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2022-02-20 | Wave-particle interaction (WPI) is one of the most fundamental processes in plasma physics in which one most prominent example is the Landau damping. Owing to its excellent energy-exchange mechanism, the WPI has gained increasing interest not only from theoretical points of view, but also its many important applications including plasma heating and plasma acceleration. In this review work, we present theoretical backgrounds of linear and nonlinear wave-particle interactions in quantum plasmas. Specifically, we focus on the wave-particle interactions for homogeneous plasma waves (i.e., waves with infinite extent rather than a localized pulse) as well as for propagating electrostatic waves in the weak and strong quantum regimes to demonstrate the modifications of several classical features including those associated with resonant and trapped particles. Finally, the future perspectives of WPI in quantum plasmas are presented. | Wave-particle interactions in quantum plasmas | 10.1007/s41614-022-00063-7 |
2022-02-17 | Aging is a phenomenon that affects the strength parameters of soil. This paper aimed to examine the time-dependent behavior of static and dynamic parameters of sands stored under natural conditions using static and cyclic simple shear tests. The goal was to better understand the effects of aging on shear modulus, damping ratio, and friction angle of sands with different gradations leaving under natural conditions up to 12 months. At each 3-momth interval, each sand was remolded with the relative density of 60% in simple shear apparatus in the dry state. In this research, two coarse-grained sand, one medium-grained sand, and one fine-grained sand were used. The findings demonstrated that the static and dynamic parameters of sands underwent significant changes due to aging. The friction angle, shear modulus, and damping ratio of sands decreased over time and at the end of 12 months, though they were experiencing some fluctuations. The maximum friction angle decrease pertained to medium-grained sand and was about 12%, while the minimum rate of about 1% pertained to fine-grained sand. After 12 months, the minimum decrease in damping ratio pertained to coarse-grained sand and was about 30%, and the maximum damping ratio decrease of 39% pertained to medium-grained sand. The maximum shear modulus decrease pertained to fine-grained sand and was about 22%, and the minimum rate to medium-grained sand was about 5%. Aging was found to have positive effects on fine sands under static conditions during one year of the study. Overall, over 12 months, aging showed a positive effect on the static shear strength of sands and a negative effect on their dynamic shear strength. | Impact of natural environment on sand aging under static and dynamic conditions | 10.1007/s10035-022-01208-8 |
2022-02-12 | The existence of pullback attractors is proved for the MHD equations with damping terms $$|u|^{\alpha -1}u$$ | u | α - 1 u and $$|B|^{\beta -1}B$$ | B | β - 1 B $$(\alpha ,\beta \geqslant 1)$$ ( α , β ⩾ 1 ) on a bounded domain $$\Omega \subset {\mathbb {R}}^{3}$$ Ω ⊂ R 3 . Based on the well-posedness of the strong solution in Song and Xiong (J Math Anal Appl 505(2):36, 2022) and under suitable assumptions on the external force, first, we establish some estimates for the strong solution. Then, the continuity of the corresponding process is verified under the assumption $$\alpha , \beta <5$$ α , β < 5 , which is guided by Gagliardo–Nirenberg inequality. Finally, the system is shown to possess an $$({\mathbb {V}},{\mathbb {V}})$$ ( V , V ) -pullback attractor and an $$({\mathbb {V}},\mathbf{H }^{2})$$ ( V , H 2 ) -pullback attractor. | Pullback attractors for 3D MHD equations with damping | 10.1007/s00033-022-01687-y |
2022-02-11 | This paper is devoted to the energy decay estimates for the coupled wave-plate system with local frictional damping in a bounded domain. The frictional damping distributes in the plate or wave domain. When the frictional damping is only acting through the plate equation, the transmission system is showed not to be exponentially stable. By the frequency domain approach and multiplier technique, it is found that the system energy has the polynomial decay rate. On the other hand, when the frictional damping only act through the wave equation, it is showed that the system energy has the exponential decay. It can be seen that only the frictional damper acting on the wave equation can stabilize exponentially the transmission plate-wave equations. | Stability of Transmission Wave-Plate Equations with Local Indirect Damping | 10.1007/s10440-022-00471-4 |
2022-02-10 | Thermoelastic damping is defined as a significant intrinsic dissipative mechanism which represents the loss of energy of micro-/nano-mechanical resonators. It remarkably affects the quality performance of the resonators. It is a very strenuous task to fabricate a resonator of good quality type so that its thermoelastic damping should be minimum. Recently, extensive attention is being paid to fabricate micro-/nano-resonators due to their numerous applications in micro- and nano-electro-mechanical systems. Present study enlightens a new mathematical model with non-local effect as well as memory effect which exhibits the lower values of thermoelastic damping and attenuation compared to the previous existing models without non-local and memory effect. Governing equations are developed in context of three-phase-lag generalized thermoelasticity in the frame of non-local and memory effect. Analytical expressions of significant factors of micro-beam resonator such as thermoelastic damping, attenuation as well as frequency shift are evaluated. Quantitative results are derived to display the influence of effective parameters such as non-local thermal parameter of heat conduction, kernel functions as well as time delay on the variations of thermoelastic damping, attenuation as well as frequency shift. Also, the size effect of micro-beam resonator is being presented on the variations of thermoelastic damping of micro-beam resonator. By discussing the computational results, utility of the present model is being proved. It is believed that the predicted results must be advantageous to design the micro-/nano-mechanical resonators of better quality. | Non-local effect on quality factor of micro-mechanical resonator under the purview of three-phase-lag thermoelasticity with memory-dependent derivative | 10.1007/s00339-022-05322-5 |
2022-02-10 | The Lorentz–Maxwell model of dispersion of light has been analysed in this paper to determine the damping coefficient of the electrons in optically transparent glasses at the true resonance frequency in the ultraviolet region where glass is opaque. For this, we needed the refractive indices of glass in the optical frequency range. We argue that the true resonance condition in the absorption region prevails when the frequency at which the absorption coefficient is maximum is the same as the frequency at which the average energy per cycle of the electrons is also a maximum. We have simultaneously solved the two equations obtained from the two maxima conditions numerically to arrive at a unique solution for the true resonance frequency and the damping coefficient at this frequency. Assuming the damping coefficient to be constant over a small frequency range in the absorption region, we have determined the frequency at which the extinction coefficient is maximum using our theory. This frequency matches well with the published experimental data for silica glasses. | Determination of the damping coefficient of electrons in optically transparent glasses at the ultraviolet absorption region | 10.1007/s12043-021-02290-y |
2022-02-02 | This article deals with an initial and boundary value problem to the following damped wave equation: u t t − Δ u − ω Δ u t + μ u t = | u | p − 2 u $$ u_{tt}-\Delta u-\omega \Delta u_{t}+\mu u_{t}=|u|^{p-2}u $$ in a bounded domain. An energy decay estimate for the solutions when ω ≥ 0 $\omega \geq 0$ and μ > − ω λ 1 $\mu >-\omega \lambda _{1}$ is obtained by adopting a new method, where λ 1 $\lambda _{1}$ is the first eigenvalue of the operator − Δ $-\Delta $ under the homogeneous Dirichlet boundary conditions. Moreover, a blow-up result is proved for solutions with high energy initial data. An estimate of the upper bounded for the lifespan of the solution is showed as well. These results give some answers to the open problems in Gazzola and Squassina (Ann. Inst. Henri Poincaré 23:185–207, 2006 ). | Decay Estimate and Blow-up for a Damped Wave Equation with Supercritical Sources | 10.1007/s10440-022-00469-y |
2022-02-01 | Background Particle damping materials convert the kinetic energy of the system into other forms of energy through friction and collision between particles and between the particles and container wall. Gear transmission is advancing toward higher speeds, heavier loads, and lower noise. Purpose In order to reduce the vibration in the gear transmission without changing the original structure, particle damping is used in the paper. Methods The equivalent displacement mapping of the gear contact load from the non-continuous domain to continuous element nodes was realized using the combined gear dynamics and discrete element method (DEM). Furthermore, the bidirectional transfer of load boundary conditions in the continuous domain and displacement boundary conditions in the discrete element domain were realized in the same calculation model. Results At low rotating speeds, the best vibration reduction occurred at the particle friction coefficient of approximately 0.43. At high rotating speeds, the best vibration reduction occurred at the particle friction coefficient of approximately 0.22. Conclusions The vibration acceleration of the gear decreases significantly after the particle damper is added, confirming its vibration damping effect. This research has significant potential for vibration and noise reduction in gear transmission systems. | Effect of Particle Friction Coefficient on Vibration Reduction in Gear Transmission | 10.1007/s42417-021-00402-x |
2022-02-01 | Damping is known to have a considerable influence on the dynamic behavior of bridges. The fixed damping ratios recommended in design codes do not necessarily represent the complicated damping characteristics of bridge structures. This study investigated the application of stress-dependent damping associated with vehicle-bridge coupling vibration and based on that investigation proposed the stress-dependent damping ratio. The results of the investigation show that the stress-dependent damping ratio is significantly different from the constant damping ratio (5%) defined in the standard specification. When vehicles travel at speeds of 30, 60, and 90, the damping ratios of the bridge model are 3.656%, 3.658%, and 3.671%, respectively. The peak accelerations using the regular damping ratio are 18.9%, 21.3%, and 14.5% of the stress-dependent damping ratio, respectively. When the vehicle load on the bridge is doubled, the peak acceleration of the mid-span node increases by 5.4 times, and the stress-related damping ratio increases by 2.1%. A corrugated steel-web bridge is being used as a case study, and the vibration response of the bridge is compared with the measured results. The acceleration response of the bridge which was calculated using the stress-dependent damping ratio is significantly closer to the measured acceleration response than that using the regular damping ratio. | Numerical analysis of vehicle-bridge coupling vibration concerning nonlinear stress-dependent damping | 10.1007/s11709-021-0804-y |
2022-02-01 | Abstract— The rotation of a thin elastic disk around its axis is considered. It is assumed that the disk is rigidly fixed in the center and performs small transverse vibrations described in the framework of the membrane model. To suppress vibrations, the flexible disk is subjected to external mechanical stress. The vibration damping process is estimated by a quadratic energy criterion and is optimized using the modern theory of optimal control. Optimality conditions are derived that are used to suppress elastic vibrations in a finite time interval, and a developed iterative algorithm for damping vibrations is presented, illustrated by the example of the analytical determination of a stabilizing effect. | DAMPING THE TRANSVERSE VIBRATIONS OF A RAPIDLY ROTATING DISC | 10.3103/S0025654422010010 |
2022-02-01 | We consider the Benjamin–Ono equation on the torus with an additional damping term on the smallest Fourier modes ( $$\cos $$ cos and $$\sin $$ sin ). We first prove global well-posedness of this equation in $$L^2_{r,0}(\mathbb {T})$$ L r , 0 2 ( T ) . Then, we describe the weak limit points of the trajectories in $$L^2_{r,0}(\mathbb {T})$$ L r , 0 2 ( T ) when time goes to infinity, and show that these weak limit points are strong limit points. Finally, we prove the boundedness of higher-order Sobolev norms for this equation. Our key tool is the Birkhoff map for the Benjamin–Ono equation, that we use as an adapted nonlinear Fourier transform. | Long time behavior of solutions for a damped Benjamin–Ono equation | 10.1007/s00209-021-02849-w |
2022-02-01 | We are concerned with a transmission problem for the Kirchhoff plate equation where one small part of the domain is made of a viscoelastic material with the Kelvin-Voigt constitutive relation. We obtain the logarithmic stabilization result (explicit energy decay rate), as well as the wellposedness, for the transmission system. The method is based on a new Carleman estimate to obtain information on the resolvent for high frequency. The main ingredient of the proof is some careful analysis for the Kirchhoff transmission plate equation. | Logarithmic stabilization of the Kirchhoff plate transmission system with locally distributed Kelvin-Voigt damping | 10.21136/AM.2021.0104-20 |
2022-02-01 | In dieser Arbeit wird untersucht, wie das Dämpfungsvermögen bei auftretenden Netzpendelungen durch den kombinierten Einsatz von Regelstrategien bei Wasserkraftwerken verbessert werden kann. Zuerst wird auf die regelungstechnischen Herausforderungen bei Wasserkraftwerken, wie den hydraulischen Druckstoß, eingegangen. Anhand eines Ein-Maschinenmodells mit starrer Netzanbindung werden der Einsatz eines Power System Stabilizers (PSS) über die Generatorerregung sowie mittels Turbinenregler als auch die Kombination beider Strategien auf ihre Wirksamkeit bezüglich ihres Dämpfungsvermögens untersucht. Zusätzlich werden diese Ergebnisse mit einem optimalen Zustandsregler mit einem Beobachter als Bedämpfungselement verglichen. Dabei dient das Modell nach Heffron-Phillips als Entwurfsmodell für den PSS als auch für den modellbasierten Regler. Die Verifikation des Dämpfungsvermögens durch die PSS-Varianten wird anhand eines Drei-Maschinenmodells im Zeitbereich und mittels Modalanalyse durchgeführt. This paper examines how the damping capability can be improved if inter-area oscillations occur by combining control strategies in hydropower plants. First, the control challenges of hydropower plants, such as the water hammer effect, are discussed. In a single-machine infinite bus system (SMIBS), the use of a Power System Stabilizer (PSS) in the generator excitation and in the governor control path as well as the combination of both strategies are examined for their effectiveness in terms of their damping capability. In addition, these results are compared with an optimal state space controller with an observer as a damping element. The Heffron-Phillips model is the design model for the PSS as well as for the model-based controller. The verification of the damping capability through the PSS variants is evaluated by using a three-machine model in the time domain and by using modal analysis. | Damping of inter-area oscillations by combining control strategies in hydropower plants | 10.1007/s00502-021-00935-9 |
