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2023-07-03 | This paper investigates the well-posedness and stability of the beam model with degenerate nonlocal damping: $$ u_{tt}+\Delta ^2u-M(\Vert \nabla u\Vert ^2)\Delta u+(\Vert \Delta u\Vert ^\theta +q\Vert u_t\Vert ^\rho )(-\Delta )^\delta u_t+f(u)=0\ \ \hbox {in} \ \ \Omega \times {\mathbb {R}}^+,$$ u tt + Δ 2 u - M ( ‖ ∇ u ‖ 2 ) Δ u + ( ‖ Δ u ‖ θ + q ‖ u t ‖ ρ ) ( - Δ ) δ u t + f ( u ) = 0 in Ω × R + , where $$\Omega \subset {\mathbb {R}}^n$$ Ω ⊂ R n is a bounded domain with smooth boundary, $$\theta \ge 1,~q\ge 0,~\rho >0$$ θ ≥ 1 , q ≥ 0 , ρ > 0 and $$0\le \delta \le 1$$ 0 ≤ δ ≤ 1 . The main purpose in the present paper is to show that the transition from the case $$q=0$$ q = 0 to the case $$q>0$$ q > 0 produces an explicit influence on the stability of energy solutions. More precisely, when $$q=0$$ q = 0 , we conclude that the energy goes to zero as t goes to infinity without an explicit decay rate; while when $$q>0$$ q > 0 , we present a polynomial decay rate of type $$(1+t)^{-\frac{2}{\rho }}$$ ( 1 + t ) - 2 ρ that depends only on the exponent $$\rho $$ ρ of the velocity term, not on $$\theta $$ θ and $$\delta $$ δ . Furthermore, we prove that the energy cannot be exponentially stable and derive more accurate decay rates of the energy. | Stability for a Class of Extensible Beams with Degenerate Nonlocal Damping | 10.1007/s12220-023-01353-3 |
2023-07-01 | This study proposes a methodology to identify the modal damping ratio of a highly damped structure. Specifically, we explain the change in the modal damping ratio of the object itself by using an existing novel multiple excitation testing method with velocity feedback (FB) control to counteract the damping force, and we propose a methodology to identify the original modal damping ratio of the object based on the methodology of modal analysis. In this methodology, the relation equation between the modal damping ratio and control gain is derived. In the numerical and experimental validations, the modal damping ratio is identified by applying velocity FB excitation to a multi-degree-of-freedom system, and it is confirmed that the original modal damping ratio of the target structure can be identified from the frequency response function after damping reduction. Therefore, the proposed method is expected to improve experimental modal analysis by facilitating the accurate identification of the modal damping ratios of the vibration mode wherein the resonance peak does not appear clearly. | Experimental modal analysis using undamped control for high damping system | 10.1007/s00419-023-02419-y |
2023-07-01 | We analyze the convergence properties when the time t tends to infinity of the trajectories generated by damped inertial dynamics which are driven by the sum of potential and nonpotential operators. Precisely, we seek to reach asymptotically the zeros of a maximally monotone operator which is the sum of a potential operator (the gradient of a continuously differentiable convex function) and of a monotone and cocoercive nonpotential operator. As an original feature, in addition to the viscous friction, the dynamic involves implicit Newton-type damping. This contrasts with the authors’ previous study where explicit Newton-type damping was considered, which, for the potential term corresponds to Hessian-driven damping. We show the weak convergence, as time tends to infinity, of the generated trajectories toward the zeros of the sum of the potential and nonpotential operators. Our results are based on Lyapunov analysis and appropriate setting of the damping parameters. The introduction of geometric dampings allows to control and attenuate the oscillations known for the viscous damping of inertial methods. Rewriting the second-order evolution equation as a system involving only first-order derivative in time and space allows us to extend the convergence analysis to nonsmooth convex potentials. The main part of our study concerns the autonomous case with positive fixed parameters. We complete it with some first results concerning the nonautonomous case, and which are based on a recent acceleration method using time scaling and averaging. These results open the door to the design of new first-order accelerated algorithms in optimization taking into account the specific properties of potential and nonpotential terms. The proofs and techniques are original due to the presence of the nonpotential term. | Convergence of Inertial Dynamics Driven by Sums of Potential and Nonpotential Operators with Implicit Newton-Like Damping | 10.1007/s10957-023-02228-x |
2023-07-01 | In this paper, we consider a Vlasov–Poisson system in the presence of radiation damping, which is a two-species Vlasov–Poisson system for electrons and ions with additional terms to describe the effect of accelerated charged particles. We obtain the global-in-time and optimal decay estimates of classical solutions to it for small initial data in the whole space $$\mathbb {R}^3$$ R 3 . Compared to the previous results, no compact support assumptions on initial data is needed in our paper. And we obtain the optimal $$L^{\infty }_x$$ L x ∞ decay estimates of the charge densities and the electrostatic field, which was not reported in previous literature. For the proofs of our results, we adapt the modified vector field method which was introduced initially by Smulevici for the classical Vlasov–Poisson system for electrons. | Optimal decay estimates for the Vlasov–Poisson system with radiation damping | 10.1007/s00033-023-02044-3 |
2023-07-01 | A curve-fitting technique using a minimum error criterion was presented for identifying higher damping ratios near the critical damping ratio in single-degree-of-freedom systems. Free vibration decay tests were performed on a linear spring–mass–damper system with constant initial conditions using a modified commercial vibration apparatus. A vibration mass was supported with an extremely low-friction air-bearing guide. Mass displacement was measured using a laser displacement sensor. The magnitude of the viscous damping forces was varied and controlled using an electromagnetic damper installed in the apparatus. Higher damping ratios ( $$\zeta$$ ζ > 0.8) were accurately identified using the curve-fitting technique, while lower and medium damping ratios $$\left( {0 < \zeta < 0.7} \right)$$ 0 < ζ < 0.7 were estimated using the conventional logarithmic decrement method from the measured free vibration decay curves. | Experimental identification of high damping ratios in single-degree-of-freedom systems | 10.1007/s00419-023-02414-3 |
2023-07-01 | Two results about the multiplicity of nontrivial periodic bouncing solutions for sublinear damped vibration systems − ẍ = g ( t ) ẋ + f ( t, x ) are obtained via the Generalized Nonsmooth Saddle Point Theorem and a technique established by Wu Xian and Wang Shaomin. Both of them imply the condition “ f ≥ 0” required in some previous papers can be weakened, furthermore, one of them also implies the condition about $${\partial F(t,x)\over{\partial t}}$$ ∂ F ( t , x ) ∂ t required in some previous papers, such as “ $$\vert{\partial F(t,x)\over{\partial t}}\vert\leq\sigma_{0}F(t,x)$$ ∣ ∂ F ( t , x ) ∂ t ∣ ≤ σ 0 F ( t , x ) ” and “ $$\vert{\partial F(t,x)\over{\partial t}}\vert\leq C(1+F(t,x))$$ ∣ ∂ F ( t , x ) ∂ t ∣ ≤ C ( 1 + F ( t , x ) ) ”, is unnecessary, where F ( t, x ) ≔ ∫ _0 ^ x f ( t, s ) ds , and σ _0, C are positive constants. | Multiplicity of Periodic Bouncing Solutions for Sublinear Damped Variation Systems via Nonsmooth Variational Methods | 10.1007/s10114-023-1166-2 |
2023-07-01 | In a stand-alone inverter, a high-quality sinusoidal output of a constant voltage and constant frequency must be supplied to the load regardless of the load condition. Therefore, the THD of the output voltage in steady-state should be low and the ability to recover from the transient period needs to be fast for the load variations. However, when the inverter employs an LC filter at the output stage, a damping technique is required to suppress voltage oscillations due to resonance when the load changes. This paper proposes a damping control method to stabilize the output voltage using cooperative control of two single-phase inverters connected in parallel. The Master inverter controls the output voltage, and the Damping inverter controls the output current to support output voltage damping and power capacity. Each inverter output stage consists of a lossless filter with no damping resistor to prevent efficiency degradation and robust against system parameter changes. The output voltage distortion is less than the conventional method, regardless of loads and load variations. We carried out PSIM simulations and experiments to verify the superiority of the proposed approach. | Cooperative Control of Two Single-Phase Full-Bridge Structures Composed of Master and Damping Inverter for Output Voltage Stabilization | 10.1007/s42835-023-01478-z |
2023-07-01 | Process damping significantly improves the machining stability in the low speed cutting process. Just because of this, it plays an important role in the avoidance of chatter vibrations for the situations in which the relatively low cutting speeds have to be used. Recently, more and more efforts have been focusing on process damping modeling. Unfortunately, from the existing models it can be seen that although aiming at the same physical or geometric features, different analytical formulas or extremely discrepant calibration results were obtained. Many famous scholars even listed it as the most challenging problem needed to be solved in the field of machining chatter. So the internal relationships between these models need to be deeply explored. To this end, this article reviews the mechanism and modeling of the machining process damping. Research progresses related to three typical processes, i.e., ploughing-based process damping model, velocity-based process damping model, unified process damping model, together with stability analysis with the considering of process damping are reviewed and introduced in detail. Especially, the ploughing-based process damping model as the most important part is detailed in the aspects of calculation of indented volume and calibration of ploughing force coefficients. The logical relationships between the development of each model are clarified. Several remaining problems are analyzed and the future trends of process damping modeling are summarized. | Mechanism and modeling of machining process damping: a review | 10.1007/s00170-023-11390-5 |
2023-07-01 | We consider the damped Newton method for strongly monotone and Lipschitz continuous operator equations in a variational setting. We provide a very accessible justification why the undamped Newton method performs better than its damped counterparts in a vicinity of a solution. Moreover, in the given setting, an adaptive step-size strategy be presented, which guarantees the global convergence and favours an undamped update if admissible. | A short note on an adaptive damped Newton method for strongly monotone and Lipschitz continuous operator equations | 10.1007/s00013-023-01858-x |
2023-07-01 | This paper deals with the distributed consensus problem for networked flexible-joint manipulator systems which are formulated by underactuated Euler-Lagrange (EL) dynamics. Based on the energy-shaping scheme of passivity-based control (PBC) with interconnection and damping assignment, a novel decentralized controller is proposed to solve the leaderless and the leader-follower consensus problems. The main feature of the present work is the systematical integration of the energy of the systems composed of underactuated and actuated components and the energy of the controller as a total energy. Then the total energy is formulated as a suitable Lyapunov function to solve distributed consensus problems for the networked underactuated EL systems. The proposed consensus scheme without the need of velocity measurement possesses a relatively simple structure and good robustness. It is shown that interconnection pattern and damping assignment of the PBC are two key factors to affect the cooperative behavior of networked flexible-joint manipulator systems, which will be used to regulate or improve the cooperative performance of networked flexible-joint manipulator systems in practice. Finally, two numerical examples of networked six flexible-joint manipulator systems are presented to validate the correctness of the proposed algorithms. | Achieving Distributed Consensus in Networked Flexible-joint Manipulator Systems via Energy-shaping Scheme | 10.1007/s12555-021-0869-3 |
2023-07-01 | Excessive vibration in civil and mechanical systems can lead to structural damage or harmful noise. Structural vibration can be mitigated by reducing the energy of the vibration source or by isolating the external disturbance from the target structure. Depending on the tunability and power consumption of the system, existing vibration control strategies are divided into active, passive and semi-active types, providing a more stable and efficient solution for vibration control. However, conventional damping structures have difficulty in meeting the requirements of wide frequency range and high precision damping under complex operating conditions. Therefore, the design of efficient damping structures is one of the key challenges in the development of vibration control technology. Organisms have evolved over millions of years to effectively damp vibrations through special structures and composite materials to ensure their survival. Opening up damping vibration isolation technology from a bionic perspective can meet the frequency requirements of vibration damping and guarantee higher output accuracy of machinery. This review summarizes the basic principles of vibration control and analyses the vibration control strategies for different damping materials and damping structures. Meanwhile, various models of bio-damped structures are outlined. Moreover, the current status and recent progress of research on bionic damped structures based on bio-vibration control strategies are discussed. Finally, new perspectives on future developments in the field of bionic damped vibration control techniques are also presented. A comprehensive understanding of existing vibration damping mechanisms and new methods of bionic damping design will certainly trigger important applications of precision vibration control in the fields of aerospace, rail transportation and mechanical systems. | Biological Vibration Damping Strategies and Mechanisms | 10.1007/s42235-023-00366-6 |
2023-07-01 | The damped nonlinear Schr $$\ddot{o}$$ o ¨ dinger equation is derived from the helicoidal Joyeux and Buyukdagli model of DNA, in which the particles of the surrounding solvent medium induces a weak viscosity. This is achieved by using a perturbation technique known as the multiple scale expansion in the semi-discrete approximation. The solitary wave solution of the amplitude equation depict breathing pulses, known for the initiation of the DNA transcription and replication processes. An increase in damping is shown to rapidly switch the exponential growth rate of the weak continuous wave perturbations to oscillatory behavior, within the frame work of modulational instability analysis. This is physically depicted as a decrease in the amplitude and corresponding broadening of the breathing modes during propagation along the DNA chain. Numerical simulations shows that the breathing pulses are quite robust entities, because they emerge unchanged after collision. It equally underscores the qualitative and quantitative influence of the helicoidal and damping parameters, on the biological processes inherent in the DNA dynamics. | Impact of helicoidal interactions and weak damping on the breathing modes of Joyeux-Buyukdagli model of DNA | 10.1007/s12648-023-02610-5 |
2023-07-01 | Bird feathers sustain bending and vibrations during flight. Such unwanted vibrations could potentially cause noise and flight instabilities. Damping could alter the system response, resulting in improving quiet flight, stability, and controllability. Vanes of feathers are known to be indispensable for supporting the aerodynamic function of the wings. The relationship between the hierarchical structures of vanes and the mechanical properties of the feather has been previously studied. However, still little is known about their relationship with feathers’ damping properties. Here, the role of vanes in feathers’ damping properties was quantified. The vibrations of the feathers with vanes and the bare shaft without vanes after step deflections in the plane of the vanes and perpendicular to it were measured using high-speed video recording. The presence of several main natural vibration modes was observed in the feathers with vanes. After trimming vanes, more vibration modes were observed, the fundamental frequencies increased by 51–70%, and the damping ratio decreased by 38–60%. Therefore, we suggest that vanes largely increase feather damping properties. Damping mechanisms based on the morphology of feather vanes are discussed. The aerodynamic damping is connected with the planar vane surface, the structural damping is related to the interlocking between barbules and barbs, and the material damping is caused by the foamy medulla inside barbs. | The Role of Vanes in the Damping of Bird Feathers | 10.1007/s42235-022-00329-3 |
