publicationDate stringlengths 10 10 | abstract stringlengths 0 37.3k | title stringlengths 1 5.74k | doi stringlengths 11 47 ⌀ |
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2023-11-01 | Excessive cumulative stroke in the longitudinal movement of long-span suspension bridge can led to premature fatigue damage in the bridge’s connecting components. However, existing control devices, like viscous damper, remain suboptimal. This paper aims to reveal the underlying mechanism of cumulative stroke control and find an effective control method to address this issue. Firstly, the statistical and frequency characteristics of longitudinal displacement were analyzed based on a 24-hour field measured data set. Secondly, the cumulative stroke control performance of nonlinear viscous damper was evaluated with a SDOF system, uncovering the reasons for their low efficiency in controlling cumulative stroke. Thirdly, the Maxwell-Coulomb friction damper was introduced to control the excessive cumulative stroke, and its effective control performance was validated. Finally, a novel parallel model combining viscous dampers and friction dampers was proposed to leverage the superior performance of friction damper in controlling the cumulative stroke under daily operation condition, while also harnessing the seismic response mitigation capacity of the viscous damper. This research enhances the understanding of cumulative stroke control in long-span suspension bridges and presents an innovative control method by introducing the Maxwell-Coulomb friction damper, highlighting its potential for practical application in bridge engineering. | An Analytical Study on Using Maxwell-Coulomb Friction Damper to Mitigate Quasi-Static Response of SDOF Systems | 10.1007/s12205-023-1365-5 |
2023-11-01 | Rheumatoid arthritis (RA) is one of the most severe inflammatory diseases that cause swelling, stiffness and pain in the joints, which pose a significant threat worldwide. Damage-associated molecular patterns (DAMPs) are danger molecules of endogenous origin, released during cell injury or cell death, interacts with various Pattern recognition receptors (PRRs) and activates various inflammatory diseases. One of the DAMP molecules, so-called EDA-fibronectin (Fn) is also responsible for causing RA. EDA-Fn triggers RA through its interaction with TLR4. Apart from TLR4, it is divulged that certain other PRR’s are also responsible for RA, but the identity and mechanism of those PRRs remain unknown until now. Hence, for the first time, we tried to reveal those PRR’s interaction with EDA-Fn in RA through computational methods. Protein–protein interaction (PPI) was checked using ClusPro between EDA-Fn and certain Pattern recognition receptors (PRRs) to explore the binding affinities of the potential PRRs. Protein–protein docking unveiled that TLR5, TLR2 and RAGE has good interaction with EDA-Fn than the well-reported TLR4. Macromolecular simulation was performed for TLR5, TLR2 and RAGE complexes along with the control group TLR4 for 50 ns to further investigate the stability, leading to the identification of TLR2, TLR5 and RAGE as the stable complexes. Hence, TLR2, TLR5 and RAGE on interaction with EDA-Fn may lead to the progression of RA that may need additional validations through in vitro and in vivo animal models. Molecular docking was used to analyse the binding force of the top 33 active anti-arthritic compounds with the target protein EDA-Fn. Molecular docking study showed that withaferin A has a good binding activity with EDA-fibronectin target. Hence, it is emphasized that guggulsterone and berberine could modulate the EDA-Fn-mediated TLR5/TLR2/RAGE pathways, thereby it could inhibit the deteriorating effects of RA which needs further in vitro and in vivo experimental validations. Graphical Abstract | Underpinning Endogeneous Damp EDA-Fibronectin in the Activation of Molecular Targets of Rheumatoid Arthritis and Identifcation of its Effective Inhibitors by Computational Methods | 10.1007/s12010-023-04451-8 |
2023-10-31 | Purpose In fact, the diagonal elements of the modal matrix are read in the form of the normalization constants, which is the case in both experimental modal analysis and analytical modal analysis. A desired performance in both above fields will require simple scaling of the mode shapes. In this study, a method to calculate the sensitivities of modal parameters based on a simple scaling scheme for asymmetric damped system is presented to meet this requirement. Methods The normalization constants are designed to be open. Also, only one equation of normalization condition is adopted to establish a series of comparatively simple formulas for the proposed algorithm. Results The influences of normalization constants on the sensitivity analysis and its numerical aspects are further investigated. A numerical example is presented to demonstrate the accuracy and good applicability of the proposed algorithm. Conclusions The major advantage of the proposed algorithm lies in the fact that, without the need for normalizing the left eigenvector or searching for its sensitivity, not only can computation be reduced, but also potential numerical problems can be avoided. | Sensitivity Analysis of Modal Parameter Based on Simple Scaling for Asymmetric Damped System | 10.1007/s42417-023-01170-6 |
2023-10-28 | In this article, a novel nonlinear displacement–velocity-dependent (NDVD) damper that takes into account the effect of momentum variation is introduced. The main goal is to improve the system’s response by designing the NDVD damper through strategic alterations to the structure of a linear damper. As a result, the damping coefficient of the proposed NDVD damper varies with respect to the displacement and velocity of the damper piston. To achieve a more accurate model in vibration analysis, the conservation of momentum is applied to the proposed NDVD damper. Besides, the displacement profile, velocity profile, damping force, and force transmitted to the base of a mass–spring system equipped with the NDVD damper are conducted. The performance of the proposed NDVD damper in practical application is also evaluated by analyzing the El Centro earthquake scenario. This study compares the results for four scenarios: free, forced, and resonance vibrations along with the El Centro earthquake problem. Additionally, a sensitivity analysis of the system concerning the orifice length is instigated. The simulation results demonstrate that the proposed NDVD damper outperforms linear and nonlinear displacement-dependent (NDD) dampers in reducing system vibrations. Moreover, increase in the orifice length in the NDVD damper contributes to a decrease in the vibration response of the system. It is observed that the damping force of the proposed damper in free vibrations is significantly higher than the NDD/linear damper with ratio of 5.68/14.14. In addition, the proposed damper exhibits substantially increasing the damping forces in forced vibrations, with ratio of 8.17/37.67, as well as during resonance with ratio of 2.7/6.31, compared to the NDD/linear damper. Furthermore, in response to the El Centro earthquake excitation, the proposed damper experiences notably amplified damping forces, with ratio of 6.37/12.61 compared to the NDD/linear damper. | Enhancing System Response with a Novel Nonlinear Displacement–Velocity-Dependent Damper Considering Momentum Variation | 10.1007/s40996-023-01263-y |
2023-10-27 | In this paper, we consider the following wave equation $$\begin{aligned} \left\{ \begin{aligned} u&_{tt} - \varDelta u + a_0 b(t, x)u_t +a_1b(t, x) u_t(t-\tau ) +\vert u\vert ^{p-1}u=0, \quad t>0, \;\; x\in {\mathbb {R}}^n\\ u&(0, x ) = u_0(x), \qquad u_t(0, x) = u_1(x) \qquad x\in {\mathbb {R}}^n\qquad \\ u&_t( t-\tau , x)=h_0(t-\tau , x),\qquad x\in {\mathbb {R}}^n, \quad 0<t<\tau ,\quad \end{aligned} \right. \end{aligned}$$ u tt - Δ u + a 0 b ( t , x ) u t + a 1 b ( t , x ) u t ( t - τ ) + | u | p - 1 u = 0 , t > 0 , x ∈ R n u ( 0 , x ) = u 0 ( x ) , u t ( 0 , x ) = u 1 ( x ) x ∈ R n u t ( t - τ , x ) = h 0 ( t - τ , x ) , x ∈ R n , 0 < t < τ , with space time dependent potential and a time delay in the internal feedback. Under appropriate conditions on the damping coefficients b and the constants $$a_0$$ a 0 , $$a_1$$ a 1 , we establish a general energy decay result of the solution where the initial data have compact support. | General energy decay for wave equation with space-time potential and time delay in
