface and inter-lamellae interface within TiN coatings can be the mechanism responsible for reducing vibration amplitudes of TiN-coated beams. | Enhancement in corrosion resistance and vibration damping performance in titanium by titanium nitride coating | 10.1007/s42452-020-2777-1 |
2020-04-15 | Röckner and Zhang (Probab Theory Relat Fields 145, 211–267, 2009) proved the existence of a unique strong solution to a stochastic tamed 3D Navier–Stokes equation in the whole space and for the periodic boundary case using a result from Stroock and Varadhan (Multidimensional diffusion processes, Springer, Berlin, 1979). In the latter case, they also proved the existence of an invariant measure. In this paper, we improve their results (but for a slightly simplified system) using a self-contained approach. In particular, we generalise their result about an estimate on the $$L^4$$ L 4 -norm of the solution from the torus to $${\mathbb {R}}^3$$ R 3 , see Lemma 5.1 and thus establish the existence of an invariant measure on $${\mathbb {R}}^3$$ R 3 for a time-homogeneous damped tamed 3D Navier–Stokes equation, given by ( 6.1 ). | Stochastic Tamed Navier–Stokes Equations on
$${\mathbb {R}}^3$$
R
3
: The Existence and the Uniqueness of Solutions and the Existence of an Invariant Measure | 10.1007/s00021-020-0480-z |
2020-04-15 | Transmission lines are prone to external excitations due to their low density and internal damping coefficient. They are vulnerable to some natural events such as wind and rain which may disrupt power transmission. Forced vibration due to external disturbances is one of the most frequent causes of failures in these lines. In this study, effects of tuned-mass-dampers (TMDs) on reduction of forced vibrations are investigated. A mathematical model for the transmission line is proposed by using mode summation technique combined with the dynamics of the absorbers. Best values for the location, stiffness and mass of the absorbers are found by using Particle Swarm Optimization algorithm (damping coefficients are obtained as zero). The objective of the algorithm is to minimize the line deflection to postpone the failure and the replacement of the lines. Results show that the designed TMDs are efficient in reduction of forced vibrations. Finally, the same procedure is implemented under resonance condition. The designed TMDs lead to a high reduction factor in the line deflection. Similarly, the proposed optimization algorithm can be used in other industrial applications of the flexible cables; under various external excitations. | Optimum design of tuned mass damper via PSO algorithm for the passive control of forced oscillations in power transmission lines | 10.1007/s42452-020-2677-4 |
2020-04-11 | In the present study, the magnetorheological fluid (MRF) samples are prepared using pure carbonyl iron particles (CIPs), CIPs/Claytone APA/Molyvan 855 additive, and friction reducer dispersed in poly-alpha-olefin oil. The scanning electron microscopy reveals that the Claytone additive morphology looks like a surface abundant in small folds, which connect the gaps between the spherical pure CIPs and prevent sedimentation in the MRF. The magnetic saturation properties are investigated through the vibrating sample magnetometer. The pure CIPs MRF shows ( M _s) value as 146.12 emu/g, and the CIPs/Claytone APA/Molyvan indicates ( M _s) as 55.12 emu/g. The magnetorheological flow curves, such as shear stress and viscosity as a function of shear rate, are investigated for the MRF samples through the magnetorheometer. The sedimentation analysis of the MRF is observed by visual inspection and shows that the CIPs/Claytone APA/Molyvan improved the sedimentation rate than the pure CIPs MRF. Finally, the experimental characterization of the prototype monotube MR damper is carried out using the hydraulic dynamic testing machine at 1.5 Hz frequency for damper peak–peak displacement length of ± 5 mm at three intervals of 0 h, 24 h, and 72 h in damper to know the effect on damping force for the prepared MRF samples against the sedimentation rate. | Investigation of sedimentation, rheological, and damping force characteristics of carbonyl iron magnetorheological fluid with/without additives | 10.1007/s40430-020-02322-5 |
2020-04-11 | In order to achieve a high performance and to ensure an operation with a unit power factor with respect to imposed reference signals, the input–output feedback linearization technique with a sliding mode controller was proposed to control the induction motor fed by matrix converter drive system. In addition, the direct space vector modulation strategy is adopted to control the matrix converter to minimize the switching losses. On the other hand, a damped input filter has been used to reduce the harmonic total distortion rate injected to the grid. Moreover, the topology and the optimization method for parameter calculation of the input filter are also clarified. The robustness of the proposed control strategy for the drive system was tested and validated by a simulation study. | Feedback linearization associated to a sliding mode controller for an operating with unity power factor of induction motor fed by matrix converter | 10.1007/s42452-020-2674-7 |
2020-04-07 | In this paper, we provide a new approach to get global well-posedness for the 3D liquid crystal system with large vertical velocity in the critical L ^2 framework. The novelty is that there is not one additional derivative when we treat the pressure. Furthermore, our idea can be applied to get global well-posedness for the 3D damped Euler equations with large vertical velocity, while the previous ideas in Wan (Dyn. Syst. 37 , 5521–5539, 2017 ) seem not effective. | A New Approach to the 3D Liquid Crystal System with Large Vertical Velocity in the Critical L^2 Framework | 10.1007/s11040-020-09335-5 |
2020-04-02 | In this research, chemically synthesized titanium oxide (TiO_2) nano-powder was utilized for upgrading mechanical and vibrational applications of pineapple, banana and sisal fibers. The substitution of TiO_2 upto 3% enhanced the tensile, impact and flexural strength of pineapple/sisal, sisal/banana and banana/pineapple hybrid combinations. Irregular dispersion of nano-filler at 4% degrades the mechanical stability of bio-composites. Pineapple and sisal hybrid combinations with 3% TiO_2 filler has the highest natural frequency due to excellent surface contact with resin/hybrid natural fibers and filter/resin interface making higher stiffness to the composites with improved natural frequency. Natural frequency and damping properties enhanced with nano-filler mixing. The factors such as frictional properties and energy dissipation at maximum strain area in the filler make increment in the damping nature of the natural composites. In the equal fiber weight% of 35, pineapple-based hybrid composites make better damping rate by the higher interface thickness and smaller diameter of pineapple fiber than other two fibers. | Effect of TiO_2 nano-filler in mechanical and free vibration damping behavior of hybrid natural fiber composites | 10.1007/s40430-020-02308-3 |
2020-04-01 | A model of process damping in milling was developed in this study. The process damping is a critical parameter to increase the stable cutting region at low cutting speed to avoid chatter. The previous studies conducted experiments to estimate the process damping. Nevertheless, it is time and cost consuming. A model of dynamic cutting force was employed in this study. The plowing force generated by the flank-wave contact is considered as the main source of process damping to dissipate vibratory energy during cutting. In addition to the material properties and plowing force, the effects of chatter amplitude and wavelength, which result in the various indentation conditions and affect the coefficient of process damping, were also considered. The consideration of wavy contact surface and indentation area in this model allows quick determination of cutting stability conditions with high accuracy. The process damping coefficient estimated by the proposed model successfully represented the effect of the tool wear on chatter because of the change of tool geometry. Experiments were conducted to verify the new model. | Estimation of Process Damping Coefficient Using Dynamic Cutting Force Model | 10.1007/s12541-019-00297-5 |
2020-04-01 | Flexible silicone tubes are nowadays broadly employing in medical applications such as drugs or blood-conveying tubes, various infusions as well as medical pumps, and ventilators tubes. Due to better resistance to corrosion and erosion, the subsequent diminishing of wall thickness and change in stiffness of silicone tubes are negligibly small. Hence, these tubes provide trouble-free operations for a prolonged period. Commonly, the fundamental frequency of fluid conveying tubes is influenced by various flow parameters. Recognizing the parameters affecting the fundamental frequency and estimating the extent of the impact of these parameters on the natural frequency are extremely important. This information is vital in the design of precision flow measuring instruments such as Coriolis flowmeter (CFM), which uses vibration techniques for flow measurements. Owing to higher accuracy and the direct fluid flow rate measurements, CFMs are universally accepted in industries for flow measuring applications. When the flexible silicone tube is excited in its sagged condition, there exists a difference in natural frequency in horizontal and vertical planes. Applying pre-stretch decreases the difference in natural frequency, which reduces the sagging and facilitates the tube to regain its cylindrical shape. This paper shows the experimental research on the influence of sagging of the silicone tube conveying fluid, the feasible methods to overcome these effects, and an effective means to capture the deformed shape of a flexible tube. Numerical analysis is carried out in ANSYS using the deformed shape acquired from the laser scanning technique, and the result shows excellent agreement with the experimental values. The damping ratio of the tube is identified by experimenting with varying flow velocities and pre-stretches. This study reveals that it is essential to eliminate the effect of sagging and the subsequent impact of frequency difference in flexible tubes when the principle of Coriolis flowmeter employs for measuring flow rates through flexible tubes. | Effect of Sagging on Dynamic Characteristics of Silicone Tube Conveying Fluid | 10.1007/s40032-019-00552-8 |
2020-04-01 | This paper presents an analysis of the vibrational behavior of a rotating viscoelastic sandwich pre-twisted beams with a setting angle and with various viscoelastic stiffness laws. The governing equations of motion are derived using the Lagrange formulation and the assumed modes method. The obtained nonlinear eigenvalue problems are solved by using an iterative nonlinear eigensolver leading to complex eigensolutions composed of damped frequencies and loss factors with high accuracy. Further, the effects of the rotating speed, pre-twist angle, thickness ratio of core layer on the dynamic characteristics are investigated with taking into account the dependence of Young modulus with respect to frequency. Different numerical tests on rotating pre-twisted beams are performed for both isotropic and sandwich materials with a constant then a variable core modulus and the obtained results coincide very well with those provided in literature. | Modal analysis of rotating pre-twisted viscoelastic sandwich beams | 10.1007/s00466-019-01806-z |
2020-04-01 | In this work we investigate asymptotic stability and instability at infinity of solutions to a logarithmic wave equation $$\begin{aligned} u_{tt}-\Delta u + u + (g\,*\, \Delta u)(t)+ h(u_{t})u_{t}+|u|^{2}u=u\log |u|^{k}, \end{aligned}$$ u tt - Δ u + u + ( g ∗ Δ u ) ( t ) + h ( u t ) u t + | u | 2 u = u log | u | k , in an open bounded domain $$\Omega \subseteq \mathbb {R}^3$$ Ω ⊆ R 3 whith $$h(s)=k_{0}+k_{1}|s|^{m-1}.$$ h ( s ) = k 0 + k 1 | s | m - 1 . We prove a general stability of solutions which improves and extends some previous studies such as the one by Hu et al. (Appl Math Optim, https://doi.org/10.1007/s00245-017-9423-3 ) in the case $$g=0$$ g = 0 and in presence of linear frictional damping $$u_{t}$$ u t when the cubic term $$|u|^2u$$ | u | 2 u is replaced with u . In the case $$k_{1}=0,$$ k 1 = 0 , we also prove that the solutions will grow up as an exponential function. Our result shows that the memory kernel g dose not need to satisfy some restrictive conditions to cause the unboundedness of solutions. | General Stability and Exponential Growth for a Class of Semi-linear Wave Equations with Logarithmic Source and Memory Terms | 10.1007/s00245-018-9508-7 |
