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2022-06-06 | This paper deals with initial-boundary value problems for a damped thin quasilinear plate. With restriction on the norms of the initial data, it will be established global weak and global strong solutions. It will also be shown that the strong solution is uniformly stable and unique. Furthermore, using a weak internal damping mechanism, an exponential decay estimate for the energy of weak solutions is established. | Remarks on thin quasilinear plates with mixed boundary conditions | 10.1007/s00028-022-00810-w |
2022-06-06 | This paper aims to study the stability of solutions for a double-Kirchhoff type viscoelastic inverse source problem with nonlocal degenerate damping term and variable-exponent nonlinearities. Proving of existence and stability of solutions to inverse problems is of high importance because inverse problems are nonlinear and improperly posed, and the presence of unknown source functions with nonstandard growth conditions causes the nonexistence and blow-up of solutions. Therefore, in this work by using the suitable auxiliary functionals and by introducing a suitable Lyapunov functional, we shall prove that the solutions of a double-Kirchhoff type viscoelastic inverse source problem are asymptotically stable in the appropriate range of variable exponents. | Stability result for a variable-exponent viscoelastic double-Kirchhoff type inverse source problem with nonlocal degenerate damping term | 10.1007/s11587-022-00713-5 |
2022-06-01 | In this paper, the five-percent maximum overshoot design of uniformly damped binomial filters (transfer functions) is introduced. First, the Butterworth filter response is represented as a damped binomial filter response. To extend the maximum overshoot response of the second-order Butterworth to higher orders, the binomial theorem is extended to the uniformly damped binomial theorem. It is shown that the five-percent uniformly damped binomial filter is a compromise between the Butterworth filter and the standard binomial filter, with respect to the filter approximation problem in the time and frequency domain. Finally, this paper concludes that in applications of interest, such as step-tracking, where both strong filtering and a fast, smooth transient response with negligible overshoot are desired, the response of the normalized five-percent uniformly damped binomial form is a candidate replacement for both the Butterworth and standard binomial filter forms. | Uniformly Damped Binomial Filters: Five-percent Maximum Overshoot Optimal Response Design | 10.1007/s00034-021-01931-2 |
2022-06-01 | Purpose The present study lies on an in-depth experimental investigation in evaluating the performance of MR damper on structure subjected to dynamic load. A novel placement, orientation and working mechanism of MR damper has been chosen for its optimal performance in reducing the dynamic response of the frame structure. This work can be beneficial where installation of control systems to the structure is not possible. Method The study, therefore, thoroughly investigates the aspects and benefits that lie in the MR damper working mechanism itself. The dynamic simulations are conducted on a six degree-of-freedom shake table. The MR damper is designed as a visco-plastic Hysteretic Bingham model to show a linear relationship between current, voltage and damper restoring force. The MR damper is placed diagonally in between the columns of the frame on top and ground floors alternatively for a comparative study. Sinusoidal loads of different amplitudes are induced on both planes of the frame. Results The estimation of acceleration response, frequency response function, interstorey drift and RMS of displacement has enumerated the performance level of the damper for each of the cases rigorously. Furthermore, a numerical comparative study is conducted to support the experimental observations. Conclusion This study furnishes the potential of MR dampers as stable, sturdy and durable semi-active dampers in vibration reduction of structural frame. | Investigation of a Diagonal Magnetorheological Damper for Vibration Reduction | 10.1007/s42417-022-00458-3 |
2022-06-01 | In non-ideal vibratory system, the excitation is a nonlinear function of system response. The dynamic behavior of such system is often characterized by an energy source with limited power. The study of instability phenomena in non-ideal rotor driven through a non-ideal energy source is of considerable current interest. The non-ideal rotor system often gets destabilized on exceeding a critical input power near the resonance. This kind of instability is termed as Sommerfeld effect marked with nonlinear jump phenomena. This paper investigates the attenuation of nonlinear jump phenomena and numerical study of bifurcations of a non-ideal unbalanced rotor system with internal damping using time-delayed feedback via active magnetic bearings. The results show that the time delay indeed plays a critical role on the suppression of the jump phenomena. Following, some new insights are also revealed through a numerical study of saddle node, Hopf and trans-critical bifurcations with time delay as a bifurcation parameter. The transient analysis confirms the results obtained analytically through the steady-state consideration. | Instability attenuation and bifurcation studies of a non-ideal rotor involving time-delayed feedback | 10.1007/s11071-022-07367-w |
2022-06-01 | Identification of rotor unbalance and support dynamic coefficient plays a critical role in operation safety of large rotating machineries. In this paper, aiming at single-disc and single-span rotors, a novel algorithm called Fine-tuning Rotating Speed and Frequency Domain Fusion Identification (FRS-FDFI) is proposed to simultaneously identify the rotor unbalance and two bearings’ 16 stiffness and damping coefficients based on the Continuous Rotor Dynamic Analysis Method (CRDAM). A major difficulty in the derivation of FRS-FDFI is that it is difficult to obtain the 18 unknown variables (rotor unbalance and bearing coefficients) by directly solving the equations developed based on CRDAM using unbalance responses as input. To overcome it, it is proposed to build six equations in which the unbalance responses at the two bearings and disc are considered as unknown variables and unbalance responses in x and y directions of three measured points are used as input. Then, a linear functional relationship between the bearing’s main coefficient and cross-coupled coefficient is obtained. However, the slope of the proposed function is constant at a fixed speed, which means it is impossible to develop another set of equations just by using more measured unbalance responses. Therefore, changing the rotating speed slightly is proposed to solve the problem and FRS-FDFI is derived. The requirement is measuring the unbalance response at two bearing positions and any other two positions on the shaft. Unbalance responses at the disc are not needed. The effectiveness of the proposed solutions are evaluated by numerical experiments. Simulation results indicate that the estimation accuracy is associated with the repeatability precision of vibration displacement measurement systems. The proposed method provides an efficient and easy implemented approach for the field identification of support stiffness and damping and rotor unbalance without test runs and external excitations. | Theoretical and Numerical Studies on Simultaneous Identification of Rotor Unbalance and Sixteen Dynamic Coefficients of Two Bearings Considering Unbalance Responses | 10.1007/s12555-021-0340-5 |
2022-06-01 | This paper presents the nonlinear dynamics of a complex 2-DOF (two degree-of-freedom) system including nonlinear stiffness and damping elements, friction as well as impact, and the purpose of study is to give an original and deep investigation on the discontinuous dynamical behaviors for such a 2-DOF system through strict mathematical consideration. Firstly, the physical model of the system consisting of a ball and an object with curved track and viscoelastic limit devices is established by Coulomb friction and non-linear spring-damping model. And the eight motion states associated with free, sliding or stick motions are defined for the oscillator. Secondly, based on the non-smoothness/discontinuity resulted from impact/friction, the phase space is divided into different domains and boundaries in absolute and relative coordinates, respectively. Thirdly, some necessary and sufficient conditions for oscillator’s motion switching at separation boundaries are given by G-functions of the flow switchability theory in discontinuous dynamical systems. Finally, in order to better understand the switching criteria and the complexity of oscillator’s motion, some illustrative examples for several typical motions in system are studied by numerical simulation. The nonlinear spring-damping model is widely used as a shock absorber in machinery, aerospace, construction and other fields, which can accurately reflect the energy loss during impact process. | Nonlinear dynamics for a class of 2-DOF systems with viscoelastic limit devices on a curved track | 10.1007/s11071-022-07375-w |
2022-06-01 | Abstract Non-ideal high-speed rotors often exhibits nonlinear jumps driven through a power drive with limited capacity. The study of nonlinear jump in such rotor system is of considerable current interest. These systems often get destabilized on exceeding a critical input power proximity to resonance. This phenomenon is known as the Sommerfeld effect. The present study investigates the dynamics of a disk mounted non-centrally on a flexible shaft driven through a brushed DC motor. Additionally, cross-coupled external and internal damping both are considered for the present study. The steady-state and transient analysis of the proposed system reveal a couple of interesting facts about the complex interaction of the gyroscopic rotor with the motor. | Dynamics of a Non-Ideal Gyroscopic Rotor System with Translational-Rotational Coupling Effect of External and Internal Damping | 10.3103/S0025654422030116 |
2022-06-01 | The simulation of complex engineering applications often requires the consideration of component-level dynamics whose nature and time-scale differ across the elements of which the system is composed. Co-simulation offers an effective approach to deal with the modelling and numerical integration of such assemblies by assigning adequate description and solution methods to each component. Explicit co-simulation, in particular, is frequently used when efficient code execution is a requirement, for instance in real-time setups. Using explicit schemes, however, can lead to the introduction of energy artifacts at the discrete-time interface between subsystems. The resulting energy errors deteriorate the accuracy of the co-simulation results and may in some cases develop into the instability of the numerical integration process. This paper discusses the factors that influence the severity of the energy errors generated at the interface in explicit co-simulation applications, and presents a monitoring and correction methodology to detect and remove them. The method uses only the information carried by the variables exchanged between the subsystems and the co-simulation manager. The performance of this energy-correction technique was evaluated in multi-rate co-simulation of mechanical and multiphysics benchmark examples. | Energy-based monitoring and correction to enhance the accuracy and stability of explicit co-simulation | 10.1007/s11044-022-09812-5 |
2022-06-01 | In this paper, we propose in a Hilbertian setting a second-order time-continuous dynamic system with fast convergence guarantees to solve structured convex minimization problems with an affine constraint. The system is associated with the augmented Lagrangian formulation of the minimization problem. The corresponding dynamics brings into play three general time-varying parameters, each with specific properties, and which are, respectively, associated with viscous damping, extrapolation and temporal scaling. By appropriately adjusting these parameters, we develop a Lyapunov analysis which provides fast convergence properties of the values and of the feasibility gap. These results will naturally pave the way for developing corresponding accelerated ADMM algorithms, obtained by temporal discretization. | Fast Convergence of Dynamical ADMM via Time Scaling of Damped Inertial Dynamics | 10.1007/s10957-021-01859-2 |
2022-06-01 | In nanoresonators, thermoelastic damping (TED) is a primary energy dissipation mechanism. As a result, when designing nanoresonators, it is critical to limit this type of dissipation. This paper investigates the nonlocal TED of circular single-layered graphene sheet (SLGS) nanoresonators in axisymmetric out-of-plane vibration utilizing the generalized dual-phase-lag thermoelasticity theory. The nonlocal elasticity and Gurtin–Murdoch surface elasticity theories are employed to capture the small-scale and surface energy effects, respectively. By incorporating these effects into the model, the non-classical equations of the coupled thermoelastic problem are first obtained and then an analytical expression is introduced to predict TED in circular nanoplates. Moreover, the results obtained herein are validated by those of the classical continuum theory which can be found in the open literature. The influences of the aspect ratio, surface elastic modulus, surface residual stress and nonlocal parameter on TED of circular SLGS nanoresonators are investigated using numerical data. The calculated results show the significance of surface and nonlocal effects in nanoplate TED continuum modeling. | Surface and Nonlocal Effects on the Thermoelastic Damping in Axisymmetric Vibration of Circular Graphene Nanoresonators | 10.1007/s10338-021-00276-2 |
2022-06-01 | We consider a simple frictionally constrained lap joint. Two identical beams were joined by a constant normal load. A periodic bending moment was applied on each beam to investigate the contact tractions at the joint interface. Predicting the dynamic behaviors of a frictionally constrained lap joint under periodic loading is challenging owing to the inherent nonlinearity of the behaviors. A dynamic response analysis of nonlinear systems is generally conducted via numerical integration in the time domain. However, owing to the nonlinear nature, time-domain analyses are computationally expensive. To address this issue, efficient reduced-order modeling (ROMs) was proposed in this paper. The proposed technique is based on the interpretation of the nonlinear characteristics of the friction force as relevant damping and stiffness terms. To increase the computation speed, the proposed method allows for the precalculation of the equivalent terms and employs response-dependent equivalent parameters in iterative solution methods. For validation, steady-state responses due to periodic bending were examined. The results obtained from the ROMs agree well with those of the time-domain analysis conducted using the full finite-element model. This study demonstrates that the equivalent expression of the nonlinear friction force can be defined by equating the energy loss or store per cycle in a hysteretic system to the energy loss or store per cycle in the corresponding amplitude. The proposed technique permits accurate predictions of the steady-state response of resonant vibrations in a primarily nonlinear hysteretic system. | Dynamic response predictions of frictionally constrained lap joints subjected to cyclic loading | 10.1007/s10999-021-09580-8 |
2022-06-01 | The moisture ingression into photovoltaic module has significant impact on the reliability as it participates in multiple degradation pathways. Damp heat test is performed at a temperature 85°C and relative humidity of 85% for 1000 h to assess the ability of a photovoltaic module under humid conditions. In this paper, we have developed an analytical model to quantify the amount of moisture ingressing into a photovoltaic module with a breathable backsheet under damp heat testing condition. The analytical model is developed with the consideration that the vertical moisture diffusion in the ethylene vinyl acetate (EVA) layer is instantaneous. The comparison with numerical model validated the assumption. The analysis of the simulated profile with the developed analytical model showed that at 85°C, the moisture profile within the rear EVA and backsheet reaches a steady state value within 10 h. Considering that the damp heat test is performed for a span of 1000 h, to simplify we can consider that the moisture profile is temporally and spatially constant in the backsheet and rear EVA, with the moisture concentration being given by the product of moisture solubility (S) and permeability (P) for that particular material at 85°C. However, the moisture profile for top EVA in regions above the solar cell does not reach a steady state value even within a span of 1000 h. The non-uniformity of the moisture profile needs consideration for quantifying the degradation in the regions of top EVA that is directly above the solar cell. | Analytical Modeling of Diffusion of Moisture in Silicon Photovoltaic Module under Damp Heat Testing Condition | 10.1007/s12633-021-01156-7 |