$${\mathbb {R}}^n$$
R
n
| 10.1007/s13370-023-01120-1 |
2023-10-26 | Purpose This paper propose a grounded-type DVA attached to a damped primary system, which can effectively suppress the vibration amplitudes by introducing a lever, focusing on the optimal design of the novel DVA. It can be utilized to the simplified model of a damped spacecraft or stay cable of cable-stayed bridges. Methods The design of DVA considers $${\mathrm{H}}_{\infty }$$ H ∞ and $${\mathrm{H}}_{2}$$ H 2 optimization criteria, and defines performance indicators separately. In the $${\mathrm{H}}_{\infty }$$ H ∞ optimization, we couple generalized fixed-point theory (GFPT) and perturbation method (PM) with particle swarm optimization (PSO) algorithm to minimize the maximum amplitude amplification factor of primary system, so that the amplitudes at two fixed points are close to the same horizontal line. Nevertheless, in the $${\mathrm{H}}_{2}$$ H 2 optimization, the GFPT and PM are combined with Newton’s method to minimize the power input to primary system. Results The numerical results indicate the consistency and effectiveness of the two optimization criteria. Compared with other classical models, the effects of different grounded stiffness ratios on the amplitude frequency responses, time histories, and vibration energies of the primary system subjected to harmonic excitation and random excitation, respectively, as well as the vibration reduction effect, are studied. Conclusions Numerical simulations display with the positive grounded stiffness, the proposed DVA outperform the existing DVAs with same mass, damping, and stiffness under the harmonic excitation and random excitation. The results can provide theoretical and computational guidance for the optimal design of DVA. |
$${\mathrm{H}}_{\infty }$$
H
∞
and
$${\mathrm{H}}_{2}$$
H
2
Optimization of the Grounded-Type DVA Attached to Damped Primary System Based on Generalized Fixed-Point Theory Coupled Optimization Algorithm | 10.1007/s42417-023-01161-7 |
2023-10-24 | This paper is concerned with extensible beams with nonlocal frictional damping and polynomial nonlinearity. By using semigroup theory, potential well method, and energy method, the well-posedness and the conditions on global existence and finite time blow-up of solutions are studied. Moreover, the upper bound of blow-up time is also given by using ordinary differential inequalities. | Well-Posedness and Dynamical Properties for Extensible Beams with Nonlocal Frictional Damping and Polynomial Nonlinearity | 10.1007/s00245-023-10070-w |
2023-10-23 | This paper presents a numerical model using the boundary element method for determining the hydrodynamic added mass and added damping of an elastic bridge pier with arbitrary cross-section. Combining the Euler–Bernoulli beam theory with the constant boundary element method, the modal superposition method is used to consider the deformable boundary conditions on the surface of elastic piers to couple the interaction between the elastic pier and water, and the equations for the hydrodynamic added mass and added damping of a general section pier considering the effect of pier-water coupling are derived. The accuracy of the developed model is verified by a benchmark experiment. The developed model is calculated for circular piers and compared with the added mass analytical formulation. The effects of oscillating frequency and structure geometry on the added mass and added damping are further investigated. Results demonstrate that the developed model can be used to solve the hydrodynamic added mass and added damping problems of the elastic bridge pier. Compared to the analytical formula, the developed method incorporates the consideration of added damping in the analysis of the pier-water coupling problem. Oscillating frequency and structure geometry have significant effects on added mass and added damping. | Numerical modeling of hydrodynamic added mass and added damping for elastic bridge pier | 10.1186/s43251-023-00104-2 |
2023-10-17 | In this work, a classical non-conservative system is quantised via canonical quantisation. A systematic approach as to how to obtain the Schrödinger equation for a general dissipative system is proposed. The free particle under linear and cubic dissipation are canonically quantised to obtain wave functions, position–momentum uncertainty relations, average energies and probability densities in each case. The method used is general and can be employed to all dissipative systems. | Quantisation of the damped free particle | 10.1007/s12043-023-02646-6 |
2023-10-10 | We discuss some of our recent work on the linear and nonlinear stability of shear flows as solutions of the 2D Euler equations in the bounded channel $$\mathbb {T}\times [0,1]$$ T × [ 0 , 1 ] . More precisely, we consider shear flows $$u=(b(y),0)$$ u = ( b ( y ) , 0 ) given by smooth functions $$b:[0,1]\rightarrow \mathbb {R}$$ b : [ 0 , 1 ] → R . We prove linear inviscid damping and linear stability provided that b is strictly increasing and a suitable spectral condition involving the function b is satisfied. Then we show that this can be extended to full nonlinear inviscid damping and asymptotic nonlinear stability, provided that b is linear outside a compact subset of the interval (0, 1) (to avoid boundary contributions which are not compatible with inviscid damping) and the vorticity is smooth in a Gevrey space. In the second article in this series we will discuss the case of non-monotonic shear flows b with non-degenerate critical points (like the classical Poiseuille flow $$b:[-1,1]\rightarrow \mathbb {R}$$ b : [ - 1 , 1 ] → R , $$b(y)=y^2$$ b ( y ) = y 2 ). The situation here is different, as nonlinear stability is a major open problem. We will prove a new result in the linear case, involving polynomial decay of the associated stream function. | On the Stability of Shear Flows in Bounded Channels, I: Monotonic Shear Flows | 10.1007/s10013-023-00656-w |
2023-10-09 | In this work, we deal with a one-dimensional Cauchy problem in Timoshenko system with temperature and microtemperature effect. The heat conduction is given by the theory of Lord–Shulman. We prove that the dissipation induced by the coupling of the Timoshenko system with the heat conduction of Lord–Shulman’s theory alone is strong enough to stabilize the system, but with slow decay rate. To show our result, we transform our system into a first order system and, applying the energy method in the Fourier space, we establish some pointwise estimates of the Fourier image of the solution. Using those pointwise estimates, we prove the decay estimates of the solution and show that those decay estimates are very slow, we prove our main result under suitable assumption. | Decay rate of the solutions to the Cauchy problem of the Lord Shulman thermoelastic Timoshenko model with microtemperature effect | 10.1007/s11868-023-00561-3 |
2023-10-09 | Magnetorheological fluid dampers are widely acknowledged for their ability to absorb kinetic energy and effectively control vibrations, offering a range of benefits in chatter suppression applications. Despite the smart features of magnetorheological fluid, the rural industry still expresses concerns about issues such as sedimentation of iron particles, oil leaks, and sealing problems in magnetorheological fluid-based dampers. Magnetorheological fluid foams, characterized by their viscoelastic behavior and composed of magnetorheological fluid, have emerged as a preferable alternative to conventional magnetorheological fluid damper. This is because magnetorheological fluid foams require a lower volume of magnetorheological fluid, which eliminates the need for seals or bearings in the damper. This study presents the development and characterization of magnetorheological fluid foam dampers for reducing chatter in boring and improving machining processes. The study examines various parameters of the polyurethane foams and magnetorheological fluid to determine their influence on absorption rate and damping capabilities. An experimental setup is used to measure damping forces, and finite element analysis is employed to verify the effectiveness of the dampers in a boring tool and applied in boring to determine vibration amplitude, surface finish, cutting force, and tool wear during machining to identify the optimum curing time and foam parameters for effective damping capabilities in boring. | Characterization and performance analysis of magnetorheological foam damper for vibration control during boring process | 10.1007/s41939-023-00259-5 |