2022-02-01 | This paper proposes the stiffness nonlinearities and asymmetric SD (smooth and discontinuous) oscillator under time-delayed feedback control with the fractional derivative damping. With the effect of displacement and velocity feedback, the oscillator can be adjusted to the desired vibration state, and then the stochastic resonance (SR) is achieved. This article discusses the contribution of various system parameters and time-delayed feedback to SR, especially which induced by fractional order. It should be noted that this paper provides effective guidance for fault diagnosis and weak signal detection, energy harvesting, vibration isolation and vibration reduction. | The effect of fractional damping and time-delayed feedback on the stochastic resonance of asymmetric SD oscillator | 10.1007/s11071-021-07105-8 |
2022-02-01 | The wide-area damping controllers showed to be effective in improving the damping ratio of the low-frequency oscillation modes. This controller requires remotes signals sent by Phasor Measurement Units located in different positions of the power system and, then, these signals are highly susceptible to communication time delays, failures and cyber-attacks that may compromise controller performance. This paper presents a procedure based on particle swarm optimization to tune the parameters of the central controller. Considering a set of operating conditions, the proposed procedure will search the central controller parameters that maximize the damping ratio of all eigenvalues of the linear model. A strategy to deal with permanent communication channel failures and time delay uncertainties in a given interval will be included in the proposed model and procedure. Then, the resulting central controller will present robustness to multiple operation conditions of the power system, to time delay uncertainties and to permanent failure of the channels of the controller. The proposed procedure was carried out in the IEEE 68-bus system and the performance of the designed controller was evaluated by modal analysis and time-domain nonlinear simulation. | Design of a wide-area damping controller to tolerate permanent communication failure and time delay uncertainties | 10.1007/s12667-020-00416-6 |
2022-02-01 | Studied are the hysteretic force–deformation response of large-scale nonlinear viscous dampers and model of the response for use in numerical simulations and seismic design. The force–deformation response of nonlinear viscous dampers with a force capacity of 600 kN are characterized under sinusoidal loading. A wide range of amplitudes and frequencies are used in the characterization tests. A nonlinear Maxwell model is presented for modeling the force–deformation response of large-scale nonlinear viscous dampers for use in nonlinear response history analyses. This paper also presents an equivalent linear model for the force–deformation response of a nonlinear viscous damper in-series with the elastic bracing and connection components needed to connect the damper to a building structure. The equivalent linear model enables the effects of the elastic flexibility of structural components on the response of the damper-brace component to be considered in seismic design. Results from tests on a 0.6-scale three-story structure with nonlinear viscous dampers validated the predictive accuracy of the equivalent linear model. Also evaluated are the effects of the elastic flexibility of structural components (e.g., bracing and connection) on the effective stiffness and damping ratio of a building structure with nonlinear viscous dampers. | Modeling of nonlinear viscous damper response for analysis and design of earthquake-resistant building structures | 10.1007/s10518-021-01306-7 |
2022-02-01 | Nonlinear Quasi-zero-stiffness (QZS) vibration isolation systems with linear damping cannot lead to displacement isolation with different excitation levels. In this study, a QZS system with nonlinear hysteretic damping is investigated. The Duffing-Ueda equation with a coupling nonlinear parameter $$\eta$$ η is proposed to describe the dynamic motion of the QZS system. By using the harmonic balance method (HBM), the primary and secondary harmonic responses are obtained and verified by numerical simulations. The results indicate that nonlinear damping can guarantee a bounded response for different excitation levels. The one-third subharmonic response is found to affect the isolation frequency range even when the primary response is stable. To evaluate the performance of the QZS system, the effective isolation frequency $${\Omega }_{e}$$ Ω e and maximum transmissibility $$T_{p}$$ T p are proposed to represent the vibration isolation range and isolation effect, respectively. By discussing the effect of $$\eta$$ η on $${\Omega }_{e}$$ Ω e and $$T_{p}$$ T p , the conditions to avoid nonlinear phenomena and improve the isolation performance are provided. A prototype of the QZS system is then constructed for vibration tests, which verified the theoretical analysis. | Dynamic analysis and experiment of Quasi-zero-stiffness system with nonlinear hysteretic damping | 10.1007/s11071-021-07136-1 |
2022-02-01 | Abstract A new model of damped vibrations of an oscillator based on the use of the mathematical apparatus of fractional integro-differentiation with an exponential-power function of dynamic memory is considered. Using the Wright function, the exact solution of the equation of motion of the oscillator is obtained. Theoretical analysis shows that the model can be effectively used to describe oscillatory processes in low- Q dynamic (in particular, mechanical or electrical) systems. | A Fractional Oscillator with an Exponential-Power Memory Function | 10.1134/S1063785022020055 |
2022-02-01 | Thermoelastic damping is a significant energy dissipation mechanism in nano-resonator, and exploring its feature would lay a foundation for designing high-quality nano-resonators. Due to the size-dependent effect and the non-Fourier heat conduction effect arising in structures in nanoscales, the traditional models may fail to characterize thermoelastic damping in nano-resonators. To further develop the thermoelastic damping model in small scales, a novel thermoelastic damping model is established in the present work based on the modified couple stress theory and the non-Fourier heat conduction law. Based on the novel model, the exact expression of thermoelastic damping is obtained by the complex frequency method. In calculation, the results are validated by degrading the present model to the classical model, and the effects of length scale parameters, boundary conditions, reference temperature, and vibration modes on thermoelastic damping are examined and discussed in detail. The obtained results show that the influence of the present model on the amount of thermoelastic damping and the critical thickness is significant in small scales. | Thermoelastic Damping Analysis to Nano-resonators Utilizing the Modified Couple Stress Theory and the Memory-Dependent Heat Conduction Model | 10.1007/s42417-021-00401-y |
2022-02-01 | This paper investigates the nonlinear dynamic behavior of a nonlocal functionally graded Euler–Bernoulli beam resting on a fractional visco-Pasternak foundation and subjected to harmonic loads. The proposed model captures both, nonlocal parameter considering the elastic stress gradient field and a material length scale parameter considering the strain gradient stress field. Additionally, the von Karman strain–displacement relation is used to describe the nonlinear geometrical beam behavior. The power-law model is utilized to represent the material variations across the thickness direction of the functionally graded beam. The following steps are conducted in this research study. At first, the governing equation of motion is derived using Hamilton’s principle and then reduced to the nonlinear fractional-order differential equation through the single-mode Galerkin approximation. The methodology to determine steady-state amplitude–frequency responses via incremental harmonic balance method and continuation technique is presented. The obtained periodic solutions are verified against the perturbation multiple scales method for the weakly nonlinear case and numerical integration Newmark method in the case of strong nonlinearity. It has been shown that the application of the incremental harmonic balance method in the analysis of nonlocal strain gradient theory-based structures can lead to more reliable studies for strongly nonlinear systems. In the parametric study, it is shown that, on the one hand, parameters of the visco-Pasternak foundation and power-law index remarkable affect the amplitudes responses. On the contrary, the nonlocal and the length-scale parameters are having a small influence on the amplitude–frequency response. Finally, the effects of the fractional derivative order on the system’s damping are displayed at time response diagrams and subsequently discussed. | Nonlinear vibration of a nonlocal functionally graded beam on fractional visco-Pasternak foundation | 10.1007/s11071-021-07081-z |
2022-02-01 | Objectives This paper characterizes how joint stiffness and damping parameters for a bolted cantilevered beam change with different number of bolts, different tightening torques on each, and with different levels of torsional excitations. Such characterization is unaddressed in the literature and is our modest contribution to the state-of-the-art. Another modest contribution is to propose and demonstrate the use of an alternative method of identifying joint characteristics using the harmonic balance method. Methods A cantilevered beam was torsionally excited at its free end using a modal shaker and the relative displacements across the bolted connection were measured. Experiments were conducted in a temperature-controlled environment. Experiments for all configurations were repeated in a randomized order. Results System dynamics were observed to be strongly dependent on the level of excitation, tightening torques, and number of bolts at the interface. Parameters identified using the harmonic balance method were found to agree with those identified using the standard and established method of using hysteresis loops. Identified parameters were used to predict the dynamic behavior of another assembled system which had a similar bolted connection, thus validating the identification. Conclusions Experimental setup and procedures described are simple and the methods of identification robust. Our results suggest that the harmonic balance method is a viable alternate method for joint parameter identification that is not very sensitive to signal processing and conditioning. Our methods and findings can guide other researchers and practitioners interested in the dynamics of assemblies with bolted joints. | Identifying Joint Dynamics in Bolted Cantilevered Systems Under Varying Tightening Torques and Torsional Excitations | 10.1007/s42417-021-00386-8 |
2022-02-01 | A multi-pad bearing profile incorporated with innovative adjustable mechanism capable of controlling the dynamic behaviour of rotor bearing system is analysed in this study. The film thickness variation occurring under pad displaced conditions are accurately predicted by utilising the developed film thickness equation. The modified form of film thickness equation also takes account of the load positions and quasi-static adjustable pad motions in radial and tilt directions. The present study evaluates the effect of different load positions on the stability performance of multi pad adjustable bearing. Linear perturbation analysis is performed to compute the dynamic coefficients of rotor system. Simulations indicated that the film thickness variation caused by pad adjustments significantly alters the bearing dynamic coefficients and attains an efficient control over bearing stability. For a given load position, negative radial adjustment of pads is found to enhance the stability regions of rotor system than other pad adjusted positions. | Stability performance of an adjustable multi-pad fluid film bearing profile under load-between-pad orientations | 10.1007/s40435-021-00818-z |
2022-02-01 | Ordinary buckling-restrained braces have a single-yielding core. A buckling-restrained brace (BRB) with three parallel yielding cores and different yield strengths is, however, introduced in this paper that will expectedly exhibit an improved seismic behavior. The new BRB was constructed using three-yielding steel cores with the different yield strengths of 180, 240, and 360 MPa to be subjected to experimental tests of cyclic axial loading in accordance with the ATC-24 loading protocol. The results obtained were subsequently compared with those obtained for equivalent single-core BRBs. The three-core brace was observed to yield an area of hysteresis loops/dissipated energy considerably larger than that produced by the equivalent single-core BRB. Moreover, the cores with lower yield strengths tended not only to yield sooner but also to dissipate the input energy, while those with higher yield strengths limited both the story drift and the chances of a structural collapse. Finally, the three-core BRBs recorded energy absorption rates and damping ratios by 16.3% and 8.8%, respectively, higher than these of the single-core brace. | Seismic Performance of Three-core Buckling-Restrained Braces An Experimental Investigation | 10.1007/s40996-021-00606-x |
2022-02-01 | In light of the vast potential for the application of modern energy absorption systems in the structures, the effectiveness of each system should be tested, analyzed, and proved before convincing the structures design companies to use them. In this research, the effectiveness of applying base isolators, viscous and friction dampers and a hybrid system consisted of lead rubber bearing with friction dampers are studied. To quantify the impact of each system, a control structure without any energy absorption system is considered. Base isolators and damper systems are designed according to available international codes. American concrete institute’s codes were used to design the concrete structure frames. All of the considered systems therewith hybrid systems including lead rubber base isolation and viscous dampers have been modeled in ETABS 2018 software. The control structure has an intermediate moment resisting frame with high importance located in a high seismic hazard zone. These models were subjected to time history analysis by using Manjil, Loma prieta, and Imperial Valley Earthquakes records. It was observed that the structural design parameters such as base shears and story drifts were significantly reduced by 76–86% and 44–92%, respectively, compared to the structure without any energy absorption system. Also, the total energy dissipated in the structures equipped with modern energy absorption systems was decreased between 32 and 86% compared to the friction dampers. It should be noted that the studied devices may be used either for the design of a new structure or seismic rehabilitation of the existing structures. | Study on Modern Energy Absorption Systems in Structures Subjected to Earthquake Forces | 10.1007/s40996-021-00677-w |
2022-02-01 | Background Squeeze Film Damper plays an important role in enhancing the dynamic stability of the rotor and damping rotor vibrations and transmitted forces when traversing critical speeds. Depending on how SFD is designed, SFD can reduce the vibration and transmission forces of the rotating system and it can have the opposite effect. In particular, depending on how the single eccentric rotor system with SFD is mathematically accurately modeled and optimize, the stability of the single eccentric rotor system with SFD is further increased. Purpose The purpose of this study is to improve the stability of the single eccentric rotor system by optimizing the variables affecting the vibration characteristics of the single eccentric rotor system with SFD. Methods By using Lagrange function, the dynamic model for the single eccentric rotor system with SFD was comprehensively and specifically mentioned, and the motion equation of centroid path of the single rotor system with SFD was formulated. Next, the optimization design of the single eccentric rotor system with SFD was carried out using a genetic algorithm and MATLAB program. Results After optimizing the design of the single eccentric rotor system with SFD, the amplitude of the single eccentric rotor system with SFD was reduced by 15.2% compared to before the optimization, and the stability of the single eccentric rotor system was further improved. Conclusion In this paper, we investigated the dynamic modeling method, the motion equation of centroid path and optimization design method of the single eccentric rotor system with SFD. This results will contribute the nonlinear dynamic behaviors of the single eccentric rotor system, and provide a theoretical basis for the analysis of the dynamic modeling, the optimization design, and the nonlinear dynamic characteristic analysis of the dual rotor system. | Optimization Design Analysis of the Eccentric Rotor System with SFD | 10.1007/s42417-021-00406-7 |