2020-04-01 | In this paper we study the stability problem of a tree of elastic strings with local Kelvin–Voigt damping on some of the edges. Under the compatibility condition of displacement and strain and continuity condition of damping coefficients at the vertices of the tree, exponential/polynomial stability are proved. Our results generalize the case of single elastic string with local Kelvin–Voigt damping in Liu and Rao (Z. Angew Math Phys 56:630–644, 2005 ), Liu and Liu (Z. Angew Math Phys 53:265–280, 2002 ). | Stability of the wave equations on a tree with local Kelvin–Voigt damping | 10.1007/s00233-019-10064-7 |
2020-04-01 | Abstract The features of identifying the damping properties of viscoelastic materials caused by their dependence on a large number of external factors are discussed. The main propositions of the international standard on the experimental method for determining the damping properties of viscoelastic materials under cyclic tension–compression are analyzed. A refined finite element model of the dynamic behavior of the Oberst beam with a damping layer of a viscoelastic material with accounting of the transverse shear and compression is constructed. A numerical analysis of the error in determining the damping properties of a viscoelastic material under tension–compression caused by the neglect of transverse shear and compression strains arising in the layer of the material being tested is carried out. | An Investigation into the ASTM E756-05 Test Standard Accuracy on Determining the Damping Properties of Materials in Tension-Compression | 10.3103/S106879982002004X |
2020-04-01 | Nub-and-sleeve of last-stage blade for steam turbine is a part-span damper. The nub is vulnerable to fretting cracking since it is in contact with the sleeve under centrifugal force, and a small-amplitude oscillatory movement occurs at the nub-sleeve contact interface due to the blade vibration during operation of turbine. The present study developed a rig test that mimics fretting behavior at the nub-sleeve contact interface and reproduces fretting cracking of the nub. The rig tests reveal that fretting cracking occurs if the contact interface is in partial slip state and the tangential contact force amplitude is sufficiently large. The minimum tangential contact force amplitude for cracking increases with the normal contact force. Moreover, under the partial slip condition, the tangential contact force amplitude increases with the imposed displacement amplitude and its maximum value increases with the normal contact force. | Fretting cracking behavior of nub of last-stage blade for steam turbine | 10.1007/s12206-020-0314-1 |
2020-04-01 | In this paper, cyclic behavior of a new type of beam-to-column connection comprising yielding damper with a circular pattern at depth of the beam was evaluated. The effects of different parameters on proposed connection behavior were also studied. Results of both finite element analysis and experimental tests showed that all the specimens of proposed connection have a stable cyclic behavior. Reliable design for damper at connection maintaining stiffness, strength, and energy dissipation in beam-to-column connections at an acceptable level concentrated inelastic deformations in damper, and also keeping structural members such as beams and columns in elastic range. | Numerical and Experimental Studies on Cyclic Behavior of Beam-to-Column Connection with Yielding Steel Damper | 10.1007/s13296-019-00298-0 |
2020-04-01 | The aseismic design of cable-stayed bridges in the transverse direction with newly proposed metallic dampers that can accommodate both longitudinal and transverse movement of the deck has recently been considered. This work focuses on developing a simplified method to design an appropriate metallic damper. The seismic performance of cable-stayed bridges with different damper stiffness, main span lengths, tower shapes and types of deck in the transverse direction are investigated. The transverse displacement of the deck of a cable-stayed bridge increases significantly with the increment of the damper stiffness, which proves that the design of the damper stiffness is crucial. A simplified model considering the damper stiffness, cable system and tower in the transverse direction is developed to evaluate the period and lateral displacement of a complicated cable-stayed bridge. Based on the simplified model, a design method is proposed and assessed using two cable-stayed bridges as examples. The results show that metallic dampers can be designed with high efficiency, and the optimal ductility of the damper can be selected. | A simplified design method for metallic dampers used in the transverse direction of cable-stayed bridges | 10.1007/s11803-020-0575-9 |
2020-04-01 | This study investigates the effect of nonlinear inertia on the dynamic response of an asymmetric building equipped with Tuned Mass Dampers (TMDs). In the field of structural engineering, many researchers have developed models to study the behavior of nonlinear TMDs, but the effect of nonlinear inertia has not received as much attention for asymmetric buildings. To consider nonlinear inertia, the equations of motion are derived in a local rotary coordinates system. The displacements and rotations of the modeled building and TMDs are defined by five-degree-of-freedom (5-DOFs). The equations of motion are derived by using the Lagrangian method. Also in the proposed nonlinear model, the equations of motion are different from a conventional linear model. In order to compare the response of the proposed nonlinear model and a conventional linear model, numerical examples are presented and the response of the modeled buildings are derived under harmonic and earthquake excitations. It is shown that if the nonlinear inertia is considered, the response of the modeled structures changes and the conventional linear approach cannot adequately model the dynamic behavior of the asymmetric buildings which are equipped with TMDs. | Effect of inertia nonlinearity on dynamic response of an asymmetric building equipped with tuned mass dampers | 10.1007/s11803-020-0577-7 |
2020-03-28 | The present study evaluates the dynamic response of connecting tubes for transient pressure measurement. A systematic study is conducted to quantify the amplitude and phase distortion of connecting tubes of diameter 1, 2 and 3 mm with different lengths (10–50 cm). The experimental measurements and theoretical predictions have been carried out with both air and water as the working medium to cover a wide range of frequencies. The study highlights the underdamped nature of all the systems studied. The natural frequency of the system increases with an increase in the tube diameter and a decrease in tube length. The difference in natural frequency obtained from the experimental results and theoretical prediction is less for the smaller tube diameter (d = 1 mm) and more pronounced for the larger tube diameter. Larger tube diameters are recommended to avoid amplitude and phase distortion errors, especially in the low-frequency range. However, resonance effects are more pronounced for larger tube diameters. The phase response of larger tube diameters remains close to zero over a large range of frequency (0–0.8 times the natural frequency); hence, this range is more suitable for applications where phase information is more important than amplitude. This study is useful for compensating the amplitude and phase distortion error encountered in transient pressure measurements. | Study on connecting tube dynamics for transient pressure measurement | 10.1007/s12046-020-1310-y |
2020-03-19 | A damped Duffing equation with a singularity is considered in this paper, where the elastic restoring force g has a singularity at origin and satisfies superlinear condition at infinity. By applying the twist theorem of nonarea-preserving map, we obtain the equation has at least one period- mT solution, where the minimal period is mT . It is also shown by bifurcation analysis that for a explicit form, the equation undergoes fold bifurcation, period doubling bifurcation and Hopf bifurcation, which leads to different solutions, including harmonic solutions, subharmonic solutions and quasiperiodic solutions. At last, we give the phase portraits and correspond Poincaré section of the solutions. | Damped superlinear Duffing equation with strong singularity of repulsive type | 10.1007/s11784-020-0774-z |
2020-03-13 | The goal of this paper is to study the system of rotating fluids between two infinite parallel plates with Dirichlet boundary conditions and with small viscosity which vanishes when the Rossby number goes to zero. We want to improve the convergence result of [ 18 ] and show the global in time convergence of the weak solution of the system of rotating fluids toward the solution of a two-dimensional damped Euler system with three components, using the decay in time of the $$H^s$$ H s -norm ( $$s>2$$ s > 2 ) of the limiting solution. | Damping effects in boundary layers for rotating fluids with small viscosity | 10.1007/s00033-020-1286-9 |
2020-03-09 | In this paper, we propose a linearly implicit Fourier pseudo-spectral scheme, which preserves the total mass and energy conservation laws for the damped nonlinear Schrödinger equation in three dimensions. With the aid of the semi-norm equivalence between the Fourier pseudo-spectral method and the finite difference method, an optimal L ^2-error estimate for the proposed method without any restriction on the grid ratio is established by analyzing the real and imaginary parts of the error function. Numerical results are addressed to confirm our theoretical analysis. | A linearly implicit structure-preserving Fourier pseudo-spectral scheme for the damped nonlinear Schrödinger equation in three dimensions | 10.1007/s10444-020-09781-3 |
2020-03-02 | An equivalent mechanical model with the equivalent physical meaning of mass-spring-damping is proposed for cylindrical lithium-ion batteries through experiments and theory. The equivalent mechanical model of a cylindrical lithium-ion battery consists of a spring-damping parallel unit. Therefore, a spring-damping parallel unit connecting a damping unit in series is selected to construct the constitutive characteristics of the battery under mechanical abuse. Comparison results show that the equivalent mechanical model can more effectively describe the mechanical properties of the batteries than most cubic fitting models, of which the average relative error of the equivalent mechanical model under different states-of-charge is less than 6.75%. Combined with the proposed equivalent mechanical model, the failure process of the batteries was simulated and analyzed using LS-Dyna and HyperWorks. Under rigid rod tests, failure occurred at the core and bottom of the batteries; under hemispherical punch tests, failure occurred at the core and top, consistent with the experimental results. The average prediction error for the failure displacement under different abuse conditions is less than 4% in the simulations. The equivalent mechanical model requires only a few parameters and can be recognized easily. In the future, the model can be used in safety warning devices based on mechanical penetration. | Mass-Spring-Damping Theory Based Equivalent Mechanical Model for Cylindrical Lithium-ion Batteries under Mechanical Abuse | 10.1186/s10033-020-00440-8 |