2023-10-06 | In this paper, we are interested in the upper bound of the lifespan estimate for the compressible Euler system with time-dependent damping and small initial perturbations. We employ some techniques from the blow-up study of nonlinear wave equations. The novelty consists in the introduction of tools from the Orlicz spaces theory to handle the nonlinear term emerging from the pressure $$p \equiv p(\rho )$$ p ≡ p ( ρ ) , which admits different asymptotic behavior for large and small values of $$\rho -1$$ ρ - 1 , being $$\rho $$ ρ the density. Hence, we can establish, in dimensions $$n\in \{2,3\}$$ n ∈ { 2 , 3 } , unified upper bounds of the lifespan estimate depending only on the dimension n and on the damping strength and independent of the adiabatic index $$\gamma >1$$ γ > 1 . We conjecture our results to be optimal. The method employed here not only improves the known upper bounds of the lifespan for $$n\in \{2,3\}$$ n ∈ { 2 , 3 } , but has potential application in the study of related problems. | Lifespan estimates for the compressible Euler equations with damping via Orlicz spaces techniques | 10.1007/s00028-023-00918-7 |
2023-10-06 | High temperature and high strain rate rolling of Mg-1.0 wt.% Al alloy at 20, 50, and 80% rolling reduction were used to investigate the effect of rolling reduction on the microstructure, mechanical, and damping properties of Mg-1.0 wt.% Al alloy. The average grain size of Mg-1.0 wt.% Al sheet gradually decreases, and the DRX volume fraction, dislocation density, and texture strength gradually increase with the increase of rolling reduction. At 80% rolling reduction, the average grain size is 8.8 μ m, and the ultimate tensile strength, tensile yield strength, and elongation of Mg-1.0 wt.% Al sheet gradually increase. The finest room temperature damping properties are shown by plates with a 50% reduction in mean dislocation density and grain size, where the damping value Q^−1 for ε _0.1 is 0.060. The damping properties in the damping capacity versus temperature curves grow with increasing reduction at a certain frequency. When the rolling reduction is certain, the damping performance decreases as the frequency increases. | The Effect of Rolling Reduction on the Microstructure, Mechanical, and Damping Properties of Mg-1.0 wt.% Al Alloy | 10.1007/s11665-023-08782-9 |
2023-10-03 | A new Bresse system with hybrid damping coming from elasticity, thermoelasticity, and viscoelasticity, is analyzed. The uniform (exponential) stabilization of semigroup solution is proved under the dynamic response of each hybrid damping effect. | Exponential Stability for a Bresse System with Hybrid Dissipation | 10.1007/s10440-023-00605-2 |
2023-10-01 | To address the problem of the flat-head tower crane in rotating motion with the large amplitude of the jib vibration and the cargo swing, based on the Euler–Bernoulli beam theory and Lagrange equation, a particle damping vibration absorber-jib-cargo coupling system (PDVA-J-C-CS) dynamics model is proposed based on the consideration of structural damping. The correlation analysis between the system operating parameters and structural parameters is carried out, and the theoretical numerical simulation and ADAMS simulation research on the characteristics of the jib vibration and the cargo swing are carried out. The simulation and theoretical results show that the jib vibration response is almost uncorrelated with the in-plane angle and significantly positively correlated with the out-plane angle, and the closer the cargo position is to the jib end, the stronger the correlation is, and the longer the cargo cable length is, the weaker the correlation is. The particle damping vibration absorber can suppress the jib vibration and the cargo swing, and the larger the mass ratio, the more the jib end vibration response and the cargo out-plane angle are reduced. These studies can provide some theoretical guidance for the vibration damping of the jib and the anti-swing of the cargo in rotary motion and have important engineering significance for the realization of fast, smooth, and safe lifting operation of the tower crane. | Research on vibration damping model of flat-head tower crane system based on particle damping vibration absorber | 10.1007/s40430-023-04496-0 |
2023-10-01 | In this paper, a nonlocal operator method combined with an explicit phase field method is applied to model the propagation of quasi-static fracture and show the computational efficiency of the proposed model compared with numerical models based on implicit method in the literature. Based on the energy form of the phase field model, the nonlocal strong form of governing equations are derived. In the implementation, both the mechanical field and phase field are updated with an explicit time integration. Several numerical benchmark problems including L-shape panel, Three-point bending, Notched plate with holes are carried out and compared with other methods, which show good agreement with previous works. Furthermore, a hybrid implicit/explicit model is proposed to improve the computational efficiency of the explicit model. This paper also presents a local damping, which decreases the ratio of kinetic energy to internal energy of the explicit phase field model to apply mass scaling method. The mass scaling for the cases studied here is examined and the computational time is saved. | Computational modeling of quasi static fracture using the nonlocal operator method and explicit phase field model | 10.1007/s00366-022-01777-5 |
2023-10-01 | The effectiveness of a particle-tuned mass damper was investigated experimentally using a small single story steel structure. Two cases were examined. First, the damper was suspended from the structure with a fixed weight inside the container and in the second case the fixed weight was replaced by particles of equal mass filling two unequal size compartments. In both cases, the frequency of the damper was close to the natural frequency of the structure. The dynamic behavior of the structure with the damper was examined under random excitation. It was found that while the root mean square (RMS) of the response acceleration was reduced in both cases, the substitution of the fixed weight with the particles increased the attenuation of the motion. Reduction of the RMS of the relative displacement was observed after the first few seconds of the excitation. The excitation level has a minimal effect on the effectiveness of the particle-tuned mass damper with the two unequal size compartments. | An Experimental Study on the Effectiveness of Particle Tuned Mass Dampers | 10.1007/s12205-023-0261-3 |
2023-10-01 | In this paper, we study the following damped vibration problem x ̈ + ( q ( t ) I N × N + B ) x ̇ + 1 2 q ( t ) B − A ( t ) x + H x ( t , x ) = 0 , t ∈ ℝ , x ( 0 ) − x ( T ) = x ̇ ( 0 ) − x ̇ ( T ) = 0 , T > 0. $$ \begin{cases} \ddot{x}+ (q(t) I_{N \times N} + B ) \dot{x}+\left( \frac{1}{2}q(t)B - A(t)\right)x+H_{x}(t,x)=0,\quad t\in \mathbb{R},\\ x(0) -x(T) = \dot{x} (0)-\dot{x} (T)=0,\quad T>0.\\ \end{cases} $$ Under a new super-quadratic condition, we obtain a sequence of periodic solutions with the corresponding energy tending to infinity by using a fountain theorem. | Multiplicity of Periodic Solutions for a Class of New Super-quadratic Damped Vibration Problems | 10.1007/s10883-022-09638-6 |