2022-06-01 | In practical engineering, we usually hope to find equivalent models for complex structures to simplify their mechanical analysis. Honeycomb structure has the characteristics of light weight, high stiffness and good energy absorption, etc., and is used in the anti-collision structure. However, As a continuum, the equivalent model of honeycomb structure is relatively rare. In order to simplify the mechanical analysis (displacement, energy absorption), we propose an equivalent model called system of mass-spring-damper (SMSD) to describe the displacement and energy absorption of honeycomb. We propose the equivalent theory by taking the hexagonal honeycomb structure as an example, and use the method of numerical simulation to prove the correctness of the theory. Besides, different forms of honeycomb structures are discussed, and the application scope of the theory is given. In this paper, the honeycomb and SMSD are considered simultaneously, which provides a new idea for the research of honeycomb structure. | Equivalent damper model for honeycomb structures | 10.1007/s10999-021-09578-2 |
2022-06-01 | Abstract The possibility of parametric control of the oscillation characteristics (amplitude and frequency) of a symmetrical thin extended flat float oscillating near the interface of two heavy ideal liquids by changing its shape (relative height) is studied. An analysis of the influence of the body shape on the characteristics of vibrations has been carried out. A numerical and asymptotic procedure for solving a self-consistent boundary value problem is proposed. | PARAMETRIC CONTROL OF FLOAT OSCILLATIONS | 10.3103/S0025654422030049 |
2022-06-01 | In recent years, energy dissipative systems have been used as effective devices in structures subjected to earthquake loads. The optimal design of dampers has gained popularity as a research topic during the last four decades. That is widely notable that dampers can contribute a unique function in dynamic structures by considerably reducing the dynamic response. The efficient design and configuration of the passive dampers are essential for the mitigation of damages due to the earthquake in the structure. Thus, finding the optimal placement of dampers has a key role in the protection of the building. However, the remaining difficulty in damping devices is determining the parameters and placement of each damper. This paper presents an overview of the optimal damper distribution as passive systems for energy dissipation in order to retrofit structures against the earthquakes. That is quite essential for determining the location of these devices for simulating the structures with dampers effectively. Nevertheless, the reaction of the structure requires to be identified for applying the dampers. General results have been achieved regarding optimal damper configuration in the structures. | An Overview of Optimal Damper Placement Methods in Structures | 10.1007/s40996-021-00752-2 |
2022-06-01 | Micro/nanobeam-based resonators have found extensive applications in the micro/nanoelectromechanical system industry. Thermoelastic damping (TED) is a major energy loss issue in micro/nanobeam resonators that limits their important performance parameter, namely, the TED limited quality factor (Q_TED). The critical length (L_c) of a micro/nanobeam is another significant parameter that accounts for the maximum peak in the energy dissipation curve at which Q_TED assumes a minimum value. To evaluate Q_TED and Lc explicitly when the size of devices is scaled down, size effects play a decisive role and classical theories are inadequate. In this work, a higher-order theory, namely, modified couple stress theory (MCST), is used to overcome the size effects by including one internal material length scale parameter (l). The material-dependent thermoelastic coupled equations for a deflected Euler-Bernoulli microbeam are presented using variational and Hamilton principles. Moreover, the solutions for Q_TED are developed on the basis of a complex frequency approach with the appropriate material indices. The effects of material length scale parameters, material performance indices, mechanical boundary conditions (clamped-clamped, simply supported, and cantilever types), mode switching, and plane stress/strain conditions on Q_TED and Lc are analyzed. Numerical results are extracted from the analytical expressions by using MATLAB R2015a to quantify thermoelastic energy dissipation. The numerically computed Q_TED and L_c values are fully investigated to design high-performance resonators. The analyses verify that Q_TED is enhanced by optimizing the structural material and augmenting the material length scale parameter. The material order in which Q_TED is enhanced is the same for classical theories and MCST, i.e., it is inversely related to the TED index parameter. The influences of boundary types and mode switching on Q_TED are relatively less in accordance with the analysis. The effect of plane stress condition compared with that of plane strain condition on Q_TED is also remarkable. The L_c of the beam is determined to be dependent on the thermal diffusion length of the material used. From an adequate material point of view, poly-silicon has been proven to provide the maximum quality factor while silicon carbide yields the maximum L_c. These observations are significant and extremely helpful when designing low-loss micro/nanobeam resonators with superior performance by suitably selecting their geometry and structural materials. | Material-dependent thermoelastic damping limited quality factor and critical length analysis with size effects of micro/nanobeams | 10.1007/s12206-022-0533-8 |
2022-06-01 | Contemplating the global concern towards the environment, the current research is intended for finding out an effective way for curbing of the undesired industrial–agro residual waste which poses a serious threat to human and environment. Extensive research is carried out in developing materials systems with elevated energy dissipation. The current study investigates the damping characteristics of aluminium reinforced with bamboo leaf ash (BLA) metal matrix composites varying the reinforcement weight percentage. The Al-BLA composites are synthesized by engaging a classic stir casting approach. The damping characteristics of the stir cast Al-BLA composites are investigated at three dissimilar frequencies by engaging a dynamic mechanical analyser. Microstructural characterization is performed by engaging a scanning electron microscope and all the pertaining mechanisms have been scrutinized thoroughly. | Energy Dissipation Behaviour of Bamboo Leaf Ash reinforced Aluminium Metal Matrix Composites | 10.1007/s40033-021-00310-0 |
2022-06-01 | A phenomenon called “beat” occurs in bell structures with slight asymmetry, wherein the vibration and the sound periodically fluctuate with respect to strength. In oriental bells, beat makes the bell sound grand and lively. The audience wants to hear the bell sound with a strong beat for as long as possible. The modal damping ratio is used as a physical factor to evaluate the duration of the beat sound. For low damping, the modal damping ratio can be extracted using the logarithmic decrement method with a single-frequency time signal. However, because the beat wave includes two adjacent frequencies, the conventional logarithmic decrement method cannot be applied. In this study, a method for extracting the damping ratio from the envelope data of beat waves was proposed and verified experimentally. Finally, the method was applied to evaluate the duration of the beat sound of the 2018 Winter Olympic bell. | Extraction of the damping ratio of a beat wave using envelope logarithmic decrement | 10.1007/s12206-022-0506-y |
2022-06-01 | Beneficial effects of nonlinear damping on energy harvesting and vibration isolation under harmonic inputs have been investigated showing that the introduction of nonlinear damping can increase the harvested energy and reduce the vibration over both the resonant and higher frequency ranges. However, the scenario becomes more complicated when the loading inputs are of more general form such as multi-tone and random inputs, which can produce system responses that are induced by an interaction of system input components of different frequencies. In the present study, by introducing the concept of power transmissibility, the study of the beneficial effects of nonlinear damping is extended to the systems subject to general inputs including both multi-tone and random inputs. A rigorous analysis is conducted based on single degree of freedom systems subject to general inputs. The analysis reveals the conditions under which the antisymmetric nonlinear damping is beneficial for improving energy harvester performance and reducing of the power of system output in vibration isolation. Moreover, the beneficial effects are demonstrated by two case studies. | Beneficial effects of antisymmetric nonlinear damping with application to energy harvesting and vibration isolation under general inputs | 10.1007/s11071-022-07444-0 |
2022-06-01 | Abstract The propagation of dust–ion–acoustic wave (DIAW) in an unmagnetized collisional dusty plasma comprised from mobile ions, negative dust particles, and non-Maxwellian trapped electrons, modeled by a kappa distribution function along with a Schamel distribution, was investigated. Reductive perturbation theory (RPT) is applied for constructing a non-planar (cylindrical and spherical) damped Schamel (NDS) equation using the basic field equations. In general, the impact of inter-particle collisions is avoided during the studies of wave dynamics of DIAW in a plasma environment, although these effects may have significant impact on wave formation. For the first time, considerable collisions effect on non-planar Schamel framework is developed and, employing the conservation law, the approximate analytical solution of NDS equation is derived. Finally, the significant effect of the damping term is described from a numerical standpoint. In addition, the effects of index κ (super-thermal) and the parameter β (characteristic trapping) on the propagation of DIAW waves are also investigated in the NDS medium. | Studies on the Dust–Ion–Acoustic Solitary Wave in Planar and Non-Planar Super-Thermal Plasmas with Trapped Electrons | 10.1134/S1063780X22100038 |
2022-06-01 | The energy dissipation in sinusoidally driven particle dampers is highly dependent on the motion mode of the particle bed. Especially, for applications of low acceleration intensity, i.e., acceleration amplitude below gravitational acceleration, only small energy dissipation rates are obtained so far, due to sticking of particles. Here, a new and more efficient design of particle dampers is introduced for such applications, whereby the focus is on horizontal vibrations. The proposed design makes use of the rolling property of spheres inside particle containers with flat bases. First, a cuboid container shape is studied. Two different motion modes are observed experimentally within this container shape. For low driving amplitudes, the particle bed is showing a scattered behavior resulting in a low damping efficiency. For high driving amplitudes instead, the rolling collect-and-collide state is observed resulting in much higher efficiency. Analytical descriptions for the energy dissipation are derived for both motion modes, being in good agreement with experimental measurements. It is obtained that the optimal working point of such dampers, i.e., the optimal stroke, is only depending on the filling ratio of the damper. Additionally, the optimal working point separates both motion modes. For lower strokes as the optimal one, the scattered state is observed, while for higher strokes the rolling collect-and-collide mode is seen. Sensitivity analyses are performed using the experimental setup and discrete element simulations. It is obtained that especially a low friction coefficient and a high particle radius are beneficial. On the other hand, a small tilt around the container’s longitudinal or pitch axis might significantly decrease the efficiency of the damper. Besides the cuboid container, the effect of a cylindrical container heading against gravity is analyzed. While the particle bed motion modes are only little influenced, the efficiency of the damper becomes independent of the excitation direction in the horizontal plane. Thus, such dampers could be applied to a large field of applications in mechanical and civil engineering. | Energy dissipation in horizontally driven particle dampers of low acceleration intensities | 10.1007/s11071-022-07348-z |
2022-06-01 | A condition that guaranties the exponential decay of the solutions of the initial-boundary value problem for the damped wave equation is proved. A method for the effective computability of the coefficient of exponential decay is also presented. | Remark on the exponential decay of the solutions of the damped wave equation | 10.1007/s11587-020-00552-2 |
2022-06-01 | In this study, the performance of rectangular added damping and stiffness (RADAS) dampers has been introduced in the diagonal element site to avoid brace buckling and energy dissipation by dampers. The innovation of this research is in the type of site of steel plates and the way of connection in the vicinity of gusset plates which can be easily replaced. To investigate the cyclic performance of the ADAS damper, 15 numerical examples have been simulated by ABAQUS software. The study of cyclic behavior on the single-bay and single-floor steel frame has been done, and the sensitivity of cyclic behavior based on the thickness, length and ratio of dimension to the thickness has been studied. The studied thicknesses of the damper were 12, 21 and 30 mm, the studied lengths of the damper were 400, 500 and 600 mm, the studied geometry of the damper was rectangular, and the studied thicknesses of the brace were 12, 21 and 30 mm. The results of this study showed that this type of damper has good behavior in the energy dissipation of the frame and the total stiffness of the steel plates forming ADAS dampers must be less than the stiffness of the brace to show acceptable frame performance. By changing the damper length parameter from 600 to 500 and 400 mm, each of the indicators of stiffness, ultimate strength and energy has increased by a maximum of 144, 46 and 149%, by changing the damper thickness parameter from 12 to 21 and 30 mm, each of the mentioned indices has increased by a maximum of 147, 52 and 160%, and by changing the brace thickness parameter from 12 to 21 and 30 mm, each of the mentioned indices has increased by a maximum of 5, 7 and 9 percent. The values of the damper thickness and length, when they are less stiff than the stiffness of the brace, cause the plastic hinge formation to be made on the damper, and the damper performance is optimized. | Performance of a New Model of Rectangular Damper in Diagonal Concentric Brace | 10.1007/s40996-021-00624-9 |
2022-05-28 | Effects of Zn/Ga ratio on microstructure, mechanical, damping and thermal properties of Mg– x Zn– y Ga ( x + y = 1 at.%, x / y = 3:1,1:1,1:3, x or y = 0) alloy solid solutions with similar grain sizes are investigated. With the lower Zn/Ga ratio, the yield strength, the elongation and the strain-amplitude-dependent damping of the alloy increase, while the strain-amplitude-independent damping decrease. More attention is paid to the effect of Zn/Ga ratio on the thermal conductivity of magnesium alloys, and the thermal conductivities of the as-cast and solutionized alloys decrease with the lower Zn/Ga ratio. In comparison with the as-cast alloys, the thermal conductivity decreases in different degree for the five alloys after solution treatment. Stacking-fault energy (SFE) and electro-negativity are also important factors affecting the thermal conductivity of the as-studied alloys. The thermal conductivity of the ternary magnesium alloy can be estimated by the known thermal conductivity of the binary alloys. Graphical abstract The mechanical, damping behavior of solid solution alloys with different Zn/Ga ratio and the thermal conductivity of the as-cast and solid solution alloys are given. Stacking-fault energy (SFE) and electro-negativity are also important factors affecting the thermal conductivity of the as-studied alloys. The thermal conductivity of the ternary alloy can be simply calculated by the known thermal conductivity values of the binary alloys, which has important guiding significance. | Effects of Zn/Ga ratio on microstructure, mechanical, damping and thermal properties of Mg–Zn–Ga alloy solid solutions | 10.1557/s43578-022-00572-8 |