2023-07-01 | Background Underwater ship has extremely high requirements for vibration and noise control. Reducing the vibration and noise level of underwater ship has always been a hot topic in various countries. With the deepening of research, a large number of new technologies continue to emerge. For specific problems, without changing the structure itself, increasing structural damping has an obvious effect on reducing structural vibration. Methods From the perspective of engineering application, the article analyzes 7 damping technologies. In view of the harsh environmental requirements of underwater vessels, particle damping technology has high application value. Combining particle damping and dynamic vibration absorbers can take advantage of both. Conclusion In order to achieve a better engineering effect, the multi-particle damping vibration absorber is a good solution, and the research on the multi-particle damping vibration absorber is prospected. Purpose The paper closely follows the actual project and provides a practical reference for solving engineering problems. | Particle Damping Vibration Absorber and Its Application in Underwater Ship | 10.1007/s42417-022-00700-y |
2023-07-01 | Convective heat and mass transfer are common phenomena in the field of engineering. In recent years, the research on convective heat and mass transfer is getting deeper and deeper. People are constantly seeking new methods to improve the efficiency of heat and mass transfer, but the research on the mechanism of heat and mass transfer is not yet systematic and mature. The theory of the field synergy has made up for this research gap, but the research progress and application of its heat and mass transfer theory lack systematic summary and evaluation. This paper summarizes the theory of enhanced heat and mass transfer based on field synergy theory, analyzes the field synergy equation of heat transfer, mass transfer, and heat-mass cooperation under laminar and turbulent conditions, and gives the evaluation standard of field synergy equation. Field synergy theory shows that improving the synergy between the velocity field and temperature gradient field, that is, reducing the angle between them, can effectively improve the heat transfer efficiency, and improving the synergy between the velocity field and concentration gradient field can effectively improve the mass transfer efficiency. Subsequently, the research progress of field synergy theory in different engineering fields is summarized. It is shown that field synergy theory can be used to analyze the cooperation between fields in heat exchangers, micro-components, nanofluids, reactors and other fields to guide the optimal design of equipment, which proves the universality of field cooperation theory. Finally, in view of the universality of the damp-heat exchange in the cooling exchangers and the research object of field synergy theory, a new idea of using the field synergy theory to guide the research on the structural design of cooling exchangers is put forward, which provides new ideas and methods for effectively improving the underground humid and thermal environment. | A review: the development of field synergy and its application to cooling exchangers in the hot-wet mining field | 10.1007/s10973-023-12220-2 |
2023-07-01 | Purpose Slender boring bars vibrate when excited by cutting forces to result in chatter. These chatter vibrations damage the part and the tool and hence must be avoided and/or suppressed. Usually, tuned absorbers integrated within the boring bar dissipate the motion of the boring bar and make stable cutting possible. However, since the boring bar’s dynamics change with loading and boundary conditions, optimally tuning the absorber becomes difficult. This prevents stable high-performance cutting. To improve the cutting performance of a potentially detuned absorber within a boring bar, this paper presents a novel hybrid damping solution. The hybrid damper is composed of an absorber working in conjunction with an eddy current damper. Methods To demonstrate the working of this hybrid damper, we model the boring bar as an Euler–Bernoulli beam. A permanent magnet is supported by a spring and damper within a copper section of a boring bar. The supported magnet acts as an absorber and the relative motion between the conductive copper bar and the magnetic field induces eddy currents that hinder the motion of the boring bar. Governing equations for the beam with an integrated damper are obtained by applying the extended Hamilton’s principle. Eddy current damping is evaluated by applying the Lorentz force law and the Biot–Savart law. Results Our analysis suggests that the improvement in the chatter-free depth of cut with a hybrid damper over the case with a detuned absorber is as much as ~ 500%. And, when the absorber is optimally tuned and the hybrid damper takes its maximum possible value, the chatter-free depth of cut for both cases was found to be the same, suggesting that if/when the absorber can be optimally tuned, the eddy current damper offers no additional benefit. Conclusion Since optimally tuning an absorber is difficult, our proposed hybrid damper offers a feasible solution to improve cutting performance with slender boring bars. Moreover, since our models are generalized, the approach may also be used to explore the integration of such hybrid dampers within other tooling systems such as milling tool holders. | Damped Chatter Resistant Boring Bar Integrated with an Absorber Working in Conjunction with an Eddy Current Damper | 10.1007/s42417-022-00684-9 |
2023-07-01 | Purpose This article presents a novel approach for synthesizing the vibration isolation system that simultaneously considers the layout of the host structure, the distribution of free or constrained damping layers, and the positions of resilient mounts. Methods The topology optimization model is established by using multi-objective optimization method. All the topological design variables (including layouts of the host structure and the damping layer, and positions of the resilient mounts) are expressed with continuous variables, making it convenient for deriving sensitivity information. Two kinds of vibration isolation systems are designed, one with a free damping layer and the other with a constrained damping layer. Different vibration isolation systems with different numbers of resilient mounts, different thicknesses of host structures, different treatments of damping, and different frequencies of excitation forces, are used to test the applicability of the proposed model. Results The proposed optimization model can clearly give the positions of the resilient mounts and effectively realize the layout design of the host structure and the damping layer while ensuring that the optimized damping layer can only be distributed in the regions where solid materials of the host structure are present. Conclusion The proposed method can be applied to the design of vibration isolation systems for better dynamic performances. | Design Synthesis of Vibration Isolation System Considering Host Structure, Damping Layer, and Resilient Mounts | 10.1007/s42417-022-00686-7 |
2023-07-01 | Structures show inelastic non-linear behaviour under cyclic loads associated with natural activities like earthquakes and wind, which impart external kinetic energy to them, consuming the lateral movement of structures, such movement may be responsible for the failure or collapse of these structures. To prevent such a collapse, it is necessary to recognize the non-linear behaviour of the structure and adopt a suitable mechanism to control the response of them and this may be possible by dissipating the seismic energy which imparts on them. The study is devoted to the development of an efficient, feasible and economical tuned mass damper for moderately high buildings. This tuned mass damper (TMD) is in form of a weak storey at the top of the buildings for square and rectangle in the plan. Incremental dynamic analysis (IDA) was implemented to investigate the benefits of TMD on structural behaviour. Using ten earthquakes scaled up to a maximum target multiplier of two, with ten increments, damage measures such as storey drift. The fragility curves in this study are represented by lognormal distribution functions with two parameters (i.e., the mean spectral displacement and the standard deviation) and developed as a function of spectral acceleration (Sa). Comparison of the fragility curves indicated that the TMD is marginally effective in attenuating seismic structural response under various earthquake ground motions. | Incremental dynamic analysis of building with weak storey at top as TMD | 10.1007/s42107-022-00559-0 |
2023-06-24 | The current study investigates the effect of viscosity of base oil and weight fraction of carbonyl iron particles on maximum yield stress and effective damping range of a short-stroke magnetorheological damper (stroke length of 2 mm) designed for tool vibration mitigation. It is difficult to find the exact composition of magnetorheological fluid (MRF) based on the design equations, as unidentified practical parameters influence their behaviour hence, optimization by experimental techniques is necessary. Optimal composition of MRF are identified by genetic algorithm through central composite design of experiment. A validation study is conducted to cross verify the optimum values delivered by the algorithm. The damper is fitted onto lathe machine with the optimal fluid composition to evaluate its performance in controlling the tool vibration. The damper has been designed for the specific speed, feed and depth of cut however, the design procedure for developing a damper for higher/other cutting conditions can be achieved by the design scheme mentioned in this article. The vibration level of tool reduced by 28.66% and the amplitude of cutting force reduced by 68.18% indicating reduction of chatter vibration with the damper. An improved surface finish has been observed from 4.8 to 1.6 μm. | Determining the optimal composition of magnetorheological fluid for a short-stroke magnetorheological damper | 10.1007/s12046-023-02195-z |
2023-06-23 | In this paper, we consider optimal portfolio selection when the covariance matrix of the asset returns is rank-deficient. For this case, the original Markowitz’ problem does not have a unique solution. The possible solutions belong to either two subspaces namely the range- or nullspace of the covariance matrix. The former case has been treated elsewhere but not the latter. We derive an analytical unique solution, assuming the solution is in the null space, that is risk-free and has minimum norm. Furthermore, we analyse the iterative method which is called the discrete functional particle method in the rank-deficient case. It is shown that the method is convergent giving a risk-free solution and we derive the initial condition that gives the smallest possible weights in the norm. Finally, simulation results on artificial problems as well as real-world applications verify that the method is both efficient and stable. | Portfolio Selection with a Rank-Deficient Covariance Matrix | 10.1007/s10614-023-10404-4 |
2023-06-22 | We consider the two-dimensional damped wave-type magnetohydrodynamic equations with fractional dissipation. We prove the global existence and uniqueness of solution for small initial data in Sobolev spaces. | Global existence and uniqueness of the 2D damped wave-type MHD equations | 10.1007/s00033-023-02042-5 |
2023-06-19 | In this paper, we study the forced flexural vibrations caused by time-harmonic concentrated loads on a transversely isotropic thin rectangular plate (TRP). A mathematical model has been formed using a new modified Green–Naghdi (GN) III theory of thermoelasticity by introducing higher-order memory-dependent derivatives (MDD). The memory-dependent derivatives represent the memory effect (i.e., the instantaneous rate of change depends on the previous state). This study not only considers the size effect but also studies the memory, mechanical, and thermal-field effects. With the help of the double finite Fourier-transform technique (DFFT), the expressions for lateral deflection, thermoelastic damping, temperature distribution, frequency shift, and thermal moment, have been found in the transformed domain for simply supported (SS) TRP. Also, we have graphically demonstrated the effect of the MDD kernel function on the lateral deflection, thermoelastic damping, temperature distribution, frequency shift, and thermal moment. | Study of a time-harmonic load on a Kirchhoff–Love plate with modified thermoelasticity theory using higher-order memory-dependent derivatives | 10.1007/s11043-023-09612-0 |
2023-06-19 | Mg-0.8Si alloy plates were rolled at high strain rates of 15, 20, and 25 s^−1, and the effects of the rolling strain rate on the microstructure, mechanical properties, and damping properties of the Mg-0.8Si alloy were studied. With the increasing strain rate, the area fraction of DRX in the HSRRed Mg-0.8Si alloy gradually increases, resulting in the decrease in dislocation density and dislocation tangles. A higher strain rate can enlarge the grain size of the Mg-0.8Si alloy, so the basal texture and tensile strength can both decrease because of the increased strain rate. The maximal elongation is 8.40% at 20 s^−1. The damping properties of HSRRed Mg-0.8Si alloy increase with the strain rate and the critical strain amplitude gradually decreases. | Microstructures, Damping and Mechanical Properties of Mg-0.8Si Alloy under Different Rolling Strain Rates | 10.1007/s11665-023-08404-4 |
2023-06-17 | A novel second-order two-scale(SOTS) asymptotic analysis and computational approach are developed for solving the quadratic eigenvalue problem(QEP) in periodic composite domain. Two typical QEPs involving the velocity damping and the Rayleigh damping are considered and the asymptotic expansions for both the eigenfunctions and eigenvalues are performed. The first-order cell functions characterizing the detailed configuration of the presentative cell are formally defined and the homogenized QEPs are obtained with the macro effective coefficients. The second-order cell functions are further derived which are used to describe the rapid oscillation of the eigenfunctions more accurately. The nonlinear relationship between the original and the homogenized eigenvalues are established by introducing the auxiliary functions defined on the composite domain and the second-order expansions of the eigenvalues are obtained successively. Then, the error estimations of the expansions of eigenvalues are established. Finally, the finite element procedure is proposed, the homogenized QEPs are solved by the linearized method and the numerical examples demonstrating the accuracy and the efficiency of our proposed model and algorithm are reported. It is indicated that the SOTS method can effectively applied to this nonlinear eigenvalue problem and the second-order correctors play an important role for describing the local behavior of eigenfunctions and obtaining better approximation of the eigenvalues at lower cost. | Multiscale asymptotic analysis and algorithm for the quadratic eigenvalue problem in composite materials | 10.1007/s40314-023-02342-6 |
2023-06-17 | We consider a swelling porous-elastic system with frictional damping and viscoelastic damping acting simultaneously and complementarily in the domain and study the effect of such competition between the two types of damping on the asymptotic behavior of the energy function. Under nonrestrictive on the growth assumption on the frictional damping and under more general assumption on the relaxation function, we establish, for the first time as per our knowledge, explicit and optimal energy decay rates for this system. Our decay results were obtained by using the multiplier method and some properties of the convex functions. These results generalize and improve some earlier related results in the literature. | Theoretical Decay Results of a Swelling Soils System with Frictional Damping Versus Viscoelastic Damping | 10.1007/s00009-023-02433-y |
2023-06-15 | In this work, damping properties of bending viscoelastic thin structures are enhanced by topology optimization. Homogeneous linear viscoelastic plates are optimized and compared when modeled by either the Kirchhoff–Love or Reissner–Mindlin plate theories as well as by the bulk 3D viscoelastic constitutive equations. Mechanical equations are numerically solved by the finite element method and designs are represented by the level-set approach. High performance computing techniques allow to solve the transient viscoelastic problem for very thin 3D meshes, enabling a wider range of applications. The considered isotropic material is characterized by a generalized Maxwell model accounting for the viscoelasticity of both Young modulus and Poisson’s ratio. Numerical results show considerable design differences according to the chosen mechanical model, and highlights a counter-intuitive section shrinking phenomenon discussed at length. The final numerical example extends the problem to an actual shoe sole application, performing its damping optimization in an industrial context. | Damping optimization of viscoelastic thin structures, application and analysis | 10.1007/s00158-023-03602-z |