2022-02-01 | Purpose This paper deals with the parametrically excited vibrations and mode transitions of a nonlinear damped triple-well oscillator in detail. The multiple timescale structure of the triple-well oscillator with resonant frequency is revealed. We present the correct predictions of the region of parameter space where the periodic orbits alternate between epochs of fast and slow motions in such excited vibrations. Methods Typically, one can treats the cosinoidal part of the perturbation as a singular variable of the whole system, which only remains autonomous form. We study the critical manifold and bifurcation structure of this system. Since the attracting manifold terminated at a fold leading to the change of local stability, the corresponding singular orbit would jump to another stable branch. Characteristic features of this method are folded singularities and structure of the critical manifold. Result Parametrically excited vibrations with resonant frequency could reflect multiple timescale structure. A singular periodic orbit can be constructed, which consists of distinct segments. Starting along the critical manifold with small damped oscillations, then there is a fast transition that flows to another attracting branch for the folded singularity. As the fifth stiffness value varies, mixed-mode oscillations with more jumps are produced. Moreover, the jump-doubling behaviors can be presented under the flip of excitation frequency ratio. Conclusion As we show in the paper, damping and external excitations with resonant frequency ratio in nonlinear vibration system could construct singular periodic orbits. It is possible for the trajectory to jump away from the folded singularity with finite speed. Then, it performs small damped oscillations about one attracting branch of stable foci. By taking advantage of time scale separation, we demonstrate the origin of such bursting behaviors. | Parametrically Excited Vibrations in a Nonlinear Damped Triple-Well Oscillator with Resonant Frequency | 10.1007/s42417-021-00408-5 |
2022-02-01 | One of the devices for passive structural control is the tuned mass damper (TMD) which consists of a mass, spring, and damping. The seismic behavior of structures equipped with tuned mass dampers is influenced by the value of damper components. Generally, the determination of TMD parameters to achieve optimal seismic behavior is defined in the framework of optimization problems. In this paper, the optimal design of TMDs is carried out using different methods and the effect of the optimization method on the optimal design of structures equipped with TMD was investigated. For this purpose, three strategies based on the meta-heuristic optimization method, inverse reliability (IR) method, and reliability-based optimization (RBDO) method are used for the optimum design of TMDs and the seismic responses of the structure are compared for each case. In the reliability-based optimization method, the optimal design is performed with the objective function based on the target reliability of the structure. The results show that the mass and damping of TMD, respectively, have the most and least important in reducing the drift of structure. The reliability index in the structures equipped with TMD is sensitive to the mass and stiffness of the TMD and is not sensitive to damping. Also, the optimal design of TMD was evaluated based on the target reliability. The results show that the RBDO strategy has a good ability to explore the search space, and the designed TMD with the RBDO method has a good performance in the reduction of seismic responses. However, due to the lack of constraints for the design variables domain, the inverse reliability strategy results are unacceptable. | A comparison of deterministic and reliability-based optimization of tuned mass damper under uncertainties | 10.1007/s42107-022-00418-y |
2022-02-01 | Retrofitting is a technique wherein the damaged structure is strengthened to original design requirements. During 2001 Bhuj earthquake in Gujarat, India many open ground storey building damaged. So there is an urgent need for retrofitting of damaged buildings. This calls for techniques that are technically sound and economically feasible to upgrade deficient and damaged buildings. Also, Portland cement (PC) production is under critical review due to high carbon dioxide gas released to the atmosphere and Portland cement is also one among the most energy-intensive construction materials. So retrofitting of existing deficient building using eco-friendly material which could promise higher structural performance than the original building is required. The main contributions is development of retrofitting technique of seismically damaged building using Geopolymer concrete and Chevron steel bracing with passive energy dissipation devices. Experimental studies are carried out using the 4 m × 4 m tri-axial shake table test facility to evaluate the seismic performance of bare frame, Open ground storey building, X-plate retrofitted building, Shear wall retrofitted building. Two three storied half scale model buildings, one open ground storey (OGS) building and a bare frame building are tested for different earthquake inputs in the shake table. The acceleration spectrum of IS1893:2002, soft soil is used as seismic input for the above tests. The failure modes and crack pattern of buildings after the seismic test are analysed. The damaged OGS building after the shake table test is retrofitted. The local retrofitting of columns and beam-column joints in the ground storey is carried out using Geopolymer concrete. The global retrofitting of building is formulated with Chevron type steel bracing incorporating X-plate damper in the ground storey. Sweep sine tests on OGS building before and after retrofitting with X-shaped metallic damper is carried out. The natural frequencies and mode shapes of the models are evaluated. The retrofitted OGS building is again subjected to shake table test to the study the seismic performance under varying amplitude as per IS 1893:2002 ground motion. The same model buildings are analysed in SAP 2000 to predict the seismic performance of the retrofitted RC frames.An innovative technique of retrofitting the seismic damaged building using Geopolymer concrete and construction of shear wall is explored. Two Reinforced Concrete shear walls are constructed inside the open ground storey building as global retrofitting technique. Sweep sine test is carried out after retrofitting with shear wall. The fundamental frequency of open ground storey building increased from 3.75 Hz to 7.25 Hz due to the addition of shear wall. The pushover test on building is carried out. The pushover analysis is carried out to study the seismic response of reinforced concrete building with local and global retrofitting using SAP 2000 software. Comparison of experimental and analytical push over curves is plotted. A significant improvement in the strength and stiffness of the open ground storey building after retrofitting with shear wall is observed. | Development of Retrofitting Technique for Seismically Vulnerable Open Ground Storey Reinforced Concrete Buildings | 10.1007/s40799-021-00456-2 |
2022-02-01 | Due to the significant effect of porosity on the mechanical response of functionally graded (FG) structures, this paper presents a comprehensive model to investigate the vibration response of FG porous thick beam under the dynamic sine pulse load including the damping effect by using adopted finite element model, for the first time. The multilayer thick beam is modeled as two-dimensional plane stress problem. The distribution of material gradation through the graded layer is described by the power law function, and the porosity is depicted by three different distributions (i.e., symmetric-distribution, X-distribution and O-distribution). The damping effect is included in the model by using the Kelvin–Voigt viscoelastic constitutive model. Constitutive equations, gradation and porosity functions are described in detail. Forced motion equations are derived by using Lagrange energy principles. Twelve-node 2D plane element with 3 × 3 integration points is proposed to discretize the beam and get the element matrices and force vectors. The numerical time integration method of Newmark is proposed to solve the system numerical and get the displacement response of the structure. Effects of layer stacking sequence, material gradation index and porosity parameter on the dynamic’s response of thick FG porous damped beam are presented. The presented mathematical model is useful in analysis and design of nuclear, marine, vehicle and aerospace structures those manufactured from functionally graded materials. | Dynamic analysis of viscoelastic functionally graded porous thick beams under pulse load | 10.1007/s00366-020-01070-3 |
2022-01-31 | Particle damping technology has been widely used in many fields to absorb the structural vibration due to its good damping effects in normal gravity environments. However, particle dampers (PDs) become less useful in weightless environments because of their structure and damping mechanism, which limits their applications in this case. To conquer the adverse effects of weightless environments, an electromagnetic particle damper with a ferromagnetic end cover (EPDF) is used, the magnetic force in a similar fashion to gravity, which is caused by the magnetized ferromagnetic end cover, is applied to all the particles in the EPDF. Firstly, a three-dimensional model of an EPDF is established based on the discrete element method (DEM), which is verified through experiments. Then, the damping capability of non-obstructive particle dampers (NOPDs) is compared with that of EPDFs in weightless environments. Moreover, the effects of the current, particle size, filling rate and material of the ferromagnetic end cover on the damping performances of EPDFs are analyzed. It is shown that there are optimum ranges of the current, particle diameter and filling rate for EPDFs, in which the damping performances in weightless environments are good, and a parameter ∆ B (calculated by subtracting the magnetic flux density of the magnetic field without the ferromagnetic end cover from that on the end surface of the magnetized end cover) is used to depict the effect of the ferromagnetic end cover material, there is also an optimum range of ∆ B for EPDFs, the permeability of the end cover is supposed to be small when the magnetic induction intensity of the magnetic field is strong. Finally, the damping effects of the NOPD in ground gravity environments are compared with that of the EPDF in weightless environments, the damping performances of them are similar. Therefore, the damping effects of PDs in weightless environments can be improved greatly by the application of EPDFs. | Study on Damping Behavior of Electromagnetic Particle Dampers with a Ferromagnetic End Cover in Weightless Environments | 10.1007/s12217-022-09930-x |
2022-01-30 | In this note, we mainly consider the trajectory attractors of the three-dimensional micropolar fluids with damping. Due to the existence of weak solutions, the existence of trajectory attractors for 3D micropolar fluids with damping term is proved for $$1\le \beta <\frac{7}{3}$$ 1 ≤ β < 7 3 with $$\sigma >0$$ σ > 0 . | Trajectory Attractors of the 3D Micropolar Equations with Damping Term | 10.1007/s00009-021-01965-5 |
2022-01-29 | In practice, principal stress rotation is a common phenomenon triggered by dynamic loading. Determining the dynamic deformation characteristics of frozen soil is extremely important for designing a structure with considering principal stress rotation under multiaxial loading conditions. In this study, cyclic rotational shear tests that considered principal stress axis rotations for different terms of CSR s and frequencies were performed using a frozen hollow cylinder apparatus (FHCA-300) to investigate the dynamic deformation features of frozen clay. From the experimental results, the evolution characteristics of accumulative plastic strains, hysteresis loops, dynamic resilient modulus, and damping ratios were analyzed. The findings suggested that increasing the CSR accelerates the growth of accumulative plastic strain, degrading stiffness and increasing the dissipation energy. A smaller loading frequency led to a larger accumulative plastic strain at a certain loading cycle, stiffness degradation increased with decreasing loading frequency, and the ability to absorb dissipation energy simultaneously increased. Moreover, the resilient modulus significantly decreased at the beginning of loading, after which it slowly increased. This implied that a stable soil structure was formed through continuous changes in particle orientations, realignments, and rearrangements during the first few cycles and that cyclic loading promoted sample densification. | Dynamic deformation characteristics of frozen clay under pure principal stress rotation | 10.1007/s12517-022-09572-8 |
2022-01-29 | Gas oil-contaminated lands are one of the main issues and concerns in the field of geoenvironmental engineering. This research has conducted studies on the dynamic properties, in particular, on two parameters of damping ratio and shear modulus of fine-grained soils contaminated with gas oil (gas oil plays a greater role in contamination because of its wide variety and use) in different emission levels (maximum 16%). Since there is, in many clay sites of nature, some non-cohesive fine-grained materials, such as silt or fine-grained sand, in addition to cohesive fine-grained materials, investigating the mentioned properties in mixed clays (up to 20% fine-grained sand) has been included in this study. In order to determine the dynamic shear modulus and damping ratio of the tested specimens in the large strain, the cyclic triaxial apparatus of the Amirkabir University of Technology and the bender elements have been used in the small strain and controlled strain conditions, respectively. Moreover, we used a scanning electron microscope (SEM) to examine and evaluate the condition of particle surfaces and observe microstructure samples before and after contamination. According to the results of the above studies, contamination in pure clay sites, up to 8% gas oil, will increase the shear modulus and decrease the damping ratio and in addition decrease the modulus and increase the damping. The mixed clay sites containing small amounts of fine-grained sand (up to about 10%) follow the same trend; however, more fine-grained sand in clayey at all emission levels will reduce the shear modulus and increase the damping ratio. | Effect of gas oil contamination on dynamic geotechnical properties of clay–sand mixtures | 10.1007/s12517-022-09515-3 |
2022-01-28 | This paper discusses a passive vibration control method to improve the shock tolerance of hard disk drives (HDDs) in operating condition (op-shock tolerance). Past works in improving the HDDs’ op-shock tolerance includes (i) parking the head when shock is detected, (ii) installing a lift-off limiter, (iii) structural modification of the suspension, and (iv) installing an external vibration isolation. Methods (i) and (iv) have practical issues, method (ii) works only on single shock direction, and method (iii) requires major engineering design/manufacturing work. Compared to these works, this paper proposes a method which has no practical issues and without requiring major engineering design/manufacturing work. The proposed method is to apply a polymer-based dampening layer on the backside of the baseplate with the purpose of increasing the damping ratio of the 1st bending mode of the baseplate. The location of the dampening layer on the baseplate is first determined by modal analysis and then fine-tuned by non-op-shock tests. The op-shock tolerance improvement is confirmed by op-shock tests where 2.5″ HDD with the dampening layer on the baseplate can withstand a 300G 0.5-ms shock without failure while unmodified HDD can only withstand 250G 0.5-ms shock without failure. | Polymer-based dampening layer application to improve the operating shock tolerance of hard disk drive | 10.1186/s44147-021-00062-4 |