2022-05-28 | Several methods are available to design piles subjected to horizontal loadings. A simplified, one-dimensional finite element model that is applicable for various types of lateral loadings such as harmonic or impact loading as well as applicable for soil with different types of inhomogeneity that can be used in preliminary design was needed. The model is based on the beam on a dynamic Winkler foundation model with the simplicity that the connected springs and dashpots at the side and at the base of the pile are frequency independent for a wide range of loading frequencies. The model is validated in two ways. First, the model results are compared with the results of a three-dimensional finite element solution. Second, the model results are compared to a case where the soil stiffness and damping are frequency dependent. For validation, the response of piles to harmonic and impact loading as well as piles in inhomogeneous soils is presented. The determination of the active length of the piles was also determined. The simplified model response is shown to be quite satisfactory. Thus, this simplified model will be of value to design engineers in their preliminary analysis. | A numerical model for analysis of a pile subjected to horizontal dynamic loading in elastic homogeneous and nonhomogeneous soils | 10.1007/s12517-022-10345-6 |
2022-05-27 | A series of polyacrylate latex films with core–shell particle structure and different damping properties were first prepared by seed emulsion polymerization and by adjusting the ratio of soft/hard monomer in the core and shell layers of the latex particles. Higher damping factor (tan δ) was obtained by using styrene that has a bulky side group instead of methyl methacrylate as the hard monomer, and the homogeneous distribution of styrene was critical for improving its damping performance. Epoxy resin/polyacrylate composite latex materials were then prepared based on this pure polyacrylate latex. Pure polyacrylate or epoxy resin/polyacrylate composite latex material with larger tan δ was obtained when acrylic acid or epoxy resin was located in both the core and the shell layers of the latex particles simultaneously, rather than in the core or shell layer only. With increasing content of epoxy resin, the tan δ of the composite latex increased slightly, and the tan δ area (TA) increased significantly, the tan δ peak temperature gradually shifted to lower temperature, and the effective damping temperature range gradually expanded. | Preparation and damping properties of polyacrylate and epoxy resin/polyacrylate composite latex materials | 10.1007/s10965-022-03096-1 |
2022-05-23 | The quantum version of cop and robber game, implemented on the quantum circuit, is investigated in the presence of noisy environment. The various noise models are applied on the initial quantum state and the final affected quantum states are studied by calculating the fidelity of the states. Specifically, amplitude damping, phase damping, phase-flip damping and bit-flip damping noise models are analyzed. From the fidelity graphs, it is inferred that by using a certain set of entangling operators, the noise can be suppressed in the quantum network. In particular, amplitude damping can be completely eliminated, though phase damping cannot be suppressed by any particular entangling operators. On the other hand, the phase-flip damping and bit-flip damping cause the entanglement sudden death in the quantum state. Thus, existence of suitable entangling operator is indicated to control the noise in the quantum networks. | Noise controlling entangling operators in the quantum network implementation of cop and robber game | 10.1007/s11128-022-03529-2 |
2022-05-16 | With the broader use of ferrofluid in industry and the sciences, ferrofluid research has produced many new branches. To obtain systematic analytical results and to help researchers gain insight into the dynamics of ferrofluid research, in this review, we first track and summarize the ferrofluid research over the past 15 years to assay how ferrofluid can contribute to modern technology. We have got several important research directions (basic physics research, medical applications, and engineering applications) using keywords as an entry point by visualizing the cluster analysis. Visualization to highlight important schools and organizations. By analyzing the number of papers and citations at a given institution, we obtained a list of influential institutions and schools and indicated the current research directions of these institutions. This list greatly helps researchers to understand the authoritative papers as well as the latest results. In particular, we draw connections between publication year and novel engineering applications and show how they impact future development—the increasing use of ferrofluids in microfluidic environments and the increasing study of their soft and reshapable properties. Next, we focus on ferrofluid applications in six engineering fields and summarize the development history and research status. Finally, by analyzing the current status of each application, we summarize two challenges, that is to strengthen the research on the micromechanism of ferrofluid and to prepare a ferrofluid with better performance. The originality of this study is that it uses visualization to describe the current state of research and development patterns instead of thousands of papers, providing valuable reference information for existing researchers and practitioners. | Systematic analysis of ferrofluid: a visualization review, advances engineering applications, and challenges | 10.1007/s11051-022-05477-5 |
2022-05-10 | In a Hilbert space setting, this paper is devoted to the study of a class of first-order algorithms which aim to solve structured monotone equations involving the sum of potential and nonpotential operators. Precisely, we are looking for the zeros of an operator $$A= \nabla f +B $$ A = ∇ f + B , where $$\nabla f$$ ∇ f is the gradient of a differentiable convex function f , and B is a nonpotential monotone and cocoercive operator. This study is based on the inertial autonomous dynamic previously studied by the authors, which involves dampings controlled respectively by the Hessian of f , and by a Newton-type correction term attached to B . These geometric dampings attenuate the oscillations which occur with the inertial methods with viscous damping. Temporal discretization of this dynamic provides fully splitted proximal-gradient algorithms. Their convergence properties are proven using Lyapunov analysis. These results open the door to the design of first-order accelerated algorithms in numerical optimization taking into account the specific properties of potential and nonpotential terms. | Newton-Type Inertial Algorithms for Solving Monotone Equations Governed by Sums of Potential and Nonpotential Operators | 10.1007/s00245-022-09846-3 |
2022-05-09 | The ball screw feed system (BSFS) is an important component of numerical control machine tools. The dynamic characteristics of BSFSs directly affect the machining precision and efficiency of machine tools. Due to the external excitation, the feed system can generate large vibrations, which can further decrease the precision of machine tools. This paper designs multiple tuned mass dampers (MTMDs) for the BSFS to reduce the vibration and proposes a dynamical model of a BSFS with MTMDs. The optimization objective is to minimize the maximum amplitudes of the lateral direction direct frequency—response function of the work table at different nut locations. The particle swarm optimization algorithm is used to optimize the stiffness and damping parameters to reach the optimal vibration reduction effect. Furthermore, the MTMDs are adjusted quantitatively to match the optimized dynamic parameters of dampers. By comparing the experimental modal results with and without the damper and the vibration signals during the reciprocating cycle operation, the effect of the damper on controlling system vibrations is verified. The results indicate that the proposed lateral vibration control method for the BSFS can effectively reduce the lateral vibration of the work table in the whole stroke. | Lateral vibration control of ball screw feed system considering the nut location | 10.1007/s40430-022-03533-8 |
2022-05-07 | The vibrations produced while machining components is annoying and yields discomfort to the operators. Also, if the vibrations are not damped properly, it reduces the machining performance and produces chatter. Magneto-rheological (MR) fluid is highly employed nowadays in dampers due to its ability of changing its viscosity that enhances damping. In this present work, a magneto-rheological fluid-assisted smart worktable is designed and fabricated to damp the vibrations produced during the drilling process. The worktable is designed in such a way that it can damp the vibrations whenever necessary just by keeping the electromagnet in ON/OFF state, which is almost suitable to use for all machine tools. Finite element method magnetics is used to determine the distribution of magnetic flux density on the worktable numerically for optimizing the electromagnet design in MR fluid-assisted worktable. The vibrations that are produced during drilling operations are acquired through an accelerometer connected to a data acquisition system (DAQ). The experiments are carried based on factorial design of experiments for three factors such as diameter of drill, speed of drill and MR effect at two different levels. The acquired vibration signals are filtered and analyzed in frequency domain and are proved to damp the vibrations efficiently when MR fluid effect is ON state. The recorded vibration signals are filtered and evaluated in the frequency domain, and it is demonstrated that when the MR fluid effect is ON, it effectively dampens vibrations by 71% to 98%. Thus, the new innovative MR fluid-assisted worktable proves to damp the vibrations produced on workpiece during all kind of machining operations. | Vibration Damping Analysis for Drilling Process Using MR Fluid-Assisted Worktable | 10.1007/s40033-022-00354-w |
2022-05-06 | In this paper, we are interested in the $$L^1-L^1$$ L 1 - L 1 estimate for the energy, the elastic energy $$\Vert |D|^\sigma u(t,\cdot )\Vert _{L^1}$$ ‖ | D | σ u ( t , · ) ‖ L 1 and the kinetic energy $$\Vert u_t(t,\cdot )\Vert _{L^1}$$ ‖ u t ( t , · ) ‖ L 1 to the Cauchy problems for a class of special time-dependent structurally damped $$\sigma $$ σ -evolution models: 0.1 $$\begin{aligned} \left\{ \begin{array}{lll} u_{tt}+(-\Delta )^\sigma u+b(t)(-\Delta )^{\sigma /2} u_t=0,\quad (t,x)\in (0,\infty )\times {\mathbb {R}}^n,\\ u(0,x)=:u_0(x),\quad u_t(0,x)=:u_{1}(x),\quad \sigma >1,\quad x\in {\mathbb {R}}^n, \end{array} \right. \end{aligned}$$ u tt + ( - Δ ) σ u + b ( t ) ( - Δ ) σ / 2 u t = 0 , ( t , x ) ∈ ( 0 , ∞ ) × R n , u ( 0 , x ) = : u 0 ( x ) , u t ( 0 , x ) = : u 1 ( x ) , σ > 1 , x ∈ R n , where $$b=b(t)$$ b = b ( t ) is a positive decreasing function. We will study the decay rate of the energies for solution to the Cauchy problem for structural damped $$\sigma $$ σ -evolution models with time-dependent structurally dissipations $$b(t)(-\Delta )^\delta u_t$$ b ( t ) ( - Δ ) δ u t . These estimates rely on more structural properties of representations of solutions. We divide our considerations in to b ( t ) is strictly decreasing, that is, $$b'(t)<0$$ b ′ ( t ) < 0 for $$t>0$$ t > 0 . By the explicit representation of the solution to the model ( 0.1 ) which allows to the radial symmetric, and to apply the theory of modified Bessel functions. Thanks to these two effects, we are able to obtain $$L^1-L^1$$ L 1 - L 1 estimate for the energy of solution structurally $$\sigma $$ σ -evolution problems. The main goal is to derive $$L^p-L^q$$ L p - L q estimates not necessarily on the conjugate line for the elastic and kinetic energy of the solution to ( 0.1 ) in the following sense: $$\begin{aligned} \Vert \partial _t^j|D|^{(1+(-1)^j)\sigma } u(t,\cdot )\Vert _{L^p}\lesssim C_0^j(t)\Vert u_0\Vert _{L^q}+C_1^j(t)\Vert u_1\Vert _{L^q}, \end{aligned}$$ ‖ ∂ t j | D | ( 1 + ( - 1 ) j ) σ u ( t , · ) ‖ L p ≲ C 0 j ( t ) ‖ u 0 ‖ L q + C 1 j ( t ) ‖ u 1 ‖ L q , for $$1+\frac{1}{r}=\frac{1}{p}+\frac{1}{q},\quad j=0,1$$ 1 + 1 r = 1 p + 1 q , j = 0 , 1 . We are interested in explaining the behavior of the functions $$C_0^j(t)$$ C 0 j ( t ) and $$C_1^j(t)$$ C 1 j ( t ) for $$ j=0,1,\,\,t\rightarrow 0^+$$ j = 0 , 1 , t → 0 + and $$t\rightarrow \infty $$ t → ∞ . |
$$L^1-L^1$$
L
1
-
L
1
Estimate for the Energy to Structurally Damped
$$\sigma $$
σ
-Evolution Models with Time Dependent | 10.1007/s00009-022-02044-z |
2022-05-05 | We consider in this article the weakly coupled system of wave equations in the scale-invariant case and with time-derivative nonlinearities. Under the assumption of small initial data, we obtain a better characterization of the delimitation of the blow-up region by deriving a new candidate for the critical curve. More precisely, we enhance the results obtained in Palmieri and Tu (Calc Var 60:72, 2021, https://doi.org/10.1007/s00526-021-01948-0 ) for the system under consideration in the present work. We believe that our result is optimal in the sense that beyond the blow-up region obtained here we may conjecture the global existence of small data solutions. | Improvement on the Blow-Up for the Weakly Coupled Wave Equations with Scale-Invariant Damping and Time Derivative Nonlinearity | 10.1007/s00009-022-02062-x |
2022-05-02 | Possibility of using non-maximally entangled states in quantum bidirectional direct communication has been shown recently by Srikanth A and Balakrishnan (Quantum Inf. Process. 19:133, 2020) [1]. The effect of noise in this protocol is analyzed by considering amplitude and phase damping models. Suitable combinations of messages and initial states are identified to minimize the effect of noise in the protocol. Further, we have shown the possibility of demarking the effects due to noise and the intruder. | Effect of Noise in the Quantum Bidirectional Direct Communication Protocol Using Non- maximally Entangled States | 10.1007/s10773-022-05115-9 |
2022-05-01 | This paper provides a practical method for estimating structural mechanical damping in sub-synchronous torsional interaction (SSTI) analysis with limited information on the generators. The risk of SSTI is generally assessed by comparing the damping of the turbine generator with that of the electrical system on a problematic mode in the frequency domain followed by time domain simulation studies to confirm the occurrence of the torsional interaction. Unfortunately, mechanical damping is often neglected in the SSTI studies simply because the structural mechanical damping data for the turbine generator is unavailable. Only modal damping ratio is provided in practice, and study results with incorrect mechanical damping should be misleading. This paper thus presents a method to accurately estimate the structural mechanical damping of the multi-mass model based on Rayleigh and Caughey damping models. Comprehensive studies in both frequency and time domain using PSCAD/EMTDC demonstrate the accuracy and efficacy of the proposed estimation method. Theoretical aspects and applicability of two damping models for the SSTI analysis are also discussed. | Estimation of Structural Mechanical Damping in Multi-mass of Turbine Generator for SSTI Study | 10.1007/s42835-022-01045-y |
2022-05-01 | Using some related concepts as well as the method of uniform estimations, we study the existence of pullback $$\mathcal {D}$$ D -attractors for the non-autonomous three-dimensional Boussinesq equations with damping in the periodic domain when $$3<\beta <5$$ 3 < β < 5 . | Pullback
$$\mathcal {D}$$
D
-Attractors of the 3D Boussinesq Equations with Damping | 10.1007/s40840-022-01253-9 |
2022-05-01 | Damping in vibrating structures is much less understood than their stiffness and inertial properties and in timber structures it is even less understood how damping is generated in motion characteristic of bending and shear separately. We analyse these contributions through application of the so-called method of complex moduli, arising in constant-hysteretic models of damping. We separate the influences on overall damping due to these independent material properties by considering a partial differential equation of undamped motion and substituting Young’s and shear moduli with their complex counterparts. We keep the rotary inertia present in the model to assess its own damping contribution and design an experimental setup in which vibration of a free-free beam is simulated so that no reaction (i.e., no contact damping) should be present, which allows us to assess the contribution due to bending, shear and rotary inertia to material damping only. We show that, in the present model, the overall loss factor is indeed smaller than in the literature, while the damping due to shear effects grows in higher vibration modes and beams with smaller length-to-height ratio. Finally, we propose a damping prediction model built on simple linear regression in which the vibration modes are processed separately. | Material Damping Prediction in Timber Beams Based on Timoshenko Free-Free Beam Model | 10.1007/s12205-022-1010-8 |