2020-03-01 | The isobaric Grüneisen parameter and the wavenumber (frequency) of various Raman modes in PbZr_1-xTi_xO_3 (PZT x = 0.48) ceramic were calculated by means of the unit cell volume of this crystal. In addition, the damping constant (linewidth) of the Raman modes studied was computed from the pseudospin-phonon coupled and from the energy fluctuation models close to the tetragonal-cubic transition temperature of T_C = 650 K. This calculation of the damping constant performed in terms of the order parameter (spontaneous polarization), which was associated with the wavenumbers of the Raman modes studied. Furthermore, the inverse relaxation time of the Raman modes in this ceramic calculated and the values of the activation energy were deduced in terms of the Arrhenius plot close to the tetragonal-cubic transition in PZT ( x = 0.48) ceramic. Finally, the temperature dependence of some thermodynamic quantities, such as the isothermal compressibility and the specific heat of this ceramic, was predicted. | A thermodynamic study on PbZr_0.52Ti_0.48O_3 ceramic close to the tetragonal-cubic transition | 10.1007/s41779-019-00386-8 |
2020-03-01 | Many physical processes in nature exhibit complex dynamics that result from a combination of multiscale, nonlinear, non-local, and memory effects. Recent experimental measurements conducted in a variety of physical domains have shown that, at the macroscale level, these effects typically result in significant deviations from the behavior predicted by classical models. Notably, the underlying dynamics was often shown to be of non-integer order and possibly better captured by fractional-order models. Fractional operators are intrinsically multiscale; thus, they provide a natural approach to account for non-local and memory effects. In this study, we present the possible application of variable-order (VO) and distributed-order (DO) fractional operators to a few classes of nonlinear lumped parameter models that have great practical relevance in mechanics and dynamics. More specifically, we present a methodology to define VO and DO fractional operators that are capable of capturing various physical transitions characteristic of contact dynamics, nonlinear reversible systems, hysteretic systems, and nonlinear damped oscillator systems. Despite using simplified lumped parameters models to illustrate the application of VO and DO operators to mechanics, we show numerical evidence of their unique modeling capabilities as well as their connection to more complex systems at the continuum scale. Further, for a selected problem involving distributed nonlinear damping, we provide approximate analytical solutions that are helpful to better understand the underlying dynamics and to quantify the accuracy of our numerical models. | Application of variable- and distributed-order fractional operators to the dynamic analysis of nonlinear oscillators | 10.1007/s11071-020-05488-8 |
2020-03-01 | In this study, inelastic floor spectra are developed for designing acceleration-sensitive nonstructural components (NSCs). The parameters response modification (reduction) factor, $$ R_{\text{cc}} $$ R cc , and inelastic displacement ratio, $$ C_{\text{cc}} $$ C cc , are evaluated to quantify the effects of NSCs inelasticity on their seismic-induced force and displacement demands, respectively. The results of the conducted response history analyses illustrate that the inelastic behavior of NSCs can significantly de-emphasize the effects of their tuning period ratio and viscous damping ratio, and of the characteristics of the primary structure and ground excitation. Due to the quasi-harmonic characteristic of building floor motions, NSC inelasticity is more effective for NSCs attached to buildings than for those attached to the ground. NSC inelasticity is most effective for a low - damping roof - mounted NSC tuned to the first modal period of an elastic building (i.e., the most critical NSC from the design point of view). Adopting even a mild level of inelasticity for tuned NSCs not only decreases their seismic force demands significantly but also reduces their displacement demands. For non-tuning conditions, particularly for rigid NSCs, achieving even a relatively small $$ R_{\text{cc}} $$ R cc (i.e., a small reduction in force demand) leads to a significant increase in NSC displacement and ductility demands suggesting that these NSCs should be designed to remain elastic. Results illustrate that the amplitude of $$ R_{\text{cc}} $$ R cc and $$ C_{\text{cc}} $$ C cc depends on the tuning ratio, viscous damping, and level of inelasticity of NSCs, and to a lesser extent, on the characteristics of the primary structure and ground motion. Simplified yet reliable equations are proposed for the estimation of the parameter $$ R_{\text{cc}} $$ R cc for non-rigid NSCs with different levels of inelasticity and viscous damping. | Inelastic floor spectra for designing anchored acceleration-sensitive nonstructural components | 10.1007/s10518-019-00760-8 |
2020-03-01 | A liquid storage container installed on the top of a fixed offshore platform is used as a tuned liquid damper (TLD) to suppress structural vibration through sloshing motion and viscous energy dissipation. To further optimize TLD capability on suppressing vibration and accurately predict nonlinear coupled processes between TLD and offshore platform, a two-way coupling numerical model was developed to investigate the nonlinear vibration of TLD and elastic supporting structural platform (SSP). Meanwhile, laboratory experiments of TLD interaction with the SSP were also conducted on a six-degree-of-freedom motion simulator to validate the developed model. The bottom plate of the SSP was fixed to the motion simulator and subjected to sinusoidal excitation in the horizontal direction. The natural frequency of bare SSP was obtained firstly by shaking table tests at a wide range of external excitation frequencies and finite element modal analysis. The developed numerical model was validated by using the present experimental data in terms of both the roof plate displacements of the SSP and the free surface elevation and waveforms in TLD. Effects of TLD in suppressing the nonlinear vibration of the elastic SSP were further investigated numerically by varying the mass and frequency ratio of TLD to the SSP. Wavelet transform was used to analyze the nonlinear interaction and energy distribution characteristics of the sloshing wave in TLD. It was shown that the peak displacement response of the roof plate had been significantly reduced, and at the same time a frequency shift occurred after TLD installed on the SSP. In addition, the sudden excitation breaks the balance of energy absorption and production in fluids, resulting in larger wave height. Finally, a mass ratio of 2% and a frequency ratio of 1 were found to be optimal by considering the frequency shift and energy dissipation. | Numerical and experimental study of tuned liquid damper effects on suppressing nonlinear vibration of elastic supporting structural platform | 10.1007/s11071-019-05447-y |
2020-03-01 | Abstract The stalk of Vorticella convallaria , a sessile ciliated protozoan, contracts in a few milliseconds at a maximum speed of ~ 10 mm/s and generates a contractile force of ~ 10 nN. After powerful contraction, the stalk slowly returns to its extended state, and this relaxation process completes and resets the contraction cycle. The stalk relaxation needs to be better characterized because it is indispensable to the contraction-relaxation cycle of V. convallaria . In contrast to the spasmoneme-based contraction force, the driving force for the stalk relaxation is thought to be the elastic restoring force of the coiled stalk. In this study, relaxing V. convallaria was modeled as the damped spring system to estimate the effective spring constant of the relaxing stalk in different viscous media. In the order of 0.1 pN/μm, the effective spring constant was found to increase with the medium viscosity, which suggests that the stalk relaxation is affected by the final status of the contraction phase. Graphical Abstract | Fluid dynamic estimation of the effective spring constant of the relaxing stalk of Vorticella convallaria | 10.1007/s42791-019-00028-x |
2020-03-01 | This study investigates the effect of damping on the seismic demands imposed on lightweight nonstructural components. The investigation was performed utilizing a total of 113 floor acceleration recordings obtained from instrumented buildings located in California. Results are presented as damping modification factors, which provide information on the seismic demands imposed on secondary systems with various levels of damping relative to 5% damped components. Evaluations of the results indicate a strong period dependence, with the effect of damping being much larger for components that are tuned or nearly tuned and much smaller for components with periods far from the modal periods of the supporting building. Therefore, a better characterization of the effect of damping is achieved if the damping modification factors are a function of the ratio of the period of the component to the modal periods of the supporting structure. As expected, record-to-record variability increases as the level of damping in the secondary component deviates from 5% damping, with an overall probability distribution that is approximately lognormal. Thus, a full probabilistic characterization of the influence of damping on component response is offered via a parametric, period- and damping-dependent model of the mean and lognormal standard deviation of the damping modification factor. | The effect of damping on floor spectral accelerations as inferred from instrumented buildings | 10.1007/s10518-019-00781-3 |
2020-03-01 | This study evaluated the use of scrap tire pads (STPs) made of used tires in a vibration control system for earthquake protection of building structures. Concepts and advantages of the seismic mass damper system using STPs, experimental investigation of a STP unit specimen, and numerical assessment of the control effects by the proposed system are presented. Dynamic loading tests under constant vertical pressures as well as vertical loading tests on the STP specimen were conducted to obtain the basic mechanical characteristics of the STP. The test results demonstrated that the STP specimen exhibited stable hysteresis loops against lateral cyclic loadings and showed a moderate damping capacity without any additional energy dissipation devices. Also, dependencies of the lateral equivalent stiffness and viscous damping factor on displacement magnitude, vertical pressure, loading frequency, and cycle number were obtained from the test results. Moreover, an earthquake response analysis was carried out to evaluate the response reduction effects if the proposed mass damper system was installed in a building. The results showed the effectiveness of the proposed system under various seismic input motions. | Use of scrap tire pads in vibration control system for seismic response reduction of buildings | 10.1007/s10518-020-00787-2 |
2020-03-01 | In this paper, we study and compare performance and robustness of linear and nonlinear Lanchester dampers. The linear Lanchester damper consists of a small mass attached to a primary system through a linear dashpot, whereas the nonlinear Lanchester damper is linked to the primary mass through dry friction forces. In each case, we propose a semi-analytical method for computing the frequency response, for different values of the design parameters, in order to evaluate the performance and robustness of the two kinds of damper. Overall, it is shown that linear Lanchester dampers perform better than nonlinear damper both in terms of attenuation and robustness. Moreover, the nonlinear frequency response curves, that include the intrinsic non-smooth nature of the friction force, may serve as reference curve for further numerical studies. | A comparison of robustness and performance of linear and nonlinear Lanchester dampers | 10.1007/s11071-020-05512-x |
2020-03-01 | This paper proposes an enhanced speed control algorithm that synchronizes the rotation speeds of the engine and the drive motor at the engine start to improve the engagement performance of the engine clutch in a parallel hybrid vehicle. The zero overshoot with active damping speed controller proposed in this paper has an active damping control structure that is robust against load variations and a control structure that does not include a zero in the control response. This feature has the advantage of reducing the engine clutch engagement time as much as possible to improve the acceleration response of parallel hybrid vehicles and to minimize the energy wasted to maintain heavy engine rotation. The proposed algorithm has been validated through simulation using Matlab and through a vehicle test. | Zero overshoot speed controller with active damping for improving engine clutch engagement performance | 10.1007/s43236-020-00052-4 |