2023-06-12 | Granular dampers are systems used to attenuate undesired vibrations produced by mechanical devices. They consist of cavities filled by granular particles. In this work, we consider a granular damper filled with a binary mixture of frictionless spherical particles of the same material but different size using numerical discrete element method simulations. We show that the damping efficiency is largely influenced by the composition of the binary mixture. | Granular binary mixtures improve energy dissipation efficiency of granular dampers | 10.1007/s10035-023-01337-8 |
2023-06-03 | Eddy current dampers (ECD) have merits such as contactless damping, no need for lubrication and almost no maintenance; due to these advantages, ECD is suitable for the use of aerospace applications, and ECD may be preferred. This research article is focused on designing and developing an eddy current damper to provide vibration isolation. It minimizes the vibration of the mechanical system used in aerospace applications. Generally, in aerospace applications, permanent magnets are used in eddy current damper (ECD), which, under extreme conditions, can lead to demagnetization of the magnet; hence, the damper stops working. In this article, the permanent magnet and an electromagnet are used for the reliable working of ECD. The proposed ECD consists of a permanent magnet, electromagnet, conductor rod, iron core and helical spring. Firstly, the ECD and its components are analyzed using the finite element modeling (FEM) with COMSOL software to optimize the dimensions and damping coefficient of the proposed damper by changing the coil current, the number of turns of the coil and the air gap between conductor and magnet. Then, based on the FEM analysis, the ECD prototype is fabricated, and vibration tests are performed at low amplitude and high variable frequency on the prototype to validate the reliability of the FEM analysis. There is a consensus between FE analysis and experimental results. The proposed design of ECD used both the permanent magnet and electromagnet. This modification helped increase the damper's overall damping coefficient from 40.28 Ns/m (without a permanent magnet) to 62.33 Ns/m. With the increase in frequency from 10 to 50 Hz, the proposed ECD's damping force (maximum magnitude) increases. Experimental and FEM results show that, with the decreases in temperature, the damping coefficient of the designed ECD increases. | Modeling and development of eddy current damper for aerospace applications | 10.1007/s40435-023-01220-7 |
2023-06-01 | This study evaluated the dynamic properties of Pisa clay and Ticino sand (shear modulus and damping ratio) for a relatively wide range of consolidation pressures using the resonant column apparatus (RC), after which the results were simulated. The study aimed at the evaluation of the soil dynamic properties at very low consolidation pressure; the results of which are used for seismic response analysis of sites particularly near the ground surface where shear modulus may be more pronounced than at other depths. The results were compared to previous studies, which led to development of a modified constitutive model for evaluating the dynamic properties. The modified constitutive model mainly concerns the reference shear strain values ( γ _r) that differently varied at low levels of consolidation stresses compared to higher levels. It was observed that reference shear strain is about 0.035% < γ < 0.1% for Ticino sand and 0.04% < γ < 0.08% for Pisa clay. The so-called “elastic threshold shear strain” was also observed in a range of 0.0005–0.001% for Ticino sand and 0.002–0.003% for Pisa clay. Case studies were conducted, whereby the above-mentioned model was integrated into a new analytical approach for site response analysis assuming a continuous variation of the shear wave velocity with soil depth. A computer program was written in a MATLAB environment based on this approach. Results were compared to those given by DEEPSOIL software. It was observed that the use of the current approach to reasonable results, while the efficiency and speeds of calculations are highly maintained by the current approach. | Experimental and Simulation Study on Dynamic Properties of Two Historical Soils in Italy | 10.1007/s40999-022-00781-6 |
2023-06-01 | This paper presents recent developments towards efficient and reliable methods for roll damping estimation based on numerical simulations as well as model tests using the harmonic excited roll motion (HERM) technique. A newly designed automatic roll damping estimation procedure shows the advantage of a just-in-time post processing of experimental measurement results. Real-time analysis of the measured roll damping values permits a considerable shortening of the test times. Thus, a large number of investigations can be carried out with relatively manageable effort in order to determine the roll damping behavior of different keel configurations or at operating conditions, e.g., different sized keels or Froude numbers. In addition, HERM measurement method is applied to investigate the memory effect. For this purpose, different excitation schemes are introduced and the results are analyzed. Moreover, a study of the scale effect on the roll damping properties is conducted, in which experimental and numerical investigations are performed for two scales of a ship model. Furthermore, a method is developed that significantly reduces the effort of Reynolds average Navier-Stokes (RANS)-based simulations of roll motion. The reduction of simulation time is achieved by introducing an artificial damping. The obtained results show that the developed method is very well applicable for numerical as well as in experimental investigations. During the model tests using HERM technique, the model is free and the rudder is used to keep the straight-ahead course. The analysis of the numerical and experimental results shows that the influence of the rudder induced force and moment during HERM tests is not negligible and the contribution of the rudder must be taken into account by estimating the roll damping. Finally, a new concept is developed to investigate the parametric roll behavior of ships, which allows neglecting the consideration of the complex modelling of free surface waves in the simulations. During the RANS computations, a potential-based method is applied to compute the variation of restoring terms due the roll motion. | Advances on numerical and experimental investigation of ship roll damping | 10.1007/s42241-023-0044-9 |
2023-06-01 | Purpose This study reports on shunt circuits enabled by low-cost, small-scale electronic circuitry and free software by combining piezoelectric materials and digital devices. This class of systems can be considered in many different vibrating problems, such as elastic and aeroelastic structures and metastructures, aiming for adaptive and reconfigurable vibration attenuation capabilities. Methods A general electronic circuit that suits for different vibration control techniques in electromechanically coupled systems is presented, while the specific technique emulation is achieved via software programming, so that the same hardware works for different techniques. Results The proposed method successfully reproduces the electrical impedance across the electrodes of a piezoelectric material obtained with consolidated analog techniques such as linear resistive shunt (R) and resistive–inductive shunt (RL), and also the nonlinear synchronized switch damping on short circuit (SSDS) and synchronized switch damping on inductor (SSDI). Conclusions The performance of the proposed digital platform is comparable to experimental data and circuit simulation obtained with analog circuits for validation for both the linear (R and RL) and the nonlinear (SSDS and SSDI) techniques. The proposed platform can be extended and applied to many different vibration control systems with electromechanical coupling. | Design and Experimental Validation of Linear and Nonlinear Digital Synthetic Impedances for Electromechanically Coupled Systems | 10.1007/s42417-022-00674-x |
2023-06-01 | In this paper, we study the following fractional damped vibration problems: $$\begin{aligned} \left\{ \begin{array}{ll} -_tD^{\alpha }_{\infty }(_{-\infty }D^{\alpha }_tu(t))+A(_{-\infty }D^{\alpha }_tu(t))-L(t)u(t)+\nabla W(t,u(t))=0,&{} \\ u\in H^{\alpha }({\mathbb {R}},{\mathbb {R}}^n).&{} \end{array} \right. \end{aligned}$$ - t D ∞ α ( - ∞ D t α u ( t ) ) + A ( - ∞ D t α u ( t ) ) - L ( t ) u ( t ) + ∇ W ( t , u ( t ) ) = 0 , u ∈ H α ( R , R n ) . By using variational methods and the generalized mountain pass theorem, the existence and the multiplicity of nonzero solutions are obtained. | On a class of fractional damped vibration problems | 10.1007/s41808-022-00188-3 |
2023-06-01 | Most dampers are designed for major earthquakes, while small earthquakes are likely to occur during the useful life cycle of buildings, and these smaller earthquakes may also damage structural and non-structural components; multi-level dampers are designed with a mechanism that works partly in minor earthquakes and partly in major earthquakes. Therefore, using these dampers prevents damage to structural and non-structural components at different levels of earthquakes. This study introduces the multi-level shear-bending TADAS damper and examines three types of multi-level TADAS dampers including: (1) a TADAS made by different steel grade materials, (2) a TADAS combined with friction pads and (3) a TADAS with different pin hole sizes. Moreover, further research is performed to evaluate the seismic performance of the multi-level TADAS damper in a 10-story building model using the incremental dynamic analysis (IDA). According to the obtained results, the considered models showed the expected seismic performance at two earthquake hazard levels which in turn indicates the usefulness of multi-level TADAS dampers in seismic energy dissipation. Examination of IDA curves shows that the effective yield and the collapse points of structures equipped with multi-level TADAS dampers occur in about 53.1% and 143.5% higher earthquake intensities compared to the structures without dampers, respectively. Moreover, due to the enhanced seismic performance of these systems, lightweight structures can be designed which is in line with the goals of sustainable development which is another advantage of this system. | Evaluation of the seismic performance of structures equipped with novel multi-level TADAS dampers | 10.1007/s42107-022-00546-5 |
2023-06-01 | The motivation of this study stems from a retaining wall made of waste tires. The wall did not suffer any earthquake or tsunami-induced damage during the 2011 Off the Pacific Coast of Tohoku Earthquake, Japan. This paper deals with a case study on this tire retaining wall. Results from a series of field and laboratory investigations are first described. A numerical simulation is also described in which whole tires were used as protective layers in an embankment. The results show that confining effect of each tire, friction between the tires, ductility, and damping inherent in tires contribute towards the excellent performance of the retaining wall during the earthquake loading. The case study also reveals that it is the isolation mechanism due to the vibration absorption capability of rubber particles in tires, which could protect tire retaining structure during the earthquake. | Performance evaluation of waste tires in protecting embankment against earthquake loading | 10.1007/s10518-023-01690-2 |
2023-06-01 | Abstract —The characteristics that confirm the positive effect of thermal barrier coatings on the rotor blades of gas turbine engines, which are made of ZhS6U, VZhL12U, and ZhS30M alloys, on the damping ability of the blades are presented. | Influence of Thermal Barrier Coatings on the Damping of GTE Turbine Blade Vibrations | 10.1134/S0036029523060010 |
2023-06-01 | The flexibility of the foundation system significantly affects the seismic and operational performance of integral abutment bridges (IAB). The so-called pile isolation system can lead to higher flexibility in pile foundations. It consists in backfilling the pile hole with high-damping materials up to a certain depth from the surface level. However, the impact of this solution in increasing the lateral flexibility and reducing the seismic demand strongly depends on the scale factor and pile diameter. Most investigations on this topic are based on experimental tests on scaled pile specimens. This paper explores the pile isolation system’s effectiveness by conducting a multivariate sensitivity analysis of the seismic demand of an IAB structural archetype. The IAB archetype is modelled as a Winkler beam with a piece-wise definition of the subgrade stiffness and equivalent viscous damping, simulating the responses of the soil and high-damping particles. The simulated data are then used to calibrate a probabilistic formulation of the seismic demand reduction due to the pre-hole. The formulation, calibrated following a Bayesian approach, is used to derive estimates of the q -factor associated with the damping pre-hole for possible use in engineering practice. The analyses demonstrate that pile isolation with high-damping material can be effective but possesses a limited dissipating capacity, with a seismic reduction factor of approximately 1 and 2. | Probabilistic formulation for the q-factor of piles with damping pre-hole | 10.1007/s10518-022-01497-7 |
2023-06-01 | Abstract This paper concerns with the initial and boundary value problem for a p -biharmonic wave equation with logarithmic nonlinearity and damping terms. We establish the well-posedness of the global solution by combining Faedo–Galerkin approximation and the potential well method, and derive both the polynomial and exponential energy decay by introducing an appropriate Lyapunov functional. Moreover, we use the technique of differential inequality to obtain the blow-up conditions and deduce the life-span of the blow-up solution. | Well-Posedness and Asymptotic Behavior for the Dissipative p-Biharmonic Wave Equation with Logarithmic Nonlinearity and Damping Terms | 10.1134/S0965542523060192 |
2023-06-01 | Damping plays an important role in the middle ear (ME) sound transmission system. However, how to mechanically characterize the damping of ME soft tissues and the role of damping in ME sound transmission have not yet reached a consensus. In this paper, a finite element (FE) model of the partial external and ME of the human ear, considering both Rayleigh damping and viscoelastic damping for different soft tissues, is developed to quantitatively investigate the damping in soft tissues effects on the wide-frequency response of the ME sound transmission system. The model-derived results can capture the high-frequency (above 2 kHz) fluctuations and obtain the 0.9 kHz resonant frequency (RF) of the stapes velocity transfer function (SVTF) response. The results show that the damping of pars tensa (PT), stapedial annular ligament (SAL) and incudostapedial joints (ISJ) can help smooth the broadband response of the umbo and stapes footplate (SFP). It is found that, between 1 and 8 kHz, the damping of the PT increases the magnitude and phase delay of the SVTF above 2 kHz while the damping of the ISJ can avoid excessive phase delay of the SVTF, which is important in maintaining the synchronization in high-frequency vibration but has not been revealed before. Below 1 kHz, the damping of the SAL plays a more important role, and it can decrease the magnitude but increases the phase delay of the SVTF. This study has implications for a better understanding of the mechanism of ME sound transmission. | Characterization of middle ear soft tissue damping and its role in sound transmission | 10.1007/s10237-023-01696-4 |
2023-06-01 | The working conditions of construction machinery are frequently harsh. To prevent excessive impact from causing mechanical failure, the performance of viscoelastic suspensions typically requires improvement. However, the elevated performance also results in increased stress, which can drastically reduce the longevity and durability of the damping structural components of the viscoelastic damper. To achieve the dual objectives of improving vibration reduction performance and ensuring longevity, an ANSYS Parametric Design Language (APDL) finite element model of the damping components is created and optimized. The damping component's rubber block radius, side shape angle, and bottom height are design variables, and the suspension's largest energy consumption under periodic load is an objective function. The superposition of zero-order and first-order optimization methods is chosen as the basic tool for structural optimization. The results show that the characteristic parameters of damping performance of the optimized damping components are significantly improved, and the corresponding stress is within the design index, which can effectively prevent premature failure. ANSYS is used to perform strength analysis on optimized results, and it indicates that its strength can meet the usage requirements of the bulldozer under various working conditions. | Structural Optimization of Damping Components of Viscoelastic Suspension Based on Preventing Failure Caused by Excessive Stress | 10.1007/s11668-023-01683-y |