2022-05-01 | A fractionally damped vibration energy harvester excited by the wide-band random noise is investigated theoretically in this paper. Firstly, by introducing the generalized harmonic transformation, an equivalent uncoupled system only with respect to the mechanical states is established, while the external circuit and the fractional derivative damping are decoupled into damping and stiffness with amplitude-dependent coefficients, respectively. Then, a stochastic averaging operator technique is carried out to derive the stationary distribution of the mechanical states and furtherly obtain the mean square electric voltage (MSEV) and mean output power (MOP) of the energy harvester theoretically. Finally, the relationships between the fractional derivative and the MSEV and MOP are explored in detail to help improve the performance of the energy harvester. | Stochastic analysis of a nonlinear energy harvester with fractional derivative damping | 10.1007/s11071-022-07338-1 |
2022-05-01 | Large MR (MR) dampers are popular due to their higher damping force capabilities which makes them suitable in the field of civil engineering, structural engineering, suspension bridge structure, mining engineering, and agricultural engineering applications. This paper presents a comprehensive review of large MR dampers. The classifications and applications of large MR dampers, the principle of operation, different fluid models, their structural design and control systems are classified and reviewed in this paper. The large MR dampers have higher damping force controllability than conventional MR dampers. The review indicates that the large MR dampers have enough vibration mitigation ability and higher damping performances. | State-of-the-art recent developments of large magnetorheological (MR) dampers: a review | 10.1007/s13367-022-00021-2 |
2022-05-01 | In practical rock engineering, Universal Distinct Element Code (UDEC) is one of the most widely used two-dimensional software packages for simulating discontinuum behaviors of rocks and rockmasses. Over the years, this software has been used to study phenomena, such as grain-scale fracturing in laboratory specimens, spalling around tunnels and roadways, shearing and separation along discontinuities in jointed rockmasses, etc. One of the lesser discussed topics in context of explicit time-stepping discontinuum modeling in UDEC is the damping mode employed for such simulations. For static analysis, the ‘local’ (default) and ‘combined’ damping modes are generally used, but their effects on the emergent model response as well as their suitability to a particular problem are not well documented in the literature. To help bridge this gap, this study contrasts the responses of a laboratory-scale model, a hypothetical granite pillar model and a hypothetical coal mine entry model with ‘Local’ and ‘Combined’ damping modes. It was found that in small-scale simulations, the results using ‘Local’ and ‘Combined’ damping modes were similar, but the differences were significant in the field-scale models. In particular, ‘Local’ damping mode tended to suppress large deformations, predicted high pillar strengths and increased model run-time significantly. Although it is difficult to definitively establish which of the two damping mode leads to more realistic excavation-scale behavior in a given scenario, the authors suggest the use of ‘Combined’ damping for models of individual excavations where large deformations and block separations are expected. | Effect of Damping Mode in Laboratory and Field-Scale Universal Distinct Element Code (UDEC) Models | 10.1007/s00603-021-02609-6 |
2022-05-01 | In a Hilbert space setting, for convex optimization, we analyze the convergence rate of a class of first-order algorithms involving inertial features. They can be interpreted as discrete time versions of inertial dynamics involving both viscous and Hessian-driven dampings. The geometrical damping driven by the Hessian intervenes in the dynamics in the form $$\nabla ^2 f (x(t)) \dot{x} (t)$$ ∇ 2 f ( x ( t ) ) x ˙ ( t ) . By treating this term as the time derivative of $$ \nabla f (x (t)) $$ ∇ f ( x ( t ) ) , this gives, in discretized form, first-order algorithms in time and space. In addition to the convergence properties attached to Nesterov-type accelerated gradient methods, the algorithms thus obtained are new and show a rapid convergence towards zero of the gradients. On the basis of a regularization technique using the Moreau envelope, we extend these methods to non-smooth convex functions with extended real values. The introduction of time scale factors makes it possible to further accelerate these algorithms. We also report numerical results on structured problems to support our theoretical findings. | First-order optimization algorithms via inertial systems with Hessian driven damping | 10.1007/s10107-020-01591-1 |
2022-05-01 | Freeze–thaw cycles, aging, and freeze–thaw cycles superimposed aging test on high-damping rubber bearings (HDR) were performed to study the durability of HDR for sea-crossing bridges in northern coastal areas. The change laws of horizontal mechanical properties of HDR under different tests were revealed. After freeze–thaw cycles, the equivalent damping ratio and yield force of HDR decreased, the post-yield stiffness increased slightly, but the horizontal equivalent stiffness wasn’t change; The ultimate shear force and displacement of HDR abated. Under aging test, horizontal equivalent stiffness and post-yield stiffness increased significantly, and the change of its yield force could be ignored, while the equivalent damping ratio decreased. The horizontal equivalent stiffness and post-yield stiffness of HDR increased; however, the equivalent damping ratio and yield force decreased after the freeze–thaw cycles superimposed aging test. Besides, experimental results indicated considering freeze–thaw cycles or aging alone cannot accurately estimate the change of HDR’s performances in the actual environment. This study is likely to provide a whole life cycle design and evaluation basis for coastal seismically isolated bridges with HDR in the cold regions of northern China. | Influence of freeze–thaw cycles and aging on the horizontal mechanical properties of high damping rubber bearings | 10.1007/s42464-022-00154-7 |
2022-05-01 | A novel numerical methodology is presented to solve the dynamic response of railway bridges under the passage of running trains, considering soil–structure interaction. It is advantageous compared to alternative approaches because it permits, (i) consideration of complex geometries for the bridge and foundations, (ii) simulation of stratified soils, and, (iii) solving the train-bridge dynamic problem at minimal computational cost. The approach uses sub-structuring to split the problem into two coupled interaction problems: the soil–foundation, and the soil–foundation–bridge systems. In the former, the foundation and surrounding soil are discretized with Finite Elements (FE), and padded with Perfectly Match Layers to avoid boundary reflections. Considering this domain, the equivalent frequency dependent dynamic stiffness and damping characteristics of the soil–foundation system are computed. For the second sub-system, the dynamic response of the structure under railway traffic is computed using a FE model with spring and dashpot elements at the support locations, which have the equivalent properties determined using the first sub-system. This soil–foundation–bridge model is solved using complex modal superposition, considering the equivalent dynamic stiffness and damping of the soil–foundation corresponding to each natural frequency. The proposed approach is then validated using both experimental measurements and an alternative Finite Element–Boundary Element (FE–BE) methodology. A strong match is found and the results discussed. | Fast simulation of railway bridge dynamics accounting for soil–structure interaction | 10.1007/s10518-021-01191-0 |
2022-05-01 | Asymmetric damping forces induce the equilibrium position of the isolated body to shift downward. Inspired by this phenomenon, this paper proposes the novel concept of shifting an isolated body based on the vibration of nonlinear systems with asymmetric damping forces. To verify the feasibility of this concept, a piecewise smooth isolation system is established. The incremental harmonic balance method is used to analyze the nonlinear vibration system and to obtain a steady-state analytical solution. The accuracy of the solution is verified by the Runge–Kutta method. Based on the analytical solution, the influences of some key parameters on the system vibration response are analyzed, revealing that the shift in the isolated body height increases with increasing excitation amplitude and damping asymmetry ratio. Additionally, this shift first increases and then decreases with increasing excitation frequency, reaching a peak near the natural frequency of the intermediate body. Finally, considering the complex structure, high energy consumption, and slow response of active suspension actuators, the proposed concept is applied to the tilt control of a vehicle. The simulation results show that the proposed methodology based on this concept can tilt a vehicle body to a certain angle in the turning direction, enabling the use of a semi-active actuator for vehicle tilt control to realize the control effect achieved by an active actuator. | Controlling the vertical shift of an isolated body based on the vibration of nonlinear systems with asymmetric damping forces | 10.1007/s11012-022-01496-7 |
2022-05-01 | This paper is focused on investigating the bifurcation and vibration resonance problems of fractional double-damping Duffing time delay system driven by external excitation signal with two wildly different frequencies $$\omega $$ ω and $$\Omega $$ Ω . Firstly, the approximate expressions of the critical bifurcation point and response amplitude Q at low-frequency $$\omega $$ ω are obtained by means of the direct separation of the slow and fast motions. And then corresponding numerical simulation is made to show that it is a good agreement with the theoretical analysis. Next, the influence of system parameters, including internal damping order $$\alpha $$ α , external damping order $$\lambda $$ λ , high-frequency amplitude F , and time delay size $$\tau $$ τ , on the vibration resonance is discussed. Some significant results are obtained. If the fractional orders $$\alpha $$ α and $$\lambda $$ λ are treated as a control parameter, then $$\alpha $$ α and $$\lambda $$ λ can induce vibration resonance of the system in three different types when the response amplitude Q changes with the high-frequency amplitude F . If the high-frequency amplitude F is treated as a control parameter, then F can induce vibration resonance of the system as well at some particular points. If the time delay $$\tau $$ τ is treated as a control parameter, not only can $$\tau $$ τ induce three types of vibration resonance, but the response amplitude Q views periodically with $$\tau $$ τ . In addition, the resonance behaviors of the considered system are more abundant than those in other similar systems since the internal damping order $$\alpha $$ α , external damping order $$\lambda $$ λ , time delay $$\tau $$ τ and cubic term coefficient $$\beta $$ β are introduced into the system which changes the shapes of the effective potential function. | Bifurcation and vibration resonance in the time delay Duffing system with fractional internal and external damping | 10.1007/s11012-022-01483-y |
2022-05-01 | Shock absorption layer is an effective measure to decrease damage of tunnels under earthquake. According to previous work, the smaller stiffness of damping material, the better damping effect of the tunnel. In order to meet the actual engineering requirements, the shock absorption layer is applied to the upper part of tunnels (not including the invert), which is called a local shock absorption layer. This study is to analyze the damping effect of different types of local shock absorption layers based on the dynamic nonlinear time-history numerical analysis. Six real ground motions with different dominant frequencies are selected, their peak ground accelerations (PGA) are set to 0.2 g, 0.4 g, 0.6 g, and 0.8 g, respectively. The damage index and total dissipated energy of secondary lining, and equivalent plastic strain of surrounding rock are used as indicators to reflect the damping performance of the local shock absorption layer. Numerical results highlight that the damping performance with double local shock absorption layer is the best, and the damping performance of shock absorption layer under large earthquake is better than that under small earthquake. | Study on Seismic Response and Damping Performance of Tunnels with Double Shock Absorption Layer | 10.1007/s12205-022-1862-y |
2022-05-01 | In this paper, a MEMS-based biosensor composed of coupled microresonators is proposed for digital microfluidics applications. This sensor consists of three parts including electrostatic comb-drive actuators, capacitive sensing, and active area located in the center of the structure. All applied resonators are in the same sizes which are connected with springs. The active area vibrates azimuthally utilizing in-phase electrostatic actuators on three sides. The manipulated droplet, encapsulating bio-particles, is driven to the immobilized active zone and makes the vibration frequency change. Due to in-plane vibration of the proposed structure, the viscous damping has less effect on the quality factor of the sensor. The total system is simulated by finite element methods and the results demonstrate that the desired vibration frequency for in-plane motion of the sensor is 18.37 kHz and the quality factor and mass sensitivity are 58 and 78 Hz/µg, respectively, which is comparable to sensors with similar applications. | Design and analysis of a new MEMS biosensor based on coupled mechanical resonators for microfluidics applications | 10.1007/s10470-021-01963-3 |
2022-05-01 | To solve the problems of low identification accuracy and complex identification methods in the Bouc-Wen model of the magnetorheological (MR) damper, a new parameter identification method using the fireworks algorithm (FWA) is proposed. According to the experimental results of the dynamic characteristics of the MR damper and the simulation data of the Bouc-Wen model, the FWA is used to identify the seven parameters of the Bouc-Wen model. On the basis of the relationship between the identification results and the command current, the current-controlled Bouc-Wen model (I-Bouc-Wen model) is constructed and compared with the experimental results under different sinusoidal excitation frequencies. Compared with the genetic algorithm (GA), differential evolution (DE) algorithm, and particle swarm optimization (PSO) algorithm, the FWA has the advantage of faster convergence, shorter calculation time, and higher stability in solving the parameter identification problem of the highly nonlinear hysteretic model. Under three harmonic excitations, the average calculation accuracies of the I-Bouc-Wen model reache 88.64 %, 90.45 %, and 81.28 %, respectively, and the dynamic characteristic curve of the model is in basic agreement with the experimental results. It can be used for the subsequent controller design and simulation research and lay a foundation for applying the parameterized model of the MR damper in vibration reduction control. | Parameter identification of the Bouc-Wen model for the magnetorheological damper using fireworks algorithm | 10.1007/s12206-022-0405-2 |
2022-05-01 | Uncertainty and disturbance (UAD) always exist and influence negatively on technical systems. Focusing on improving the effectiveness of smart dampers (SDs)-based semi-active train-car suspensions (SD-TCSs), we present the fuzzy-compensator-enhanced fractional-derivative (FD) order sliding control of a class of SD-TCSs subjected to UAD, in which the disturbance time-varying rate (DTVR) may be high but bounded. To reduce uncertainty related to the mathematical model error, we propose a fractional derivative (FD)-based sliding mode controller (FDSMC) for specifying the main control signal. Whereas, to estimate the compensation for external disturbance, first, we utilize the well-known DO to build an initial framework of the compensator. To avoid conflict between the update-laws of the DO and FDSMC, as well as to make the system dynamic response converge stably to the desired state even if the DTVR increasing but bounded, constraints along with a fuzzy-based adjusting mechanism are then discovered. Thus, we obtain an improved DO (imDO), update-laws of the imDO and FDSMC, and their combination model (imDO-FDSMC) of the proposed controller. The survey results reflect the positive capability of the method. | SD-TCSs Control Deriving from Fractional-order Sliding Mode and Fuzzy-compensator | 10.1007/s12555-020-0115-4 |