2023-10-01 | In robotic arm-based noncooperative spacecraft-capture missions, the gripper of the robotic arm collides with the target’s surface and graspable structure. The former can cause the graspable structure to collide with the gripper multiple times or escape from the gripper. The adverse of the latter is that the momentum transfer can result in a sudden change in motion of the service spacecraft. If the service spacecraft is required to be in the desired configuration, the control system needs to generate a considerable control output. This paper designs a new capturing strategy to avoid these adverse phenomena, which divides the capture process into two phases: colliding and locking. In the colliding phase, the gripper will actively contact the target’s surface and should maintain the contact, i.e., form a stable contact. This study proposes an improved damping-control scheme for forming a stable contact to realize this objective. Unlike the existing control scheme, this one allows the base of the service spacecraft to move, which helps to reduce the control force acting on the base, saving fuel. After establishing the stable contact, the gripper begins to close. The locking phase starts after forming a force-closure grasp. In this phase, the gripper will continue to close in a controlled manner. However, the states of the service spacecraft’s base and robotic arm should transform from the controlled state to the uncontrolled state. A significant benefit is that the control system does not need to produce large control outputs to resist the colliding impact. Meanwhile, since the service spacecraft has a large inertia, the momentum transfer caused by the collision does not cause significant changes in its configuration. Numerical simulations are performed to evaluate the validity of the proposed control scheme and capturing strategy at the end of this paper. The results indicate that the proposals allow the space robot to grasp the target spacecraft with less control cost. | A new strategy for capturing a noncooperative spacecraft by a robotic arm | 10.1007/s11044-022-09868-3 |
2023-10-01 | In this paper, new simple tuning rules for the fractional order PID controller cascaded with a first order lead compensator are extracted analytically for standard transfer functions of time delay systems. The proposed direct synthesis controller is designed to achieve exact desired frequency domain specifications with guaranteed iso-damping property. Furthermore, the effect of the pure time delay is compensated locally around the gain crossover frequency point ω_c using a direct inversion of the proposed time delay approximation. In addition, the flexibility of the fractional order PID controller is exploited by using specific structures that allow simplifying the derivation of explicit expressions of the five parameters from desired specifications and the plant’s model. These special structures can be used either by deleting the proportional action or by adding another integral or derivative action depending on the process transfer function. Tuning formulas are summarized for ten types of standard transfer functions with illustrative examples which demonstrate the implementation simplicity of the proposed tuning method with significant robustness and performance improvement. | An explicit tuning of the fractional order controller using a novel time delay approximation | 10.1007/s40435-023-01132-6 |
2023-10-01 | Modal parameters are critical for wind resistant design and vibrational serviceability assessments of long-span cable-supported bridges. In contrast to the successful research efforts into natural frequencies, there are still challenges in modeling the damping ratio due to the following aspects: (1) inherent errors in damping estimates, (2) lack of insight into the damping mechanisms, and (3) epistemic uncertainties on the effects of environmental and operational conditions (EOCs). This paper proposes a probabilistic regression model for damping using Deep Gaussian Processes (DGP) on damping estimates compiled from 2.5 years of structural health monitoring (SHM) data from a cable-stayed bridge. Input features representative of EOCs theorized to be related to damping ratios from past literature were used. Two data cleaning strategies based on statistics and knowledge-based criteria were used for enhancing the model performance. A comparative study with DGPs and different regression models were carried out to confirm the robustness of DGPs across different datasets. A knowledge-based feature engineering process examined the most significant predictor of the damping ratios. The proposed data-driven regression model can enable a probabilistic consideration of damping in structural design and vibrational serviceability assessments. | Deep Gaussian process regression for damping of a long-span bridge under varying environmental and operational conditions | 10.1007/s13349-023-00710-8 |
2023-10-01 | The growing complexity of interconnected power systems, with significant penetration of intermittent renewable sources, makes the tasks of devising power system models and defining the operating point challenging. In this context, the large amount of data available from wide-area monitoring systems (WAMS) encourages the application of data-driven methods to power system stability and control. In the present work, a data-driven control design method, called Virtual Reference Feedback Tuning (VRFT), is formulated to design oscillation damping controllers for power systems using remote input signals from phasor measurement units (PMU). The only requirement is a reference model for the closed-loop dynamics. A strategy is proposed to build such model, based on the characteristics of the inter-area mode and measured output response. The use of remote signals in a wide-area damping controller (WADC) approach leads to very efficient inter-area damping controllers. Also, the fast-solving characteristic of the method is explored in an online implementation, where a previously designed controller is re-tuned to re-establish the damping performance after a change in operating condition. The proposed method is tested with two IEEE benchmark power systems, with one having a high penetration of Inverter-Based Source (IBS) generation. In both cases, the critical inter-area oscillation mode is successfully damped. | A Data-driven Approach for the Design of Wide-Area Damping Controllers | 10.1007/s40313-023-01026-0 |
2023-10-01 | The present study focuses on the investigation of mechanical, thermal, and corrosion behaviors of cast hybrid nano-metal matrix composites of AA7075 with Al_2O_3 and coconut shell ash (CSA) nano- and micro-sized particulates, respectively, as reinforcements. Using an ultrasonic assisted stir-casting technique, the hybrid composites were fabricated using 2, 4, and 6% by weight of CSA and 0.5% by weight of Al_2O_3 in equal proportions. SEM, EDS, XRD, porosity, tensile, damping, dislocation density, coefficient of thermal expansion, and polarization tests were used to characterize four different combinations. The findings indicated that the nano- and micro-sized particulates were spread evenly in the matrix. The dislocation density, which is caused by a thermal mismatch between the matrix and the reinforced particles, as well as composite porosity, have been found to have a significant impact on the damping behaviors of hybrid composites. Also, the thermal expansion coefficient of HMMCs decreased with the addition of Al_2O_3 and CSA. The corrosion resistance was gradually increased by increasing the weight percentage of reinforcement in the AA7075 matrix. | Investigation of Microstructure and Several Quality Characteristics of AA7075/Al_2O_3/Coconut Shell Ash Hybrid Nano Composite Prepared through Ultrasonic Assisted Stir-Casting | 10.1007/s11665-022-07780-7 |