2020-03-01 | This paper considers a method of determining a chatter-free milling mode using time-domain milling dynamics simulation. The simulation is using a depth-buffer algorithm, an adaptive finite element model of the in-process workpiece, and a phenomenological model of cutting forces. The frequency characteristics of the in-process workpiece are obtained from the experimental modal analysis. The simulation analyzes the in-process workpiece vibration and actual cutting forces for the specified machining trajectory, as well as part surface quality after machining. The chatter-free milling mode is determined using a milling map produced by a multiple simulation for different spindle speed values. The milling map specifies regions where chatter may occur during milling and indicates the variation of the optimal spindle speed along the machining trajectory. The proposed method is used to determine a chatter-free milling mode for the finish milling of a jet-engine compressor blade. The blade is machined under the chatter-free milling mode, and it has good surface finish quality without chatter marks, whereas a blade machined under constant spindle speed contains chatter marks. The method can be used to engineer milling processes for other thin-walled workpieces with complex geometry and low stiffness. | Optimal milling modes identification of a jet-engine blade using time-domain technique | 10.1007/s00170-020-05129-9 |
2020-03-01 | Large-scale simulations and forensic analyses of the seismic behaviour of real case studies are often based on simplified analytical approaches to estimate the reduction in fundamental frequency and the amount of radiation damping induced by dynamic soil-foundation-structure (SFS) interaction. The accuracy of existing closed-form solutions may be limited because they were derived through single degree-of-freedom structural models with shallow rigid foundations placed on a homogeneous, linear elastic half-space. This paper investigates the effectiveness of those formulations in capturing the dynamic out-of-plane response of single load-bearing walls within unreinforced masonry buildings having either a shallow foundation or an underground storey embedded in layered soil. To that aim, analytical predictions based on the replacement oscillator approach are compared to results of two-dimensional dynamic analyses of coupled SFS elastic models under varying geotechnical and structural properties such as the soil stratigraphy, foundation depth and number of building storeys. Regression models and a relative soil-structure stiffness parameter are proposed to quickly predict the frequency reduction induced by SFS interaction, accounting for the presence of an embedded foundation, an underground storey and a layered soil. The effects of SFS interaction are also evaluated in terms of equivalent damping ratio, showing the limitations of simplified approaches. Since the geometric layouts considered in this study are rather recurrent in the Italian and European built heritage, the proposed procedure can be extended to similar structural configurations. | Effects of soil-foundation-structure interaction on fundamental frequency and radiation damping ratio of historical masonry building sub-structures | 10.1007/s10518-019-00748-4 |
2020-03-01 | This study aims to investigate the nonlinear added mass moment of inertia and damping moment characteristics of large-amplitude ship roll motion based on transient motion data through the nonparametric system identification method. An inverse problem was formulated to solve the first-kind Volterra-type integral equation using sets of motion signal data. However, this numerical approach leads to solution instability due to noisy data. Regularization is a technique that can overcome the lack of stability; hence, Landweber’s regularization method was employed in this study. The L-curve criterion was used to select regularization parameters (number of iterations) that correspond to the accuracy of the inverse solution. The solution of this method is a discrete moment, which is the summation of nonlinear restoring, nonlinear damping, and nonlinear mass moment of inertia. A zero-crossing detection technique is used in the nonparametric system identification method on a pair of measured data of the angular velocity and angular acceleration of a ship, and the detections are matched with the inverse solution at the same discrete times. The procedure was demonstrated through a numerical model of a full nonlinear free-roll motion system in still water to examine and prove its accuracy. Results show that the method effectively and efficiently identified the functional form of the nonlinear added moment of inertia and damping moment. | Nonparametric Identification of Nonlinear Added Mass Moment of Inertia and Damping Moment Characteristics of Large-Amplitude Ship Roll Motion | 10.1007/s11804-020-00129-3 |
2020-03-01 | Impact dampers are usually used to suppress single mode resonance. The goal of this paper is to clarify the difference when the impact damper suppresses the resonances of different modes. A cantilever beam equipped with the impact damper is modeled. The elastic contact of the ball and the cantilever beam is described by using the Hertz contact model. The viscous damper between the ball and the cantilever beam is modeled to consume the vibrational energy of the cantilever beam. A piecewise ordinary differential-partial differential equation of the cantilever beam is established, including equations with and without the impact damper. The vibration responses of the cantilever beam with and without the impact damper are numerically calculated. The effects of the impact absorber parameters on the vibration reduction are examined. The results show that multiple resonance peaks of the cantilever beam can be effectively suppressed by the impact damper. Specifically, all resonance amplitudes can be reduced by a larger weight ball. Moreover, the impacting gap is very effective in suppressing the vibration of the cantilever beam. More importantly, there is an optimal impacting gap for each resonance mode of the cantilever beam, but the optimal gap for each mode is different. | Suppression of multiple modal resonances of a cantilever beam by an impact damper | 10.1007/s10483-020-2588-9 |
2020-03-01 | The paper presents a new concept of absorbing car body vibrations, which consists in a modification of the construction of the classical mono-tube hydraulic shock absorber by the introduction of an additional inner cylinder with an auxiliary piston. By making an appropriate selection of the system parameters, one may obtain the damping force characteristics dependent on the excitation amplitude and frequency. In the case of driving on a good-quality road surface, the shock absorber displays the soft characteristics which are desired as far as the driving comfort is concerned. In the case of worse-quality roads or while overcoming large obstacles, the hard characteristics ensure a higher level of safety and protect the shock absorber from getting damaged. The developed nonlinear model makes it possible to effectively analyse the system responses to harmonic, impulse and random excitations. On the basis of the analysis of the impact of harmonic excitations on the driving comfort and safety indexes, one may estimate the optimal values of the shock absorber construction parameters. Impulse and random excitations are applied in order to finally verify the effectiveness of the operation of the proposed shock absorber. | Nonlinear dynamics of a vehicle with a displacement-sensitive mono-tube shock absorber | 10.1007/s11071-020-05532-7 |
2020-03-01 | Resonant ultrasound spectroscopy was used to analyze magnetoelastic damping in Ni–Mn–Ga single crystals in austenite and premartensite phases. Crystals with different treatment were studied, exhibiting different density of antiphase boundaries (APBs), as confirmed by magnetic force microscopy, and different magnetic behavior. For a quenched single crystal with high density of APBs, extremely strong damping was observed in a broad temperature range in the austenite phase. It was shown that this damping is history-dependent, i.e., non-ergodic, appearing only during heating runs preceded by a premartensite → austenite transition. We suggest that this non-ergodicity results from the pinning of the fine magnetic domain structure on APBs and other defects. | Large Non-ergodic Magnetoelastic Damping in Ni–Mn–Ga Austenite
| 10.1007/s40830-020-00272-4 |
2020-03-01 | This paper analyzed the hydroelastic behaviors of hydrofoils and marine propellers immersed in incompressible, inviscid and irrotational fluids. Strongly coupled fluid–structure interaction analyses were performed using a three-dimensional (3-D) potential-based panel method in conjunction with a 3-D finite element method. The present method is developed for hydroelastic analyses of geometrically complex-shaped propeller blades, and the application of the method to the hydroelastic problems of hydrofoils is straightforward. The parameters dominating the added-mass and -damping matrices of the hydrofoils and propellers are examined. The effects of the translational motion of the hydrofoil and the rotational motion of the propeller on the added-mass and -damping matrices are compared based on different non-penetration boundary conditions and distributions of the inflow velocity. It is found that for hydroelastic analyses of propellers, the reduced frequency, i.e., the ratio of excitation frequency to rotational frequency, is a key parameter for determining the added-mass and -damping matrices of the propellers. The effect of the advance ratio on the added-mass and -damping matrices of the propeller blade depends upon the ratio of excitation frequency to rotational frequency. For hydrofoils, the added-damping matrix is significantly affected by the ratio of the excitation frequency multiplied by chord length and divided by axial inflow velocity. | Parametric analysis on hydroelastic behaviors of hydrofoils and propellers using a strongly coupled finite element/panel method | 10.1007/s00773-019-00638-z |
2020-03-01 | A prominent weakening in equatorial Atlantic sea surface temperature (SST) variability, occurring around the year 2000, is investigated by means of observations, reanalysis products and the linear recharge oscillator (ReOsc) model. Compared to the time period 1982–1999, during 2000–2017 the May–June–July SST variability in the eastern equatorial Atlantic has decreased by more than 30%. Coupled air–sea feedbacks, namely the positive Bjerknes feedback and the negative net heat flux damping are important drivers for the equatorial Atlantic interannual SST variability. We find that the Bjerknes feedback weakened after 2000 while the net heat flux damping increased. The weakening of the Bjerknes feedback does not appear to be fully explainable by changes in the mean state of the tropical Atlantic. The increased net heat flux damping is related to an enhanced response of the latent heat flux to the SST anomalies (SSTa). Strengthened trade winds as well as warmer SSTs are suggested to increase the air–sea specific humidity difference and hence, enhancing the latent heat flux response to SSTa. A combined effect of those two processes is proposed to be responsible for the weakened SST variability in the eastern equatorial Atlantic. The ReOsc model supports the link between reduced SST variability, weaker Bjerknes feedback and stronger net heat flux damping. | Weakened SST variability in the tropical Atlantic Ocean since 2000 | 10.1007/s00382-020-05138-0 |