2023-06-01 | Eucommia ulmoides gum (EUG) was a biobased hard rubber with the prospected broad applications in rubber products, whereas possessed poor elasticity and weak damping functionality at room temperature. After modification of EUG by triazolinedione-based Alder-ene reaction, the modified EUG containing varied amount of polar and branched pendants could become a new type of soft rubber and functional material with excellent damping properties, and especially exhibited the unique damping plateau with a wide effective damping temperature range of 132 °C covering from −35 °C to 97 °C, large loss factor of 0.8, high damping coefficient of 0.53, and more hysteresis loss of 0.35. Therefore, this sustainable elastomeric material with adjustable damping performance would absorb more vibrational mechanical energy in a wide temperature range, and have broadened applications in energy-absorption devices and shock-absorbing materials. | Unique Damping Properties of Modified Eucommia Ulmoides Gum Bearing Polar and Branched Pendants | 10.1007/s10118-023-2899-1 |
2023-06-01 | Purpose In this study, the effective damping coefficient of the fluid viscous dampers (FVDs) used for coupling two adjacent multi-story frames was investigated, considering soil-structure interaction (SSI) effects under seismic excitation. Methods A numerical procedure was employed to obtain the dynamic response of the interconnected frames-soil system. The two-dimensional (2D) finite elements were used for the numerical treatment of the adjacent frames and soil region. Viscous boundary conditions were used as special non-reflecting boundaries on the edges of finite soil region. Five different damping coefficients of FVDs are considered to determine the effective damping coefficient. The effective damping coefficient of FVDs was determined by comparing the results from coupled frames with those of the uncoupled frames. Results The results showed that the most affecting parameter on the system response was found to be soil type. It was also found that the sufficient damping coefficient of the viscous damper is equal to 1 × 10^5 N s/m for minimum response. Conclusion When the effective damping coefficient of the FVDs was provided, the maximum values of the roof displacements, the roof accelerations, and the base shear forces are found to decrease by more than 40%. | Effective Damping Coefficient of Fluid Viscous Dampers for Dynamic Response Mitigation of Coupled Frames | 10.1007/s42417-022-00673-y |
2023-06-01 | Background Reduction in structure vibration by dampers during a defined time has attracted widespread attention in the aerospace and automobile industries. Therefore, the comparative study of curved panel structure vibration reduction is very important. Purpose This paper aims to study the damping effect of a curved panel in the presence of unconstrained and constrained composite NBR elastomeric layers, both unaged and aged (high temperature, low temperature, and QUV). Methodology The modal strain energy approach is used to determine placement strategies for elastomeric layer patches. The comparative study shows that the constrained layer damping patches are a more effective way to attenuate vibration for the curved panel when placed at maximum modal strain energy locations. Furthermore, vibration tests of curved panel are conducted by preparing a number of separate samples of unconstrained and constrained composite NBR elastomers patches for each configuration to increase the damping of different modes. Results and Conclusion The results show the effectiveness of modal strain energy technique for placement of constrained composite NBR elastomers patches on the curved panel to achieve desired damping characteristics over a broad frequency range. Subsequently, it also demonstrates that, damping of the curved panel is more influenced due to QUV aged elastomeric patches than high and low temperature aged elastomers patches. Moreover, the reduction in damping of the curved panel is more resisted due to the presence of nano carboxylic graphene (CG)/SiO_2 in the aged composite NBR elastomer. The present method elaborates the utility of the technique for placement of constrained elastomeric patches to attenuate structure vibration by modal strain energy and damping reduction resistance against ageing by composite NBR elastomer. Graphical Abstract | Vibration Attenuation Study of Curved Panel Treated with Partially Constrained Composite Unaged and Aged NBR (Acrylonitrile–Butadiene Rubber) Elastomers | 10.1007/s42417-022-00657-y |
2023-06-01 | Purpose The objective of this paper is to investigate with simulations how non-linear spring and non-linear damper components of isolators can be employed to effectively reduce both the oscillations and the force transmitted to ground in the whole spinning range of unbalanced rotating machines. Methods The principal goal of this paper is twofold. First, to present a concise and consistent formulation based on the harmonic balance approach for the vibration response of spinning machines mounted on linear/non-linear, softening/hardening, un-tensioned/pre-tensioned springs and linear/non-linear dampers. Second, to provide a comprehensive overview of the vibration and force transmission control with non-linear isolators specifically tailored to unbalanced machines. Results The study has shown that, the best vibration isolation is provided by a pre-tensioned linear and cubic softening spring combined with a linear and negative quadratic damper. The pre-tensioned spring should be designed in such a way as it holds the weight of the machine and thus produces on the vibrating machine a symmetric elastic restoring force proportional to the linear and cubic powers of the displacement. The cubic softening stiffness should then be tuned to minimise the frequency, and thus the amplitude, of the resonant response of the fundamental mode of the machine and elastic suspension system, while preserving stability and a desired static deflection. In parallel, to reduce the force transmission to ground above the fundamental resonance frequency, the negative quadratic damping effect should be tailored to maximize the energy absorption at higher frequencies. Conclusion The study has shown that non-linear spring and non-linear damper components can be effectively employed to control the vibration and force transmission in the whole spinning range of the machine. In particular, a pre-tensioned softening cubic non-linear spring can be used to mitigate the vibration and force transmission at low frequencies, close to the fundamental natural frequencies of the elastically suspended machine. Also, a negative quadratic non-linear damper can be used to tailor the energy dissipation of the isolator in such a way as to have high damping at low frequencies and low damping at higher frequencies, which enhances the vibration and force transmission control at low frequencies and, rather importantly, mitigates the force transmission at higher frequencies. | Non-linear Isolator for Vibration and Force Transmission Control of Unbalanced Rotating Machines | 10.1007/s42417-022-00668-9 |
2023-06-01 | Geotechnical Seismic Isolation (GSI) can be defined as a new category of seismic isolation techniques that involve the dynamic interaction between the structural system and geo-materials. Whilst the mechanism of various GSI systems and their performance have already been demonstrated through different research methods, there is a missing link between fundamental research and engineering practice. This paper aims to initiate the development in this direction. A new suite of equivalent-linear foundation stiffness and damping models under the same framework is proposed for four GSI configurations, one of which is a novel combination of two existing ones. The exact solutions for the equivalent dynamic properties of flexible-base systems have also been derived that explicitly include the foundation inertia and the strain-dependent equivalent damping of foundation materials, which are both significant for GSI systems. The application of the proposed analytical design models has been illustrated through response history analyses and a detailed hand-calculation design procedure has also been outlined and demonstrated. | Analytical design models for geotechnical seismic isolation systems | 10.1007/s10518-022-01469-x |
2023-06-01 | Over the past years, multiple fire accidents have been witnessed in ancient wooden buildings around the world, thereby causing major losses of cultural relics and social impact. Because of the damage of the ancient wood structure caused by the problem of aging, this enables its thermal conduction properties to change. For this reason, the way how the fire spread also changes. This study was based on the concept that the environmental characteristics of ancient building wood subjected to long-term natural aging, and so the artificially accelerated and alternate process of dry and wet aging method used for wood materials was determined. To that end, the common wood types of ancient buildings were selected as the research objects, so as to obtain the varying degrees of dry and wet aging wood materials. Furthermore, the characteristics of pores on the outer surface of aging wood materials were analyzed through the experiments conducted with a scanning electron microscope. Through the thermophysical property test, the variation law of thermophysical property parameters of aging wood materials with temperature was appraised, and the influence mechanism of the alternate process of dry–wet aging on the thermal conductivity of wood was revealed. The results demonstrated that the cell wall of wood underwent plastic deformation during the alternate process of dry and wet aging. Also, the local wood structure collapsed to different degrees, and so the surface tear degree increased. Because of the joint influence of the elastic stress and the mechanical adsorbed creep stress generated in the alternate process of dry and wet aging, the surface pore deformation of wood was periodic and dampened with the aging degree, so that the heat conduction properties of wood all manifested the change law of sinusoidal damping with the deepening of the aging degree. It is hoped that the research results could provide a theoretical basis for both the early prediction about and the accurate warning of fire spread in ancient wooden structures. | Influence mechanism of dry and wet alternate aging on thermal property characteristics of wood | 10.1007/s10973-023-12015-5 |
2023-06-01 | In recent years, the importance of nanoparticles, which are high-tech products, has been increasing. Nanoparticles are used in many fields as well as in the field of composite materials. These materials are widely used in some areas such as materials and manufacturing, computer technologies, aerospace and military, environment, and energy. In this study, woven composites produced in five different stacking sequences without nanoparticle reinforcement and different mass ratios (0.5%, 1%, and 3%), and with Al_2O_3, CuO, and MgO nanoparticle reinforcement were subjected to fatigue tests. Fatigue tests were performed by means of a Shimadzu brand Servo-Hydraulic Fatigue Tester with a 100 kN load cell. In order to determine the fatigue limits of the samples, fatigue tests were performed by applying R = – 0.1 load ratio, 6 Hz frequency, and sine wave load. Load level (%)–cycle number (N) diagrams, damping ratios, and hysteresis loops of woven composites were investigated, and the results were interpreted. When the hysteresis loops were examined, it was seen that the areas between the hysteresis loops increased and the stiffness of the composite materials decreased with the increment of nanoparticle reinforcement to the composite materials. The highest stiffness values were observed in 0.5% CuO nanoparticle-reinforced composite materials with KM-3 stacking sequence. In addition, SEM analyses of damage mechanisms in woven composite materials were observed. | Investigation of Effect of Nanoparticle Reinforcement Woven Composite Materials on Fatigue Behaviors | 10.1007/s40997-022-00543-8 |
2023-06-01 | Purpose: The stability problem for non-conservative multi-parameter dynamical system is usually associated with labor-intensive calculations, and numerical methods do not always allow one to obtain the desired information. The presence of circulatory forces often leads to the so-called ”destabilization effect” of the system under the influence of small dissipative forces. In this regard, it seems important to develop analytical approaches that make it possible to use a simplified scheme for checking the stability conditions. Methods: When obtaining and analyzing stability conditions, the algebra of polynomials and elements of mathematical analysis are applied. To obtain a simplified scheme for checking the stability conditions, an asymptotic method is used. Results and Conclusion: A mechanical system with four degrees of freedom which is under the action of dissipative, potential and non-conservative potential (circulatory) forces is considered. The stability problem of friction-induced vibrations is studying. In the case of weak damping an analytical approach is proposed that makes it possible to simplify the analysis of stability conditions, which, due to the presence of many uncertain parameters, are very cumbersome. With the help of numerical testing, the adequacy of the results obtained for the reduced conditions and full stability conditions was established. The results of the analysis make it possible to single out the ”advantageous” regions in the space of dimensionless parameters, which makes it possible to improve the design of the system to increase its reliability. | Analytical Scheme of Stability Analysis for 4-DoF Mechanical System Subjected to Friction-Induced Vibrations | 10.1007/s42417-022-00665-y |
2023-06-01 | Abstract The authors investigate geophysical parameters of water-saturated and frozen rock samples, and compare the results with the data of natural rocks. The samples were subjected to dynamic loading, an acceleration signal was recorded and a spectral density was calculated. On this basis, later on, the authors determined the longitudinal vibration velocity, the logarithmic decrement of damping, the internal friction factor and the acoustic Q-factor. The water-saturated and frozen rock samples demonstrated the increased velocities of longitudinal vibrations. The samples, which had the high acoustic Q-factors in the frozen conditions, fractured under much higher loads. The degree of water saturation affected the strength of the test samples: their strength reduced with the higher water saturation. Freezing of the samples generated microseismic vibrations in the region of high frequencies. In the uniaxial compression tests to failure of the samples under critical loading, a high frequency signal was recorded during initiation of an extension fracture, and the signal spectrum shifted toward lower frequencies as the fracture grew. | Acoustic Characteristics of Rock Samples under Negative Temperatures | 10.1134/S1062739123030201 |
2023-06-01 | Strain glass, a short-range strain-ordered state of martensitic/ferroelastic material, has drawn much interest in recent years due to its novel properties unattainable in martensitic materials. So far, typical or conventional strain glasses have been reported to be characterized by nano-sized martensitic domains formed from a homogeneous parent phase matrix. This article reviews the recent progress in “non-conventional strain glass,” which is different from the conventional strain glasses reported so far. We first introduce a “reentrant strain glass,” where strain glass nanodomains are formed from a martensitic phase instead of from a parent phase. The reentrant strain glass can show low modulus and high damping properties over a wide temperature range. The second non-conventional strain glass is a “spinodal strain glass” produced by a spinodal decomposition in its early stage. This unique strain glass is formed from a nanoscale compositionally inhomogeneous parent phase (by spinodal decomposition). The spinodal strain glass demonstrates high-damping Elinvar effect over an ultrawide temperature range. These non-conventional strain glass alloys may have potential for novel applications as new structural–functional materials. | Non-conventional Strain Glasses | 10.1007/s40830-023-00448-8 |