2023-10-01 | In this paper, a new hysteresis model with resistor–capacitor (RC) operator for magnetorheological dampers (MRD) is proposed, which takes the excitation current, frequency, and amplitude as input variables. A hysteresis model based on RC operator is established, and the influence of each parameter in the model on the nonlinear behavior of MRD is given. The parameters are fitted based on the test result of an MRD with double rod. The fitting result of parameters shows that the amplitude and frequency of the excitation also affect the parameter values of the model. Base on this, the new hysteresis model is proposed. The parameter fitting results of the proposed model is good. The accuracy of the proposed model and the ability of the model to predict the nonlinear behavior of MRD has been validated by comparing with the experimental data and the RC operator-based model. The comparison results show that the proposed model has higher description accuracy and stronger prediction ability for nonlinear characteristics of MRD. | A New Hysteresis Model with Resistor–Capacitor Operator for Magnetorheological Dampers | 10.1007/s42417-022-00744-0 |
2023-10-01 | The dynamic performance degradation of high-speed trains (HSTs) under complicated operating environment, such as low-temperature condition, has attracted increasing attention. This paper presents a study on the nonlinear dynamic characteristic variations of yaw dampers under variable temperature conditions and their effects on the nonlinear hunting stability of HSTs. An accurate physical parameter model that considers temperature variation is formulated for the yaw dampers. This model is capable of predicting the nonlinear dynamic characteristics of hydraulic yaw dampers subjected to variable temperature operation of HSTs. The hunting stability of HSTs considering the variations in the yaw damper dynamic characteristics caused by complicated low-temperature conditions is investigated by the HST vehicle system dynamics simulations. The results demonstrate that the reduction of environment temperature significantly increases the dynamic stiffness and damping of the HST yaw dampers. The dynamic performance degradation in the yaw damper influences the nonlinear hunting stability of the HSTs. The grazing bifurcation of HST vehicles exists under low temperature and low equivalent conicity, which triggers the serious low-frequency hunting motion and deteriorate the operational stability of HSTs. Moreover, the operation speed range of the grazing bifurcation becomes narrower as the temperature increases. | Modelling and simulation of nonlinear dynamic characteristics of yaw dampers subjected to variable temperature operation condition of high-speed trains | 10.1007/s11071-023-08831-x |
2023-10-01 | Computational fluid dynamics (CFD) provides a powerful tool for investigating complicated fluid flows. This paper aims to study the applicability of CFD in the preliminary design of linear and nonlinear fluid viscous dampers. Two fluid viscous dampers were designed based on CFD models. The first device was a linear viscous damper with straight orifices. The second was a nonlinear viscous damper containing a one-way pressure-responsive valve inside its orifices. Both dampers were detailed based on CFD simulations, and their internal fluid flows were investigated. Full-scale specimens of both dampers were manufactured and tested under dynamic loads. According to the tests results, both dampers demonstrate stable cyclic behaviors, and as expected, the nonlinear damper generally tends to dissipate more energy compared to its linear counterpart. Good compatibility was achieved between the experimentally measured damper force-velocity curves and those estimated from CFD analyses. Using a thermography camera, a rise in temperature of the dampers was measured during the tests. It was found that output force of the manufactured devices was virtually independent of temperature even during long duration loadings. Accordingly, temperature dependence can be ignored in CFD models, because a reliable temperature compensator mechanism was used (or intended to be used) by the damper manufacturer. | Application of computational fluid dynamics in design of viscous dampers - CFD modeling and full-scale dynamic testing | 10.1007/s11803-023-2209-5 |
2023-10-01 | This article is about vibration-damping robotic eating devices designed for use by people who have difficulty in eating due to hand tremors due to neuromuscular system disorder. The robotic eating device has two degrees of freedom (DoF). It contains an active controller structure to absorb vibrations in the y - and z -directions. In the handle part of the robotic eating device, there are two DC motors placed on the y - and z -axis, a three-axis IMU inertia sensor, an embedded system board, and a power unit. To absorb the vibration measured from the IMU sensor, the position control of the two motors to which the spoon is connected is provided by PID controllers. The part of the spoon (the pit surface) where the food is placed is tried to be kept constant. To test the vibration-damping performance of the control method, the dynamic model of the spoon along the eating kinematic trajectory was simulated in the SimMechanics environment using vibration data from ten tremor patients. The results show that the stabilization method can absorb the vibration in the hand of the person in the range of 84–99.409% and successfully provide the stabilization of the spoon tip. This damping rate is promising for providing a healthy diet for hand tremor patients. Graphical Abstract | FiMec tremor stabilization spoon: design and active stabilization control of two DoF robotic eating devices for hand tremor patients | 10.1007/s11517-023-02886-z |
2023-10-01 | Earthquake disasters in seismically active zones revealed the phenomenon of liquefaction which plays a key role in monitoring its severity. Liquefaction affects the stability of the soil by reducing the effective stress which makes soil flows like a liquid. Cohesionless soils under undrained conditions are highly vulnerable to liquefaction, whose effect will be added if it is nearer to the river basin. The present paper investigates the performance of Gangetic sand obtained from the Indo-Gangetic River basin by examining its static and dynamic behavior using triaxial tests. Static as well as cyclic trials were extended for similar three confining pressures and two different densities. The static behavior of the Gangetic Sand was examined on the basis of stress–strain, effective stress path, and pore pressure generation. In addition to the above, the evolution of cyclic stress ratio and dynamic properties including degradation of shear modulus and damping coefficient were analysed while assessing the cyclic behavior. The effect of loading conditions, density, pressures, state of the soil, and stress history were also explored in the current paper. | An Experimental Study on Static and Cyclic Undrained Behaviour of Gangetic Sand | 10.1007/s40098-023-00727-2 |
2023-10-01 | Introduction Electromagnetic dampers, that are composed of a permanent-magnet DC motor, a ball screw, and a nut, are one of the devices currently being inspected to regenerate energy from the vehicle suspension system. In view of that, this research paper focuses on developing mathematical model for an energy storage system in conjunction with the electromagnetic damper for the sake of energy regeneration of the vehicle suspension system. Methods The energy storage system considered herein comprises of a unidirectional converter, a full wave rectifier, and an ultracapacitor stack. Some of non-idealities that affect the act of the converter are considered for modeling of the energy storage system. Subsequently, the vehicle suspension system performance analysis along with energy regeneration is carried out based on the developed mathematical model and the role of resistance R (design parameter) in the electric circuit on the vehicle suspension system performance is revealed. Furthermore, considering the variable resistance, a simple method to adjust the parameter of the continuous skyhook control strategy for the semi-active electromagnetic suspension system is proposed in this paper. Results The simulation results demonstrate that the designed semi-active electromagnetic suspension system has the better performance and more energy regeneration than the passive electromagnetic suspension system. | Energy Regeneration Effects on the Vehicle Suspension System Performance Considering Non-idealities | 10.1007/s42417-022-00732-4 |