2022-01-24 | In this paper, we consider a nonlinear coupled Kirchhoff system with viscoelastic damping and a distributed delay. We established a general stability result, where an exponential result in the literature is only a particular case. We illustrate the stability result with some examples. | A general stability result for a nonlinear viscoelastic coupled Kirchhoff system with distributed delay | 10.1007/s13370-021-00947-w |
2022-01-24 | Under-platform dampers (UPDs) are traditionally used in aircraft engines to reduce the risk of high cycle fatigue. By introducing friction in the system, vibrations at resonance are damped. However, UDPs are also the source of nonlinear behaviours making the analysis and the design of such components complex. The shape of such friction dampers has a substantial impact on the damping performances, and topology optimisation is seldomly utilised—particularly for nonlinear structures. In the present work, we present a numerical approach to optimise the topology of friction dampers in order to minimise the vibration amplitude at a resonance peak. The proposed approach is based on the moving morphable components framework to parametrise the damper topology, and the efficient global optimisation algorithm is employed for the optimisation. The results demonstrate the relevance of such an approach for the optimisation of nonlinear vibrations in the presence of friction. New efficient damper geometries are identified in a few iterations of the algorithm, illustrating the efficiency of the approach. Results show that the most efficient geometry divides the vibration amplitude at resonance by 3, corresponds to a lower mass (80%) and a smaller frequency shift compared to the non-optimised case. More generally, the different geometries are analysed and tools for clustering are proposed. Different clusters are identified and compared. Thus, more general conclusions can be obtained. More specifically, the most efficient geometries correspond to geometries that reduce the mass of the damper and increase the length of the contact surface. Physically, it corresponds to a reduction of the initial normal contact pressure, which implies that the contact points enter stick/slip earlier, bringing more damping. The results show how topology optimisation can be employed for nonlinear vibrations to identify efficient layouts for components. | Topology optimisation of friction under-platform dampers using moving morphable components and the efficient global optimization algorithm | 10.1007/s00158-021-03158-w |
2022-01-24 | The present study deals with the primary damped natural frequency of dielectric composite beam reinforced with graphene platelet (GPL). The beam is subjected to pre-stress in the longitudinal direction and external electrical loading throughout the beam thickness direction for tuning the frequency characteristics. The material properties of the composites required for structural analysis are determined by effective medium theory (EMT) and rule of mixture. Using Timoshenko beam theory and Hamilton’s principle, the governing equations for damped nonlinear free vibration of the beam are derived and solved numerically by differential quadrature (DQ) and direct iterative methods. The effects of the attributes of the electrical loading and the GPL fillers on the damped free vibration characteristics are investigated. The analysis shows that when the GPL concentration is greater than the percolation threshold, the voltage of the electrical loading and GPL aspect ratio start to play a vital role in the damped vibration. The nonlinear damped frequency of the hinged-hinged (H–H) beam decreases by 83.8% when the voltage increases from 0 to 30 V. It is found that there exist two critical AC (alternating current) frequencies, i.e., approximate 10^−3 Hz and 10^2 Hz, around which the primary damped natural frequency has a sudden jump as AC frequency either slightly increases or decreases. The vibration characteristics presented demonstrate the potential of developing smart composite structures whose vibration characteristics can be actively tuned by changing the attributes of the applied electrical loading. | Primary nonlinear damped natural frequency of dielectric composite beam reinforced with graphene platelets (GPLs) | 10.1007/s43452-021-00369-2 |
2022-01-24 | Background Detection of locally increased blood concentration and perfusion is critical for assessment of functional cortical activity as well as diagnosis of conditions such as intracerebral hemorrhage (ICH). Current paradigms for assessment of regional blood concentration in the brain rely on computed tomography (CT), magnetic resonance imaging (MRI), and perfusion blood oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI). Results In this study, we developed computational models to test the feasibility of novel magnetic sensors capable of detecting hemodynamic changes within the brain on a microtesla-level. We show that low-field magnetic sensors can accurately detect changes in magnetic flux density and eddy current damping signals resulting from increases in local blood concentration. These models predicted that blood volume changes as small as 1.26 mL may be resolved by the sensors, implying potential use for diagnosis of ICH and assessment of regional blood flow as a proxy for cerebral metabolism and neuronal activity. We then translated findings from our computational model to demonstrate feasibility of accurate detection of modeled ICH in a simulated human cadaver setting. Conclusions Overall, microtesla-level magnetic scanning is feasible, safe, and has distinct advantages compared to current standards of care. Computational modeling may facilitate rapid prototype development and testing of novel medical devices with minimal risk to human participants prior to device construction and clinical trials. | Development of computational models for microtesla-level magnetic brain scanning: a novel avenue for device development | 10.1186/s42490-022-00058-y |
2022-01-19 | We introduce a unitary operator which may be constructed conveniently by exploiting the properties of the Glauber displacement and parity operators. We show that it can be considered as a constant of motion of a quantum system including pure dephasing interaction of a central qubit with a nano-mechanical resonator. Using the eigenvectors of the Glauber displacement operator, we paves a way for an extensive study of the dynamics of resonator-qubit states. In addition, we show that the establishment of such a constant of motion, which includes the parity operator, provides a way to introduce a capable mechanical framework to generate some desired mechanical state as superposition of the Glauber coherent states. We investigate nonclassical properties of the generated mechanical states, by evaluating mechanical-squeezing, Wigner function, position–momentum entropic squeezing, and entanglement between spin-mechanical modes. Furthermore, the pairwise classical and quantum correlations are derived based on a necessary and sufficient condition for the zero-discord state. Finally, in order to study the mechanical state’s behavior in an environment, we consider that the output state is subject to amplitude (phase)-damping channels and their dissipative properties are analyzed. | Entanglement dynamics of a nano-mechanical resonator coupled to a central qubit | 10.1007/s11128-021-03372-x |
2022-01-19 | In this paper, we investigate the exponential stability of an Euler-Bernoulli beam system with distributed damping subjected to a time-delay in the boundary. At first, applying the semigroup theory of bounded linear operators we prove the well posedness of the system. And then we give the exponential stability analysis of the system by constructing an appropriate Lyapunov function. Different from the earlier results, we use the damping coefficient α $\alpha $ and delay coefficient β $\beta $ together with the parameters of the system to give a description of the stability region. The simulation are presented to prove the effectiveness of this results. | Stabilization of an Euler-Bernoulli Beam with Distributed Damping Under Time Delays in the Boundary | 10.1007/s10440-022-00466-1 |
2022-01-11 | Forced vertical vibration tests were carried out in the field on 5.8 m long driven single steel pipe pile with external and internal diameter of 0.166 m and 0.154 m. Tests were conducted on single on 2 × 2 group piles under a static load ( W _ s ) of 15 kN. The field test results include the determination of frequency-amplitude responses and soil-pile separation length for single pile and group piles, respectively. The frequency-amplitude responses from the experimental results were compared to the theoretical predictions based on the continuum approach analysis utilizing the soil-pile separation depth from the experimental investigation. It was noticed that the theory well anticipates the nonlinear characteristics of the frequency-amplitude responses of the soil-pile system. | Vertical nonlinear response of single and 2 × 2 group pile under strong harmonic excitation | 10.1007/s12046-021-01789-9 |
2022-01-04 | The A.D. 1803 and 1934 Bihar-Nepal border earthquake affected Indo-Gangetic Plain with evidences of liquefaction in cities like Patna, Varanasi, Agra, and Delhi in historical past. Recent strong shaking all along the Indo-Gangetic Plains and seismic induced damage to the buildings in Bihar during M_w 7.8 Gorkha earthquake raises the concern for site specific liquefaction potential estimation of alluvial soils. Cyclic triaxial tests were conducted on soil samples from Kanpur, Allahabad, Patna city to know the cyclic behavior, estimate the dynamic soil properties and the effect of relative density, confining pressure and frequency of loading on the cyclic behavior of the soil tested. The test results indicate the cyclic strength of Allahabad soil is less than Patna and Kanpur soil. The Allahabad soil with 80% sand, 10% silt and clay each is more prone to liquefaction than Kanpur soil (82% silt, 16% clay and 2% sand) and Patna soil (10% Kankar, 95% sand, 5% silt). This study indicates soils having sand with silt percentage are more liquefiable than clean sand or silty soil. It can be concluded that the soil of Allahabad and Patna city is more prone to liquefaction than Kanpur soil. | Cyclic behavior of late quaternary alluvial soil along Indo-Gangetic Plain: Northern India | 10.1186/s40703-021-00167-y |
2022-01-01 | Polymer materials are being used in several mechanical and aerospace engineering applications. However, their applications to high-performance components and structures, in particular, those operating under dynamic loadings and service conditions are still limited. To overcome this limitation, their mechanical properties, especially the dynamic properties, need to be enhanced. This enhancement can be achieved in an efficient way by using carbon nanotubes as reinforcement material. The resulting nanocomposite material is called as “nanocomposite material.” However, experimental investigations to characterize the material behavior, especially the dynamic behavior of nanocomposite materials have limitations. Computational modeling and simulation encompassing multiscale material behavior provide an efficient alternate approach in this regard. In the present chapter a multiscale computational framework for the Representative Volume Element (RVE) of Carbon-Nanotube-Reinforced-Polymer-Composite (CNTRPC) materials, is presented to characterize their dynamic mechanical behavior. The focus is set on the energy dissipation capability and the modal response. A three-dimensional multiscale finite element model of the polymer matrix, the Single-Walled-Carbon-Nanotube (SWCNT) and the interface region is constructed. The SWCNT is modeled as a space frame structure by using the Morse potential and as a thin shell model based on Donnell’s Shell Theory. The polymer matrix is modeled with the Mooney-Rivlin strain energy to calculate its nonlinear response and the interface region is modeled via van der Waals links based on the Lennard-Jones Potential. The developed model and simulation methodology are validated using the existing results available in the literature. The elastic modulus and two types of damping properties, that are, viscous damping and structural damping are characterized based on the developed multiscale finite element model. The natural frequencies are also determined. | Characterization of the Dynamic Response of CNT-Reinforced-Polymer-Composite (CNTRPC) Materials Based on a Multiscale Approach | 10.1007/978-3-030-91346-5_25 |
2022-01-01 | Damping is a phenomenon that can be observed in connection with all kind of materials: solid, liquid, or gaseous. Any kind of time-dependent change in stresses or strains of the material results in a loss of mechanical energy, which in most cases is transformed into thermal energy. However, all the other mechanisms such as the conversion into electrical energy or any kind of radiation over the system’s boundaries play a role. Typical observations that can be made in connection with damping are the occurrence of creep and relaxation processes or hysteresis curves in the case of cyclic loadings. The overall damping is influenced by a variety of mechanisms, especially for structures assembled from different components. No matter whether the presence of damping is sought or should be avoided in technical applications, for any kind of tuning or optimization of a system under consideration, a basic understanding of the underlying physics is needed. This is especially true if calculations or simulations have to be run in order to predict the dynamical behavior of a system. This chapter intends to introduce the reader into the subject and provide an extensive overview on the different aspects of damping regarding the fundamentals, mathematical, and numerical models as well as experimental techniques for the detection of damping properties. It shall give an overview of the state of knowledge and experience gathered in various fields of application and research. For further information, the reader is referred to various publications and textbooks whenever needed. This chapter is organized as follows: Sect. 1 provides an extensive overview on the topic, the classification of damping phenomena, and some remarks on computer-based programs. Section 2 refers to the damping of solids, while Sect. 3 extends the view on structures assembled from different components. Section 4 deals with different mathematical models toward the description of damping and relevant numerical approaches. Experimental techniques for the detection of the damping parameters needed for calculations are described in Sect. 5. This includes possible instrumentation as well as analytical methods. Finally, in Sect. 6, an application of the whole subject covering the detection of damping properties, its mathematical representation, and parameter identification along with a numerical simulation is presented as an example. Conclusions from this chapter are drawn in Sect. 7. | Damping of Materials and Structures | 10.1007/978-1-4614-4547-0_19 |