2020-03-01 | Abstract To solve various engineering problems, it is often necessary to record signals in the 0.1–2000 Hz range. The lower limit of this range is beyond the operating band of geophones. This article considers extending of geophone frequency responses in two ways: multiplication of the transfer functions and introduction of negative resistance. The applicability limits of these methods are estimated. The upper limit of the velocity recorded by the geophone is determined by the gap in which the coil is shifted relative to the sensor frame. The lower limit depends on the total instrument noise of the measurement channel, the main contribution to which is the Brownian noise of the mechanical oscillatory system and the noise of the measuring circuit. A prototype was constructed using multiplication of the transfer functions. Laboratory measurements on a shaking table and microseismic noise recordings demonstrated that the modified geophone operates as a velocity sensor with an eigenfrequency of 2 Hz. This value depends on the microseismic conditions of where of the measurement system is placed. Recording seismicity with the modified geophone made it possible to record massive blasts in mines and quarries in the frequency range up to 2 Hz. Thus, the research demonstrates that the modified geophone can be used to monitor local and regional seismicity as a counterpart to short-period seismometers. | Instrumental Methods for Extending the Amplitude-Frequency Responses of a Geophone | 10.3103/S0747923920020048 |
2020-03-01 | The co-placement of mine tailings and fly ash (CMF) can reduce acid mine drainage (AMD) production and decrease metal mobilization. This aids in waste management construction. However, few people have studied a large number of tailing sand–fly ash mixtures under the condition of neutral saturated solution in tailing ponds, wherein the pozzolanic reaction is highly gradual. In this study, a series of tests were conducted to determine the monotonic and cyclic shear characteristics of a mixture of fly ash and tailings. In particular, the effects of the fly ash content on the monotonic shear peak, shear strength parameters, dynamic modulus, and damping ratio of the mixture were analyzed. The results reveal that in a monotonic shear test, the peak shear strength of the saturated CMF mixture decreases as the fly ash content increases. The shear strength parameters (cohesion c and internal friction angle φ ) were observed to increase and decrease linearly, respectively, as the fly ash content increased. Furthermore, the maximum dynamic shear modulus was observed to decrease by 41.4% as the fly ash content increased from 0 to 50%, during the cyclic cutting process. Moreover, the experimental results fit well with the fitting formula for the variation in shear modulus in the cyclic shear process of the saturated CMF mixture with varying fly ash content. Meanwhile, the initial damping ratio of the cyclic shear was observed to increase from 10.3 to 13.6% as the fly ash content increased. Therefore, when the CMF method is used to treat AMD waste, it is necessary to consider the extent to which the design stability of the tailing pond may be reduced. These experimental results can be used as a reference for similar CMF projects. | Shearing resistance of tailing sand waste pollutants mixed with different contents of fly ash | 10.1007/s11356-019-07419-6 |
2020-03-01 | A method of determining the amplitude-frequency characteristics and phase-frequency characteristics of a power system by the exposure of the output adder of an automatic excitation regulator to a white noise signal containing a spectrum of the frequency range of the electromechanical oscillations for different tuning parameters of the regulator is presented. The safety of the method and the possibility of using it for verification of physical and digital models of power systems are demonstrated. | Determination of Frequency Characteristics of a Power System in the Course of Commissioning Operations Performed on the Excitation System of the TG5 Turbogenerator of the Beloyarskaya Nuclear Power Plant | 10.1007/s10749-020-01153-7 |
2020-03-01 | In this paper, we consider the random dichotomous fluctuations on both mass and damping in a fractional oscillator, which is subjected to an additive fractional Gaussian noise and driven by a periodic force. In order to investigate the generalized stochastic resonance (GSR) phenomena, we acquire the exact expression of the first-order moment of system’s steady response by applying generalized fractional Shapiro–Loginov formula and Laplace transform. Meanwhile, we discuss the evolutions of the output amplitude amplification (OAA) with driving frequency, noise parameters, fractional order, and damping strength. It is observed that the non-monotonic resonance behaviors of one-peak GSR, double-peak GSR and triple-peak GSR existing in this fractional system. Moreover, the interplay of mass fluctuation, damping fluctuation, and memory effect can generate a rich variety of non-equilibrium cooperation phenomena, especially the stochastic multi-resonance (SMR) behaviors. It is worth emphasizing that the triple-peak GSR was not observed in previously proposed fractional oscillator subjected to dichotomous noise. Finally, the numerical simulations are also carried out based on predictor-corrector approach to verify the effectiveness of analytic result. | Generalized Stochastic Resonance for a Fractional Noisy Oscillator with Random Mass and Random Damping | 10.1007/s10955-020-02494-3 |
2020-03-01 | The damping of cutting system is an important factor influencing stability in boring and milling process. However, systematical and thorough studies of the influencing mechanism of damping, especially on the chatter stability of rotating cutter bar, are still absent. The damping of a cutting system mainly consists of external damping and internal damping. This study focuses on these damping effects on chatter stability of the cutting system with a rotating tapered cutter bar. The partial differential equation of motion of the cutter bar is derived based on the Hamilton principle combined with the Euler-Bernoulli beam theory. It is assumed that the cutter bar is tapered, and its free ends acts on a two-dimensional regenerative cutting force with time-delay effect. The damping mechanisms of external and internal are described by the viscous damping model and the strain-rate-dependent Kelvin-Voigt model, respectively. The partial differential equation of motion is discretized as an ordinary differential equation using the Galerkin method. The Campbell diagram and the decay rate plots including critical rotating speed and instability threshold of the cutter bar are obtained by free vibration analysis. Also, the chatter stability lobes in the cutting process are plotted and the predicted results of stability in frequency domain are compared with those in time domain. The results indicate that the structural parameters of a cutter bar, including the rotation, the ratio of internal and total damping, damping ratio, and taper and aspect ratios have significant effects on cutter bar dynamics and chatter stability of cutting process. In particular, a new chatter instability is observed for the cutting system in higher rotating speed ranges due to the effects of rotation and internal damping. The onset rotating speed of the new chatter instability equals to the instability threshold of rotor system of cutter bar. Finally, the present model is validated by comparing both stability prediction given by previous study and natural frequencies and decay rates by ANSYS FE code. | Investigation of chatter stability of cutting process with a rotating tapered cutter bar considering internal and external damping | 10.1007/s00170-020-05049-8 |
2020-03-01 | MEMS capacitive accelerometers are ubiquitously used in wide-ranging applications. Different applications require a trade-off between design parameters to realize either high sensitivity or precision or wide-dynamic range or speed of response. Planar MEMS structures for sensors usually have a large area compared to thickness or gap. In such structures, squeeze film damping properties of the gas (or air) in the narrow gap significantly affect the dynamic performance of the device. Schemes to reduce the damping effect normally include perforations in the structure to reduce path-lengths of air movement in the narrow gap. But perforations in the structure decrease the mass of the structure leading to a reduction in sensitivity. Therefore, the structural design requires selection of perforation parameters that can provide an optimal trade-off between sensitivity and damping coefficient. This paper discusses our studies through numerical computation when using different configurations of perforations on a typical SOI-based capacitive square accelerometer structure with 1 µm air gap. Both static analysis and analysis at first resonant frequency were carried-out on a range of structures to characterize sensitivity and damping coefficients. The ratio of perforation size versus perforation pitch, η, is used as a basis for sensitivity normalization and studies were carried out to compute damping coefficients for structures with different values of η and count of perforations. Studies reveal a reduction in damping coefficient by 90% to 97% for the η range 0.3 < η < 0.55. The corresponding reduction in effective change in capacitance of the device is limited to the range of 10–25%. | Analysis of damping optimization through perforations in proof-mass of SOI capacitive accelerometer | 10.1007/s10470-019-01560-5 |
2020-03-01 | This paper presents the design concept of a hinged-type wave energy converter, Sea Wave Energy Extraction Device (SeaWEED), and associated numerical and experimental studies of its performance in regular waves. The device is considered as an improved attenuator. A SeaWEED unit consists of four modules that are connected by rigid truss structures. The four-module array includes a non-energy producing nose module in the front, followed by two energy producing modules, and another non-energy producing module at the rear. A potential-flow-based time-domain program with the Lagrange multiplier approach was developed to simulate the dynamics of multiple constrained bodies. Model tests of a 1:35 scale model with and without the power take-off (PTO) units were carried out to validate the numerical method. Friction dampers were designed and manufactured to mimic the PTO units. The validated time-domain method was applied to predict the absorbed power by the device in regular waves. | Experimental studies and time-domain simulation of a hinged-type wave energy converter in regular waves | 10.1007/s40868-020-00073-5 |
2020-03-01 | The effectiveness of a tuned mass damper (TMD) in dynamic vibration mitigation of a 20-storey steel benchmark structure (SBB) under real earthquake ground motions is presented. To study the positioning and tuning effect, a TMD is positioned at the largest or relatively larger of the normalized amplitude of mode shape of the selected structure. At each location, a TMD is tuned with different modal frequencies, while mitigating first five modal responses. The response of the SBB equipped with a TMD is obtained by numerically solving the differential equations of motion under different earthquakes, and subsequently compared with the corresponding uncontrolled building (NC), in order to investigate the efficiency of a TMD in seismic response control of buildings. Parameters considered for this study to be varied are (1) placement, (2) tuning frequency, and (3) mass ratio. The changes in the performance criteria (response) under various seismic excitations are calculated to evaluate the effectiveness of a TMD tuned to various modal frequencies, which are placed at different locations. It is noticed that the TMD tuned to the fundamental modal frequency and placed at the topmost floor leads to the best performance under earthquakes. It is also observed that controlling the higher modal response by a TMD will be efficient to substantially mitigate the seismic response of the SBB. | Seismic response control of steel benchmark building with a tuned mass damper | 10.1007/s42107-019-00206-1 |