2023-10-01 | Abstract The characteristics of spatial relaxation of the average electron energy in pure helium and in helium containing an admixture of water vapor in a constant electric field have been investigated by Monte Carlo simulation. The conditions under which the spatial relaxation in helium has a form of damped oscillations are considered. It is shown that even a small (0.1%) additive of water vapor leads to a significant decrease in the relaxation length, and the spatial oscillations almost disappear at 3% H_2O. Calculations were also performed for a mixture He : (H_2O : H_2 : O_2 : H), where the composition of atoms and molecules in the parentheses correspond to the composition formed from the initial water vapor in discharge plasma due to the dissociation of water molecules and subsequent plasma-chemical reactions. | Influence of Water Vapor on the Spatial Oscillations of the Average Electron Energy in Helium in a Constant Electric Field | 10.3103/S1541308X23050023 |
2023-10-01 | This paper proposes some modifications to the method of studying the fractional mass-spring-damper system in order to meet the high reliability requirements of the mechanical system. These changes mainly depend on two things, the discovered drawback of the fractional methods, and the general behavior of the mechanical damping system. The defects discovered in fractional calculus are summarized in the results of differences between the variance of fractional definitions and the constant coefficients. Therefore, it became necessary to introduce some modifications and suggestions for compatibility with the system to make the proposed fractional definition more intuitive and usable. In this paper, the numerical and theoretical results were compared using our proposed definition and Caputo’s. We found that there is a clear difference in the results between them. We believe that our proposed method distinguished by its compatibility with the basics of damped mechanical system behavior. In first method the vibration takes place around the reference axis, while in Caputo’s method vibration occurs around different axes when changing the fractional differential orders. The method proposed is based on a modification in conformable fractional derivative. | A novel approach to study the mass-spring-damper system using a reliable fractional method | 10.1007/s00419-023-02461-w |
2023-10-01 | A one-component strain gauge dynamometer with a force measurement range of 0–0.33 N was developed and manufactured at the N. E. Zhukovsky Central Aerohydrodynamic Institute, to measure the unsteady friction force of the boundary layer on the wind tunnel walls at remarkably high Reynolds numbers. The static and dynamic characteristics of the dynamometer and its systematic errors were also investigated. The effects of the temperature, longitudinal, normal, and lateral forces, as well as the position of the longitudinal force application, were analyzed during the calibration. A block was designed and manufactured to calibrate the dynamometer using dead weights in a wind tunnel. Special experiments were performed in laboratory conditions to determine the friction force acting on the block axis. The developed dynamometer represents a dynamic system with its natural frequency of oscillations. The correction for the dynamics of the dynamometer is suggested on the basis of the method developed earlier. The mass of the metric part of the dynamometer, its natural oscillation frequency in the absence of damping in the direction of measuring the friction force, and the damping coefficient were determined to calculate the correction. The correction is verified by experiment with the application of a stepwise force. The effect of static and dynamic temperature components (the influence of the average temperature value and its change over time, respectively) on dynamometer readings was investigated. Corrections are proposed to eliminate the systematic errors due to the effect of temperature based on the previously developed method. Results revealed that the lateral force does not affect the dynamometer readings, while the effect of the normal force is 1.1% of the sensitivity coefficient of the longitudinal force. The temperature sensitivity of the sensitivity coefficient of the dynamometer is 0.017%/°C. The total measurement uncertainty of the friction force dynamometer was estimated as the standard deviation of the measurement results from the average value not exceeding 0.076% of the measurement range, and the relative uncertainty of the sensitivity coefficient is not more than 0.03%. The measurement uncertainty of the unsteady friction force will not exceed 0.86% of the dynamometer range with natural oscillations of the sensitive element. The developed single-component strain gauge dynamometer can be used to determine the friction coefficient of the boundary layer on a flat surface. | Strain gauge dynamometer for measuring the boundary layer friction force on the walls of wind tunnels | 10.1007/s11018-023-02251-4 |
2023-10-01 | Bio-based interpenetrating polymer networks (IPNs) with tunable thermal and mechanical properties were prepared by bio-based polyurethane (PU) and epoxy resin (EP) derived from plant oils. The cure reaction, dynamic mechanical properties, thermal stability, mechanical performance and morphology of bio-based PU/EP IPNs were characterized by Fourier transform infrared spectroscopy, dynamic mechanical analysis, thermogravimetry, universal test machine and scanning electron microscopy. Dynamic modulus, glass transition temperature, thermal stability and tensile strength of bio-based EP/PU IPNs decreased in the content of soybean oil-based PU prepolymers. However, the damping properties of bio-based EP/PU IPNs increased in the content of soybean oil-based PU prepolymers. The elongation at break of bio-based EP/PU IPNs was greatly higher than that of the plant oil-based EP. The elongation at break of the bio-based EP/PU IPN containing 20% soybean oil-based PU prepolymer was fourfold higher than that of the plant oil-based EP. Soybean oil-based PU prepolymer significantly improved the damping properties and the elongation at break of the plant oil-based EP. By adjusting the mass ratio of the plant oil-based EP to the soybean oil-based PU, the glass transition temperature, damping and mechanical properties of bio-based PU/EP IPNs can be optimized. | Bio-based epoxy/polyurethane interpenetrating polymer networks (IPNs) derived from plant oils with tunable thermal and mechanical properties | 10.1007/s10973-023-12368-x |
2023-10-01 | Seismic isolation has been widely accepted as one of the techniques that can be used to protect structures during earthquake ground motions. However, some challenges still exist such as the optimal control of excessive isolator shear strains imposed by some ground motions. The main purpose of this study was to assess the effects of building height variation and earthquake ground motion type on the optimal performance of the seismic isolation using lead core rubber bearing (LCRB). Nonlinear time history analysis for building models of various storeys isolated by LCRB and exposed to different real earthquakes was performed. To achieve this, the equations governing the motion of the isolated three different building models were presented, and an approach for solving the equations while taking into consideration of the optimized mechanical properties of the LCRB was developed. The LCRB performance was measured in terms of elastomer shear strains, derived after an optimal criterion leading to reliable substructure and superstructure responses was reached. The results showed that the combined effects of the earthquake type and building height significantly affect the substructure responses (maximum isolator displacement, energy dissipation capacity, maximum isolator force) and the superstructure responses (storey shear forces, storey drifts, floor displacements, and floor accelerations), which in some cases lead to a need for adding a fluid damper. In this regard, an attempt to couple the LCRB with nonlinear fluid viscous damper was made, and the performance of the hybrid was assessed. It was generally found that the hybrid can positively improve the substructure responses, thereby reducing the unwanted large elastomer shear strains without adversely affecting the superstructure responses. | Effects of Building Height and Seismic Load on the Optimal Performance of Base Isolation System | 10.1007/s13369-023-07660-9 |