2023-06-01 | In this article, we studied the approximate analytical soliton solution of dust acoustic waves in the framework of damped Korteg–De Vries (DKdV) equation. Using the reductive perturbation technique, the evolution equation with additional damping term is derived from a collisional dusty plasma model. As the DKdV equation is not integrable, a numerical solution to the DKdV equation is found and is obtained by using the Adomian decomposition method, taking the solution of the standard KdV equation as an initial approximation. The comparison between the current solution with the existing solution proposed earlier by other authors for smaller values of the damping parameter shows a very good agreement between these two. A significant difference in the solution is observed for the higher value of collision frequency. The effect of some relevant plasma parameters on the proposed solution is also analyzed. | Application of Adomian decomposition method to study collision effect in dusty plasma in the presence of polarization force | 10.1007/s12648-023-02588-0 |
2023-06-01 | In this paper, we prove the existence of a random exponential attractor (a positively invariant, compact, random set with finite fractal dimension that attracts any trajectory exponentially) for the 3D non-autonomous damped Navier–Stokes equation with additive noise, which implies that the asymptotic behavior of solutions for the equation can be described by finite independent parameters. The key and difficult point of this proof lies in proving the Lipschitz continuity and the random squeezing property in mean sense for the non-autonomous random dynamical system generated by solutions of the equation. | Random Exponential Attractor for the 3D Non-autonomous Stochastic Damped Navier–Stokes Equation | 10.1007/s10884-021-09951-x |
2023-06-01 | Purpose The vibration resonance of a high-pressure rotor system is a research topic with a series of support structures and the elastic ring squeeze film damper (ERSFD). A dynamic equation with the multiple degrees of freedom rotor system was estimated for multi-support structures, the ERSFD, and the rotor. Semi-analytical and semi numerical solutions were analyzed for their dynamic characteristics. Methods According to the finite length bearing theory based on the partial differential equation, four oil film pressure models were established and derived to construct four contact models proposed by Russian scholars, considering the geometrical structure of the elastic ring with bosses and oil holes. The semi-analytical and semi-numerical approximate analytical solutions of dynamic equations were derived theoretically using the incremental harmonic balance (IHB) and arc-length methods, which were established for the excitation force, oil film force, and eccentricity. Finally, the sudden imbalance and eccentric faults were analyzed by numerical simulations, and the vibration response was obtained. Results The smaller the oil film gap, the more significant the oil film force produced by the elastic ring and rotor squeezing each other. The amplitude of the rotor increases with an increase in unbalanced values and the static eccentric moment. When the center of the axis orbit changes significantly, it causes rubbing and grinding of the rotor. Conclusion Four different contacts and the approximate analytical solution of the oil film force describe the movement process and force of the elastic ring and the rotor more clearly. The IHB method is more effective and feasible than the Runge-Kutta method for obtaining the unstable solution of the dynamic equation. It provided a theoretical basis for fault diagnosis and the dynamic design of complex rotor systems. | Study on the Semi-numerical and Semi-analytical Solutions of the Dynamics Equation of an Aero-engine Rotor System with ERSFD | 10.1007/s42417-022-00650-5 |
2023-05-31 | In this paper, we consider the long time behavior for a coupled system on Riemannian manifold consisting of the plate equation and the wave equation with nonlocal weak damping, nonlocal anti-damping and critical nonlinearity. We obtain the existence of the global attractor for the coupled system by semi-group method and multiplier method. | Global Attractor for a Coupled Wave and Plate Equation with Nonlocal Weak Damping on Riemannian Manifolds | 10.1007/s00245-023-09998-w |
2023-05-31 | In a Hilbert framework, for general convex differentiable optimization, we consider accelerated gradient dynamics combining Tikhonov regularization with Hessian-driven damping. The temporal discretization of these dynamics leads to a new class of first-order optimization algorithms with favorable properties. The Tikhonov regularization parameter is assumed to tend to zero as time tends to infinity, which preserves equilibria. The presence of the Tikhonov regularization term induces a strong property of convexity which vanishes asymptotically. To take advantage of the fast convergence rates attached to the heavy ball method in the strongly convex case, we consider inertial dynamics where the viscous damping coefficient is proportional to the square root of the Tikhonov regularization parameter, and hence converges to zero. The geometric damping, controlled by the Hessian of the function to be minimized, induces attenuation of the oscillations. Under an appropriate setting of the parameters, based on Lyapunov’s analysis, we show that the trajectories provide at the same time several remarkable properties: fast convergence of values, fast convergence of gradients towards zero, and strong convergence to the minimum norm minimizer. We show that the corresponding proximal algorithms share the same properties as continuous dynamics. The numerical illustrations confirm the results obtained. This study extends a previous paper by the authors regarding similar problems without the presence of Hessian driven damping. | Accelerated Gradient Methods Combining Tikhonov Regularization with Geometric Damping Driven by the Hessian | 10.1007/s00245-023-09997-x |
2023-05-31 | This paper studies a Balakrishnan–Taylor viscoelastic wave equation with strong time-dependent delay. Under suitable assumptions on the coefficients of the delay term, we establish a generalized stability result, which improve some earlier results in the literature. | Uniform stability of a strong time-delayed viscoelastic system with Balakrishnan–Taylor damping | 10.1186/s13661-023-01749-8 |
2023-05-31 | In this work, we approach the minimization of a continuously differentiable convex function under linear equality constraints by a second-order dynamical system with an asymptotically vanishing damping term. The system under consideration is a time rescaled version of another system previously found in the literature. We show fast convergence of the primal-dual gap, the feasibility measure, and the objective function value along the generated trajectories. These convergence rates now depend on the rescaling parameter, and thus can be improved by choosing said parameter appropriately. When the objective function has a Lipschitz continuous gradient, we show that the primal-dual trajectory asymptotically converges weakly to a primal-dual optimal solution to the underlying minimization problem. We also exhibit improved rates of convergence of the gradient along the primal trajectories and of the adjoint of the corresponding linear operator along the dual trajectories. We illustrate the theoretical outcomes and also carry out a comparison with other classes of dynamical systems through numerical experiments. | Time Rescaling of a Primal-Dual Dynamical System with Asymptotically Vanishing Damping | 10.1007/s00245-023-09999-9 |
2023-05-30 | This paper presents an output feedback based Variable Structure Controller (VSC) is described for a series vectorial compensator (SVeC) in order to enhance the dynamic stability of electric power system. The input to the VSC is speed deviation and it is employed to design the switching surface of the proposed VSC. SVeC is a new series Flexible AC Transmission System (FACTS) device and this can regulate the line reactance by vary the duty ratio of PWM switches. The main aim is to check the effectiveness of the SVeC with VSC to enhance the stability in unique system. For this cause, proposed a novel SVeC current injection model incorporated in the test system. The mathematical model of VSC sliding controller gain proposed. The test system is derived using Heffron–Phillips model. The dynamic stability of the system with this proposed Variable Structure SVeC is analysed through eigenvalues and nonlinear time domain simulations for a unique system at nominal load. The performance of the proposed system is compared with SVeC with Feedback control, with PSS control and without control. From the results, it is concluded that the dynamic stability of the system is enhanced with proposed Variable Structure Feedback based SVeC controller compared with other methods. | Design of an output feedback variable structure series vectorial compensator to enhance dynamic stability | 10.1007/s40435-023-01183-9 |
2023-05-30 | Excellent damping characteristics and effective control strategy are important guarantees for semi-active suspension systems to give vehicles excellent driving performance. Based on the theoretical and experimental analysis of the damping characteristics, this study applies continuous damping control (CDC) shock absorber to the semi-active suspension system. A two-degree-of-freedom semi-active suspension system model of 1/4 vehicle based on CDC shock absorber is established. The influences of suspension damping coefficient, suspension stiffness, and wheel stiffness on the vibration characteristics of suspension system are analyzed from the perspectives of time domain and frequency domain. Results show that the suspension damping coefficient is the key factor affecting the vibration characteristics of suspension. Based on this, three control strategies of PID control, self-adaptive fuzzy PID control, and parallel-compound fuzzy and PID control are introduced to adjust the output damping force of semi-active suspension system, and the vibration suppression effect is compared and analyzed. | Vibration analysis and control of semi-active suspension system based on continuous damping control shock absorber | 10.1007/s40430-023-04183-0 |
2023-05-26 | It is well-known that a second-order ODE system admits a general matrix form of notation. In this work, we study general relations between system stability/robustness properties and special kinds of matrix stabilities, such as D - and diagonal stability. Basing on these concepts, we provide new stability conditions for second-order dynamical systems and analyze the stability of a parameter-dependent second-order model. Next, we study the relations between transient response properties of a second-order ODE system and certain generalizations of D -stability concept obtained in Kushel (SIAM Rev 61(4):643–729, 2019). We provide the conditions when the system has a given minimal decay rate $$\alpha $$ α and when the minimal decay rate of a system is preserved for some variations of positive parameters. A certain way of gyroscopic stabilization of an unstable parameter-dependent system is also considered. | Novel Versions of D-Stability in Matrices Provide New Insights into ODE Dynamics | 10.1007/s00009-023-02434-x |
2023-05-25 | It has been confirmed that structures with micro dimensions display size-dependent thermomechanical behaviors. Moreover, according to the findings of empirical and theoretical researches, thermoelastic damping (TED) has been recognized as one of inescapable causes of energy dissipation in microstructures. The current article is an effort to provide a novel size-dependent framework for approximating the amount of TED in microring resonators with rectangular cross section. To include size effect into structural and thermal constitutive relations, the modified couple stress theory (MCST) and the Moore–Gibson–Thompson (MGT) heat equation are utilized, respectively. By solving the coupled heat equation in the purview of MGT model, the fluctuation temperature throughout the ring is determined. By employing the obtained temperature distribution and constitutive relations of MCST, the peak values of strain and wasted thermal energies during one cycle of vibration are computed. Based on the description of TED in the energy dissipation (ED) method, a mathematical expression containing the scale parameters of MCST and MGT model is derived for estimating TED value. To ensure the correctness and veracity of the established solution, a comparative study is carried out on the basis of the data released by other researchers for more plain models. A section is also designated for an all-out study to ascertain the association between TED spectrum and some influential factors like scale parameters of MCST and MGT model, vibration mode number, one-dimensional (1D) and two-dimensional (2D) heat conduction, geometry and material. The extracted data enlighten that the impact of applying MCST and MGT model on TED has a close relationship with the vibration mode number of the ring. | Couple stress-based thermoelastic damping in microrings with rectangular cross section according to Moore–Gibson–Thompson heat equation | 10.1007/s43452-023-00694-8 |
2023-05-24 | An improved time-marching procedure based on a composite explicit method is proposed for non-viscous damping systems. In this method, an improved integral approximation scheme is developed to improve the convolution solution accuracy and is applicable to any causal kernel function. The mathematical derivation and calculation procedure based on the composite explicit method are formulated for non-viscous damping systems. The adopted composite explicit method shows more desirable stability and accuracy properties than other competitive explicit methods. Numerical simulations of some representative examples demonstrate the proposed time-marching procedure is efficient for the dynamic analysis of non-viscous damping systems. | A time-marching procedure based on a sub-step explicit time integration scheme for non-viscous damping systems | 10.1007/s00366-023-01838-3 |
2023-05-23 | In this study, we investigate the nonlinear dynamics of solitary waves in saturated ferromagnetic materials with an external field of zero conductivity. Here, we talk about how damping mechanisms affect the Kraenkel–Manna–Merle system, which controls wave propagation and expresses nonlinear ultra-short wave pulse movements in ferromagnetic materials. By using a good computational integration method called the extended Fan-sub equation technique, a number of solitary wave solutions in diverse shapes, such as hyperbolic, Jacobi’s elliptic, and trigonometric functions solutions are found. Not only do we protect periodic solutions with unknown parameters, but we also extract bell, kink, singular mixed complicated solitons. These findings demonstrate the theoretically incredibly rich soliton structures present in the system. For clarity in comprehending the solutions generated with the values of unknown parameters, two-dimensional, three-dimensional, and their contour wave profiles are plotted. The findings reveal that the integration method utilized is clear and may be extended to more complicated phenomena by using symbolic computations. | Dynamics of diverse wave propagation to integrable Kraenkel–Manna–Merle system under zero damping effect in ferrites materials | 10.1007/s11082-023-04879-6 |
2023-05-19 | A particle damper (PD) is an enclosure partially filled with small particles that can help to dampen the vibration of a structure. Despite its simplicity, the reliable prediction of the behavior of such a device in arbitrary operative conditions appears to be very difficult due to the complex non-linear interactions between the particles and the system. An experimental methodology is defined with the aim of minimizing the bias due to the PD non-linear response. The effect of the mutual orientation of motion, gravity, and enclosure and of different disturbance inputs on the performance of a PD is investigated in order to make available a set of reference experimental results for correlation purposes with prediction tools. An open-access database, gathering all the test results, is made available. Graphical abstract | An open-access database for the assessment of particle damper simulation tools | 10.1007/s10035-023-01333-y |
2023-05-18 | This work is devoted to presenting Massera-type theorems for the Kawahara system, a higher-order dispersive equation, posed in a bounded domain. Precisely, thanks to some properties of the semigroup and the decay of the solutions of this equation, we can prove its solutions are periodic, quasi-periodic, and almost periodic. | Massera’s Theorems for a Higher Order Dispersive System | 10.1007/s10440-023-00575-5 |