2022-04-27 | In this paper we consider a transmission problem for the wave equations with past history and acoustic boundary conditions, involving two distinct domains connected through a common interface. The frictional dampings are only distributed in a small neighbourhood of the interface. Under some geometric conditions, we obtain the energy decays at the rate quantified by the solution to a certain nonlinear ODE dependent on the damping terms. Our method is based on using appropriate weighted multipliers to establish the necessary observability inequality that allows to obtain the energy estimate. | Stabilization of a transmission problem with past history and acoustic boundary conditions | 10.1007/s00033-022-01751-7 |
2022-04-27 | Dynamics of ion-acoustic wave (IAW) are observed in a magnetized collisional four-component dusty plasma comprising cold ions, inertialess two-temperature electrons, and immobile negatively charged dust grains. Employing the reductive perturbation technique (RPT), the damped forced modified Zakharov–Kuznetsov (DFMZK) equation is derived and assuming that the conservation principle holds in the system, an approximate analytical solution of the DFMZK equation is obtained; however, the solution is valid for very small values of perturbed damping and forcing term. In that circumstance, using the bifurcation theory of the dynamical system, a qualitative study on ZK medium in the presence of damping and forcing terms has been performed. The significant effects from small damping and forcing terms are presented from a numerical standpoint. Further, utilizing the bifurcation diagram the periodic and quasi-periodic orbits of IAW in the DFMZK framework are analyzed. It is found that both the initial condition and the damping term play a significant role in forming complexity in the dynamic system. Finally, the effective role of the strength ( $$f_0$$ f 0 ) of the externally applied force perturbation is studied in detail and the existence of chaotic motion of the DFMZK equation is confirmed through time series analysis and Poincare analysis. | Qualitative studies of the influence of damping and external periodic force on ion-acoustic waves in a magnetized dusty plasma through modified ZK equation | 10.1007/s13538-022-01083-x |
2022-04-27 | The aim of this paper is to investigate the existence of uniform random attractor for a non-autonomous stochastic strongly damped wave equation driven by multiplicative noise defined on $${{\mathbb {R}}}^{N}$$ R N ( $$1\le N\le 3$$ 1 ≤ N ≤ 3 ). First, we prove the equation can generate a non-autonomous random dynamical system (NRDS), which is continuous in both phase space $$H^1({\mathbb {R}}^{N})\times L^2({\mathbb {R}}^{N})$$ H 1 ( R N ) × L 2 ( R N ) and symbol space. Then, we derive the uniform estimates of solutions for the equation and obtain a uniform random absorbing set with respect to the symbols. Finally, we get the uniformly asymptotic compactness of the NRDS by using the method of tail estimates and obtain the existence of a uniform random attractor for the dynamical system. Furthermore, we can also obtain that the uniform random attractor with respect to the deterministic non-autonomous symbols belonging to hull space coincides with the uniform random attractor with respect to initial time belonging to $${\mathbb {R}}$$ R . | Uniform random attractors for a non-autonomous stochastic strongly damped wave equation on
$${{\mathbb {R}}}^{{\mathbb {N}}}$$
R
N
$$^{\dag }$$
†
| 10.1007/s00033-022-01719-7 |
2022-04-27 | We examine how amplitude noise in queries to the oracle degrades a performance of quantum search algorithm. The Grover search and similar techniques are widely used in various quantum algorithms, including cases where rival parties are fighting over confidential data. Hence, the oracle-box wires become the subject of competing activity with an alteration of their normal functioning. Of course, many kinds of errors could arise in this way. Possible influence of dephasing on quantum search was already addressed in the literature. Amplitude damping is another type of errors that should be analyzed first. To study the problem, we introduce a simple model of collective distortions with the use of amplitude damping channel. All the quantities of interest should be considered as functions of the number of Grover’s iterations. In particular, we investigate the success probability with respect to the parameter that characterizes the level of amplitude errors. The success probability degrades significantly even if the error amount is not essential. Namely, this probability soon enough reduces to a value close to one half. We also study trade-off relations between quantum coherence and the success probability in the presence of amplitude noise. | Quantum search degeneration under amplitude noise in queries to the oracle | 10.1007/s11128-022-03501-0 |
2022-04-19 | In the framework of a real Hilbert space, we address the problem of finding the zeros of the sum of a maximally monotone operator A and a cocoercive operator B . We study the asymptotic behaviour of the trajectories generated by a second order equation with vanishing damping, attached to this problem, and governed by a time-dependent forward–backward-type operator. This is a splitting system, as it only requires forward evaluations of B and backward evaluations of A . A proper tuning of the system parameters ensures the weak convergence of the trajectories to the set of zeros of $$A + B$$ A + B , as well as fast convergence of the velocities towards zero. A particular case of our system allows to derive fast convergence rates for the problem of minimizing the sum of a proper, convex and lower semicontinuous function and a smooth and convex function with Lipschitz continuous gradient. We illustrate the theoretical outcomes by numerical experiments. | Second Order Splitting Dynamics with Vanishing Damping for Additively Structured Monotone Inclusions | 10.1007/s10884-022-10160-3 |
2022-04-12 | The performance of a wide area damping controller (WADC) can be affected considerably if a photovoltaic (PV) power plant is integrated with the power system. A WADC using state feedback control law is proposed in this paper to eliminate the frequency oscillation of interconnected power system integrated with solar PV cell. Output power of the solar PV cell varies with irradiation. This variation in power degrades the performance of the WADC. Communication delay, which is always present in case of wide area measurement system (WAMS) also has a detrimental effect on the effectiveness of WADC. Another non-linear phenomenon which is always present in the WADC is the saturation of the actuator which reduces the effectiveness of the controller. The damping controller developed in this paper contemplates the effect of saturation of the actuator, time varying delay and changing operating condition using linear matrix inequality (LMI) criterion. The changing operating conditions are considered using a linear parameter varying (LPV) modelling of the system. After developing the LPV model of the system, the model is converted into a tensor product (TP) model. A supplementary damping controller (SDC) is considered in this paper as the WADC. The actuator of the damping controller is a thyristor controlled series capacitor (TCSC). A modified two area 11-bus power system with PV power plant and modified IEEE 39-bus power system with PV power plant is used as a test system to understand the usefulness of the designed controller. | Delay dependent wide area damping controller design for a linear parameter varying (LPV) power system model considering actuator saturation and changing environmental condition | 10.1007/s12046-022-01831-4 |
2022-04-08 | Modified negative stiffness amplifying damper (MNSAD) is a novel vibration control device expected to consist of a negative stiffness spring with flexible cladding material. In this system, a dashpot is used in conjunction with the negative stiffness spring, and the damping magnification effect is greatly enhanced by amplifying the stoke of the dashpot. The negative stiffness property is preserved, and the MNSAD takes into account significant damping magnification effects. In this study, displacement and acceleration responses of SDOF systems under air blast load equipped with an MNSAD are investigated, which takes stochastic responses into account. Next, the optimum designed parameters yield three key parameters: stiffness ratio, damping ratio, and negative stiffness ratio. Following that, the SDOF system's responses to air blast load are calculated. It was observed that a significant damping effect is achieved by adding small damping (i.e., 2.8%) to the SDOF system with the proposed MNSAD. It was also discovered that replacing NSAD with MNSAD increases the long period structure's energy dissipation capacity from 16 to 28%. | Rehabilitation of SDOF systems under air blast loading with a modified negative stiffness amplifying damper | 10.1007/s41024-022-00178-x |
2022-04-06 | We consider an elastic/viscoelastic problem for the Bresse system with fully Dirichlet or Dirichlet–Neumann–Neumann boundary conditions. The physical model consists of three wave equations coupled in certain pattern. The system is damped directly or indirectly by global or local Kelvin–Voigt damping. Actually, the number of the dampings, their nature of distribution (locally or globally) and the smoothness of the damping coefficient at the interface play a crucial role in the type of the stabilization of the corresponding semigroup. Indeed, using frequency domain approach combined with multiplier techniques and the construction of a new multiplier function, we establish different types of energy decay rate (see the table of stability results at the end). Our results generalize and improve many earlier ones in the literature (see El Arwadi and Youssef, in: On the stabilization of the Bresse beam with Kelvin–Voigt damping, Applied Mathematics and Optimization, pp. 1–27, 2019) and in particular some studies done on the Timoshenko system with Kelvin–Voigt damping (see for instance Ghader and Wehbe in A transmission problem for the Timoshenko system with one local Kelvin–Voigt damping and non-smooth coefficient at the interface, 2020. arXiv:2005.12756 ; Tian and Zhang in Z Angew Math Phys 68:20, 2017; Zhao et al. Acta Math Sin Engl Ser 21:655–666, 2005). | Polynomial stabilization of non-smooth direct/indirect elastic/viscoelastic damping problem involving Bresse system | 10.1007/s00033-022-01728-6 |
2022-04-05 | Cement stabilization is one of the chemical stabilization techniques carried out to improve sabkha soil engineering properties. Cement can be mixed with sabkha at natural water content. However, there is a lack of information concerning the dynamic properties of cemented sabkha. Therefore, this study’s primary purpose is to determine the dynamic properties of cemented sabkha, at cement content of 5% and 10%, which satisfied static requirements and compare it with untreated sabkha in literature. The tests were carried out using the cyclic triaxial test at several effective stresses and cyclic stress ratios (CSR). The averages of shear modulus of cemented sabkha of 5% cement are 38, 32, and 21 MPa for cyclic stress ratio of 0.15, 0.35, and 0.65, respectively; they are 85, 45, and 43 MPa for 10% cement. Furthermore, the averages of damping of 5% cement are 0.03, 0.016, and 0.014 for CSR of 0.15, 0.35, and 0.65, respectively; they are 0.027, 0.012, and 0.01 for 10% cement. The results indicate that the increasing cement content to sabkha from 5 to 10% decreases the shear strain ratio by 0.05, 0.04, and 0.22 for CSR of 0.15, 0.35, and 0.65, respectively. For CSR of 0.15, the change in cement content from 5 to 10% leads to increased shear modulus by 1.4 to 3 times of shear modulus of untreated sabkha; the shear modulus ratio of cemented sabkha to shear modulus to sabkha increases with the increasing number of cycles. The cement content of 5 and 10% leads to a decrease in the normalized damping ratio of cemented sabkha to damping ratio of sabkha with a range from 0.55 to 0.85. | Cyclic behavior of cement-stabilized sabkha soil | 10.1007/s12517-022-09968-6 |
2022-04-02 | This study presents an observer-based anti-windup robust proportional–integral–derivative controller with state estimator method for damped outrigger structure using magneto-rheological damper to mitigate the seismic response. In this approach, full-order Kalman observer is designed for estimating the states of the damped outrigger system from the feedback of the system output with optimum observer gain. However, due to the computational complexity, the integral windup is observed in the loop; therefore, integral anti-windup is introduced for the internal stability in the loop to produce the desired output. The semi-active magneto-rheological damper is integrated with the proposed system, to produce the required force by the system that ranges between the maximum and minimum values as regulated by the voltages produced by the controller in action for every instant of the seismic energy. The proposed strategy is designed in MATLAB and Simulink to find the adequacy of the damped outrigger system in terms of mitigating the following seismic responses like displacement, velocity, and acceleration. The dynamic analysis of the damped outrigger structure with the proposed control strategy shows enhanced performance in reducing the response of the structure as observed in peak response values. The evaluation criteria show a significant reduction in the vibration of the structure. | Observer-based anti-windup robust PID controller for performance enhancement of damped outrigger structure | 10.1007/s41062-022-00798-9 |
2022-04-01 | This article presents a nonlinear displacement based finite elements model to study and analyze the nonlinear dynamic response of flexible double wishbone structural vehicle suspension system considering damping effect which was not previously discussed elsewhere. Due to large deflection and moderate rotation encountered during passing over road bumps, the kinematic nonlinearity is included through von Kármán strain component. Elastic undamped as well as viscous and viscoelastic damping mechanism are considered and compared. Considering the viscoelastic damping mechanism, the viscoelastic damping mechanism is modeled based on the integral constitutive form, which is recast into an incremental form suitable for finite element implementation. Additionally, the revolute joint element is adopted to incorporate the joint flexibility in the double wishbone system. The plane frame element is adopted to model the suspension links by using Timoshenko beam theory. The developed nonlinear finite element equations of motion are solved through the incremental iterative Newmark technique. The developed procedure is verified by comparing the obtained results with analytical solution and excellent agreement is observed. The applicability of the developed procedure is demonstrated by conducting parametric studies to show the effects of the road irregularities profiles, the vehicle speed, and the material damping coefficients on the nonlinear vibrations response of the double wishbone suspension systems. The obtained results are supportive in the design and manufacturing processes of these structural systems. | Nonlinear dynamics of viscoelastic flexible structural systems by finite element method | 10.1007/s00366-020-01141-5 |
2022-04-01 | Abstract For quantitative estimation of the spectral sensitivity of matrix photodetectors, a method based on Fourier transforms for a more detailed parsing of characteristics in frequency and time domains by the value of the bandwidth index, shape of the impulse (time) response curve, vibration degree, value of damping factor, and energy losses is proposed. A strong influence of electron-phonon interaction in the semiconductor on noise generation in matrix photodetectors relative to the human eye is found. | Comparative Analysis of the Spectral Sensitivity of Three-Color Matrix Photodetectors | 10.3103/S8756699022020121 |
2022-04-01 | We study existence, uniqueness, continuous dependence, general decay of solutions of an initial boundary value problem for a viscoelastic wave equation with strong damping and nonlinear memory term. At first, we state and prove a theorem involving local existence and uniqueness of a weak solution. Next, we establish a sufficient condition to get an estimate of the continuous dependence of the solution with respect to the kernel function and the nonlinear terms. Finally, under suitable conditions to obtain the global solution, we prove the general decay property with positive initial energy for this global solution. | Continuous dependence and general decay of solutions for a wave equation with a nonlinear memory term | 10.21136/AM.2022.0200-21 |