2023-09-27 | Assessing the dynamic response of soft and compressible soils is a prerequisite for many earthquake geotechnical engineering applications. Dynamic characterization is represented in terms of strain-dependent dynamic soil properties ( G _max, G / G _max, and damping ratio- D variation with shear strain- γ ) and liquefaction potential. The current study aims to investigate the dynamic response of two soft-natured cohesive soils sampled from one of the most active seismic regions of India (Assam). Four advanced dynamic characterization techniques have been employed for strain-dependent dynamic soil characterization. Bender element tests are adopted for low-strain testing, resonant column tests for intermediate-strain range, dynamic simple shear tests for high-strain testing, and cyclic triaxial apparatus for assessing the liquefaction potential of the chosen soil specimens. The obtained results are discussed in terms of shear modulus degradation and damping ratio variation with γ as influencing parameter. The independent equipment-specific results are combined to form a set of comprehensive dynamic soil properties over a wide strain range (0.001 to 5%) which can be readily adopted for earthquake geotechnical applications for similar soils from northeastern India. Easy-to-use analytical expressions have been developed utilizing the experimental results and nonlinear regression analyses. Further, a case study of nonlinear effective stress–based ground response analysis has been conducted to demonstrate the applicability of established dynamic soil characteristics. It has been realized from the case study that the soft soil deposits in northeastern India are prone to seismic wave amplification for low seismic motions and attenuation for high-intensity seismic motions. The wide range of results presented in this article will prove advantageous in carrying out nonlinear effective stress analysis and developing constitutive models for numerical simulations of foundations and soils in northeastern India. | Comprehensive dynamic characterization of two cohesive soils of northeastern India for effective stress–based seismic ground response analysis | 10.1007/s12517-023-11651-3 |
2023-09-25 | We present a computational study of sliding between gold clusters and a highly oriented pyrolytic graphite substrate, a material system that exhibits ultra-low friction due to structural lubricity. By means of molecular dynamics, it is found that clusters may undergo spontaneous rotations during manipulation as a result of elastic instability, leading to attenuated friction due to enhanced interfacial incommensurability. In the case of a free cluster, shear stresses exhibit a non-monotonic dependency on the strength of the tip-cluster interaction, whereby rigid clusters experience nearly constant shear stresses. Finally, it is shown that the suppression of the translational degrees of freedom of a cluster’s outermost-layer can partially annihilate out-of-plane phonon vibrations, which leads to a reduction of energy dissipation that is in compliance with Stokesian damping. It is projected that the physical insight attained by the study presented here will result in enhanced control and interpretation of manipulation experiments at structurally lubric contacts. | A Computational Study of Cluster Dynamics in Structural Lubricity: Role of Cluster Rotation | 10.1007/s11249-023-01785-6 |
2023-09-24 | Composite structures based on magnetorheological elastomers are widely used in many industrial sectors, such as the automotive, naval, railway, aeronautical, aerospace, and building industries because of their adjustable mechanical properties by an external stimulus. In this work, the experimental tests and the numerical simulation carried out have shown that the use of these new structures, developed from a honeycomb core and a MRE core with aluminum skins, makes it possible to improve in a particular way the overall rigidity and to reduce the vibration amplitudes. The results showed that these new hybrid structures have a very good mechanical resistance due mainly to the honeycomb core and a very good shock absorber due mainly to the core of the magnetorheological elastomer. The elaborated composite structure is intended to be used in industrial sectors subject to great efforts and a high amplitude of vibration such as helicopter wings and air turbines. | Experimental analysis and numerical simulation of the behavior of smart sandwich beams in magnetorheological elastomer–honeycomb | 10.1007/s40430-023-04452-y |
2023-09-24 | Adjustable mass dampers are widely used to reduce the seismic vibrations of engineering structures. The efficiency of these systems requires a proper setting of its parameters. In this study, an efficient and effective method for designing optimal multi-tuned mass dampers (MTMD) is proposed to reduce the vibration response of structures, which is based on the definition of a multi-objective optimization problem. Therefore, the multi-objective optimization algorithm of the cuckoo has been used to solve the issue. MTMD setting parameters are considered as design variables. Since the setting of MTMD parameters is basically a multi-objective optimization problem, three objective functions including minimizing the maximum displacement of the roof, the maximum acceleration of the roof and the maximum displacement of TMDs have been considered in the optimization problem. The results of numerical simulations for a ten-story shear frame exposed to an earthquake show that the cuckoo multi-objective optimization algorithm is able to find appropriate solutions in the form of Parreto curves to set the optimal parameters of MTMDs according to the design objectives. Provided that they are caused by creating a suitable compromise between the objective functions in conflict with each other. Therefore, MTMDs reduce the seismic responses of the structure in a favorable way. Based on the results, it was found that MTMD performance depends on incoming earthquake, TMD mass ratio and number of TMDs. By increasing the number of TMDs, up to a certain limit (10), the seismic response of the seismic system is reduced in a favorable way, but many changes in reducing the seismic response of the structure are not observed. Also, the seismic response of the system is reduced to a certain value (6%), by increasing the mass ratio of TMDs, but the process of reducing the seismic response of structures does not undergo many changes with its further increase. | Optimum Setting Parameters of Multiple Tuned Mass Damper for Passive Control of Structures Using Cuckoo Algorithm | 10.1007/s40996-023-01233-4 |
2023-09-22 | As a continuity to the study by Ouchenane (Georgian Math J 21(4):475–489, 2014). We consider a nonlinear thermoelastic system of Timoshenko type with a time-varing delay and forcing term. We show the well-posedness of the system by using the semigroup theory, and we prove an exponential stability result under the usual assumption on the wave speed by the energy method. | Well-posedness and exponential stability of Timoshenko system of second sound with time-varying delay and forcing terms | 10.1007/s11565-023-00474-5 |
2023-09-19 | In this paper, we study the initial boundary value problem for the following viscoelastic wave equation with Balakrishnan–Taylor damping and a delay term where the relaxation function satisfies g ′ ( t ) ≤ − ξ ( t ) g r ( t ) $g'(t)\leq -\xi (t)g^{r}(t)$ , t ≥ 0 $t\geq 0$ , 1 ≤ r < 3 2 $1\leq r< \frac{3}{2}$ . The main goal of this work is to study the global existence, general decay, and blow-up result. The global existence has been obtained by potential-well theory, the decay of solutions of energy has been established by introducing suitable energy and Lyapunov functionals, and a blow-up result has been obtained with negative initial energy. | Initial boundary value problem for a viscoelastic wave equation with Balakrishnan–Taylor damping and a delay term: decay estimates and blow-up result | 10.1186/s13661-023-01781-8 |