2023-05-17 | Purpose The signum function is highly non-linear and discontinuous in nature, hence obtaining a closed-form solution is extremely difficult. The available analytical solution by Den Hartog gives a piece-wise continuous solution but is not applicable for initial velocity conditions. The purpose of this work is to provide an analytical solution that can be applied to both initial displacement and initial velocity problems. Methods The nonlinearity of dry friction damping or Coulomb damping in its simplest form is modeled using a ‘signum’ function. A mathematical basis for the linear decay envelope when a harmonic oscillator is subjected to weak Coulomb damping is presented in this work based on Krylov–Bogolyubov averaging method as well as harmonic balance method. A novel analytical solution is presented for a spring mass system subjected to Coulomb damping by considering the dissipation of energy and the ensuing reduction in the amplitude of the dry friction oscillator in the phase plane. The accuracy of the proposed analytical solution is investigated by comparing it with numerical simulations and experimental results. The validity of the solution for varying values of non-dimensional frictional damping co-efficient $$(\gamma )$$ ( γ ) is presented. Also, the initial velocity condition for which piecewise continuous solution by Den Hartog is not applicable is demonstrated. Results and conclusion The free response of such a system primarily and predominantly dependent on the first harmonic of the ‘signum’ function is established by direct comparison with experimental results. The study is concluded with the applicability of the said analytical solution to a 2-DOF symmetric system to propose superposition of individual solutions. | Krylov–Bogolyubov Averaging Method-Based Analytical Solution of an Unforced Nonlinear Coulomb Damped Oscillator | 10.1007/s42417-023-00985-7 |
2023-05-15 | In this paper we study the long-time dynamics of elasticity-viscoporosity system consisting of two coupled hyperbolic equations with nonlinear dissipation. The first equation of the system is vectorial while the second is scalar. By considering nonlinear dampings and sources of critical exponents, we establish the existence of a smooth finite dimensional global attractor. To our best knowledge, the existence of attractors for dynamics of elasticity-viscoporosity systems has not been studied before. | Quasi-stability and smooth global attractors for a elasticity-viscoporosity system with nonlinear damping and source of critical exponents | 10.1007/s00030-023-00861-z |
2023-05-15 | The magnetorheological damper (MRD) is a smart damper that can produce a wide range of damping forces with respect to the different current supply. The said damper contains magnetorheological fluid (MRF), whose property helped to achieve controlled viscous force that enables to attenuate the system’s vibration. This paper analyzes the weight reduction and damping force variations by changing MRD’s piston configuration and annular gap. The annular gap is varied from 0.5 to 1 mm with a step size of 0.25 mm, and the piston has a chamfer of 2 mm at different locations. Six different MRD models are designed with different configurations named MRD1 to MRD6, respectively. The magnetic flux density is also calculated through the magnetic reluctance circuit of the MRD model. The damping force is estimated by considering the magnetic flux density at different magnitudes of current in the annular gap of the damper model. The MRD4 having both sides chamfer on the piston of the pole length zone shows a lesser weight by 1.5% than the simple MRD model. The MRD4 model obtains a significant amount of magnetic force, which is 22% more than the MRD1. The analytical results were compared with the simulated result, and it found the magnetic flux density was altered by 3.5%. This study may be beneficial for the selection of the best MRD model with respect to maximum magnetic force and reduced weight. | Augmentation of damping force by modifying the geometrical shape of the MR damper | 10.1007/s40430-023-04243-5 |
2023-05-10 | In this paper, opening characteristics of a pneumatically operated valve and methodology for controlling the valve opening duration have been investigated through numerical simulation. The valve has a poppet mounted with spring which is actuated by a pneumatic command pressure to provide a displacement of 30 mm in fully open condition. The spring housing comprises of columns of two fluids, namely air and oil, and an orifice which communicates with an adjacent auxiliary chamber. As the poppet is actuated, air initially passes through the orifice leading to a fast opening of the valve. Subsequently, opening rate of the valve is reduced as oil column encounters the orifice. The governing differential equations of motion for the valve poppet were solved using a fourth-order Runge–Kutta method, and the resistance offered by the orifice to oil flow was considered using a quadratic damping model. Simulations were carried out for two different orifice sizes, and results were validated with experiments. It was noted that for the same valve assembly, the opening duration can be controlled by varying the length of oil column and/or the orifice diameter, with no change in command pressure. | Control of opening duration in a pneumatically operated valve with two-fluid combination and quadratic damping | 10.1186/s44147-023-00207-7 |
2023-05-08 | A constitutive model is developed to efficiently capture the nonlinear hysteretic properties of a new type of high-damping metal wire mesh (HDMWM). In the HDMWM, the metal wire mesh is woven with multi-strand twisted wires in a certain regularity. In the quasi-static test, six batches of metal wire mesh (MWM) and HDMWM specimens with different densities and varying number of strands are prepared and their mechanical properties are characterized by secant stiffness, energy consumption and loss factor. Results show that for the same density, the energy consumption and loss factor of HDMWM specimens are higher than MWM specimens by 10.69 ~ 22.83% and 44.19 ~ 48.44%, respectively. Additionally, HDMWM is found to have a higher damping level than MWM. A constitutive model is proposed that comprises a cantilever beam as the force analysis element where the change of the arc angle of the element mesh is similar to a normal distribution. The accuracy of the model is verified by error analysis, which shows that the relative percentage error between model results and test results is 0.97 ~ 12.13%. Therefore, the constitutive model can reflect the mechanical properties of HDMWM with reasonable accuracy. | Research on Mechanical Properties and Constitutive Model of High-Damping Metal Wire Mesh | 10.1007/s11665-023-08169-w |
2023-05-01 | The power system industry is one of the pioneers in implementing machine learning (ML) methods which have acquired a lot of attention across various facets of contemporary life. Low-frequency oscillation (LFO) is purportedly a non-threatened but slowly poisoning concern with electrical power networks that, if not adequately addressed in a reasonable timeframe, could appear as the cause of a total network failure. The function of a well-known member of the ML family, the adaptive neuro-fuzzy inference system (ANFIS), is proposed in this paper for optimizing LFO damping in real-time in the power system networks. It adopts two power system networks, one in which the synchronous machine is equipped solely with a power system stabilizer (PSS). In the second one, PSS relates to a second-generation flexible alternating current transmission system (FACTS) device named the unified power flow controller (UPFC). The well-known genetic algorithm (GA) supports the proposed ML algorithm in generating the dataset and training them well. The designed approach is examined using various statistical performance measures and well-recognized stability performance measures, such as the minimal damping ratio, eigenvalue, and time-domain simulation. The article also includes comparing and discussing the results from the reference works to make inferences on the viability of the proposed GA-tuned ANFIS technique for improving real-time power system stability. | Real-Time Solution of PSS Parameter Tuning by GA-ANFIS in Stabilizing the Electrical Power System | 10.1007/s13369-023-07666-3 |
2023-05-01 | The paper proposes and develops new globally convergent algorithms of the generalized damped Newton type for solving important classes of nonsmooth optimization problems. These algorithms are based on the theory and calculations of second-order subdifferentials of nonsmooth functions with employing the machinery of second-order variational analysis and generalized differentiation. First we develop a globally superlinearly convergent damped Newton-type algorithm for the class of continuously differentiable functions with Lipschitzian gradients, which are nonsmooth of second order. Then we design such a globally convergent algorithm to solve a structured class of nonsmooth quadratic composite problems with extended-real-valued cost functions, which typically arise in machine learning and statistics. Finally, we present the results of numerical experiments and compare the performance of our main algorithm applied to an important class of Lasso problems with those achieved by other first-order and second-order optimization algorithms. | Generalized damped Newton algorithms in nonsmooth optimization via second-order subdifferentials | 10.1007/s10898-022-01248-7 |
2023-05-01 | In order to demonstrate the relevance of considering Vortex-Induced Vibrations (VIV) in the structural design of marine structures, this study proposes an alternative experimental and analytical approach in wet conditions to measure the fluid–structure interaction in the near field and quantify the viscous damping with measured structural and 3D hydrodynamic accelerations. It was demonstrated that VIV caused and incremented 5.00% of the structural damping coefficient, and the extreme wind loading increased 74% of the offshore monopile’s structural damping, demonstrating the relevance of the high non-linear hydrodynamics effects during selecting parameters into the structural design in offshore applications. | Vortex-induced vibration effect of extreme sea states over the structural dynamics of a scaled monopile offshore wind turbine | 10.1007/s40722-022-00272-9 |
2023-05-01 | Optimizing the mechanical properties and damping capacity of the duplex-structured Mg-Li-Zn-Mn alloy by tailoring the microstructure via hot extrusion was investigated. The results show that the Mg-8Li-4Zn-1Mn alloy is mainly composed of α-Mg, β-Li, Mg-Li-Zn, and Mn phases. The microstructure of the test alloy is refined owing to dynamic recrystallization (DRX) during hot extrusion. After hot extrusion, the crushed precipitates are uniformly distributed in the test alloy. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of as-extruded alloy reach 156 MPa, 208 MPa, and 32.3%, respectively, which are much better than that of as-cast alloy. Furthermore, the as-extruded and as-cast alloys both exhibit superior damping capacities, with the damping capacity ( Q ^−1) of 0.030 and 0.033 at the strain amplitude of 2 × 10^−3, respectively. The mechanical properties of the test alloy can be significantly improved by hot extrusion, whereas the damping capacities have no noticeable change, which indicates that the duplex-structured Mg-Li alloys with appropriate mechanical properties and damping properties can be obtained by alloying and hot extrusion. | Optimization on microstructure, mechanical properties and damping capacities of duplex structured Mg-8Li-4Zn-1Mn alloys | 10.1007/s12613-022-2572-7 |
2023-05-01 | The present work aims at studying the damping response of a NiTi auxetic structure fabricated through additive manufacturing. Furthermore, an electropolishing route has been accounted for improving the roughness on the external surface of the printed samples. The damping capacity of the manufactured auxetic NiTi components is evaluated through the amount of energy dissipated per cycle and through the loss factor index. Results show that the damping capacity of the auxetic NiTi cell takes advantage of electropolishing and it is superior to that of traditional materials. Particularly, a maximum dissipated energy of 55 mJ was registered in the austenite state after 10 min of electropolishing; additionally, the loss factor shows a maximum of 0.0523 in the R-phase. | Damping property of a NiTi auxetic structure fabricated through selective laser melting | 10.1007/s00170-023-11106-9 |
2023-05-01 | An integral nonlocal stress gradient viscoelastic model is proposed on the basis of the integral nonlocal stress gradient model and the standard viscoelastic model, and is utilized to investigate the free damping vibration analysis of the viscoelastic Bernoulli-Euler microbeams in thermal environment. Hamilton’s principle is used to derive the differential governing equations and corresponding boundary conditions. The integral relations between the strain and the nonlocal stress are converted into a differential form with constitutive constraints. The size-dependent axial thermal stress due to the variation of the environmental temperature is derived explicitly. The Laplace transformation is utilized to obtain the explicit expression for the bending deflection and moment. Considering the boundary conditions and constitutive constraints, one can get a nonlinear equation with complex coefficients, from which the complex characteristic frequency can be determined. A two-step numerical method is proposed to solve the elastic vibration frequency and the damping ratio. The effects of length scale parameters, viscous coefficient, thermal stress, vibration order on the vibration frequencies, and critical viscous coefficient are investigated numerically for the viscoelastic Bernoulli-Euler microbeams under different boundary conditions. | Nonlocal stress gradient formulation for damping vibration analysis of viscoelastic microbeam in thermal environment | 10.1007/s10483-023-2981-7 |
2023-05-01 | The implementation of the nonlinear tuned vibration absorber (NLTVA) for the suppression of shimmy vibration in towed wheels is addressed in this study. We adopt a modified straight tangent tyre model of a single-degree-of-freedom towed wheel system with an attached NLTVA. Stability analysis illustrated that the NLTVA can significantly improve the stability of the equilibrium of the wheel. Bifurcation analysis highlighted the existence of large bistable regions, which undermines the system’s safety. However, numerical continuation analysis, coupled with a dynamical integrity investigation, revealed that the addition of an intentional softening nonlinearity in the absorber restoring force characteristic enables the complete suppression of the bistable regions, also reducing the amplitude of shimmy oscillations in the unstable region. Quasiperiodic motions were also identified; however, their practical relevance seems marginal. | Towed wheel shimmy suppression through a nonlinear tuned vibration absorber | 10.1007/s11071-023-08314-z |
2023-05-01 | The main goal of this research was to develop highly durable, low-cost eco-friendly biocomposites from apricot kernel shell ( AKS ) wastes and ultrasonic characterization of AKS -based obtained biocomposites. Natural AKS wastes were chemically modified using 5 wt% sodium hydroxide ( NaOH ) and 99 wt% glacial acetic acid ( AA ). These modified apricot kernel shells (MAKS) and unmodified apricot kernel shells ( UMAKS ) were added into bisphenol-A type epoxy resin ( ER ) in varied compositions such as 10–50 wt% to prepare the MAKS/ER and the UMAKS/ER biocomposites. The epoxy resin-mixture in the weight ratios of resin/hardener/accelerator was 100:30:1. The effect of AKS powder ratios and modifiers on the elastic properties (Young’s moduli [ E ], bulk moduli [ K ], longitudinal moduli [ L ], shear moduli [ G ], and Poisson’s ratio [ µ ]), density ( ρ ), damping properties (attenuation coefficient [ α ], loss tangent [ tanδ ], and quality factor [ Q ]), ultrasonic micro-hardness ( H ), and acoustic impedance ( Z ) of biocomposites was investigated by the ultrasonic testing ( UT ) method. The morphological structure of the ER and biocomposites was figured out using scanning electron microscopy ( SEM ) and X-ray powder diffraction ( XRD ). The results revealed an increase in elastic properties of most of the AKS/ER biocomposites compared to the neat ER . On the other hand, results have shown that SEM and XRD images’ analysis confirmed the amorphous structure of ER and biocomposites. The highest ρ, v _ L , v _ S , L, G, E, H, and Z values were obtained in MAKS-AA/ER-5 biocomposite. Thus, it can be stated that the MAKS-AA/ER-5 biocomposite sample has the best mechanical properties. Also, the results revealed that the MAKS-AA/ER-1 sample can be used as an alternative material for its high Q-factor value instead of wood in producing musical tools. | Characterization of unmodified and modified apricot kernel shell/epoxy resin biocomposites by ultrasonic wave velocities | 10.1007/s00289-022-04328-6 |