2022-04-01 | Background Flexible aerospace structures present dynamic characteristics of low natural frequency. For a long-term free-floating spacecraft, theses flexible aerospace structures are prone to vibrate due to various excitation. However, it is extremely difficult to eliminate these low-frequency vibrations. Purpose The main aim of this paper is to verify the damping performance of a novel ferrofluid inertial damper with the optimal stiffness in reducing the low-frequency free vibration of structures. Methods The ferrofluid inertial damper consists of an inertial mass block, ferrofluids, and two magnetic field sources. The inertial mass block is levitated in two layers of ferrofluid absorbed on magnetic field sources. When the main system vibrates, the ferrofluid can generate a very small restoring force and damping force between the inertial mass block and the main system. A series of simulations and experiments are used to optimize the restoring force. Furthermore, the influence of the ferrofluid mass on the restoring force is studied. The damping performance is verified by the free oscillation of a flexible copper plate. Results Two sets of geometric parameters whose restoring forces meet the requirement of the optimal stiffness are obtained. Compared to the copper plate damped by itself, the oscillation time of the copper plate with the ferrofluid inertial damper can be reduced by 97.73%. Conclusion The inertial mass block has a fast response to external vibrations. The ferrofluid inertial damper has very excellent performance for damping the free oscillations of a copper plate. | Force Optimization and Damping Performance of a Novel Ferrofluid Inertial Damper Based on the Levitation Principle of Ferrofluids | 10.1007/s42417-021-00416-5 |
2022-04-01 | Liquid containing tanks are very common civil engineering systems used chiefly for storage purposes. Very often, the tank is placed atop a primary structure and contains considerable amount of liquid mass, sufficient for designing the tank to function as an inertia-based supplemental damping device for the primary structure under lateral excitation. However, due to low inherent energy dissipation capacity and a high proportion of impulsive liquid mass, the proper utilization of deep tanks as dynamic vibration absorbers (DVAs) has not taken place. It thereby requires special attention and innovative design modifications. In this paper, the characteristics of liquid motion in a laterally excited deep tank are first analyzed to explain its inadequate inherent damping. A state-of-the-art review of existing literature on the special design of deep tanks as DVAs is then carried out. A brief comparative performance study on a deep tank, with and without baffles, and a shallow tank, as well as a cost analysis of a deep liquid-containing tank as a DVA for structures, are presented. It is seen that available deep tanks fitted with flow damping devices have the potential to serve as very effective and economical structural vibration control devices. The means to further enhance the effectiveness of deep tanks is also identified. | Use of Deep Liquid-Containing Tanks as Dynamic Vibration Absorbers for Lateral Vibration Control of Structures: A Review | 10.1007/s40996-021-00679-8 |
2022-04-01 | In this work, we prove the existence of global (in time) small data solutions for wave equations with two dissipative terms and with power nonlinearity $$|u|^p$$ | u | p or nonlinearity of derivative type $$|u_t|^p$$ | u t | p , in any space dimension $$n\geqslant 1$$ n ⩾ 1 , for supercritical powers $$p>{\bar{p}}$$ p > p ¯ . The presence of two dissipative terms strongly influences the nature of the problem, allowing us to derive $$L^r-L^q$$ L r - L q long time decay estimates for the solution in the full range $$1\leqslant r\leqslant q\leqslant \infty $$ 1 ⩽ r ⩽ q ⩽ ∞ . The optimality of the critical exponents is guaranteed by a nonexistence result for subcritical powers $$p<{\bar{p}}$$ p < p ¯ . | Global small data solutions for semilinear waves with two dissipative terms | 10.1007/s10231-021-01128-z |
2022-04-01 | This paper considers the scalable control of power systems, i.e., control with the constraint that controllers of all generators are the same. Imposing this constraint reduces the time and effort required to construct large-scale power systems because we can obtain controllers of all generators merely by designing one controller. Power system control with this constraint has not been discussed in existing studies where controllers of generators have been assumed to be separately designed and implemented. The problem addressed here is to find the same controllers for stabilizing an equilibrium point of the resulting feedback system and improving the performance in terms of the time response. As a solution to this problem, we present controllers to increase the damping forces of generators uniformly. Then, we prove that the equilibrium point of the resulting feedback system is stable under certain conditions. Further, we present a design method of the controller gain to minimize a performance index for evaluating the time response of the resulting feedback system. The proposed controllers and design method are verified via numerical simulation. | Scalable control of power systems | 10.1007/s00202-021-01364-9 |
2022-04-01 | This paper is concerned with the 3D inhomogeneous incompressible Navier-Stokes equations with damping. We find a range of parameters to guarantee the existence of global strong solutions of the Cauchy problem for large initial velocity and external force as well as prove the uniqueness of the strong solutions. This is an extension of the theorem for the existence and uniqueness of the 3D incompressible Navier-Stokes equations with damping to inhomogeneous viscous incompressible fluids. | Global regularity for the 3D inhomogeneous incompressible Navier-Stokes equations with damping | 10.21136/AM.2022.0166-21 |
2022-04-01 | This work extends the sediment-laden mixture model with consideration of the turbulence damping and particle wake effects under the framework of improved efficiency and accuracy. The mixture model consists of the continuity and momentum equations for the sediment-laden mixture, and the continuity equation for the sediment. A theoretical formula is derived for the relative velocity between the water and sediment phases, with consideration of the effects of the pressure gradient, the shear stress and the lift force. A modified expression of the particle wake effect, inducing the local turbulence enhancement around the sediment particle, is employed to improve the turbulent diffusion of the coarse sediment. The k _ m - ε _ m model is proposed to close the mixture turbulence, with the turbulence damping effect due to the high sediment concentration expressed by the density-stratification term without an empirical parameter. The k _ m - ε _ m turbulence model requires smaller computational work and offers better results than an empirical density-stratification turbulence model in high sediment concentration cases. Consequently, with the proposed mixture model, the sediment transport in the open channel under a wide range of sediment sizes and concentrations can be revealed with the results in good agreement with experimental data for the velocity, the sediment concentration and the turbulent kinetic energy. | A general two-phase mixture model for sediment-laden flow in open channel | 10.1007/s42241-022-0023-6 |
2022-04-01 | In this paper, we consider the existence of homoclinic solution for a class of damped vibration problem $$\begin{aligned} \ddot{x}(t)+(q(t)I_{N\times N}+B){\dot{x}}(t)+\left( \frac{1}{2} q(t)B-A(t)\right) x(t)+H_{x}(t,x(t))=f(t). \end{aligned}$$ x ¨ ( t ) + ( q ( t ) I N × N + B ) x ˙ ( t ) + 1 2 q ( t ) B - A ( t ) x ( t ) + H x ( t , x ( t ) ) = f ( t ) . For every $$k\in {\mathbb {N}}$$ k ∈ N , we obtain the 2 kT -periodic solution $$x_{k}$$ x k by a standard minimizing argument. By taking the limit of $$\{x_{k}\}$$ { x k } , we get a solution $$x_{0}$$ x 0 of this problem. We prove that $$x_{0}$$ x 0 satisfies $$x_{0}\rightarrow 0$$ x 0 → 0 and $${\dot{x}}_{0}\rightarrow 0$$ x ˙ 0 → 0 as $$t\rightarrow \pm \infty $$ t → ± ∞ , and therefore $$x_{0}$$ x 0 is a homoclinic solution of the problem. | Existence of Homoclinic Solutions for a Class of Damped Vibration Problems | 10.1007/s12346-022-00584-z |
2022-04-01 | In this paper, we deal with the nonlinear second-order differential equation with damped vibration term involving p -Laplacian operator. Of particular interest is the resolution of an open problem. An interesting outcome from our result is that we can obtain the fast homoclinic solution with general superlinear growth assumption in suitable Sobolev space. To our knowledge, our theorems appear to be the first such result about damped vibration problem with p -Laplacian operator. | On a Damped Vibration Problem Involving p-Laplacian Operator: Fast Homoclinic Orbits | 10.1007/s10255-022-1083-7 |
2022-04-01 | Existing studies primarily focus on stiffness and damping under full-film lubrication or dry contact conditions. However, most lubricated transmission components operate in the mixed lubrication region, indicating that both the asperity contact and film lubrication exist on the rubbing surfaces. Herein, a novel method is proposed to evaluate the time-varying contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions. This method is sufficiently robust for addressing any mixed lubrication state regardless of the severity of the asperity contact. Based on this method, the transient mixed contact stiffness and damping of spiral bevel gears are investigated systematically. The results show a significant difference between the transient mixed contact stiffness and damping and the results from Hertz (dry) contact. In addition, the roughness significantly changes the contact stiffness and damping, indicating the importance of film lubrication and asperity contact. The transient mixed contact stiffness and damping change significantly along the meshing path from an engaging-in to an engaging-out point, and both of them are affected by the applied torque and rotational speed. In addition, the middle contact path is recommended because of its comprehensive high stiffness and damping, which maintained the stability of spiral bevel gear transmission. | Contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions | 10.1007/s40544-020-0479-8 |
2022-04-01 | We study the critical transition problem for a stochastically forced birhythmic vibro-impact (BVI) model with improved memory damping regime (IMDR) effect. This paper then reports a detailed probabilistic description on the random distribution of the oscillator response. Analytical criteria for critical transitions are obtained successively relying on the amplitude probability, the most probable amplitude (MPA), the joint probability, its cross-sectional view, and the contour projection, which can complement each other. Besides, numerical simulations are carried out to check the theoretical evaluation results. Detect the control parameter source inducing the transition between monorhythmicity and birhythmicity, also indicating the tipping interval of stochastic P-bifurcation and the critical evolution of the half-shaped stochastic attractor mode determined by the vibro-impact constraint, which can also be visually displayed by the intermittent behavior of time history responses. The alternation of feedback gains design of IMDR can subvert the utility direction of transitions caused by some control parameters. Shannon entropy measure is added to display a quantitative indication of the reference interval for the parameters triggering bifurcations, so as to lock effectively in the rhythm mode required by engineering application issues. | Transitions in a noisy birhythmic vibro-impact oscillator with improved memory damping regime | 10.1007/s11071-022-07261-5 |
2022-04-01 | Time-history analysis is a versatile tool for studying structural dynamic behaviors. The run-time is, however, considerable. A Step-Enlargement-Based Time-History Analysis Acceleration Technique (SEB THAAT) was proposed in 2008 for structural dynamic problems when the excitation is in a digitized format. Many successful tests were carried out on the technique, and some are in progress. In this paper, for the first time, it is demonstrated, via four seismic examples, that the technique can reduce the analysis run-time, when the damping is non-classical. A general rule is also developed that explains the observations and can anticipate the technique’s performance when applied to analysis of non-classically damped structural dynamics. Accordingly, the performance is well, provided a slight condition on the integration scheme. The achievement is significant, because of reasons, such as the fact that non-classical damping is more realistic than classical damping and that the additional requirement is not very restrictive. | Performance of a Time Integration Acceleration Technique Applied to Seismic Analysis of Non-classically Damped Structural Dynamics | 10.1007/s40996-021-00666-z |
2022-04-01 | In this paper, a novel time-marching procedure is proposed for dynamic analysis. The proposed new technique is fourth-order accurate for undamped models; third-order accurate for numerically damped models; and second-order accurate for physically damped models. The method is very straightforward to implement and to apply, allowing providing higher-order accurate time-domain solutions taking into account basically the same computational effort of standard single-step first- or second-order accurate time-marching procedures. Numerical examples are presented at the end of the paper, illustrating the excellent accuracy of the novel approach. | A straightforward high-order accurate time-marching procedure for dynamic analyses | 10.1007/s00366-020-01129-1 |
2022-04-01 | This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay, silt, and fine sand soils obtained from the Bohai Sea, China. Emphasis is placed on the major factors for predominating the dynamic shear modulus ( G ) and damping ratio ( λ ) in the shear strain amplitude ( γ _ a ) from 10^−5 to 10^−2, involving depth, sedimentary facies types, and water content of marine soils. The empirical equations of the small-strain shear modulus ( G _max) and damping ratio ( λ _min) using a single-variable of depth H are established for the three marine soils. A remarkable finding is that the curves of shear modulus reduction ( G / G _max) and the damping ratio ( λ ) with increasing γ _ a of the three marine soils can be simply determined through a set of explicit expressions with the two variables of depth H and water content W . This finding is validated by independent experimental data from the literature. At the similar depths, the G value of the marine soils of terrestrial facies is the largest, followed by the neritic facies, and the G value of the marine soils of abyssal facies is the smallest. The sedimentary facies types of the marine soils have slight effect on the λ value. Another significant finding is that the shear modulus reduction curves plotted against the γ _ a of the three marine soils at the similar depths are significantly below those of the corresponding terrigenous soils, while the damping curves plotted against γ _ a are just the opposite. The results presented in this paper serve as a worthful reference for the evaluation of seabed seismic site effects in the Bohai Sea due to lack of experimental data. | Dynamic shear modulus and damping ratio characteristics of undisturbed marine soils in the Bohai Sea, China | 10.1007/s11803-022-2093-4 |
2022-04-01 | The simulation of multibody systems with frictional contacts is a fundamental tool for many fields, such as robotics, computer graphics, and mechanics. Hard frictional contacts are particularly troublesome to simulate because they make differential equations stiff, calling for computationally demanding implicit integration schemes. We suggest to tackle this issue by using exponential integrators, a long-standing class of integration schemes (first introduced in the 1960s) that in recent years has enjoyed a resurgence of interest. This scheme can be applied to multibody systems subject to stiff viscoelastic contacts, leading to integration errors similar to implicit Euler, but at much lower computational costs (between 2 to 100 times faster). In our tests with quadruped and biped robots, our method demonstrated a stable behavior with large time steps (10 ms) and stiff contacts ( 10 5 $10^{5}$ N/m). Its excellent properties, especially for fast and coarse simulations, make it a valuable candidate for many applications in robotics, such as simulation, model predictive control, reinforcement learning, and controller design. | Exponential integration for efficient and accurate multibody simulation with stiff viscoelastic contacts | 10.1007/s11044-022-09818-z |