2022-01-01 | The present chapter is devoted to the investigation of the nonlinear dynamics of DNA molecules in the helicoidal Peyrard-Bishop DNA model with long-range interactions. The power law long-range interactions with distance dependence $$|l|^{-s}$$ on the elastic coupling constant between different DNA base pair units are considered. We take into account the Stokes and the hydrodynamic damping forces in the long-range approximation. In the short wavelength modes, using the discrete difference operator technique, we show that the discrete lattice equation of motion is reduced to the complex Ginzburg-Landau equation, allowing breather soliton solutions. In the non-viscous limit, the system is shown to be governed by the nonlinear Schrödinger equation. We considered the relevant case $$s=3$$ , and showed analytically, that the method leads to a more appropriate expression for the breather soliton parameters as compared to the popular semi-discrete approximation. | Nonlinear Dynamics of DNA Chain with Long-Range Interactions | 10.1007/978-981-19-5323-1_4 |
2022-01-01 | In this chapter, the steady-state and transient responses of systems are presented. Most of the input signals to systems have arbitrary amplitude and it is difficult to characterize the response of the systems. Therefore, the response of the systems is determined for some standard signals, which is sufficient for the design and characterization of systems. When an input signal, such as the unit-step signal, is applied to a system, the output cannot follow the input instantaneously. This is so, due to the resistance offered by the system to the build-up of the output signal. For practical purposes, the duration of the resistance, called the transient interval or the interval of signal formation, lasts only for a short time for stable systems. The remaining asymptotic behavior is called the steady-state or stationary or permanent state. The steady-state error can be obtained from the open-loop transfer function. The transient response of systems is characterized by the damping ratio and the undamped natural frequency. Typical parameters of the transient response are rise time, delay time, settling time, peak time, and maximum overshoot. Often, the performance characteristics of control systems are specified in terms their unit-step responses. | Steady-State and Transient Responses | 10.1007/978-3-030-98445-8_6 |
2022-01-01 | The present study focuses on variation of dynamic properties of soils with change in stress path. Cyclic triaxial test, which is the most common laboratory test used to evaluate the dynamic properties of soils, suffers several limitations. Two major limitations are its inability to introduce continuous rotation of principal stress axes and the difference in simulated stress path when compared to vertically propagating shear waves. Present study focuses on quantifying one of these limitations, effect of change in stress path on the dynamic properties of soils, including shear modulus and damping ratio. Also, cyclic triaxial tests are created and performed in a way to simulate more realistic stress paths through slow dynamic loading. To keep the stress path vertical, minor principal stress is decreased with the increase in major principal stress by reducing the confining pressure. These tests showed that hysteresis loops became considerably broader with the stress path getting vertical, shear modulus decreased by about 25–45% and damping ratio increased by about 40–70% compared to conventional cyclic triaxial test. These results proved that the shear modulus is overestimated, and damping ratio is underestimated in a conventional triaxial test with inclined stress path, which does not actually represent a field scenario. The new tests with vertical stress path provide more realistic estimates of dynamic soil properties. | Dynamic Properties of Soils—A Stress Path Approach | 10.1007/978-981-16-5669-9_14 |
2022-01-01 | This chapter features discussions of the effects of cone mass, suspension/box compliance, and damping on the fundamental low-frequency resonance and the Q and bandwidth of that resonance. The analytical results are also closely correlated with precision lab measurements and the factors of electromagnetic and overall system damping, QE and QT, were compared. | Resonance, Q, and Measurements | 10.1007/978-3-030-91634-3_14 |
2022-01-01 | The controller tuning is first described in time, Laplace , and frequency domains. There are empirical methods based on settability of plants without building mathematical models of the plant such as methods of Ziegler / Nichols , Strejc , Chien/Hrones/Reswick , Kuhn , and Latzel . Then follow methods based upon integral criteria of the given transfer function of the plant with and without actuator limitations. The tuning in the Laplace domain is represented with classical methods like Hurwitz stability criteria, optimum magnitude, symmetrical optimum, and pole placing. The tuning in the frequency domain is described in the classic method of the Nyquist stability criterion. | Controller Tuning | 10.1007/978-3-031-13483-8_3 |
2022-01-01 | The article provides a brief classification of electromechanical dampers in vehicle suspensions. As investigated version of design of electromechanical shock absorber is suggested model with ball-screw drive of generator as investigated version of design of electromechanical shock absorber. The main components of the damping force are indicated: the force of inertia and the force of electromagnetic resistance. The given resistance forces are expressed taking into account the drive parameters. Presented mathematical model of electromechanical suspension damper of vehicle wheels considers parameters of motion as vehicle speed and height, and length of overcome irregularity is taken into account. Suggested model makes it possible to determine kinematic parameters of movable elements of electromechanical damper values of inertial and electromagnetic components of damping force and also generated electric energy, on conditions of vehicle movement and connected external load. Due to the presented dependencies, it was revealed that when determining the power of the generator for operation as part of an electromechanical damper, the most significant parameters are the rotation speed and efficiency of the generator, which in turn depend on the rotation speed of its rotor and the load connected to the stator outputs. The interrelationships presented in the work make it possible to investigate the influence of mass size and electromagnetic parameters of elements of electromechanical dampers on their operating characteristics, to use them as recommendations when designing electromechanical dampers. | Development of a Mathematical Model of Electromechanical Dampers with a Regenerative Effect in Vehicle Wheel Suspensions | 10.1007/978-3-030-85230-6_23 |
2022-01-01 | In this chapter, the modeling, controller design, and stability analysis of islanded microgrid using enhanced hierarchical control structure with multiple current loop damping schemes are proposed. And then, a small-signal model for the primary and secondary controls with additional phase-shift loop is presented, and the moving average filter-based sequence decomposition method is proposed to extract the fundamental positive and negative sequences, and harmonic components. Next, the multiple inner current loop damping scheme is presented, including the virtual positive, virtual negative, and variable harmonic sequence impedance loops for reactive and harmonic power sharing purposes and the proposed active damping scheme using capacitor current feedback loop of the LCL filter, which shows enhanced damping characteristics and improved inner-loop stability features. Then, the simulation results obtained from EMTP-ATP under nonidentical line impedance scenario are presented, and the effect of the low-bandwidth communication delay is also simulated and compared with ideal scenario. Finally, the experimental results are also provided to validate the feasibility of the proposed approach, which can be widely applied in practical applications. | Enhanced Hierarchical Control for Islanded Microgrid Using Advanced Damping Methods | 10.1007/978-3-030-74513-4_8 |
2022-01-01 | A pickup is an example of what an engineer would call a transducer . A transducer is a device that transforms a non-electrical quantity (temperature, strain, pressure, velocity, etc.) into an electrical signal. Of course, here we are interested in converting the vibration of a string into a corresponding electrical signal. | Pickups and Volume and Tone Controls | 10.1007/978-3-031-10758-0_2 |
2022-01-01 | Modern production is impossible without developing and improving lifting and transport mechanisms, which is indispensable for various technological processes. The article concerns the optimal control on the swing mechanism regarding speed and simultaneous damping of load oscillations. It is shown that the law of change in the dynamic torque of an electric drive obtained using the Pontryagin maximum principle ensures the damping of the load oscillations by the end of the transient process the turning mechanism and to minimize the duration of these processes. The necessity of joint use of the mechanism for changing the boom outreach as the second control action, which, according to the derived law, changes the radius of rotation of the load suspension point for damping the deflection angle's normal component, has been substantiated. The mathematical model was created for calculating the transient start (braking) process in the Matlab mathematical modeling package for optimal control over the swing mechanism. Analysis of the graph of transient processes allows us to conclude that the proposed method fully satisfies conditions. | Control Optimization of the Swing Mechanism | 10.1007/978-3-030-91327-4_2 |
2022-01-01 | The basics of the dynamics of the closed loop control (CLC) are described in a compact way according to [16–20] to make it easier to get started with the next chapters on controller setting and management of controllers. The description starts by presenting the single CLC blocks in the time domain as differential equations. Then the Laplace-transform is briefly presented and the transition from Laplace-domain to frequency domain is shown. The controlling plants are divided according to their dynamical behavior in P, I, and D types and are summarized in tables corresponding to differential equations, transfer functions, and bode plots. The same classification is done in tables concerned P-, I-, and D-terms of controllers. The definition of transfer functions of an open loop and closed loop is given, and the transfer functions of setpoint and disturbance behavior are defined. The stability and performance criterion of CLC are discussed. The tuning of controllers is separated in the next chapter. | Basics of System Dynamics and Control Theory | 10.1007/978-3-031-13483-8_2 |
2022-01-01 | In this study, phase compensated hydro-turbine governor for stabilizing power system oscillations. As per deregulation in electricity market, much pressures are imparted on optimal use of resources like mechanical turbine governor action. Since mechanical torque control and excitation control of generator are decoupled, regulating generator voltage is not affected by turbine governor control. Also, mechanical torque control is less influenced by system operating condition. So here optimal phase compensation has been included with turbine governor for enhancing damping efficiency of governor which has been found to provide much improvement in dynamic stability: without hampering voltage control and power frequency regulation. The gains of compensation block and governor have been tuned by DE, PSO and squirrel search algorithm (SSA). The results with only governor action and proposed SSA optimized compensated governor have been compared with different case studies like change in mechanical input and reference voltage with system eigenvalues analysis for justifying effectiveness of proposed governor control. | Optimal Compensation of Hydro Governor for Power Oscillation Damping | 10.1007/978-981-16-7076-3_5 |
2022-01-01 | This paper presents a passivity-based control strategy dealing with underactuated two-degree-of-freedom (2-DoF) mechanical systems. Such a methodology, which is based on the interconnection and damping assignment passivity-based control (IDA-PBC), rooted within the port-controlled Hamiltonian framework, can be applied to a very large class of underactuated 2-DoF mechanical systems. The main contribution, compared to the previous literature, is that the new methodology does not involve the resolution of any partial differential equation, since explicit solutions are given, while no singularities depending on generalised momenta are introduced by the controller. The proposed strategy is applied to two case studies: a) the stabilisation of a translational oscillator with a rotational actuator (TORA) system; b) the gait generation for an underactuated compass-like biped robot. The performances of the presented solution are evaluated through numerical simulations. | A Constructive Methodology for the IDA-PBC of Underactuated 2-DoF Mechanical Systems with Explicit Solution of PDEs | 10.1007/s12555-020-0839-1 |
2022-01-01 | The paper presents an analysis of force versus displacement characteristics of mechanical, magnetic, and electromagnetic springs. Since electromagnetic spring force can be controlled by altering the current in coil, they can be used for damping the vibrations. New physical model of magnetic springs have been proposed and have been subjected to experimental verification on a specially designed and built experimental stand. The stand consists of an aerostatic guide that has one degree of freedom. Thanks to aerostatic supports, we can neglect dry friction. This article presents a method of changing the characteristics of magnetic springs by controlling the current in the coil. A novel method for tailoring electromagnetic force characteristic has been presented. Numerous experiments were carried out to determine the characteristics of specific system components and validate the proposed mathematical models. To damp the movement of the whole system, a current controller with a feedback loop has been developed and presented in this work. | Magnetic and Electromagnetic Springs Forces: Determination and Usage in Damping Vibrations | 10.1007/978-3-030-81166-2_11 |
2022-01-01 | This paper analyzes the dynamic performance of the energy harvesting shock absorber (EHSA), which contains overrun clutch and rack and pinion. The results show that the output force of EHSA is composed of the inertial force and the damping force. The inertial force is produced by the motion of the moving parts of the EHSA, and the inertial mass of the moving parts can be equivalent to the negative equivalent stiffness. The damping force is generated by the motor, and it is dependent on the transmission efficiency and the transmission ratio. Due to the change in transmission path, the dynamic performances of EHSA in upward stroke and downward stroke are different. The equivalent stiffness in downward stroke is larger than that in upward stroke, and the equivalent damping coefficient and the output voltage in upward stroke are larger than that in downward stroke. The difference between upward stroke and downward stroke is related to the transmission ratio i _p. | Dynamic Modeling for a Mechatronic Energy Harvesting Shock Absorber | 10.1007/978-3-030-81170-9_19 |
2022-01-01 | Strapdown Inertial Navigation Systems (SINS) have advantage of simplified construction, modular design, low cost and less life cycle support as compared to navigation systems that employee gimbaled platforms. This paper presents full mathematical modeling and simulation of a typical SINS system starting from modeling of IMU errors and generation of IMU output for a known reference trajectory. While considering the output of IMU as the input for SINS, the IMU data is solved while employing determination of quaternion rate differential equations to reconstruct the original trajectory. Finally coupling of vertical channel is performed with barometric 3rd order damping loop to minimize error in the vertical direction. Moreover, selection of appropriate damping loop gains is performed on the basis of comparison of errors calculated in vertical direction against each set of loop gains. | SINS Integration with Baro-Inertial Vertical Channel Damping for Error Optimization | 10.1007/978-981-15-8155-7_95 |