2020-03-01 | Considering the effect of soil–structure interaction in dynamic analysis of structures can change their responses. It is generally assumed that the structure is located on a rigid foundation and the flexibility effect of the soil is not considered. Researches on the soil–structure interaction show that the dynamic response of the structures located on a soft and flexible soil is completely different from the dynamic response of the same structure located on a stiff soil. In this paper, the effect of the soil–structure interaction on the response of a single-degree-of-freedom system (Nagasaki airport tower) that is controlled by a modified tuned liquid damper is investigated. The soil effect is modeled using an approximate cone method based on the semi-infinite boundary conditions. First, the governing equations for describing the fluid sloshing obtained with shallow water wave theory are solved by Lax’s finite-difference scheme. Then, the dynamic equilibrium equations for a structure controlled with a modified tuned liquid damper are obtained by considering the effect of soil–structure interaction using Lagrange’s method. These equations are solved numerically by Newmark’s method. The controlled structural responses are calculated in different time steps and compared with the responses of the uncontrolled structure. Results show that the seismic design of the modified tuned liquid damper system can be more effective to reduce the structural responses. Also, this system can reduce efficiently the maximum responses of the structures considering soil–structure interaction effect during a near-fault earthquake. | Modified Tuned Liquid Dampers for Seismic Protection of Buildings Considering Soil–Structure Interaction Effects | 10.1007/s40996-019-00302-x |
2020-02-14 | In order to improve the damping characteristics of a photosensitive resin structure filled with viscous fluid, two improved structures with grooves and holes are investigated. Numerical simulation models of photosensitive resin damping structures are established using the finite element method. The force–displacement curves at low frequency are obtained by calculations. Then the structure with the best damping characteristics is chosen to be analyzed. The pressure and stress contours of the solid area and the fluid area are obtained. At the same time, the force–displacement curves of the improved structural part at different frequencies were obtained. It can be seen by calculation that the damping output was improved significantly. Then the influence of the structural parameters and the number and radius of the damping holes, on the damping output, was analyzed. The research has good reference values for the design and optimization of high stiffness and high damping elements and the application of fluid damping parts in reducing vibration and designing vibration isolation device. | Improvement of high damping structures using a photosensitive resin filled with viscous fluid | 10.1007/s40430-020-2205-x |
2020-02-05 | This paper presents design of an self contained actuators unit in wide area damping control of power system in stabilizing system response for both nominal system condition and during actuator faults. First it is presented that use of multiple actuators in wide area control aid in improving damping in power system. A wide area damping controller feeding multiple actuators to satisfy multiple objectives in wide area damping control of power system is designed. Minimization of infinity norm of closed loop transfer function of power system with wide area controller in feedback path & closed loop poles placement techniques are used in controller synthesis. Second a reconfigurable control on the lines of fault hiding principle is added to the controller design to maintain system damping to pre-fault level in case of actuator faults. A reconfiguration component(RC) is activated on occurrence of actuator fault thereby reconfiguring system dynamics and redistributing wide area control signal among remaining active actuators. RC together with remaining active actuators and under same wide area damping controller maintains system damping to pre-fault level thereby preserving system dynamic response. In the reconfigurable control design presented here no new actuators outside the unit of actuators designed for wide area damping control is required. This makes for an self contained actuators unit in wide area damping control of power system both for nominal system condition and for system affected by actuator faults. A two area power system model is considered here for demonstrating effectiveness of designed robust damping controller with multiple outputs feeding multiple actuators in wide area control and illustrating the idea of self contained actuators unit for maintaining system damping in case of actuator faults. | Reconfigurable control as actuator fault-tolerant control design for power oscillation damping | 10.1186/s41601-020-0151-3 |
2020-02-01 | We study the dynamics of many charges interacting with the Maxwell field. The particles are modeled by means of nonnegative distribution functions $$f^+$$ f + and $$f^-$$ f - representing two species of charged matter with positive and negative charge, respectively. If their initial velocities are small compared to the speed of light, $$\mathrm{c}$$ c , then in lowest order, the Newtonian or classical limit, their motion is governed by the Vlasov–Poisson system. We investigate higher-order corrections with an explicit control on the error terms. The Darwin order correction, order $$|\bar{\mathrm{v}}/\mathrm{c}|^2$$ | v ¯ / c | 2 , has been proved previously. In this contribution, we obtain the dissipative corrections due to radiation damping, which are of order $$|\bar{\mathrm{v}}/\mathrm{c}|^3$$ | v ¯ / c | 3 relative to the Newtonian limit. If all particles have the same charge-to-mass ratio, the dissipation would vanish at that order. | A Post-Newtonian Expansion Including Radiation Damping for a Collisionless Plasma | 10.1007/s00332-019-09580-1 |
2020-02-01 | Design and analysis of geosynthetic-reinforced soil structures subjected to repeated loading (e.g. compaction, traffic and earthquake loads) require a proper understanding of the cyclic soil–geosynthetic interface behaviour. This research is undertaken to study the interface properties between sand-expanded polystyrene (EPS) mixtures and geogrid reinforcement under cyclic loading. A series of cyclic tests is performed and the influences of normal stresses, cyclic shear amplitudes and number of cycles are studied. The experiments are conducted using a large-scale direct shear test device allowing to perform displacement-controlled cyclic tests. Accordingly, the influence of the aforementioned parameters on interface shear stiffness and damping ratio is discussed. The results of the experiments showed that adding 0.9% EPS beads to the sand bed leads to the decrease in interface shear stiffness by 30% to 63%, depending on the shear displacement amplitude. In contrast, for the same EPS content ratio, the interface damping increases roughly twice, irrespective of the applied shear displacement amplitude. The value of hardening factor was also found to increase with cycle number under different normal stress levels. | An Experimental Study for the Cyclic Interface Properties of the EPS–sand Mixtures Reinforced with Geogrid | 10.1007/s40999-019-00424-3 |
2020-02-01 | 与传统电厂不同,风能在电力系统中具有不同的结构和功能。这些不同影响电网的能量交换。 因此,电力系统的稳定性将受到风电厂性能的影响,特别是在发生故障时。本文通过基于电压源变换 器传输系统的高压直流电压控制器的辅助设计,以提高风电厂系统的动态稳定性。考虑了VSC 高压 直流系统和风电厂对提高系统稳定性的影响。此外,还提出了一种基于可控性(可观测性)概念的算法, 以选择系统在不同工况下的输入输出信号之间最合适和最有效的耦合。选择耦合应用于阻尼控制器信 号。最后,设计了一种基于交易市场算法的分数阶PID 控制器(FO-PID)作为阻尼控制器。分析结果表 明,风电厂对提高电力系统动态稳定性没有直接贡献。然而,它可以增加振荡模式的可控性,提高辅 助控制器的性能。 Wind energy sources have different structures and functions from conventional power plants in the power system. These resources can affect the exchange of active and reactive power of the network. Therefore, power system stability will be affected by the performance of wind power plants, especially in the event of a fault. In this paper, the improvement of the dynamic stability in power system equipped by wind farm is examined through the supplementary controller design in the high voltage direct current (HVDC) based on voltage source converter(VSC) transmission system. In this regard, impacts of the VSC HVDC system and wind farm on the improvement of system stability are considered. Also, an algorithm based on controllability (observability) concept is proposed to select most appropriate and effective coupling between inputs-outputs (IO) signals of system in different work conditions. The selected coupling is used to apply damping controller signal. Finally, a fractional order PID controller (FO-PID) based on exchange market algorithm (EMA) is designed as damping controller. The analysis of the results shows that the wind farm does not directly contribute to the improvement of the dynamic stability of power system. However, it can increase the controllability of the oscillatory mode and improve the performance of the supplementary controller. | Damping controller design based on FO-PID-EMA in VSC HVDC system to improve stability of hybrid power system | 10.1007/s11771-020-4305-2 |
2020-02-01 | Key message During pruning, shortening branches to decrease crown size significantly affected the vibration properties and mass of trees, but the progressive removal of lower branches only altered mass—not vibration properties. Abstract During pruning, arborists often intend to increase a tree’s resistance to wind loading by selectively removing branches, but there are few studies examining the efficacy of these interventions, especially for large, open-grown trees. This study examined the vibration properties (frequency and damping ratio) and mass of Senegal mahogany ( Khaya senegalensis ) and rain tree ( Samanea saman ) before and after a series of pruning treatments: crowns were either raised or reduced at incremental severities between 0 and 80%. For both species, mass decreased faster on reduced than raised trees. The frequency and damping ratio of trees varied with the severity of pruning for reduced, but not raised, trees. The frequency of reduced trees generally increased with pruning severity. In contrast, damping ratio of reduced trees generally decreased with the severity of pruning, except for the unique increase in damping ratio on Senegal mahoganies reduced by 10–20%. Although the vibration properties and mass will change as trees grow after pruning, the results suggest that arborists can reduce trees to change their vibration properties and concomitant response to wind loads, but arborists should reduce trees by a small amount to avoid the adverse decrease in damping ratio. | Effect of pruning type and severity on vibration properties and mass of Senegal mahogany (Khaya senegalensis) and rain tree (Samanea saman) | 10.1007/s00468-019-01912-8 |
2020-02-01 | Abstract The effect of preliminary preparation of a stoichiometric hydrogen–air mixture (decomposition of a part of molecular hydrogen and molecular oxygen into atomic gases) on the characteristics of a propagating detonation wave is numerically studied using a detailed kinetic mechanism of chemical interaction. It is revealed that this preliminary dissociation leads to a significant reduction in the transverse size of the detonation cell with a slight increase in the propagation velocity of the self-sustained wave, which allows using this preparation to prevent detonation damping in channels with both a single obstacle and multiple barriers. | Detonation Combustion Control Using Preliminary Preparation of the Gas Mixture | 10.1134/S1063785020020248 |
2020-02-01 | The initial boundary value problem for the nonlinear wave equations with damping and logarithmic nonlinearity is investigated in this paper. By making use of modified potential well theory and the technique of Logarithmic-Sobolev inequality, we establish global existence as well as asymptotic behavior of solution, under the assumption that the initial energy is small. Moreover, we obtain an exponential decay which is much faster than the decay in polynomial nonlinear case of Gazzola and Squassina (Ann I H Poincaré AN 23:185–207, 2006). These results generalize and extend work in application of potential well theory to wave equations. | Global well-posedness for the nonlinear damped wave equation with logarithmic type nonlinearity | 10.1007/s00500-019-04660-6 |
2020-02-01 | The present article highlights the development of hybrid-fiber-reinforced composites using a vacuum-assisted resin transfer molding technique on low-cost flax fibers, carbon fiber, glass fibers and a vinyl ester resin system. Flax fibers are introduced to modulate mechanical properties, green credentials, cost, and the weight of carbon/glass/vinyl ester composites. The hybridization effect of flax, carbon, and glass fibers on mechanical properties, including tensile and flexural strengths, flexural modulus, impact strength, interlaminar shear strength, and damping is evaluated, which is also observed by SEM. The dynamic mechanical analysis was carried out for the composites with a three-point bending mode within a frequency range of 0 to 100 Hz. The results of the experiment reveal that hybrid composites with flax fabric and glass fabric had the highest flexural strength (727.8 MPa) and impact strength (0.171 J/mm^2) compared with other composites. The dynamic mechanical analysis also showed that the highest value of Tan δ (0.0722) and damping ratio (2.75 %) were obtained compared with those of other composites. | Effect of Hybrid Reinforcement on the Mechanical Properties of Vinyl Ester Green Composites | 10.1007/s12221-020-9632-2 |