2022-04-01 | In the manufacturing of dies and molds, vibrations may represent serious problems, since the finishing tool used is usually slender (high length/diameter ratio) in order to machine deep cavities with complex geometries, typical of these products. Vibration is an undesirable phenomenon in any machining operation as it can lead to poor surface finish, low material removal rate, and high tool wear rate. Impact dampers have been put into the tools as a method for reducing vibration in machining processes. Damping occurs through energy dissipation and linear momentum exchange during intermittent collisions between the main structure (in this case the milling tool) and a free mass (spheres or cylinders placed within a tool cavity). Although efficient, these types of dampers are highly nonlinear. Thus, the aim of this work is to analyze the effect of different materials and geometries (steel spheres, tungsten spheres and steel cylinders) acting as impact damper elements inside a ball nose end milling tool. To perform this task, a comparison of commercial tool holders and dampened tool holders was done in the milling of a convex D6 steel surface, comparing commercial tool holders with dampened ones. The results showed that the tools with impact dampers generated lower values of roughness in the workpiece (around 30% of the value observed in the conventional steel tool holder for the case of steel cylinders and around 40% for both spheres) and presented lower levels of vibration when compared to the same tool without the impact damper, mainly in the machining of workpiece regions where radial and tangential forces are predominant. The tool which used tungsten spheres as damper elements generated roughness surfaces similar to those obtained with steel spheres, while the tool which used steel cylinders only generated lower roughness in the regions where the axial force component is not predominant, which shows that its performance is highly dependent on the resulting force direction. | An experimental evaluation of particle impact dampers applied on the tool for milling of hardened steel complex surface | 10.1007/s00170-022-08782-4 |
2022-04-01 | A multiple rocking wall-frame (MRWF) system, in which the wall panels are directly connected to the adjacent beams and foundation is presented herein. In the MRWF system, the unbonded post-tensioned (PT) tendons are used to promote the self-centering ability, and O-shaped steel dampers are applied to enhance the energy dissipation capacity and reparability of the structure. First, analytical equations are proposed to determine the behavior of the O-shaped dampers. Then, the MRWF system is numerically evaluated for five different models consisting of rocking walls with varying numbers and arrangements while keeping the total effective width of wall panels constant. The numerical results show that with an increase in the number of wall panels and a decrease in the wall width, the hysteretic behavior of the MRWF system tends to the ideal flag-shaped pattern, resulting in little damage to the beams, insignificant strain in the wall toe, negligible residual drifts and damage index of less than 0.2 under severe earthquakes. In contrast, the conventional model demonstrates extensive damage to the structural elements due to undesirable wall-to-frame interaction, which leads to a damage index of 0.78 and residual drifts of 0.42% under seismic loads. | Numerical study of a multiple post-tensioned rocking wall-frame system for seismic resilient precast concrete buildings | 10.1007/s11803-022-2096-1 |
2022-04-01 | Nonlinear forced response analyses of mechanical systems in the presence of contact interfaces are usually performed in built-in numerical codes on reduced order models (ROM). Most of the cases these derive from complex finite element (FE) models, resulting from the high accuracy the designers require in modeling and meshing the components in commercial FE software. In the technical literature several numerical methods are proposed for the identification of the nonlinear forced response in terms of a kinematic quantity (i.e. displacement, velocity and acceleration) associated either to the master degrees-of-freedom retained in the ROM, or to the slave ones after having expanded the reduced response through the reduction matrix. In fact, the displacement is the quantity usually adopted to monitor the nonlinear response, and to evaluate the effectiveness of a partially loose friction interface in damping vibrations, with respect to a linear case where no friction interfaces exist and no energy dissipation can take place. However, when a ROM is used the engineering quantities directly involved in the mechanical design, i.e. the strains and stresses, cannot be retrieved without a further data processing. Moreover, in the case of a strong nonlinear behavior of the mechanical joints, the distributions of the nonlinear strains and stresses over the structure is likely different than the one obtained as a superposition of linear mode shapes whose definition require a-priori assumptions on the boundary conditions at the contact interface. This means that the mentioned approximation cannot be used to predict the safety margins of a structure working in real (nonlinear) operative conditions. This paper addresses this topic and presents a novel stress recovery algorithm for the identification of the strains and stresses resulting from a nonlinear forced response analysis on a ROM. The algorithm is applied to a bladed disk with friction contacts at the shroud joint, which make the behavior of the blades nonlinear and non-predictable by means of standard linear analyses in commercial FE software. | Stress recovery algorithm for reduced order models of mechanical systems in nonlinear dynamic operative conditions | 10.1007/s11071-022-07241-9 |
2022-04-01 | Abstract The influence of the dust–ion collision effect on the propagation of ion–acoustic waves (IAWs) in a collisional magnetized dusty plasma containing positive ions, dust grains with a negative charge and the electrons that follow combined Kappa–Cairns distribution is observed. Employing reductive perturbation technique (RPT), the damped Kadomtsev–Petviashvili (DKP) equation is derived from the basic governing equations and it is observed that there are some critical points for the plasma parameters for which the amplitude of solitary solution of DKP equation diverges. Then modified damped Kadomtsev–Petviashvili (MDKP) equation is derived by stretching the dependent variables in a different manner and the finite-amplitude soliton is explored there. The influence of various plasma parameters viz. entropic index (κ), nonthermal parameter ( $${{\alpha }_{e}}$$ ), dust–ion collisional frequency ( $${{\nu }_{{id0}}}$$ ), ratio of normalized electron density to ion density (μ), etc. on wave propagation is investigated numerically. Finally, comparative studies are drawn between the solitary wave solutions for different models. | Studies on the Effect of Dust–Ion Collision on Dust–Ion Acoustic Solitary Waves in a Magnetized Dusty Plasma in the Framework of Damped KP Equation and Modified Damped KP Equation | 10.1134/S1063780X22040018 |
2022-04-01 | Purpose Semi-active devices are showing a greater prominence in several engineering applications in recent times. This work makes an attempt to evaluate the performance of semi-active damper when used with a class of smart material called magneto-rheological (MR) fluid. Method Initially an MR damper is developed and characterized using an in-house prepared MR fluid. The rheological study is also performed for the prepared MR fluid at different input currents. The behavior of the MR damper through characterization testing is modeled using a hysteretic modeling technique known as Kwok model and the parameters are converted into current-dependent variables. The force simulation through Kwok model is used in quarter car simulation model for different dynamic conditions with off-state, constant current and current through Skyhook control. Results The comparative results with different current conditions are analyzed. An attempt has been made to replicate these conditions in the experiments using quarter car test rig. Conclusion Both simulation and experimental analyses revealed greater vibration suppression capability of MR damper when used with skyhook control. On an average, 24% peak amplitude reduction is observed when compared to off-state condition. | Performance Evaluation of Magneto-Rheological Damper Through Characterization Testing, Modeling and its Implementation in Quarter Car | 10.1007/s42417-021-00422-7 |
2022-04-01 | Accurate damping estimation is critical to the serviceability assessment of large and flexible civil infrastructure. However, the frequency of sensor faults found in the long-term monitored data of large-scale structures is a potential cause of errors in the damping estimates. A machine-learning-based fault-data management approach is proposed whereby erroneous data are identified and removed automatically. A support Vector Machine (SVM) is used to automatically detect and recover/isolate multiple types of sensor faults from measured accelerations. The labeled training samples are artificially augmented using digital simulation of a random process. An envelope function is introduced to reflect the time-varying trends of signals. A new feature, the Maximum Correlation Factor, is proposed to measure similarities between the simultaneously measured signals in order to classify faulty and normal data. The performance of the trained SVM classifier was validated via long-term data from the wireless sensor network of a cable-stayed bridge in South Korea. The modal damping ratios were then estimated from the faulty and recovered data. The improved performance of the damping estimation via spike removal and fault isolation was evaluated in terms of the correlation function and stabilization diagram in the output-only modal analysis. The recovered data provided a more robust and consistent damping estimate, and demonstrated the efficacy of the proposed fault-data management strategy that uses a new SVM feature. | Automated damping identification of long-span bridge using long-term wireless monitoring data with multiple sensor faults | 10.1007/s13349-022-00556-6 |
2022-04-01 | Previous studies about optimizing earthquake structural energy dissipation systems indicated that most existing techniques employ merely one or a few parameters as design variables in the optimization process, and thereby are only applicable only to simple, single, or multiple degree-of-freedom structures. The current approaches to optimization procedures take a specific damper with its properties and observe the effect of applying time history data to the building; however, there are many different dampers and isolators that can be used. Furthermore, there is a lack of studies regarding the optimum location for various viscous and wall dampers. The main aim of this study is hybridization of the particle swarm optimization (PSO) and gravitational search algorithm (GSA) to optimize the performance of earthquake energy dissipation systems (i.e., damper devices) simultaneously with optimizing the characteristics of the structure. Four types of structural dampers device are considered in this study: (i) variable stiffness bracing (VSB) system, (ii) rubber wall damper (RWD), (iii) nonlinear conical spring bracing (NCSB) device, (iv) and multi-action stiffener (MAS) device. Since many parameters may affect the design of seismic resistant structures, this study proposes a hybrid of PSO and GSA to develop a hybrid, multi-objective optimization method to resolve the aforementioned problems. The characteristics of the above-mentioned damper devices as well as the section size for structural beams and columns are considered as variables for development of the PSO-GSA optimization algorithm to minimize structural seismic response in terms of nodal displacement (in three directions) as well as plastic hinge formation in structural members simultaneously with the weight of the structure. After that, the optimization algorithm is implemented to identify the best position of the damper device in the structural frame to have the maximum effect and minimize the seismic structure response. To examine the performance of the proposed PSO-GSA optimization method, it has been applied to a three-story reinforced structure equipped with a seismic damper device. The results revealed that the method successfully optimized the earthquake energy dissipation systems and reduced the effects of earthquakes on structures, which significantly increase the building’s stability and safety during seismic excitation. The analysis results showed a reduction in the seismic response of the structure regarding the formation of plastic hinges in structural members as well as the displacement of each story to approximately 99.63%, 60.5%, 79.13% and 57.42% for the VSB device, RWD, NCSB device, and MAS device, respectively. This shows that using the PSO-GSA optimization algorithm and optimized damper devices in the structure resulted in no structural damage due to earthquake vibration. | Development of hybrid optimization algorithm for structures furnished with seismic damper devices using the particle swarm optimization method and gravitational search algorithm | 10.1007/s11803-022-2088-1 |
2022-03-30 | Background Isoproterenol (ISO), a synthetic on selective β-adrenergic agonist, provides a simple and non-invasive method for inducing myocardial injury with lower mortality and higher reproducibility. Phlegm-damp syndrome, as known as “Tanshi” in Chinese, is one of Traditional Chinese Medicine (TCM) syndrome differentiation, which plays an important role in the development of cardiovascular diseases. However, the underlying mechanism remains unknown. Methods In our present study, a myocardial injury mouse model was introduced by ISO administration combined with high temperature and high humidity and high-fat diet to simulate phlegm-damp syndrome. Nontargeted metabolomics with LC–MS/MS was adopted to reveal serum metabolism profile for elucidating the possible molecular mechanism. Results The results of our study showed that phlegm-damp syndrome promoted ISO-induced myocardial injury by aggravating left ventricular hypertrophy and fibrosis, and increasing cardiac index. Our study also confirmed the presence of specific metabolites and disturbed metabolic pathways by comparing ISO mice and Tanshi mice, mainly including glycerophospholipid metabolism, arginine–proline metabolism, and sphingolipid signaling pathway. The lysoPCs, PCs, SMs, Sphingosine, and L-Arginine were the main metabolites that showed a difference between ISO and Tanshi mice, which might be the result of the underlying mechanism in the promotion of ISO-induced myocardial injury in mice with high temperature and high humidity and high-fat diet. Conclusion Our current study provides new insights into contribution of metabolism disorder in promotion of ISO-induced myocardial injury in mice with high temperature and high humidity and high-fat diet, and new targets for clinical diagnosis and pharmacologic treatment of cardiovascular disease with phlegm-damp syndrome. | Metabolism disorder promotes isoproterenol-induced myocardial injury in mice with high temperature and high humidity and high-fat diet | 10.1186/s12872-022-02583-z |
2022-03-22 | Stay cables in cable-stayed bridges experience vibrations due to wind, rain, and traffic-induced excitations and may suffer fatigue damage. Shape memory alloy (SMA) material can protect cable damages from fatigue issues. This paper summarizes the applications and effectiveness of SMAs for mitigating cable vibration. SMA wires have greatly enhanced the performance of cable structures because of its super-elasticity and shape memory effect. SMA wire hysteresis behavior is analyzed on Mechanical ANSYS Parametric Design Language in order to obtain the stress–strain response. Because of the above properties, shape memory alloy wires exhibit large hysteresis loops under cyclic loadings with negligible or no residual strains. The effect of temperature under the influence of loading was also studied. The ambient temperature has its marked effect on the superelasticity and shape memory behaviors. It is concluded that the passive dampers made of the shape memory alloy Ni–Ti wire quashes the stay cable vibration effectively. It is expected that the information collected in this paper would serve as a repository of information for SMA damper. An artistic view of a SMA damper has been presented. The future research would focus to develop an improved SMA-based damper, which may be effective in quashing the vibration effects developed by wind or earthquake. | Application of SMA wire in vibration mitigation of bridge stay cable: a state-of-the-art review | 10.1007/s41062-021-00733-4 |
2022-03-14 | Microporous metal entangled structure (MES) can reduce various hazards caused by vibration due to its good damping energy dissipation. However, its bearing capacity is weak and cannot realize the multi-functional characteristics of high damping and high stiffness. In this work, a kind of interpenetrating metal entangled structure/silicone rubber composite (MES-SRC) is developed, which is composed of MES as the skeleton and the silicone rubber as the matrix. The dynamic mechanical tests of MES-SRC, MES, and silicone rubber are conducted, and their dynamic properties, including bearing capacity, damping energy dissipation, and damping, are quantitatively characterized. The test results show that the bearing capacity and damping energy dissipation of MES-SRC are higher. Through the analysis of the mesostructure of MES-SRC, the damping energy dissipation mechanism of MS-SRC is studied. The effects of vibration conditions and process parameters of MES on dynamic properties of MES-SRC are studied, and the reasons for the effects are explained from the mesostructure. Graphical abstract | Study on dynamic properties of metal entangled structure/silicone rubber interpenetrating composite | 10.1557/s43578-022-00500-w |