2022-01-01 | Preliminary design of piles is performed by considering the static loads, but the final design must include the dynamic loads, especially in earthquake-prone regions. The soil nonlinearity under seismic loading is evaluated using the modulus degradation curves in the total-stress approach. In this study, two different centrifuge tests were simulated in FLAC^3D. The nonlinear elastic method (hyperbolic model) and the elastoplastic Mohr-Coulomb (MC) model were employed in the study. The soil-single pile-structure systems were analyzed under the specific earthquake events, and the soil-pile-structure response was compared. The analyses with the low-intensity input motions show that the superstructure accelerations and the bending moments in the single pile are estimated with reasonable accuracy. However, the superstructure accelerations might be underestimated, especially in the MC model, compared to the centrifuge test results due to the increase in the amplitude of the input motion. The low accelerations can be attributed to the high damping ratios in the perfectly plastic constitutive model. Although the nonlinear elastic model is less complex, closer results might be obtained since the more realistic damping ratios are implemented. The results show that even the less elaborate models, such as the hyperbolic model with an indefinite failure criterion, might give reasonably accurate results in the total-stress approach, thanks to the limited damping ratios. As a result, the responses of the superstructure and the pile in soil-pile-structure interaction problems are highly dependent on the soil damping; in turn, the due account must be given to the selection of the constitutive model. | The Effect of Soil Damping on the Soil-Pile-Structure Interaction Analyses in Liquefiable and Non-liquefiable Soils | 10.1007/978-3-031-11898-2_83 |
2022-01-01 | Suspension vibrations occur when a vehicle moves across a rough surface. These vibrations, with vibration frequency equal to that of the suspension, lead to resonance. When resonance occurs, the dynamic loads increase many times over, which may lead to fatigue in the metal elements of the body structure. The use of rubber bushings and shock absorbers reduces the amplitude of vibrations but does not eliminate them. To localize and dampen them, a use of a damping device in a car's suspension is proposed. The recommended solution provides absorption of longitudinal vibrations of the suspension elements near resonant frequencies. The principle of dynamic vibration absorption is principal in the design of the structural diagram. A design of a car suspension damper is considered. A mathematical model of the car suspension with a damper and the results of its computer simulation by a numerical method are presented. According to the mathematical analysis of the results obtained, the parameters of the absorber for a specific car model are determined. | Dynamic Damping of Vibrations in the Suspension of Cars | 10.1007/978-3-030-85230-6_38 |
2022-01-01 | We consider asymptotic behaviors of the Vlasov-Poisson system with radiation damping in three space dimensions. For any smooth solution with compact support, we prove a sub-linear growth estimate of its velocity support. As a consequence, we derive some new estimates of the charge densities and the electrostatic field in this situation. | Asymptotic growth bounds for the Vlasov-Poisson system with radiation damping | 10.1007/s10473-022-0104-1 |
2022-01-01 | Impact dampers are passive devices used to attenuate vibrations by means of momentum transfer and dissipation of energy. This paper deals with investigations carried out to evaluate the damping ratio of an impact damper system for case without and with impact ball of same size made of different materials. Finite element modelling of the system is carried out using ANSYS FEA (finite element analysis) software. Simulation studies are carried out using Augmented Lagrangian Multiplier (ALM) contact algorithm to obtain the transient response of the system. The transient response of the system is evaluated from the forces generated due to impact of ball on the primary system. Theoretical studies are carried out with impact mass placed at tip of cantilever beam by varying base excitation frequency in vicinity of systems fundamental frequency to obtain the frequency response curve. The response curves thus obtained with impact mass made of different materials show that damping achieved with higher impact mass is very effective in attenuating the vibration response. Results from simulation studies show good agreement with experimental data. The effect of damping with different mass ratio is also investigated. | Numerical Simulation of an Impact Damper System by Finite Element Method | 10.1007/978-981-16-4138-1_25 |
2022-01-01 | Resonant Ultrasound Spectroscopy estimates the stiffness coefficients of a material from the free resonant frequencies of a single specimen. It is particularly suitable for complete stiffness characterization of anisotropic materials available only as small samples (typically a few mm), and it does not suffer from some limitations associated to quasi-static mechanical test and ultrasound wave velocity measurements. RUS has been used for decades on geological samples and single crystals, but was until recently not applied to mineralized tissues such as bone. The reason is the significant mechanical damping presents in these materials, which causes the resonant peaks to overlap and prevent a direct measurement of the resonant frequencies. This chapter describes the use of RUS for the elastic characterization of mineralized tissues, cortical bone in particular. All steps are described, from sample preparation and measurement setup to signal processing and data analysis, including the developments and adaptions necessary to overcome the difficulties linked to damping. Viscoelastic characterization, from the width of the resonant peaks, is also presented. Mostly technical aspects are developed in this chapter, while the data obtained from RUS on several collections of mineralized tissues specimens are presented and discussed in Chap. 13. | Measurement of Cortical Bone Elasticity Tensor with Resonant Ultrasound Spectroscopy | 10.1007/978-3-030-91979-5_12 |
2022-01-01 | In this paper, we consider the following nonlinear viscoelastic wave equation with variable exponents: $$u_{tt}-\Delta u+\int_{0}^{t} g(t-\tau)\Delta u(x,\tau)\rm{d}\tau+\mu u_{t}=\vert u\vert^{p(x)-2}u,$$ u t t − Δ u + ∫ 0 t g ( t − τ ) Δ u ( x , τ ) d τ + μ u t = | u | p ( x ) − 2 u , where μ is a nonnegative constant and the exponent of nonlinearity p (·) and g are given functions. Under arbitrary positive initial energy and specific conditions on the relaxation function g , we prove a finite-time blow-up result. We also give some numerical applications to illustrate our theoretical results. | Theoretical and numerical study of the blow up in a nonlinear viscoelastic problem with variable-exponent and arbitrary positive energy | 10.1007/s10473-022-0107-y |
2022-01-01 | An eigenvalue problem for a pair of harmonic functions is considered; it contains a spectral parameter in the Steklov condition on a part of the boundary. This problem concerns eigenvalues of fluid’s free oscillations in a vertical, cylindrical container; its cross-section is arbitrary, whereas a porous medium occupies a bottom-adjacent layer. Assuming the fluid to be inviscid, incompressible and heavy, properties of its eigensolutions are investigated. | Sloshing in a Vertical Cylinder in the Presence of a Porous Layer | 10.1007/978-3-030-93076-9_19 |
2022-01-01 | Earthquakes are the most disastrous forces which cannot be stopped but their effects can be diminished with minimal causalities. Over the period of time, the seismic design procedure has evolved in many ways. Traditional force-based design cannot be design structure for a particular intended performance objective. The latest approach for seismic design of the structure is displacement-based, because displacement is a batter indicator of damage. Direct displacement-based design is one kind of displacement-based design, firstly proposed by Priestley ( 1993 ). In this approach the structure is converted into an equivalent single-degree of freedom system. With the help of displacement spectrum for the known limit of design displacements one can determine the effective period. After calculating the effective time period, the stiffness and the base shear are calculated. Further, this design philosophy has been developed by other researchers and the multi-degree of freedom system also has been used in place of the equivalent single-degree of freedom system. This method not only consider the higher mode effect but also considers the P-Δ effect. Finally, unified performance-based seismic design also been advocated which can accommodate both drift and member performance level in the design process. | Advancement in Direct Displacement-Based Design: A Review | 10.1007/978-3-031-04793-0_23 |
2022-01-01 | High damping rubber bearings (HDRB) is a useful seismic resistant device that is widely used in buildings due to many outstanding advantages. However, the mechanical characteristics of HDRB are complicated such as temperature-dependent, rate-dependent. This paper is devoted to investigate the low temperature dependence of HDRB’s mechanical behavior. For this purpose, the experiments on HDRB conducted at −30 °C, −10 °C, and 23 °C is to investigate the low temperature dependence of mechanical behavior of HDRB. A numerical calculation to determine the viscosity of HDRB was conducted to investigate the low temperature dependence of HDRB’s viscosity. Experimental results show that a significant increase in the rate-dependent overstress at low temperatures. This behavior can be ascribed to the temperature dependence of HDRB’s viscosity. It means that the viscosity effect of the material increases when temperature decreases. In addition, the experimental observations indicate that the rate sensitivity of HDRB depends on the low temperatures. On the contrary, the dependence of the rate-independent equilibrium stress at the end of the relaxation process is quite weaker. Furthermore, the results of the numerical calculation to identify the viscosity of HDRB also agree with the conclusions obtained from the experimental observations. | Low Temperature Effect on Dynamic Mechanical Behavior of High Damping Rubber Bearings | 10.1007/978-981-16-3239-6_16 |
2022-01-01 | Nonlinear vibration isolation systems with both stiffness and damping nonlinearities are promising for a broad-band and high-efficient isolation performance. In this research, a novel nonlinear isolator is proposed via a compliant mechanism with negative stiffness and wire ropes with hysteretic damping. The compliant mechanism consists of two pairs of tilted flexure beams, and the nonlinear restoring force is modelled based on a beam constraint model. The hysteretic restoring force of the wire ropes is characterized by a Bouc–Wen model. A dynamic model of the nonlinear isolator is established, and a semi-analytical method is adopted to analyze the model. Generalized equivalent stiffness and a generalized equivalent damping ratio are defined, respectively, for dynamic systems with multiple nonlinearities. The compliant mechanism exhibits negative stiffness in a limited stroke and endows the isolator with a lower resonant frequency and a smaller resonant amplitude. The complaint mechanism with a symmetric restoring force is more preferred for a broader band of vibration isolation and fewer harmonics in the responses. The wire ropes improve the high-frequency isolation efficiency at the cost of a higher resonant frequency. The incorporation of the compliant mechanism and the wire ropes is beneficial for vibration isolation. Furthermore, the influences of the dimensions of the complaint mechanism on the negative-stiffness stroke, load capacity and vibration isolation performances of the nonlinear isolator are revealed. | Nonlinear vibration isolation via a compliant mechanism and wire ropes | 10.1007/s11071-021-06588-9 |
2022-01-01 | Lightweight composite materials require a healthy combination of mechanical strength, wear resistance, and good damping Damping behavior capacity for purpose of selection and use in engine and structural parts of the industries spanning automobile and aerospace. In this short and succinct paper, the salient aspects of an aluminium alloy reinforced with particulates of titanium diboride (TiB_2) are presented and discussed. Salient aspects specific to measurement of damping capacity using experimental modal analysis are neatly presented. The tribological behaviour Tribological behavior of the engineered aluminium alloy metal matrix composite and the role and contribution of different sliding variables are presented and adequately discussed through pin-on-disc tests. The damping Damping behavior capacity of the TiB_2 particulate-reinforced aluminium alloy revealed an observable improvement over the as-cast counterpart and comparable to grey cast iron. The intricacies specific to tribological behaviour Tribological behavior of the engineered aluminium alloy composites Aluminium alloy composite is highlighted with respect to microscopic segregation of the particulate reinforcement Reinforcement (TiB_2) coupled with the role of test parameters. The fundamental strengthening and damping Damping behavior mechanism governing behaviour of the chosen composite is neatly detailed considering the conjoint and mutually interactive influences of reinforcement Reinforcement agglomeration, nature of loading, and interfacial bonding. | The Damping Capacity and Sliding Wear Behavior of an Aluminum Alloy Metal Matrix Composite: Role of Reinforcement | 10.1007/978-3-030-92567-3_5 |
2022-01-01 | This chapter contains a comprehensive discussion of the forces on the driver’s moving parts (cone and voice coil), including the Lorentz force law (f = Bli), motor resistance and electromagnetic damping, a correlation with Beranek’s classic cone-velocity expression, and relations to the driver power-to-loss ratios presented earlier in the text. The chapter closes with an analysis of the key electromagnetic force factors and motional equations for the system under sinusoidal drive. | Force | 10.1007/978-3-030-91634-3_10 |
2022-01-01 | When developing lighter structures for space applications, which will allow additional payload as well as increased design freedom, the use of Magnesium–Lithium (Mg–Li)-based alloys has potential benefits over commonly used aluminium (Al) alloys and is investigated here. The effect of age-hardening Age hardening treatment on Mg–Li in comparison to Al-based alloys on material damping performance was analysed using Dynamic Mechanical Analysis (DMA). Dynamic cantilever bending was performed for measuring the viscoelastic properties. Of particular interest is how the loss factor varies with temperatures under solution-treated, age-hardened Age hardening and over-aged conditions. A direct link between the second phase formation and viscoelastic properties of the alloys was determined. | Development of Magnesium–Lithium-Based Alloys for Space Applications: The Relationship Between Precipitation Hardening and Damping Capacity | 10.1007/978-3-030-92533-8_13 |