2020-02-01 | The present paper is aimed to investigate the behavior of Natural Rubber Bearing incorporated with steel ring damper (NRB-SRD). These types of dampers are integrated of several steel rings which are considered with two configurations namely, continual steel ring damper and separate steel ring damper and are inserted between top and bottom plates. The performance characteristics of the system such as effective horizontal stiffness, energy dissipation, equivalent viscous damping and residual deformation are calculated and then compared with the results of high damping rubber bearings and also shape memory alloy (SMA)-lead core rubber bearing (SMA-LRB). The results show that the energy dissipation in steel rings are mainly based on plastic deformation due to flexural behavior of the rings. NRB-SRD shows better performance in energy dissipation comparing to SMA-LRB and HDRB. These additional dampers show higher stability and energy dissipation in low shear strains due to developing of link between structure and substructure having desirable initial stiffness under weak earthquakes and wind loads and also in higher shear strains due to creation of higher energy dissipation, stability and secondary stiffening. | Natural Rubber Bearing Incorporated with Steel Ring Damper (NRB-SRD) | 10.1007/s13296-019-00267-7 |
2020-02-01 | Purpose The paper is an attempt to evaluate the efficiency of passive control techniques such as base isolation system (e.g. Lead/Rubber Bearing) and fluid viscous dampers subjected to earthquake ground motions and underground blast-induced vibrations. Two moment-resisting steel frame buildings are analyzed to evaluate the structural responses under dynamic excitations. The effect of vertical irregularity on the performance of passive control techniques in mitigating the responses of the building is also studied. Methods Non-linear dynamic analysis has been conducted on regular and irregular steel structures. The study investigates the effect of isolation period on the structural responses. The isolators are designed based on the design procedures developed by various researchers. The technical specifications of fluid viscous dampers have been selected from M/s Taylor Devices, USA. Results The structural responses and energy dissipated by these control techniques is evaluated and a comparative study is also carried out amongst control techniques under blast and seismic excitations. Conclusions Both the selected passive control techniques have proved to be very effective in reducing the structural responses and forces induced in the building owing to ground-induced vibration. | Performance Evaluation of Moment-Resisting Steel Frame Buildings Under Seismic and Blast-Induced Vibrations | 10.1007/s42417-018-0027-2 |
2020-02-01 | This study focuses on energy harvesting from vehicle suspension by employing a regenerative rotational shock absorber. Designing, manufacturing and testing of a prototype device is done step by step to provide a useful manual for researchers. The prototype damper was especially designed for low frequency applications. A rack-pinion mechanism was proposed to transform linear motion to rotational one. Unidirectional motion was realized by using a new combination of bearings and gear chain mechanism. This mechanical rectifier was coupled to light weight gear box with high reduction factor. Experimental studies were conducted in laboratory by utilizing a damper testing device. Excitation vibration motion on prototype was in constant amplitude (25 mm) and at variable low frequencies (0.16, 0.32 and 0.48 Hz). Additionally, different resistances were tested as an external load for electric generator (0.66 ∼ 10.4 Ω). Generated voltage and power in different case studies were presented. The maximum power was found to be 35 W and the maximum performance achieved was 34.36%. The range of calculated damping coefficient is in between 4800 Ns/m and 16000 Ns/m that is convenient for passenger and commercial vehicles. | Experimental Study of Regenerative Rotational Damper in Low Frequencies | 10.1007/s12239-020-0009-8 |
2020-02-01 | Modern rotating machines operate at higher shaft speeds, crossing a few bending critical speeds, which often induce large dynamic loads on the bearing supports that may increase the rotor orbital whirl motion. Accurate prediction of squeeze-film damper (SFD) forces is the key issue for designers to arrive at a suitable design. An experimental setup was developed with eccentric shaft to find the damper forces. Submerged type damper with relatively large clearance was considered for the present work. It results in higher gap Reynolds number (Re) which varies from 1.5 to 15 in the present case. Four force sensors are used to measure the damper forces and two eddy current probes were used to measure the damper orbit. Circular-centered orbit (CCO) of eccentricity ratio ( ε ) 0.176 was used in the present work. Theoretical modeling of SFD forces is considered with viscous, inertial, temporal contributions under laminar and turbulent conditions. Modified Reynolds equation with short damper approximation is used to derive the SFD forces for 2π- film. Fourier coefficients of measured forces and displacements are estimated and used to extract the 1× components and phase information. Radial and tangential forces were calculated from the measured total forces to find the contributions of viscous and inertial forces. Experimental forces are compared with theoretically predicted forces and they are in good agreement with the experimental results. | Experimental and Analytical Investigation of Short Squeeze-Film Damper (SFD) Under Circular-Centered Orbit (CCO) Motion | 10.1007/s42417-019-00100-9 |
2020-02-01 | It is shown that a passive vibration absorber can completely quench the self-excited vibration only for certain parameter values, like the strength of instability in the primary system. The present paper numerically explores the performance of semi-active vibration absorber in controlling self-excited vibration. In the proposed semi-active scheme, the damping force of the absorber is switched between the maximum and the minimum values according to certain control logics. Four different control strategies are considered—these are on–off velocity-based ground-hook control (VBG), on–off displacement-based ground-hook control (DBG), continuous VBG and continuous DBG. Numerical simulations are performed in the MATLAB Simulink to explore the efficacy of the control strategies. It is shown that the on–off DBG control is superior to all other control strategies. | Efficacy of Semi-active Absorber for Controlling Self-excited Vibration | 10.1007/s40032-019-00521-1 |
2020-02-01 | This paper takes into consideration a damped harmonic oscillator model with delayed feedback. After transforming the model into a system of first-order delayed differential equations with a single discrete delay, the single stability switch and multiple stability switches phenomena as well as the existence of Hopf bifurcation of the zero equilibrium of the system are explored by taking the delay as the bifurcation parameter and analyzing in detail the associated characteristic equation. Particularly, in view of the normal form method and the center manifold reduction for retarded functional differential equations, the explicit formula determining the properties of Hopf bifurcation including the direction of the bifurcation and the stability of the bifurcating periodic solutions are given. In order to check the rationality of our theoretical results, numerical simulations for some specific examples are also carried out by means of the MATLAB software package. | Multiple stability switches and Hopf bifurcation in a damped harmonic oscillator with delayed feedback | 10.1007/s11071-019-05389-5 |
2020-01-30 | By the measurement of the frequency and damping time of surface oscillations, excited by a short pulse on a freely floating liquid droplet, the surface tension and viscosity of the liquid can under certain conditions contactlessly be determined. The conventional physical models linking these material properties to the corresponding measurement quantities are the Rayleigh and the Lamb formula. However, both these equations are derived under the assumption of undamped or very weakly damped oscillations. In the following the basic characteristic equation of the linear Navier–Stokes equation, representing a corresponding physical model for the whole damping range, is theoretically investigated. A comparison of its accurate results with those of Rayleigh and Lamb reveal, that the Rayleigh formula provides, even in the case of strongly damped oscillations, an approximation which is still good enough for most practical purposes, whereas the Lamb formula deviates by more than 10 % from the accurate value. An improvement of the Lamb formula is derived from the characteristic equation which extends its practical applicability also to strongly damped oscillations. | Viscosity Measurement by the
“Oscillating Drop Method”: The Case of Strongly Damped
Oscillations | 10.1007/s10765-020-2608-z |
2020-01-16 | We investigated the effect of magnetically modified natural zeolite on the mechanical and damping properties of natural rubber-nanosilica compounds. We used natural rubber SIR 20 technical specified rubber (TSR) reinforced with a nanosilica filler. The results showed that using zeolite modified with magnetite and titanate coupling agent (TCA), which are alternative coupling agents to replace silane coupling agents, and amorphous silica as the filler in natural rubber TSR SIR 20 compounds enhanced the mechanical properties of the TSR vulcanization products. The relationships among the crosslink density, mechanical properties and damping properties were also explored. We also identified that an improvement in the properties resulted from a modification of the white oil softener and filler comprising the zeolite-nanosilica-magnetic blends. The results of magnetically modified zeolite showed that the crosslink density, mechanical properties and damping properties increased significantly. The damping ratio in the sample comprising Si + Fe + Z with or without the white oil softener was higher than that of the other samples herein (ζ > 0.03). Based on this result, a reinforced nanosilica filler with magnetically modified zeolite has the potential to replace carbon black and is applicable to damping devices. | Effects of magnetically modified natural zeolite addition on the crosslink density, mechanical, morphological, and damping properties of SIR 20 natural rubber reinforced with nanosilica compounds | 10.1007/s10965-020-2013-0 |
2020-01-09 | Damping is an important dynamic characteristic of rock masses and has an important impact on seismic engineering. In this paper, a multi-level cyclic loading-unloading triaxial compression experiment was conducted on granite and red sandstone under different confining pressures with two stress paths: one with different amplitudes and the other with the same amplitude. The effects of the two stress paths on the damping ratio, damping coefficient, and elastic modulus evolution characteristics under different confining pressures were studied. The damping parameters and dynamic elastic modulus of the two types of rock under different confining pressures were calculated, and the variation in the damping parameters with the stress level and strain level was determined. The linear interrelation of the damping ratio, damping coefficient, and dynamic elastic modulus was explored. The results show that the damping coefficients of the red sandstone and granite can be expressed as a linear function of the dynamic elastic modulus. The dynamic elastic moduli of the red sandstone and granite increased with increasing strain ratios and stress ratios. Under the variable-amplitude stress path, the dynamic elastic modulus growth rate of the red sandstone was approximately 60% of that of the granite. Under the fixed-amplitude stress path, the dynamic elastic modulus growth rate of the red sandstone was approximately 20% of that of the granite. | Experimental study of nonlinear damping characteristics on granite and red sandstone under the multi-level cyclic loading-unloading triaxial compression | 10.1007/s12517-019-5022-8 |