2023-05-01 | The challenges of providing national metrological organizations with category 1 working standards are considered with regard to the current needs in the field of reference ultrasonic measurement in solids. An upgraded reference installation is presented for performing precise measurements of the propagation velocities of longitudinal and shear ultrasonic waves, as well as the damping coefficient of longitudinal ultrasonic waves in solids. Measurements of the acoustic parameters of solids are performed by pulse-echo and resonance methods using contactless broadband capacitance methods of excitation and registration of ultrasonic waves. This installation is used as a category 1 working standard in accordance with the State verification schedule for the instruments designed to measure the propagation velocities and damping coefficient of ultrasonic waves in solids. The technical instruments included in the installation (mechanical and electronic parts) have been upgraded, analog measuring devices have been replaced with digital ones, methods for measuring the acoustic parameters of solids based on the use of digital measuring instruments have been developed, and the thickness range of installed ultrasonic standards has been expanded. The composition and main components of the reference installation along with the used measurement methods and principles of operation of the installation under various operating conditions are described. The technical and metrological characteristics of the installation are provided. The sources of measurement error (uncertainty) have been analyzed. The field of application of the results includes high-precision measurements of the acoustic characteristics of solid media, as well as metrological support of ultrasonic nondestructive testing and diagnostics. | Reference Installation for Complex Measurements of the Acoustic Parameters of Solids | 10.1007/s11018-023-02201-0 |
2023-05-01 | A new type of torsional metallic damper was proposed. The restraint device, loading control component, energy dissipating metallic tube, rotating arm and pin bearing were composed the proposed damper. A total of six specimens were fabricated. The quasi-static low-cycle reciprocating loading tests were carried out, while the mechanical and finite element model of the damper was established. The results show that compared with the damper under combined bending-shear-torsion deformation, the damper under pure torsional deformation possesses higher bearing capacity, higher energy dissipation capacity and better ductility performance. The yielding bearing capacity of the damper with the wall thickness of 2 mm and 3 mm of energy dissipating metallic tube is increased by 10.3% and 8.1%, respectively. While the ultimate bearing capacity of that is increased by 16.3% and 10.1%, respectively. The yielding area of the energy dissipating metallic tube of the damper under pure torsional deformation diffuses from the middle to both ends. Besides, the yielding areas of that are more dispersed. Moreover, the distribution of stress and strain of that is more uniform. The mechanical model of the damper is established based on the theory of material mechanics. Theoretical calculation results about the initial stiffness and the yielding bearing capacity are basically consistent with that obtained from the test. The established finite element model can accurately predict the mechanical properties of the damper. The suggested formulas about the yielding bearing capacity, the ultimate bearing capacity and the cumulative energy dissipation of the damper under different parameters were also given. | Experimental Research and Theoretical Analysis of Mechanical Behavior of Torsional Metallic Damper | 10.1007/s40999-023-00818-4 |
2023-05-01 | High-speed locomotives are prone to carbody or bogie hunting when the wheel-rail contact conicity is excessively low or high. This can cause negative impacts on vehicle dynamics performance. This study presents four types of typical yaw damper layouts for a high-speed locomotive (Bo-Bo) and compares, by using the multi-objective optimization method, the influences of those layouts on the lateral dynamics performance of the locomotive; the linear stability indexes under low-conicity and high-conicity conditions are selected as optimization objectives. Furthermore, the radial basis function-based high-dimensional model representation (RBF-HDMR) method is used to conduct a global sensitivity analysis (GSA) between key suspension parameters and the lateral dynamics performance of the locomotive, including the lateral ride comfort on straight tracks under the low-conicity condition, and also the operational safety on curved tracks. It is concluded that the layout of yaw dampers has a considerable impact on low-conicity stability and lateral ride comfort but has little influence on curving performance. There is also an important finding that only when the locomotive adopts the layout with opening outward, the difference in lateral ride comfort between the front and rear ends of the carbody can be eliminated by adjusting the lateral installation angle of the yaw dampers. Finally, force analysis and modal analysis methods are adopted to explain the influence mechanism of yaw damper layouts on the lateral stability and differences in lateral ride comfort between the front and rear ends of the carbody. 目 的 以中国某型 Bo-Bo 高速机车为研究对象, 分析四种典型的抗蛇行减振器布置方式及横向安装角对机车横向动力学性能和参数匹配关系的影响, 并解释其作用机理. 创新点 1. 通过多目标优化方法来同时优化机车低锥度和高锥度横向稳定性, 获得四种抗蛇行减振器布置方式下机车最优横向动力学性能及横向安装角的不同选取原则; 2. 当抗蛇行减振器横向安装角存在时, 引入抗蛇行减振器附加作用力和作用力矩, 结合车体横向和摇头模态相位差来解释抗蛇行减振器布置方式对机车蛇行稳定性和车体前后横向平稳性差异的影响机理. 方 法 1. 基于搭建的 MATLAB/SIMPACK 联合仿真平台, 采用多目标优化方法得到机车最优横向动力学性能及对应悬挂参数分布结果 (图 4 和 5); 2. 通过拉丁超立方采样对机车直线运行性能和曲线通过性能评价指标进行蒙特卡洛仿真, 并采用基于径向基函数的高维模型表示的敏感性分析方法对关键悬挂参数进行全局敏感性分析 (图 6); 3. 采用根轨迹法分析不同抗蛇行减振器布置方式下横向安装角对机车蛇行稳定性影响规律, 并提取蛇行模态中对应的车体横移和摇头模态相位差 (图 8 和 9). 结 论 1. 抗蛇行减振器的布置方式对机车横向稳定性和平稳性具有显著影响, 且不同布置方式下横向安装角的选取原则存在差异. 2. 全局敏感性分析结果显示: 机车曲线通过性能对抗蛇行减振器阻尼和一系横向刚度的敏感性较强, 但对抗蛇行减振器横向安装角的敏感性较弱. 3. 机车采用抗蛇行减振器开口向外布置时, 优化横向安装角可以减小车体前后端横向平稳性差异, 而机车采用其他三种抗蛇行减振器布置方式时没有这个特点. | Influence of yaw damper layouts on locomotive lateral dynamics performance: Pareto optimization and parameter analysis | 10.1631/jzus.A2200374 |
2023-04-29 | Fretting wear phenomena arise when the tube collides with an intermediate support plate (ISP) under flow-induced vibrations and these vibrations can cause severe damage to the heat exchanger tubes. So, it is important to perform wear scar analysis of tubes to understand wear trends that lead to failure. This experimental study deals with scar analysis using a low-speed closed-loop water tunnel for an aluminium tube with a diameter of 12.7 mm. Three different ISP were used alternatively in the centre of the tube bundle. The tubes in the bundle are arranged parallelly in a triangular configuration with a Pitch-to-Diameter (P/D) ratio of 1.45. The experiments have been performed for each support plate thickness against six different time durations with an increment of half an hour and a cross-flow velocity of 0.5 m/s. The triaxial wireless accelerometer was used to measure the vibration response. The analysis revealed that the ISP tends to wear the circumferential length of the tube surface when they interacted for maximum time. When the thickness of the ISP increases, the film thickness between the tube and the baffle hole increases; resulting in a low amplitude of vibration because of the increased damping effect. Wear work rate and wear volume rate analysis indicated that the ISP of smaller thickness caused an earlier tube failure. | Fretting Wear Analysis of Flexible Vibrating Tube Interacting with the Support Plate in Low-Speed Water Tunnel | 10.1007/s42417-023-00987-5 |
2023-04-25 | Abstract During 2017–2019, a temporary seismic network of fifty-five 3-component broadband seismometers was installed by CSIR-NGRI, Hyderabad, Telangana, in the Uttarakhand Himalayan region, India. We used digital waveform data of 21 local earthquakes of M _w 2.9–4.3 from nineteen 3-component broadband seismic stations of the above seismic network for computing source parameters of local earthquakes, through simultaneous inversion of shear wave (S-wave) spectra. Here, we used the ω square circular source spectral model of Brune (1970) to formulate the iterative inversion scheme to compute earthquake source parameters. The modelled corner-frequency ( f _c), source radius ( r ), seismic moment ( M _o) and stress-drop (Δ σ ) vary from 2.4 to 4.0 Hz, 247–693 m, 2.4 × 10^13 to 6.6 × 10^15 N-m, 0.2–5.4 MPa, respectively. The maximum stress-drop (Δ σ _max) is computed to be 5.4 MPa for an event of M _w 4.3 while the minimum stress drop (Δ σ _min) is computed to be 0.2 MPa for an event of M _w 2.9. The scaling relations between M _o and f _c is obtained as M _o = 3.2E + 17 f _c^−5.5, while M _o and Δ σ are modelled to be related as M _o = 4.59E + 13∆ σ ^2.5. This relationship could be very useful for the future seismic-hazard assessment of the Uttarakhand Himalayan region. Research Highlights Modelled source parameters of local earthquakes and scaling relationship in the Uttarakhand Himalayan region. Local earthquakes magnitude range of 2.9–4.3. M _o, r , f _c, and ∆ σ are 2.4×10^13–6.6×10^15 N-m. 247.0–693.0 m, 2.4–4.0 Hz, 0.2–5.4 MPa, respectively. M _o f _c^5.5 $$\propto$$ ∝ constant & M _o∆ σ ^2.5 $$\propto$$ ∝ constant. | Modelling of earthquake source parameters and scaling relations in the Uttarakhand Himalayan region, India | 10.1007/s12040-023-02082-5 |
2023-04-19 | Emerging sub-synchronous interactions (SSI) in wind-integrated power systems have added intense attention after numerous incidents in the US and China due to the involvement of series compensated transmission lines and power electronics devices. SSI phenomenon occurs when two power system elements exchange energy below the synchronous frequency. SSI phenomenon related to wind power plants is one of the most significant challenges to maintaining stability, while SSI phenomenon in practical wind farms, which has been observed recently, has not yet been described on the source of conventional SSI literature. This paper first explains the traditional development of SSI and its classification as given by the IEEE, and then it proposes a classification of SSI according to the current research status, reviews several mitigation techniques and challenges, and discusses analysis techniques for SSI. The paper also describes the effect of the active damping controllers, control scheme parameters, degree of series compensation, and various techniques used in wind power plants (WPPs). In particular, a supplementary damping controller with converter controllers in Doubly Fed Induction Generator based WPPs is briefly pronounced. This paper provides a realistic viewpoint and a potential outlook for the readers to properly deal with SSI and its mitigation techniques, which can help power engineers for the planning, economical operation, and future expansion of sustainable development. | Review of sub-synchronous interaction in wind integrated power systems: classification, challenges, and mitigation techniques | 10.1186/s41601-023-00291-0 |
2023-04-18 | An accelerometer is a transducer that, on its own or in conjunction with electronics, instantly transmits an electrical signal corresponding to the force applied to its base. To measure vibrations with a capacitive accelerometer, it is important to know its accuracy, exact sensitivity, and reliability but sometimes the phase of the signal or the frequencies of interest. This paper chooses the capacitive accelerometer through its advantages over other types. The modeling of this type of accelerometer has been the subject of extracting from new formulas linked to the characteristics of the capacitive sensor and the simulation of the developed models makes it possible to minimize the measurement error, maximize the measurement accuracy, and reduce the electrical energy consumption by the appropriate choice of the damping rate and the frequency margin. A new equation for damping rate according to error is extracted by using the developed model. This equation makes easier the choice of damping rate that will minimize error to a very low value and maximize accuracy. This developed model is confirmed by experimental tests and finally, a new design of the capacitive accelerometer is proposed. | A capacitive sensor with high measurement accuracy and low electrical energy consumption | 10.1007/s00339-023-06644-8 |
2023-04-17 | In this paper, we consider a viscoelastic Petrovsky equation with localised nonlinear damping in bounded domain. The nonlinear damping is effective only in a neighborhood of a suitable subset of the boundary. Using the Faedo–Galerkin approximations together with some energy estimates, we prove the global existence of the solutions. Under the same assumptions, exponential decay results of the energy are established via suitable Lyapunov functionals. | Well-posedness and stability for a viscoelastic Petrovsky equation with a localized nonlinear damping | 10.1007/s40324-023-00325-5 |
2023-04-17 | The friction judder characteristics during clutch engagement have a significant influence on the NVH of a driveline. In this research, the judder characteristics of automobile clutch friction materials and experimental verification are studied. First, considering the stick-slip phenomenon in the clutch engagement process, a detailed 9-degrees-of-freedom (DOF) model including the body, each cylinder of the engine, clutch and friction lining, torsional damper, transmission and other driveline parts is established, and the calculation formula of friction torque in the clutch engagement process is determined. Second, the influence of the friction gradient characteristics on the amplification or attenuation of the automobile friction judder is analyzed, and the corresponding stability analysis and the numerical simulation of different friction gradient values are carried out with MATLAB/Simulink software. Finally, judder bench test equipment and a corresponding damping test program are developed, and the relationship between the friction coefficient gradient characteristics and the system damping is analyzed. After a large number of tests, the evaluation basis of the test is determined. The research results show that the friction lining with negative gradient characteristics of the friction coefficient will have a judder signal. When the friction gradient value is less than −0.005 s/m, the judder signal of the measured clutch cannot be completely attenuated, and the judder phenomenon occurs. When the friction gradient is greater than − 0.005 s/m, the judder signal can be significantly suppressed and the system connection tends to be stable. | Study of the Judder Characteristics of Friction Material for an Automobile Clutch and Test Verification | 10.1186/s10033-023-00864-y |
2023-04-15 | Soils contaminated with hydrocarbons is a repetitive site condition that may occur at locations adjacent to underground fuel tanks and other facilities. The main purpose of this study is to characterize and assess possibilities of reusing contaminated soil in useful applications such as roadway embankments. Accordingly, controlled amounts of diesel were mixed with clays and sands using percentages ranging from 0 to 13.5%. Unconfined compression, direct shear, California bearing ratio, and other tests were conducted on the diesel-mixed soil, along with the ultrasonic test. The ultrasonic test provided measures for the pulse wave velocity and received frequency, which was correlated with other soil parameters such as elastic modulus, resilient modulus, and California bearing ratio. From the main outcomes, it was found that small amounts of diesel can help improved soil shear strength. For instance, adding 5% diesel increased the soil cohesion by 63% and the unconfined compressive strength from 0.14 to 0.21 N/mm^2. In sands, the California bearing ratio increased by almost double by adding 5% diesel, which is essential for roadway embankments especially in remote locations. Damping coefficient of soil was determined at different levels of diesel using the ultrasonic wave decay envelops. The ultrasonic waves were analyzed using fast Fourier transform to determine useful correlations between the wave frequency and the diesel content starting from 0 to 13.5%, and it was realized that an uncomplicated ultrasonic test can be acceptably used to assess static and dynamic properties of clean as well as contaminated soils. | Controlled diesel-mixed soils for roadway embankments: laboratory and ultrasonic characterization | 10.1007/s12517-023-11397-y |
2023-04-06 | Shell folded footings have drawn the interest of researchers for decades as an alternative to typical flat isolated footings because folded footings can reduce the needed amount of reinforced concrete in addition to enhancing the overall geotechnical performance of the supporting soil medium. The main setback of utilizing such folded footings is the relatively complex geometry of the bottom cavity, which requires proper compaction of the soil used to fill that cavity. Current geosynthetic materials such as geofoam or expanded polystyrene (EPS) proved efficiency in many geotechnical applications, where EPS was adopted herein as a cavity-filling material for folded footings. EPS and footing concrete properties were determined using the ultrasonic test device, such as modulus of elasticity and damping coefficient. The main aim of this study was to experimentally assess the behavior of folded footings with and without EPS filling using seven fully instrumented footing models with folding angles ranging from 0° to 45°. Reinforcement was placed in the footing models and limited along the perimeter to act as a hidden ring beam. The models were load tested inside a sandbox to measure internal stresses induced in the soil and the overall settlement. Results showed a significant enhancement in the soil behavior after using EPS. Modification factors were developed for the standard bearing capacity and settlement equations to account for the folding angle and EPS filling effects. | Shell folded footings using different angles and EPS cavity filling: experimental study | 10.1186/s40703-023-00187-w |