2022-03-01 | In this paper, we investigate the stability of a class of wave equations with local coupling effect and indirect mixed-type dampings. Some optimal (so far best) stability results for the energy of the system are established under much weak basic assumptions on the locally coupled terms and the damping terms. In particular, it is worth noting that the local coupling terms here only play a role on a part of the domain but not on entire domain, and the coefficients of the coupling terms may have variable sign. On the other hand, the memory-effect regions do not have to include a part of boundary in present paper, while the condition is a necessity in almost all the previous literature. As will be seen, to overcome the difficulties encountered in obtaining these results, we combine the higher order energy method with positive definite kernel theory through the multiplier technique, which are utilized in our proofs. | Stability for Locally Coupled Wave-Type Systems with Indirect Mixed-Type Dampings | 10.1007/s00245-022-09830-x |
2022-03-01 | With the purpose of improving the frequency support capability of high voltage direct current (HVDC) transmission equipment and ensuring the stable and reliable operation for the receiving end power grid, a virtual synchronous generator (VSG) control algorithm for high voltage direct current converter was proposed in this paper. The virtual synchronous generator control method is analyzed in detail, and the small-signal model of grid-tied high voltage direct current converter is established, and further established the small signal-model of the three-area power system. On the basis of the proposed models, considering the factors such as different short circuit ratios, decoupling performance, stability, dynamics, the selection principle of inertia factor J and damping factor D of virtual synchronous generator is proposed. Finally, the effectiveness of the proposed inertia and damping coefficient selection method is verified by simulation. | Inertia Parameter Selection Method for HVDC Converter Station Based on VSG Control | 10.1007/s42835-021-00981-5 |
2022-03-01 | Elastomeric layers, that serve as the base of a viscoelastic (VE) damping system in structures, dissipate energy through shear deformation and transform vibration energy into heat by internal friction between polymer chains. In this study, two compounds, based on natural rubber (NR) matrix and butyl rubber (IIR) matrix, were designed and manufactured. Then, the mechanical and dynamic properties of elastomeric layers were investigated. Dynamic loading tests were conducted on the elastomeric layers using a frequency range of 0.1–1.5 Hz and a shear strain range of 10–150% under harmonic loading in order to analyze their hysteretic behavior. The output of the experiments shows that the both of elastomeric layers have a large deformation capability with a high damping performance, but the IIR damper can provide high energy dissipation capacity compared with the NR damper that has a large restoring force. The results also show an increase in storage modulus and loss factor of VE dampers with increasing frequency and their decrease with increasing strain. However, the dependency of VE damper on strain and strain rate based on NR is more remarkable than that of VE damper based on IIR. The experimental data were also used for validation and calibration of numerical simulation by ABAQUS software. The results proved to be satisfactory. | Experimental and numerical study on developed elastomeric layers based on natural and butyl matrix rubbers for viscoelastic dampers | 10.1007/s11043-021-09484-2 |
2022-03-01 | Thermoelastic damping is becoming a leading factor for determining the quality of the micromechanical resonators in terms of their sensitivity. The present study is devoted to the analysis of thermoelastic damping of a micro-beam resonator by employing the concept of three-phase-lag (TPL) theory of thermoelasticity in the context of the memory-dependent derivative (MDD). The memory-dependent derivative is characterized by its time delay and the kernel function that can be chosen freely with imposed restrictions. Analytical expressions of thermoelastic damping, attenuation as well as frequency shift have been derived. Computational results for the prominent parameters of micromechanical resonators such as thermoelastic damping, attenuation, and frequency shift are obtained. The influence of the constituents of memory-dependent derivative, i.e. time-delay and kernel functions, on the parameters of the micro-beam resonator has been analyzed through graphical results. Furthermore, numerical results are compared with the results obtained in the absence of a memory-dependent derivative through numerical simulations. The significant role of the memory-dependent derivative has been identified and it has been found that the insertion of the memory-dependent derivative is capable of providing accurate results as compared to the results obtained in its absence. | Significance of memory-dependent derivative approach for the analysis of thermoelastic damping in micromechanical resonators | 10.1007/s11043-020-09477-7 |
2022-03-01 | Abstract A method is proposed for calculating the parameters of a spring compensator in a piston pump. The method takes account of the deficiencies of existing models describing a system with a piston pump and a pressure-fluctuation compensator. If no account is taken of the compensator’s parameters and the physical characteristics of the pumped liquid, the description of the system will be distorted, and the operational efficiency of the compensator will be low. The proposed system permits effective quenching of the output pressure pulsations, taking account of hydrodynamic processes resembling the actual operating conditions of a piston pump. | Calculating the Parameters of a Spring Compensator in a Piston Pump | 10.3103/S1068798X22030273 |
2022-03-01 | Due to the substantial role of damping in the performance of real-life structures, many researchers are interested in analyzing its various effects on the dynamic behavior of systems. In this work, a theoretical investigation is performed on the wave propagation in monoatomic nonlinear chains in the presence of energy dissipation. Both linear and quadratic damping models are considered and the time-dependent dispersion relations for the weakly nonlinear monoatomic chains are obtained using the multiple-scale method. Also, a numerical simulation is carried out to verify the results obtained by the analytical formulations. In addition to the comparison of the dispersion relations for chains with hardening and softening nonlinearities, their wave-filtering performances in the presence of linear and quadratic damping are compared. According to the results, increasing the damping ratio in chains with hardening nonlinearity leads to lower dispersion branches compared to their linear counterparts. On the other hand, in systems with softening nonlinearity, higher dispersion branches than the linear chains are achieved by increasing the damping ratio. The results of this work bring us one step closer to modeling the real behavior of nonlinear phononic crystals and lattice materials to have a better perception of their extraordinary dynamic capabilities. | Wave propagation in nonlinear monoatomic chains with linear and quadratic damping | 10.1007/s11071-021-07184-7 |
2022-03-01 | The primary goal of this work is to design a novel magnetorheological damper with selectable performance parameters to improve the environmental adaptability of vibration systems equipped with such a damper and to provide a new idea for the design of magnetorheological dampers. The feasibility of the new idea is verified in both principle and experiment. The conceptual design, working principle analysis, magnetic design and prototype development of the magnetorheological damper are carried out. The damper prototype is tested on the dynamic testing system and the results show that the field-off force, peak force and dynamic range of the damper vary with the working modes, which proves that the performance parameters of the proposed damper are selectable during usage. Compared to conventional magnetorheological dampers, this new type of damper has a greater potential to achieve a large adjustment range. In addition, the damper can automatically switch the working channel in accordance with actual stroke, thus improving the response of the vibration system to unanticipated increasing loads. | Design of multi-channel bypass magnetorheological damper with three working modes | 10.1007/s10999-021-09567-5 |
2022-03-01 | The primary objective of this article is to demonstrate that Rayleigh’s quotient and its variants retain the usual properties of boundedness and stationarity even when the linear vibratory system is non-classically damped, extending previously accepted results that these quotients could attain stationarity when damping was proportional or the modal damping matrix was diagonally dominant. This conclusion is reached by allowing the quotients to be defined in complex space and using complex differentiation. A secondary objective is to show how these quotients and their associated eigenvalue problems can be combined to generate bounds on the system’s eigenvalues, an immediate consequence that follows from establishing boundedness and stationarity in complex space. The reported bounds are simple to compute and appear to be tighter than previous bounds reported in the literature. | Rayleigh’s quotients and eigenvalue bounds for linear dynamical systems | 10.1007/s00419-022-02105-5 |
2022-03-01 | Quasi-zero-stiffness (QZS) vibration isolators have been widely studied, because they show excellent high static and low dynamic stiffnesses and can effectively solve low-frequency and ultralow-frequency vibration. However, traditional QZS (T-QZS) vibration isolators usually adopt linear damping, owing to which achieving good isolation performance at both low and high frequencies is difficult. T-QZS isolators exhibit hardening stiffness characteristics, and their vibration isolation performance is even worse than that of linear vibration isolators under a large excitation amplitude. Therefore, this study proposes a QZS isolator with a shear-thinning viscous damper (SVD) to improve the vibration isolation performance of the T-QZS isolators. The force-velocity relation of the SVD is obtained, and a dynamic model is established for the isolator. The dynamic responses of the system are solved using the harmonic balance method (HBM) and the Runge-Kutta method. The vibration isolation performance of the system is evaluated using force transmissibility, and the isolator parameters are analyzed. The results show that compared with the T-QZS isolators, the proposed QZS-SVD isolator achieves the lower initial vibration isolation frequency and peak value, and exhibits better vibration isolation performance at medium and high frequencies. Moreover, the proposed isolator can withstand a large excitation amplitude in the effective vibration isolation range. | A quasi-zero-stiffness isolator with a shear-thinning viscous damper | 10.1007/s10483-022-2829-9 |
2022-02-28 | Integrally bladed disks (blisk) have been widely used in the turbo-machinery industry due to its high aerodynamic performance and structural efficiency. A friction ring damper (FRD) is usually integrated in the system to improve its low damping. However, the design of the geometry of this FRD become complex and computationally expensive due to the strong nonlinearities from friction interfaces. In this work, we propose an efficient modelling strategy based on advanced nonlinear modal analysis and Kriging surrogate models to design and optimize the geometry of a 3D FRD attached to a high fidelity full-scale blisk. The 3D ring damper is parametrised with a few key geometrical parameters. The impact of each geometric parameter and their sensitivities to nonlinear dynamic response can be efficiently assessed using Kriging meta-modelling based on a few damped nonlinear normal modes. Results demonstrate that the damping performances of ring dampers can be substantially optimized through the proposed modelling strategy whilst key insights for the design of the rings are given. It is also demonstrated that the distribution of the contact normal load on the contact interfaces has a strong influence on the damping performances and can be effectively tuned via the upper surface geometry of the ring dampers. | Geometric design of friction ring dampers in blisks using nonlinear modal analysis and Kriging surrogate model | 10.1007/s00158-021-03093-w |
2022-02-26 | In this paper, we focus on the global regularity of smooth solutions for 2D incompressible generalized magnetohydrodynamics equations with a velocity damping term and the standard Laplacian magnetic diffusion. We show that this system has the unique global smooth solutions when the initial data in Besov space are suitably small. | Global regularity of the 2D generalized MHD equations with velocity damping and Laplacian magnetic diffusion | 10.1007/s00033-022-01699-8 |
2022-02-26 | In the present study, Complex Eigenvalue Analysis (CEA) was used for predicting squeal noise generation in a commercial drum brake. By using a CEA model, Rayleigh damping properties were added to the computer simulation on ANSYS, and a discussion about its implications and proposed calculations are also shown. The Rayleigh damping coefficients ( α and β ) were obtained through impact tests carried out in a commercial drum brake. Three different cases of damping levels were simulated: (a) Undamped condition, (b) Damped–0 bar, and (c) Damped–2 bar. Results of experimental tests showed that increasing brake pressure from 0 to 2 bar in the damped condition leads to a shift in the resonant frequencies towards higher values, as well as to increase the damping response of the drum brake system. Results of CEA showed a large number of vibration modes occurred within a narrow range of frequencies (0–4500 Hz). This means the drum brake is prone to modal coupling, which may lead to noise generation. The first model simulated by CEA (undamped case) showed five instabilities in the frequency range considered, from this point, the second model was built (damped–0 bar case) and only three instabilities were identified. Thus, the third model (damped–2 bar case) was analyzed and it showed only one unstable frequency, which means over-predictions could be avoided due to the addition of damping. Thus, it was noticed a significant negative offset caused by the damping effect, however, the system instabilities for all five modes remain. CEA models were validated by comparison of predicted and vehicle noise frequencies, which were very close. | Damping effect on nonlinear drum brake squeal prediction | 10.1007/s40430-022-03398-x |
2022-02-25 | Corrosion of steel reinforcement is one of the most common durability issues for reinforced concrete (RC) structures, especially when located in marine areas. The study of the mechanical consequences of this pathology is of great importance to assess their performance. Experimental campaigns have been carried out on corroded structures. So far, assessing quasi-static behavior or predicting the dynamic response of structures have been based exclusively on quasi-static loadings. In particular, the dissipated energy and the damping capacity, which are important features to study when assessing the seismic performance of corroded RC members, are evaluated based on quasi-static loadings. The objective of this study is to characterize these two significant engineering demand parameters (EDP) using both quasi-static and dynamic tests. To reach this goal, an experimental campaign is conducted on large-scale RC beams. The corroded and non-corroded RC beams are subjected to a four-point bending loading and to dynamic loading keeping the same loadings and boundary conditions. The dynamic loading is applied on the specimen by means of the AZALEE shaking table. In this paper, a brief description of the experimental campaign is made. Then, results showing the influence of the corrosion rate on the dissipation capacity of RC structures are exposed. Especially, the consistency between quasi-static and dynamic results is assessed and discussed. | Experimental study of corroded RC beams: dissipation and equivalent viscous damping ratio identification | 10.1617/s11527-022-01906-y |
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