2020-01-07 | We consider a locally damped wave equation in a bounded domain. The damping is nonlinear, involves the Laplace operator, and is localized in a suitable open subset of the domain under consideration. First, we discuss the well-posedness and regularity of the solutions of the system by using a combination of the nonlinear semigroup theory and the Faedo–Galerkin scheme. Then, using the energy method combined with the piecewise multipliers method and relying on the localized smoothing property, we derive the exponential decay of the energy when the nonlinear damping grows linearly, the damping coefficient is smooth enough and further satisfies a structural condition; this is in agreement with what is known in the case of a linear damping of Kelvin–Voigt type. The novelty of our approach lies on the fact that: (1) we are using a nonlinear damping, which makes it trickier to study the regularity of solutions as well as the exploitation of the localized smoothness property, in order to prove that the energy decays exponentially; (2) the energy estimates are carried out directly in the time domain, unlike the frequency domain method utilized in all earlier works on the stabilization of the wave equation involving a localized Kelvin–Voigt damping. | Stabilization of the wave equation with a localized nonlinear strong damping | 10.1007/s00033-019-1240-x |
2020-01-01 | This chapter is concerned with damped oscillators. Nonlinear oscillators are mainly dealt with, but linear oscillators are also considered or referred to for the sake of comparison or clear extension of the related methodology. First, Lagrangians and conservation laws of viscously damped linear oscillators as well as Duffing oscillators are presented. Then, quadratically damped purely nonlinear oscillators are studied and exact expressions for their energy-displacement functions are derived based on energy considerations. Further, oscillators with fractional derivative damping are studied by the averaging technique that includes the use of trigonometric functions for finding their approximate response. A similar technique but with the use of Jacobi elliptic function is also presented for purely nonlinear oscillators with different types of damping. Finally, the averaging technique that includes the use of wave functions is applied for finding the approximate response of damped constant restoring force oscillators. | Free Damped Oscillators | 10.1007/978-3-030-53172-0_3 |
2020-01-01 | The circuit analysis techniques that we have presented thus far work very well when only resistors Resistors are present in the circuit. | Reactive Circuit Transient Response | 10.1007/978-3-030-31355-5_6 |
2020-01-01 | The stayed-cable is one of vital component of cable-stayed bridges. Stayed-cable is often very long with a small diameter and low mass, which can be considered horizontal flexible structure with very low natural frequency. Under the influence of cyclic load in specific conditions, stayed-cable can store the energy and vibrate with large amplitude. This paper focuses on studying the methods of two-friction damper combination for reducing the cable vibration, and evaluates the capacity of friction-damper parameters in mitigating the vibration of stayed-cable. The results show the relationship between the damping factor of stayed-cable and various parameters such as Equivalent viscous constants, friction, spring constant, points attached damper to stayed-cable. For long-span cable-stayed bridges, cable has relatively large diameter and it is normally covered by grouting mortar or Epoxy. Consequently, its bending stiff-ness is considerably increased. Therefore, it is necessary to take into account its bending stiffness during the vibration analysis process. From these results, designers can assess and choose the attaching point as well as parameters of friction damper, which are optimal for specific stayed-cable. | A Study on Combination of Two Friction Dampers to Control Stayed-Cable Vibration Under Considering its Bending Stiffness | 10.1007/978-981-15-0802-8_10 |
2020-01-01 | Adaptive shock absorbers improve the ride quality by changing the damping characteristic depending on road excitation. An adjustable bypass valve allows to switch between different force characteristics. This paper introduces a new generic damper model which uses a modular damping function (MDF) to adapt the resulting force output through position-, stroke- and frequency-dependent adjustments. The piston motion is used to determine the shock absorber’s basic force and the state-dependent force difference, which results from the adjustable bypass. In contrast to established modeling approaches that are used for digital performance predictions in the early stage of the development process, MDF includes both the maximum and the minimum force characteristic, thus allowing the implementation of adaptive shock absorbers. Few additional parameters are required to specify both hysteresis and the adjustable bypass effect. In later stages, measurement data can be used to fit the model quality to the increasing maturity level of the described shock absorber. | A New Generic Model for Adaptive Shock Absorbers | 10.1007/978-3-030-38077-9_207 |
2020-01-01 | This paper proposes a novel method (PSOMSF) to unified power flow controller (UPFC) for dynamic stability enhancement of single machine infinite bus system (SMIB). This method consists of multi stage fuzzy damping controller and particle swarm optimization (PSO) method used for fixing the fuzzy bounds. Two stages of fuzzy controllers are designed in such a way the first fuzzy controller exhibits PI behavior and second fuzzy controller exhibits PD behavior and the combination exhibits PID behavior. PSO adjusts the bounds of fuzzy sets to get minimum error in frequency deviations and hence to improve the dynamic stability. The proposed method designed in Matlab environment and tested SMIB system. Effectiveness of the proposed controller is compared with conventional power system stabilizer (PSS) and genetic algorithm based multi stage fuzzy damping controller (GAMSF). | A Novel Method for Dynamic Stability Enhancement of SMIB System | 10.1007/978-981-13-8942-9_30 |
2020-01-01 | The damping mechanism of damping system using granules—applied to reduce vibration in structures with high natural frequency and small vibration displacement—was investigated. A computational model of a single-degree-of-freedom vibration system with a granular-material damper was constructed and used to study the mechanism of the granular-material damping system. On the basis of the fundamental idea that the damping effect of the granular-material damper is governed by the motion of the granules, the granules were classified as the following mass components: “relative-motion mass” and “equivalent added mass” in the translational motion and “rotational-motion mass” and “non-rotational-motion mass” in the rotational motion. The relationships of these mass components with the damping characteristics of the damper were then considered. Moreover, as for structures with high natural frequency and small vibration displacement, the relationships between the motion of the granules, “relative-motion mass” and “rotational-motion mass”, and damping ratio were investigated by experiments and calculations. | Damping Mechanisms of a Vibration-Reduction System Using Granules | 10.1007/978-3-030-55061-5_2 |
2020-01-01 | The proposed work is based on the Synchronized Switch Damping technique (SSD) which has already been applied in reducing and suppressing structure vibration, a new approach called Synchronized Switch Damping with Diode (SSDD) for enhanced vibration damping of smart structure is developed, and it applies on energy redistribution with the piezoelectric elements network. The SSD technique reveals that the damping performance is strongly related to a build-up voltage which results from the continuous switching. It hints that the enhanced piezoelectric voltage results in the improved damping performance. In SSDD technique, diodes and switches are used to form a combinational network, and it is able to achieve a low-loss energy transfer from the source piezoelectric elements which extract the vibration energy of the structure to a target end piezoelectric element for increasing its operative energy aiming to improve a given mode damping. In this work, the simulation of a clamped plate with four piezoelectric elements modelled in the Matlab/SimulinkTM environment is shown. The damping performance can achieve an increase of 8 dB at least in some weak excitation case, for example, the coupled piezoelectric elements are excited in the pulse stimulus. The simulation results show the relationship between the damping performance on a given targeted mode and the established power flow. The importance of non-linear multi-actuator approach for improved vibration damping of extended smart structure is revealed by the experimental data. | Synchronized Switch Damping with Diode (SSDD) Based on a Network of Piezoelectric Elements for Improved Vibration Damping of Smart Structure | 10.1007/978-981-15-0860-8_37 |
2020-01-01 | In this study, the Mg_97Zn_1Y_2–Al alloy was selected as a high damping material, anelastic and microplastic damping were analyzed by studying strain amplitude-dependent damping curves of the alloy. The C_1 and C_2 values of the Granato–Lücke (G–L) model, the theoretical basis of anelastic damping, can be calculated for each alloy, then, the corresponding numbers of strong and weak pinners are deduced. However, since the occurrence of microplastic damping in a high strain amplitude cannot be explained by the G–L model, a new microplastic damping theory was introduced, by comparing the activation volume of the material dislocation slip, the microplastic damping capacity of the Mg_97Zn_1Y_2–xwt%Al (x = 0.3, 1, 3) alloys at the microplastic stage are compared. The elastic and plastic deformation of the materials could be sensitively reflected by studying the damping behavior of these two stages. | Anelastic and Microplastic Damping of an Mg–Zn–Y–Al Alloy | 10.1007/s12540-019-00302-6 |
2020-01-01 | Sounds originate from vibrational waves traveling in a material. Animals take advantage of sounds to get and send notice of opportunities and impending dangers. Within the science of acoustics, we have applied mechanical principles to study how life forms detect and generate sounds, how these sounds carry information and energy, and how life utilizes sound, including for communication. Covered are acoustical analysis, biogeneration, biodetection, music and acoustical dosimetry. | Acoustics in Biology and Medicine | 10.1007/978-3-030-44146-3_5 |
2020-01-01 | This survey provides an insight into the modeling and testing of uniaxial friction dampers. The focus is on attenuating the linear relative movement along planar surfaces for frequencies between 10 Hz and 1 kHz. An overview of the different approaches seen in the literature concerning friction damping is provided. Examples and evaluation of such dampers excited over a wide range of frequencies are presented. The information required to develop models of friction dampers is covered. To that end, different modeling approaches are presented for dry friction. Dynamic friction models with an internal state are covered, and their advantages are described. Other modeling approaches are reported for complete systems with friction dampers. Both numerical and analytical models are covered. Experimental configurations from a selection of authors are also included. Finally, a series of suggestions for the numerical modeling and experimental testing of a friction damper are given. | A review of friction damping modeling and testing | 10.1007/s00419-019-01600-6 |
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