2023-04-04 | We study the mathematical theory of second order systems with two species, arising in the dynamics of interacting particles subject to linear damping, to nonlocal forces and to external ones, and resulting into a nonlocal version of the compressible Euler system with linear damping. Our results are limited to the 1 space dimensional case but allow for initial data taken in a Wasserstein space of probability measures. We first consider the case of smooth nonlocal interaction potentials, not subject to any symmetry condition, and prove existence and uniqueness. The concept of solutions relies on a stickiness condition in case of collisions, in the spirit of previous works in the literature. The result uses concepts from classical Hilbert space theory of gradient flows (cf. Brezis, Operateurs maximaux monotones et semi-groupes de contractions dans les espaces de Hilbert, 1973 ) and a trick used in Brenier et al. (J. Math. Pures Appl. 99(5):577–617, 2013 ). We then consider a large-time and large-damping scaled version of our system and prove convergence to solutions to the corresponding first order system. Finally, we consider the case of Newtonian potentials - subject to symmetry of the cross-interaction potentials - and external convex potentials. After showing existence in the sticky particles framework in the spirit of Brenier et al. (J. Math. Pures Appl. 99(5):577–617, 2013 ), we prove convergence for large times towards Dirac delta solutions for the two densities. All the results share a common technical framework in that solutions are considered in a Lagrangian framework, which allows to estimate the behavior of solutions via L 2 $L^{2}$ estimates of the pseudo-inverse variables corresponding to the two densities. In particular, due to this technique, the large-damping result holds under a rather weak condition on the initial data, which does not require well-prepared initial velocities. We complement the results with numerical simulations. | Second Order Two-Species Systems with Nonlocal Interactions: Existence and Large Damping Limits | 10.1007/s10440-023-00564-8 |
2023-04-04 | This paper is concerned with the blow-up of solutions to the initial boundary value problem for the wave equation with scale invariant damping term on the exterior domain, where the nonlinear terms are power nonlinearity | u | p $|u|^{p} $ , derivative nonlinearity | u t | p $|u_{t}|^{p} $ and combined nonlinearities | u t | p + | u | q $|u_{t}|^{p}+ |u|^{q} $ , respectively. Upper bound lifespan estimates of solutions to the problem are obtained by constructing suitable test functions and utilizing the test function technique. The main novelty is that lifespan estimates of solutions are associated with the well-known Strauss exponent and Glassey exponent. To the best of our knowledge, the results in Theorems 1.1 – 1.3 are new. | Blow-up of solutions to the semilinear wave equation with scale invariant damping on exterior domain | 10.1186/s13661-023-01722-5 |
2023-04-01 | In this article, we study the Cauchy problem for a weakly coupled system of semi-linear wave equations with different structural damping terms. The main goal is to find the threshold, which classifies the existence of small data global (in time) solutions or the nonexistence of global solutions under the growth condition of the nonlinearities. | Existence and Nonexistence of Global Solutions for a Wave System with Different Structural Damping Terms | 10.1007/s10013-021-00517-4 |
2023-04-01 | Flank face chamfers are an effective way to suppress vibrations and increase the productivity of milling processes. The underlying process damping mechanism is the so-called indentation effect. The effect describes the process damping as a result of an additional force due to the indentation of workpiece material under the flank face. In literature, this force is commonly modeled by the volume indented under the flank face and a process damping coefficient. To determine the process damping coefficient, various approaches with partly contradictory results exist. In this paper, a novel method to calculate the process damping coefficient based on process forces measurements in orthogonal cutting is applied for steel machining. The method considers ploughing effects of flank face chamfer and cutting edge rounding as well as plastic deformation effects. In the current investigation, the approach is applied to different cooling strategies, chamfer widths, and cutting speeds. The results show that the cutting speed has the most significant influence on the process damping coefficient. With increasing cutting speed, the process damping coefficient increases, which can be attributed to strain rate hardening effects. | Identification of the process damping coefficient in dry and wet machining of steel | 10.1007/s00170-023-11082-0 |
2023-04-01 | Power System Oscillations followed by transient effects, adversely affects the stability in interconnected Power systems. This issue can be addressed using power oscillation damping controllers (PODC). For dynamic systems with varying system conditions, a robust PODC is required, which adjust the parameters as the system conditions changes. The robust PODC design is a multimodal optimization problem, which cannot be solved using conventional optimization techniques. An artificial Intelligence based grey wolf optimization technique (GWO) can be used for this purpose. This algorithm estimates the optimal control parameters of a fraction order PID based damping controller. A 4 machine, 2 area, 11 bus power system network with Static Synchronous Series compensator based PODC is considered in this research work. The performance of the PODC with GWO-FOPID controller under different system conditions are simulated and evaluated the performances indices under these conditions. | Grey wolf optimization based fractional order PID controller in SSSC on damping low frequency oscillation in interconnected multi-machine power system | 10.1007/s41870-023-01253-3 |
2023-04-01 | In this paper, a grid impedance estimation procedure based on the injection of active and reactive powers through a grid-tied inverter is proposed. The estimation is based on Newton–Raphson algorithm acting on the phasors of the voltages and currents at the point of common coupling between the inverter and the grid. Unlike, similar procedures, based on power injections, the method is implemented in the $$\alpha \beta $$ α β frame, avoiding Park transformations. This is an advantage because d q quantities are prone to be too noisy, or oscillating in unbalance grid conditions or in the presence of voltage harmonics. Moreover, the proposed method allows variations of active and reactive to be imposed simultaneously, differently of methods relying on d q voltages and currents. This feature speeds up the estimation. The voltages and current phasors used to estimate the impedance are determined with the aid of a positive sequence extractor and Fourier algorithm providing the method robustness against unbalance grid conditions and harmonic distortions. Besides the impedance estimation, this paper proposes a technique in which the impedance information is applied to enhance the inverter’s control. Here, the impedance value is used with a Routh criterion to assure the system’s stability. The propositions are verified with PSIM simulations and with a Hardware-in-the-Loop real-time platform. | A Grid Impedance Estimation Method Robust Against Grid Voltages Unbalance and Harmonic Distortions | 10.1007/s40313-022-00963-6 |
2023-04-01 | It is a crucial requirement for structure-damping materials to attain both stiffness and damping; unfortunately, the two properties are usually mutually exclusive. This study interestingly demonstrates that introducing Ni atoms into the interface of carbon nanotube (CNT) reinforced aluminum-matrix composites can defeat the conflict of stiffness versus damping. This originates from the gradient variation of the modulus and energy dissipation in the effective interfacial zone. The rule of mixture is modified by taking the interface contribution into account, and a gradient damping model is proposed to account for the contribution of the interface energy dissipation. Molecular dynamics simulations confirm that the proposed multiscale modulus and damping models can describe the elastic modulus and damping behavior of the composites with different volume fractions and different diameters of CNTS. The gradient interface slip caused by the lattice mismatches and misfit dislocations between Ni-coated CNT and aluminum is one of the pathways for achieving unprecedented levels of the product of stiffness and damping. | Damping of aluminum-matrix composite reinforced by carbon nanotube: Multiscale modeling and characteristics | 10.1007/s11431-022-2297-3 |
2023-04-01 | The nonlinear behavior of sabkha soil was investigated in two stages. In the first stage, a physical model representing a vibrating foundation resting on cement-stabilized sabkha soil overlying saturated and untreated sabkha soil was developed. The cement-stabilized sabkha soil samples used in the study contained 5 and 10% cement and had thickness ratios (which is the thickness of cement-stabilized sabkha soil/Foundation diameter) of 0.2, 0.4, and 0.6. In the second stage, a simplified method was developed to compute the stiffness and damping ratio of steady state physical models and predict the resonant displacement amplitude and resonant frequency of the models on the basis of the cyclic behavior of both untreated sabkha and cement-stabilized sabkha soils. The results revealed that the displacement amplitude of the models decreased with the increase in the cement content and thickness ratio of the sabkha soil. The natural frequency of the models slightly increased as the cement content and thickness ratio of the soil increased. The values obtained for the natural frequency of the models using the simplified method and the finite element method were the same with a maximum relative difference of only 15%. Nevertheless, the values of the maximum displacement amplitude of the models obtained using the two methods were different with the maximum relative difference standing at 59%. | Vibrating Behavior of Foundations Resting on Salt-Encrusted Flat (Sabkha) Soil Improved Using Cement | 10.1007/s13369-022-07382-4 |
2023-04-01 | This manuscript aims to enhance vehicle stability and ride comfort. The long-term vibration from the uneven road surface affects the stability of the vehicle, the rider’s safety, health and comfort. The resonance between the excitation and the vehicle cannot be avoided by conventional MR suspension without stiffness control, though it can reduce the vibration energy. With this motivation, a new hybrid vibration isolator with adjustable stiffness and damping is proposed. The proposed isolator is a combination of Magneto-rheological (MR) fluid and MR elastomer to generate the independent variable damping and independent variable stiffness characteristics, respectively. Two road profiles namely sinusoidal and random, are considered to provide input to the proposed system. The passive, semi-active with variable damping and proposed isolator for a quarter car model have been designed to analyze their dynamic performance. The results reveal that in comparison with passive system, the proposed model reduces settling time, peak displacement and root mean square (RMS) acceleration value by 42.86%, 83.33% and 89.35% for sinusoidal road profile, whereas for random road profile the value of peak displacement and RMS acceleration is reduced by 90.77% and 94.90%, respectively. Furthermore, the proposed model compared to the semi-active with variable damping has 20% less settling time, 56.26% less value of peak displacement and 47.27% less RMS acceleration value for sinusoidal road profile. The proposed model for random road profile reduces the peak displacement by 53.85% and RMS acceleration by 54.10% compared to semi-active with variable damping. The designed model’s results are better than passive and semi-active with variable damping in terms of better vehicle stability and ride comfort. | Dynamic analysis of quarter car model with semi-active suspension based on combination of magneto-rheological materials | 10.1007/s40435-022-01024-1 |
2023-04-01 | Herein, we report the theoretical investigation to understand the role of size-dependent damping (SDD) due to electron–surface scattering on the Al nanoparticle-based deep ultraviolet surface-enhanced fluorescence. First, the absorption spectra and electric field enhancement (EFE) inside and outside Al nanoparticles of different sizes are plotted without and with considering SDD. Later, the role of SDD on the near- and far-field plasmonic properties of Au and Ag nanoparticles of different sizes is investigated for comparison. Finally, Al nanoparticle-based SEF enhancement is estimated for different nanoparticle sizes, emission wavelengths, and separations between nanoparticle and fluorophore without and with considering the SDD. | Role of Size-Dependent Damping Due to Electron–Surface Scattering on the Al Nanoparticle-Based Deep Ultraviolet Surface-Enhanced Fluorescence | 10.1007/s11468-023-01805-0 |
2023-04-01 | Purpose The purpose of the current study is to enable an economical use of the existing mass of an overhead water tank for effective control of the building vibrations under lateral excitation, without hampering the tank’s primary functionality. Methods A practically feasible mechanism is developed that adjusts the stiffness of the support of the overhead water tank as the water mass changes in it. The overhead water tank is thereby converted into a liquid tank damper with stiffness-varying support (LTD-SVS), which maintains a constant frequency of the impulsive mass of the tank, despite liquid level fluctuations. The detailed working mechanism of the LTD-SVS, considering two different schemes for the adjustment of the tank support stiffness, is presented. An analytical model of the building structure-LTD-SVS system is developed and the equivalent tuning and damping parameters are formulated. Results and Conclusion The effectiveness of the LTD-SVS system is evaluated through a time-domain study on an example building subjected to harmonic and recorded seismic ground motions. The LTD-SVS is found to provide an effective and consistent performance as a dynamic vibration absorber (DVA), despite water level fluctuation in a wide range of 20–100% tank-full conditions. Through the proposed design, which is easy to operate and economical, an overhead water tank can effectively serve the dual function of water storage and supply, as well as of a DVA for building structures. | Adaptive Design of an Overhead Water Tank as Dynamic Vibration Absorber for Buildings by Use of a Stiffness-Varying Support Arrangement | 10.1007/s42417-022-00611-y |
2023-04-01 | Background The direct-drive linear motor system is usually a low-damping system, which will cause residual vibration and deteriorate the accuracy of the equipment especially in the high-speed start-stop motion. Purpose By employing an eddy current damper (ECD), the residual vibration can be effectively reduced. However, the ECD secondary is normally made of a pure copper plate with low magnetic permeability, resulting in low airgap magnetic density and therefore small damping force. In this paper, a dual-sided hybrid excitation ECD which implements high-conductivity and high-permeability plate as the secondary is proposed to enhance the vibration suppression for the linear motor system. Methods An analytical model is developed to quantitatively analyze the relationship between the damping force and the secondary thickness. Three dimensional finite element analysis (3D FEA) is employed to investigate the effects of different secondary materials and the secondary layer thicknesses on ECD performance. Results and Conclusion Experiments are conducted to evaluate the damping force and the vibration suppression effect of the designed ECD. Compared with the pure copper secondary under the same secondary dimensions, the damping force is increased by 30.5% with the copper-steel-copper secondary, and the peak amplitude of the position error and the settling time of the system are reduced by 1.94 times and 1.80 times, respectively. | A Dual-Sided Hybrid Excitation Eddy Current Damper with High-Conductivity and High-Permeability Secondary Plate for Vibration Suppression Enhancement | 10.1007/s42417-022-00638-1 |
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