2022-01-01 | Blast-resistant gates are necessary for critical infrastructure, such as embassies, ministries, or parliaments. Lightweight doors/gates equipped with “energy absorbers” have more desirable operational performance than the traditional costly and bulky options. Auxetic damping systems have not yet been used in the supporting structure of blast-resistant gates. Consequently, this chapter tries to propose a complete system consisting of a steel gate, auxetic dampers, and RC supporting structure. The system is supposed to withstand high-intensity blast pressure of 6.6 MPa. Blast behavior of a steel gate was assessed, with and without the proposed uniaxial graded auxetic damper (UGAD), using Abaqus/Explicit solver. Results revealed that the attachment of the proposed UGAD to the gate led to a dramatic drop in permanent deformations (a critical factor for gate operability after a blast event). Hence, a lighter, more economical gate (with 50% reduction of mass) was required to satisfy the operability condition. Moreover, 49% of peak reaction forces were diminished that had a direct impact on the concrete supporting frame. Additional plastic dissipation energy was gained from those sacrificial lightweight auxetics, which justifies the significant reduction in permanent deformations, mass of the gate, and reaction forces. Finally, the impact of the blast pressure and the auxetic dampers on the reinforced concrete supporting structure was thoroughly covered using CDP and J-C material models. Results of the designed structure showed that the reinforcement stays in the elastic range. In terms of the concrete, no damage in compression was observed with very limited tension cracks that can be neglected. The complete gate system proposed here can be considered as a novel robust solution for blast vulnerable structures. | Auxetic Damping Systems for Blast Vulnerable Structures | 10.1007/978-3-030-60242-0_71 |
2022-01-01 | This article deals with control problems for dynamical systems with non-local convolution type terms. A method is proposed to get conditions under which the moving system will go into complete rest. The force acting on the system is distributed over the entire moving domain. Domains of one, two and three dimensions are considered. For these three cases of dimension and two types of fluids (Oldroyd fluid and Kelvin-Voigt fluid), the initial conditions are formulated for the problem posed, with the help of which the proposed method can bring these systems to complete rest in a finite time. Sufficient conditions are given that must be satisfied by the initial oscillations of the systems, under which the spectral method we use can bring these initial oscillations to complete rest. This is a condition on the smoothness of the initial functions and some additional boundary conditions for them. The article presents a new technique for damping unwanted vibrations in visco-elastic building materials. | Vibration Damping Problems for Some Models of Viscous Fluids | 10.1007/978-3-030-79983-0_2 |
2022-01-01 | This chapter presents the theoretical formulation for torsional vibration analysis in internal combustion engines. The methodology can be applied to several crankshaft geometries with different cylinder configurations. The steady-state solution of the equations considers the state transition matrix and the convolution integral. Here, this formulation is applied to the mathematical model of a six-cylinder diesel engine with 7.2 l of volumetric displacement and a viscous damper assembled at the crankshaft front end to reduce the vibration amplitude. With the results of the torsional vibration analyses, it is possible to determine the dynamic torque at each region of the crankshaft. Finally at the end of the chapter, the calculated torsional vibration amplitudes at the crankshaft front end are compared with measured values from an engine to validate the proposed methodology. | Crankshaft Torsional Vibration Analysis in a Mid-Size Diesel Engine: Simulation and Experimental Validation | 10.1007/978-3-030-91869-9_2 |
2022-01-01 | Passive control systems are practical systems that use the system's energy to absorb its energy to control the dynamic effects on the structure. In the control of these systems, which store energy with the help of a spring and mass, the effect of mass and spring is great. Based on this logic, different types of passive control systems are derived according to the type of material used. Tuned mass dampers (TMD) and tuned liquid dampers (TLD) in the passive control group are often used to solve various engineering problems. In these two systems, which have the same properties, a solid mass is usually chosen for TMD, while this mass is liquid for TLDs. In this study, passive control systems, which have important effects on building control, are explained in general terms, the historical development of TMDs and TLDs from the early times when the concept of structural control emerged until today, and the studies that have been done are included. | Passive Control via Mass Dampers: A Review of State-Of-The-Art Developments | 10.1007/978-3-030-98343-7_2 |
2022-01-01 | The demand for vibrational energy harvesting systems has increased over the past decade. The motivation for the researchers in this area is to decrease the requirement of the external power sources and reduce the maintenance cost. In the present analysis, the energy harvesting capability of a tapered laminated composite beam integrated with piezoelectric stacks is studied with respect to geometry and material properties. The substrate material is made up of laminated carbon fiber-reinforced epoxy composite with different fiber orientations, and piezoelectric patches are attached on top and bottom surfaces. In order to solve the dynamic analysis, three-dimensional finite element analysis is carried out. Here, the piezoelectric layers are modeled using PZT-5H material type. Initially, the model is validated with the available literature results and is found to be in good agreement. Furthermore, the laminated composite beam is base excited at the resonant frequency and the effect of different geometrical parameters, material parameters, and stacking sequences of the lamina on the voltage and power output is studied. Both series and parallel configurations are accounted in the present analysis. | Parametric Analysis of Tapered Laminated Composite Beam in Piezoelectric Vibration Energy Harvesting | 10.1007/978-981-16-6738-1_52 |
2022-01-01 | The processing route has an influence on the damping capacity, and in this study, the influence of silicon carbide particle (SiCp) size on the damping capacity of AA6061 processed through friction stir processing was investigated. Specimens were extracted from the stir zone and analyzed for their damping properties, and the same was correlated with the obtained microstructures. The samples were also characterized for the change in dislocation density, plastic zone size, grain boundary area and crystallite size through x-ray diffraction and electron microscopy. The average grain size remarkably reduced after friction stir processing (45 to 5.64 μm) and it further decreased with an increase in reinforcement particle size (9, 29.4 and 109 µm). The damping capacity was measured through dynamic mechanical analyzer from 25 to 300°C and was observed to increase for the samples subjected to friction stir processing and with increasing particle size. It was found that the plastic zone radius around the SiC particle increased with the particle size, and the contribution of plastic zone was found to be significant than the dislocation density for damping below 125°C. | Damping Property of AA6061/SiCp Surface Composites Developed through Friction Stir Processing | 10.1007/s11665-021-06201-5 |
2022-01-01 | The introduction of virtual inertia and damping coefficient of the virtual synchronous generator effectively improves the frequency response characteristics of the system. After the microgrid is disturbed by the load, the output power of the system will overshoot and oscillate. According to the relationship between the angular frequency deviation and quotiety of vary of the synchronous generator and the virtual inertia and damping coefficient, a fuzzy controller is devised. On that basis, the ant colony algorithm is accustomed to optimize the membership function and fuzzy rules in the fuzzy control. Compared with the traditional VSG fuzzy control strategy, the ant colony optimization fuzzy strategy has smaller overshoot and oscillation, and the system recovery adjustment time is shorter, which makes the system robust. Through Matlab/Simulink simulation, comparing the traditional VSG fuzzy control and the ant colony optimization fuzzy virtual synchronous generator parameter adaptive control, the validity of the control method is verified. | Parameter Adaptive Control of Virtual Synchronous Generator Based on Ant Colony Optimization Fuzzy | 10.1007/978-981-16-9735-7_34 |
2022-01-01 | In this article, we deal with a damped Navier–Stokes equations in $$ I\!\!R^3$$ I R 3 with slip boundary conditions. Sufficient conditions for the existence of the solutions to the Navier–Stokes system are established in a bounded domain $$\varOmega \subset I\!\!R^3.$$ Ω ⊂ I R 3 . Further, we show that the solutions derived by Rothe’s method are satisfying the local energy inequality. | On Generalized Energy Inequality of the Damped Navier–Stokes Equations with Navier Slip Boundary Conditions | 10.1007/978-981-19-9307-7_38 |
2022-01-01 | This work entails an analysis of secondary resonances in the parametrically damped van der Pol equation, with and without external excitation. An application of this system is a vertical-axis wind-turbine blade, which can have cyclic damping, aeroelastic self-excitation, and direct excitation. We analyze the system using the method of multiple scales and numerical solutions. For the case without external excitation, the analysis reveals nonresonant phase drift (quasiperiodic responses), and sub-harmonic resonance with possible phase drift or phase locking (periodic responses). The case of external excitation consists of a constant load and a harmonic load with the same frequency as the parametric term. Hard excitation is treated for nonresonant conditions and secondary resonances. Primary resonance is observed but not analyzed here. | Resonances of a Forced van der Pol Equation with Parametric Damping | 10.1007/978-3-030-81162-4_42 |
2022-01-01 | Cartesian impedance control has been widely used in controlling robotic manipulators for manipulation and assembly tasks to compute the required joint torques and/or end-effector forces. Current congruence mapping of the Cartesian stiffness and damping matrices to joint spaces are not valid for general cases. In this paper, we derive from first principles, the general form of the mapping of the stiffness and damping matrices between Cartesian and joint space, which applies to all general cases. The new results show the coupling of Cartesian damping in the stiffness after mapping to the joint space, which is not found in the literature. By applying principle of vibration analysis and including the null space tasks, we can choose the stiffness and damping matrices in order to achieve prescribed dynamic response. Such analysis also enables us to gain a deeper understanding of the responses versus the parameters of robot manipulators; for example, certain elements only affect dynamic responses in specific directions. | Joint Space Stiffness and Damping for Cartesian and Null Space Impedance Control of Redundant Robotic Manipulators | 10.1007/978-3-030-95459-8_25 |
2022-01-01 | This paper presents the concept of the variable admittance network (VAN) with indirect energy supply for semiactively controlled systems and the admittance analysis of three basic VANs with indirect energy supply in resonance vibration control. A mechanical network is describable with the admittance, which includes the damping, stiffness, and inertance information. The VAN with variable admittance parameters is beneficial for the resonance vibration control of the suspension. However, according to the energy analysis, the variation of inertance and stiffness parameters without direct energy supply to compensate kinetic energy will cause the mechanical itemsʼ physical discontinuity as the inerter and spring can store kinetic energy. The variable damping (VD) device applies the indirect energy supply that is only related to the damping control but not to the exchange with kinetic energy. This paper proposes the VAN with indirect energy supply to achieve the VD, variable equivalent inertance (VEI), and variable equivalent stiffness (VES) characteristics by controlling a VAN with only the VD device in it. The vibration transmissibility of a suspension equipped with VD, VEI, and VES devices is investigated, respectively, to verify their effectiveness in resonance vibration control. The VAN with indirect energy supply is realizable in different applications; the admittance analysis method can facilitate the VAN design and optimization in practice. | Variable Admittance Network with Indirect Energy Supply for Semiactive Vibration Control | 10.1007/978-981-16-5912-6_73 |
2022-01-01 | Dynamic response of structures is of extreme importance for the evaluation of seismic behaviour of structures. In vibration analysis, we are generally concerned with damping in terms of system response. The energy absorption devices increase the damping of the structure by plastic deformation or by viscous resistance of devices such as visco-elastic dampers. For structures subjected to dynamic loading, it is excited by a suddenly applied non-periodic excitation as transient response, since steady-state oscillations are not generally produced. Such oscillations take place at the natural frequencies of the system with the amplitude varying in a manner dependent on the type of excitation. The response of visco-elastic dampers under transient loading for seismic vibrations has been examined in this study. A finite element model is created using numerical software ANSYS for studying the response of visco-elastic damper. From the analysis, it is clear that shear strain is maximum in the visco-elastic material such that during earthquake vibrations, the rubber will absorb the energy and the damage is reduced in structures. | Numerical Investigation of Visco-Elastic Damper for Seismic Vibration | 10.1007/978-3-030-98335-2_1 |
2022-01-01 | In this work, design a proportional-integral-derivative (PID) controller using direct synthesis method for the control of critical damped second order plus time delay (CDSOPTD) systems. The different categories of CDSOPDT systems are considered based on the ratio of time delay to system time constant. CDSOPTD systems performance is analyzed using PID controller. The gains of PID controller are obtained using direct synthesis method with tuning parameter $$\alpha$$ α ranging from 0.1 to 1. The various PID parameters are used for the control CDSOPTD systems, and the simulation results are obtained. For low value of $$\alpha$$ α , the closed-loop responses exhibit that, the unstable behavior, oscillations in a controlled variable, and peak overshoot in responses. In direct synthesis method, the higher value of tuning parameter $$\alpha$$ α is used for PID controller tuning, and it is delivered better closed-loop performance for the control of CDSOPTD systems. | Direct Synthesis Method-Based PID Controller for Critically Damped Time Delay Systems | 10.1007/978-981-16-8550-7_13 |
2022-01-01 | On the night of December 26th, 2018, a strong earthquake, with a magnitude of 4.9 on the Richter scale, hit the southeastern side of the Mt. Etna Volcano (Sicily), with the epicenter between the Municipalities of Viagrande and Trecastagni. The hypocenter of the strong earthquake was located just 1 km deep and, for this reason, the effects of the shock were greatly amplified on the ground surface. They have been counted not only material damages to churches and buildings, but also 10 injured around the epicenter area. Therefore, an investigation campaign was carried out with the aim of planning the reconstruction of the damaged areas. In situ soil investigations were carried out in order to determine the soil profile and the geotechnical parameters for the area under consideration. Among in situ tests, borings, Down Hole Tests (D-H), Multichannel Analysis Surface Wave Tests (MASW), Seismic Refraction Tomography and Horizontal to Vertical Spectral Ratio Tests (HVSR) were carried out, with the aim to evaluate the soil profile of shear wave velocity (V_s). Moreover, laboratory tests were carried out on undisturbed samples in the static field: Shear Tests (ST). The results have been grouped and allowed the characterisation of the following soil categories: clay, sandy clay, silica sand, volcanic sand, volcanic rock. The seismic behaviour of these soil categories has been used for the site response analysis and for the seismic microzonation of the studied area. | A Seismic Microzonation Study for Some Areas Around the Mt. Etna Volcano on the East Coast of Sicily, Italy | 10.1007/978-3-031-11898-2_61 |
2022-01-01 | The article constructs differential equations of motion of a gyroscopic rigid unbalanced rotor with nonlinear cubic damping and nonlinear stiffness, taking into account the anisotropy of the linear stiffness of the elastic support material and interaction with a non-ideal DC motor with a linear characteristic, and the dynamics of the rotor is studied by a numerical method. Two jumping nonlinear effects are observed during the accelerated resonant transition from a large amplitude to a smaller one, accompanied by Sommerfeld effects, during the resonant transition with the decelerated motor from a smaller amplitude of oscillations to a larger one, corresponding to two critical speeds. Nonlinear cubic damping suppresses the maximum amplitudes in the regions of critical velocity and amplitude after similar resonant increasing and damping beats oscillations. At sufficiently close critical velocities, exit from the resonance at a lower critical velocity can lead to capture at another resonance at a higher critical velocity, the severity of the Sommerfeld effect on each of the resonant regions becomes comparable. Therefore, the evaluation of the response of the dynamics of resonant transients is of paramount importance for the correct design of the vibration insulation of the rotor machine. | Non-stationary Resonance Transition of the Gyroscopic Rigid Rotor with Nonlinear Damping and Non-ideal Energy Source | 10.1007/978-3-031-10776-4_14 |
2022-01-01 | In this study, we proved that damped quadratic nonlinear oscillators similar to Duffing and Helmholtz–Duffing damped equations which emerge in bubble dynamics with time-periodic straining flows and solitary-like wave's dynamics may be derived from a new functional approach based on nonstandard Lagrangians and fractional frictions. The solutions of these equations are given in terms of the Jacobi elliptic functions. It was observed that the dynamical model constructed in this study is comparable to dynamical systems with natural Lagrangians for which the Riemann structure is conformally flat which has important implications in dynamical systems with position-dependent mass. | A new approach to nonlinear quartic oscillators | 10.1007/s00419-021-02062-5 |
2022-01-01 | In this paper, analysis of the nonlinear dynamics responses of a structure equipped with a vehicle suspension that uses a fluid with magneto rheological characteristics to control the possible instability and chaotic motion. It is a spray orchards of tower type, with an unbalanced electric motor (Non-ideal) located at the top of the tower representing the concentrated mass of their fans, which represents the real system the best way possible. The simulations show that the MR suspension reduce the amplitude of oscillations of all the masses of the system, being the most important the mass of the cart and fans. The influence of the non- ideal motor is important to check the influence of a possible imbalance of fans. | On a Vehicular Suspension for a Non-ideal and Nonlinear Orchard Tower Sprayer Through an Inverted Pendulum Using Reologic Magneto (MR) | 10.1007/978-3-030-96603-4_10 |
2022-01-01 | The aim of this research is to develop an advanced hysteresis model of High Damping Rubber (HDR) bearing. Based on the experimental research so far, various dependences and nonlinearities can be confirmed in the experimental hysteresis curves of HDR. In particular, the gap in the stiffness between the first cycle and the cycle after the second of the hysteresis curve is confirmed due to the dependence of the maximum shear strain. The advanced hysteresis model of HDR, tentatively named the bilinear Double Target model, was proposed by conducting the dynamic loading test in this research. To assess the technical feasibility of this hysteresis model, three phases were performed in this research. The preliminary proportion was carried out to confirm the mechanical behaviors of HDR by performing a dynamic loading test. Subsequently, based on the experimental results, a modeling procedure of the bilinear Double Target model was proposed and the hysteresis curve of HDR was modeled. Finally, dynamic analyses by design seismic motion are performed on the structural model of the actual bridge pier. The validity of the proposed model was confirmed by investigating the behavior of the bearing part and the lower part of the pier. As a result, it was possible to propose a hysteresis model considering the dependence of HDR and to conduct seismic response analysis. | Dynamic Analysis of Bridge Pier Considering Hysteresis Characteristics of High Damping Rubber Bearings | 10.1007/978-981-16-6932-3_25 |
2022-01-01 | Friction dampers are commonly used to reduce the vibration amplitude of aircraft turbine blades. However, the shape of such friction dampers can affect significantly damping characteristics and the overall nonlinear dynamic behaviour of the structure. This chapter exploits topological optimisation to identify damper geometries that minimise response amplitude. The (near-)maximum responses are efficiently computed by solving the harmonic balance equations and a phase quadrature condition. Moving Morphable Components (MMC) are used to describe the damper geometry, and an Efficient Global Optimisation (EGO) algorithm is used for the optimisation. | Topological Optimisation of Friction Dampers for Nonlinear Resonances Mitigation | 10.1007/978-3-030-81166-2_1 |
2022-01-01 | Purpose In this paper, a radically new concept of a Stiff Seismic Base Absorber (SBA) is proposed for seismic protection of multistory building structures. Methods An inerter is first implemented, connecting directly the structure to the ground. This results in the decrease of the natural frequency of the structure, without decreasing its structural stiffness. Parallel, a negative stiffness-based absorber is used to increase the apparent damping behavior of the inerter. The additional mass of the SBA is connected to the structure with a negative stiffness (NS) element and to the base with a positive one. Also, an artificial damper is placed in parallel with each stiffness element. The design of the SBA includes the following novel features: (1) the SBA foresees variation in all stiffness elements, (2) the optimal system parameters are selected based on engineering criteria with proper constraints and limitations to the system dynamic responses, (3) the earthquake input motion is selected according to the seismic design codes, (4) a displacement-dependent non-linear configuration is proposed for the realization of the NS element, and (5) the detuning phenomena are observed via sensitivity analysis. Results Compared to other vibration absorbers, the SBA presents several advantages. An improved superstructure dynamic behavior is observed combined with small base displacements, in the order of a few centimeters. Conclusion The drastically reduced base displacements render the implementation of the SBA feasible using conventional structural elements. As a result, the SBA is a realistic retrofitting option for seismic protection. | Feasibility Assessment of Stiff Seismic Base Absorbers | 10.1007/s42417-021-00362-2 |
2022-01-01 | This paper focuses on the effect of optimally damped dynamic vibration absorber (DVA) to attenuate vibration caused by the rotating mass unbalance. The exact solution for DVA damping factor has been determined by using higher-order L’Hospital rule as a function of mass ratio. The effect of exact solution has been compared numerically with approximate solutions obtained by using H∞ method, equivalent linearization method, solution proposed by Ioi and Ikeda and also without DVA. Compared with optimal damping factor solution given by all the listed methods, the required DVA damping factor percentage reduction 85% to 75% for the mass ratio range 0.05 to 0.125, respectively, is found with the exact solution. | Determination of Exact Optimal Tuning of Dynamic Vibration Absorbers to Control Vibration Due to Rotating Mass Unbalance | 10.1007/978-981-16-4222-7_62 |
2022-01-01 | In actual engineering application, Quasi-zero-stiffness (QZS) vibration isolation systems may not achieve expected low-frequency isolation effect. In this study, a QZS system with nonlinear hysteretic damping was investigated to discuss the reasons for failure of isolation performance. The results indicate there are two main reasons for the above failure phenomenon: a) the nonlinearity of the system and b) the stiffness error in actual structure. The latter includes two cases of the system is at equilibrium position and disequilibrium position. The dynamic behavior of the system under above situation are analyzed. By using the harmonic balance method (HBM) to discuss the primary and secondary harmonic transmissibility responses, the methods to avoid the effect of nonlinearity are provided. The results were verified by numerical simulations. | Analysis of Dynamic Behavior Affecting the Isolation Effect of the QZS System with Nonlinear Hysteretic Damping | 10.1007/978-981-16-5912-6_24 |
2022-01-01 | Development of low cost, energy efficient cellular communication systems are very essential due to the ubiquitous use of mobile technology. To overcome the scarcity of energy resources, low loss component design in transceivers is an emerging trend and lots of research works are focused on it. RF transceivers can be designed with MEMS resonators and switches which have the advantages of energy efficiency and reduced fabrication costs. Thermoelastic damping is a major energy dissipation mechanism which limits the maximum attainable quality factor (Q_TED) of structures in microscales which is an important design parameter. When the devices are scaled down, in order to accurately model micro/nanoscale resonators, nonclassical elasticity theories like Modified Couple Stress Theory are essential. By including a material length scale parameter ( l ), the size effects are incorporated in the analysis and quality factor is found to be enhanced by increasing l . In this paper, the conventional thermoelastic damping analysis is modified by applying Modified Couple Stress Theory and the impacts of length scale parameter on energy dissipation and Q_TED were analyzed with different structural materials. The maximum Q_TED was attained for beams with polySi as the structural material with the highest material length and that of lowest is for SiC. Vibrating cantilever micro/nanobeams with properly selected material length scale parameters in higher modes provide large Q_TEDs which can be utilized for designing low loss MEMS components in RF transceivers. | Energy Dissipation Analysis in Micro/Nanobeam Cantilever Resonators Applying Non-classical Theory | 10.1007/978-981-16-5640-8_41 |
2022-01-01 | Components of the rail tracks are designed to withstand the continuous moving load and transfer it effectively to the subgrade and foundation. Apart from stresses and strains developed, the moving load also induces vibrations, causing damage to components of the rail track, amplifying already existing track defects such as head checks, corrugation, shelling and causing discomfort to passengers. Understanding vibrations and successfully isolating them is a challenging task. Rail pad plays a vital role to reduce vibration. It also attenuates the impact load of moving train and protects different components of track assembly from failure. Due to globalization and advancement in technology, freight traffic and speeds of the train have substantially increased in recent years, and thus it is now more important to understand vibration and its effects. This paper mainly discusses the dynamic properties of the rail pad and its stiffness and damping properties. First, the article gives a basic overview of the rail pad, its development over the years, fundamental theories and equations used and materials used for making the rail pad have also been discussed. Then, it reviews different experimental and numerical techniques used to determine the rail pad’s dynamic properties and effects of preload, frequency and temperature on rail pad properties. It discusses different mathematical models and equations used to couple rail pad dynamics with overall vibrations. Also, it discusses the result of considering rail pad dynamics into overall train-track coupled vibrations and how it influences the output result is being discussed and compared with experimental results. | Rail Pad Dynamic Properties: A Review | 10.1007/978-981-16-9613-8_6 |
2022-01-01 | We study the stability problem of a tree of elastic strings with local Kelvin–Voigt damping on some of the edges. Under appropriate conditions on the damping coefficients at the vertices, exponential/polynomial stability are proved. This is a new representation of Ammari et al. (Semigroup Forum 100:364–382, 2020), where we considered a tree. Then as indicated in paragraph four of Ammari et al. (Semigroup Forum 100:364–382, 2020), we obtain (under more generalized conditions on the damping coefficients) the same results. | Stability of a Graph of Strings with Local Kelvin–Voigt Damping | 10.1007/978-3-031-14268-0_6 |
2022-01-01 | BTA deep hole drilling is used to produce bore holes with high bore hole qualities and high length-to-diameter ratios. The tool system consists of a drill head and a drill tube. However, the length of the drill tube required to achieve high drilling depths leads to an increased tendency of the tool system to vibrate. The strong torsional vibrations increase tool wear at the cutting edges and the guide pads and influence the drilling quality. The dynamic behaviour of the tool system and thus the process reliability can be improved through the vibration damping effect resulting from the inhomogeneous structure of fiber-reinforced plastics (FRP). In this paper, a wound FRP drill tube is designed based on the experimental determination of mechanical and thermal loads of the drilling process. Compression and twisting of the FRP tube are evaluated simulatively and com-pared to a conventional steel drill tube. The vibration damping effect of the FRP drill tube is analysed in experimental investigations for the material 42CrMo4 + QT. In addition to the feed force and the drilling torque, chip shape, surface quality and noise exposure during the process are evaluated. | Lightweight FRP Drill Tubes for Vibration Damping in BTA Deep Hole Drilling | 10.1007/978-3-030-78424-9_25 |
2022-01-01 | In this paper, an active structural control method called active tuned mass dampers (ATMDs) was applied to reinforced concrete frame structures. ATMD is positioned on the top of the structure and uses a proportional integral derivative (PID) controller. Both damper and PID controller properties are optimized via an improved harmony search algorithm. During the optimization, the limit of control force, stroke capacity of ATMD and time-delay of the control system is considered. As the numerical example, a 15-story frame building is presented and the optimum ATMD is effective to reduce maximum displacement by 37.5% for critical excitation. | Control of Reinforced Concrete Frame Structures via Active Tuned Mass Dampers | 10.1007/978-981-19-2948-9_26 |
2022-01-01 | The propagation of dust-acoustic waves in a dusty plasma bounded in finite symmetrical cylindrical geometry has been theoretically investigated. By using the reductive perturbation method, we obtain a quasi-nonlinear Schrödinger equation. It is shown that there is a dark envelope soliton under certain conditions, while its amplitude will decrease with the time. The dependence of both the dispersion relation and group velocity of envelope solitary waves on the radius of cylinder has been given. Moreover, we define the duration time of dark envelope solitons and give the theoretical ones. It is found that the duration time increases as the radius of cylinder increases, while it decreases as the viscosity coefficient of dusty plasmas increases. | Damping of dark envelope soliton in a viscous bounded dusty plasma | 10.1007/s12648-020-01965-3 |
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