2023-09-18 | Destruction caused by excessive moisture is a common problem in heritage buildings made of brick. Historic buildings usually have walls that of different constructions, i.e. walls with all joints filled, walls without filled vertical joints, and walls with a layered arrangement. Excessive moisture causes brick cavities, reduces the load-bearing capacity of walls, is unsightly, and can lead to the destruction of walls or the failure of a building. Secondary anti-damp insulation is used to protect the brick walls of historic buildings. However, there has not been enough research to confirm the effectiveness of secondary anti-damp insulation. This type of insulation is performed with the use of the injection method, with various factors (such as soils, the type of injection material, etc.) that affect the effectiveness of the insulation being taken into account. There is also insufficient research on how injection material penetrates brick. This article presents the current state of knowledge, research gaps, and research regarding anti-damp insulation in historic buildings made of brick, and also the perspectives of future research. The authors propose the use of non-destructive and destructive methods to assess the effectiveness of anti-damp insulation in brick walls. | Assessment of the effectiveness of secondary anti-damp insulation in heritage buildings made of historic brick: the current state of knowledge, research gaps and perspectives | 10.1186/s40494-023-01043-x |
2023-09-13 | Phase transition from the over-damping to under-damping states is a ubiquitous phenomenon in physical systems. However, what kind of symmetry is broken associated with this phase transition remains unclear. Here, we discover that this phase transition is determined by an anti-parity-time (anti- $${\cal P}{\cal T}$$ P T ) symmetry hidden in a single damping linear resonator, which is significantly different from the conventional anti- $${\cal P}{\cal T}$$ P T -symmetric systems with two or more modes. We show that the breaking of the anti- $${\cal P}{\cal T}$$ P T symmetry yields the phase transition from the over-damping to under-damping states, with an exceptional point (EP) corresponding to the critical-damping state. Moreover, we propose an optomechanical scheme to show this anti- $${\cal P}{\cal T}$$ P T symmetry breaking by using the optical spring effect in a quadratic optomechanical system. We also suggest an optomechanical sensor with the sensitivity enhanced significantly around the EPs for the anti- $${\cal P}{\cal T}$$ P T symmetry breaking. Our work unveils the anti- $${\cal P}{\cal T}$$ P T symmetry hidden in damping oscillations and hence opens up new possibilities for exploiting wide anti- $${\cal P}{\cal T}$$ P T symmetry applications in single damping linear resonators. | Anti-parity-time symmetry hidden in a damping linear resonator | 10.1007/s11433-023-2187-7 |
2023-09-12 | The FEAST eigensolver is extended to the computation of the singular triplets of a large matrix A with the singular values in a given interval. The resulting FEAST SVDsolver is subspace iteration applied to an approximate spectral projector of $$A^TA$$ A T A corresponding to the desired singular values in a given interval, and constructs approximate left and right singular subspaces corresponding to the desired singular values, onto which A is projected to obtain Ritz approximations. Differently from a commonly used contour integral-based FEAST solver, we propose a robust alternative that constructs approximate spectral projectors by using the Chebyshev–Jackson polynomial series, which are shown to be symmetric positive semi-definite with the eigenvalues in [0, 1]. We prove the pointwise convergence of this series and give compact estimates for pointwise errors of it and the step function that corresponds to the exact spectral projector of interest. We present error bounds for the approximate spectral projector and reliable estimates for the number of desired singular triplets, prove the convergence of the resulting FEAST SVDsolver, and propose practical selection strategies for determining the series degree and the subspace dimension. The solver and results on it are directly applicable or adaptable to the real symmetric and complex Hermitian eigenvalue problem. Numerical experiments illustrate that the FEAST SVDsolver is substantially more efficient than the contour integral-based FEAST SVDsolver, and it is also more robust and stable than the latter. | A FEAST SVDsolver Based on Chebyshev–Jackson Series for Computing Partial Singular Triplets of Large Matrices | 10.1007/s10915-023-02342-y |
2023-09-08 | In this article, we consider the long-time behavior of extensible beams with nonlocal weak damping: $$\varepsilon(t)u_{tt}+\Delta^{2}u-m(\Vert\nabla u\Vert^{2})\Delta u+\Vert u_{t}\Vert^{p}u_{t}+f(u)=h$$ ε ( t ) u t t + Δ 2 u − m ( ∥ ∇ u ∥ 2 ) Δ u + ∥ u t ∥ p u t + f ( u ) = h , where ε ( t ) is a decreasing function vanishing at infinity. Within the theory of process on time-dependent spaces, we investigate the existence of the time-dependent attractor by using the Condition ( C _ t ) method and more detailed estimates. The results obtained essentially improve and complete some previous works. | Attractor for the Extensible Beam Equation with Nonlocal Weak Damping on Time–Dependent Space | 10.1007/s10114-023-1295-7 |
2023-09-04 | It has been proven that mechanical elements display size-dependent behavior in structural and thermal fields at microscales. It has also been found that thermoelastic damping (TED) is one of the dominant reasons in confining the quality factor (Q-factor) of such elements. This paper aims to develop a novel formulation for evaluating TED in microbeams by accounting for the size effect on the mechanical and thermal areas via the nonclassical theory of modified strain gradient (MSG) and the non-Fourier heat conduction model of Moore-Gibson-Thompson (MGT). In the first step, the heat equation for beams is derived within the framework of MGT model. Through this equation, the function of temperature fluctuation can be obtained. Then, the constitutive relations of the beam according to MSG theory (MSGT) are extracted. By using the temperature distribution and nonclassical constitutive relations obtained, the maximum amounts of potential and wasted thermal energies during one cycle of beam vibration are calculated. Finally, by placing the value of these energies in the existing relationship for computing the value of TED, an explicit expression for TED is presented. With the aim of clarifying the sensitivity of TED value to the characteristic parameters of MSGT and MGT model, a variety of numerical data are provided. According to the obtained outcomes, the inclusion of size effect in the structural and thermal equations can cause a remarkable difference compared to the classical model. The dependency of TED on some factors like beam thickness and aspect ratio, vibration mode number and material of the beam is also investigated numerically. | Analysis of thermoelastic damping in a microbeam following a modified strain gradient theory and the Moore-Gibson-Thompson heat equation | 10.1007/s11043-023-09632-w |
2023-09-01 | In this work, we are concerned with the well-posedness of solutions as well as the asymptotic behavior of the energy related to the semilinear coupled heat-wave equations, posed on a bounded domain of $$\mathbb {R}^n.$$ R n . Inspired by the works (Cavalcanti and Oquendo SIAM J Control Optim. 42:1310-24, 2003) and (Nicaise and Pignotti SIAM J Control Optim. 5(45):1561-85, 2006), we consider dampings in the wave equation and the heat equation, and both dampings have a delay in time. The damping acting on the heat equation is localized and not strategically distributed. In these conditions, we prove that the solutions of this system are exponentially stable. | Exponential Stabilization of a Parabolic-Hyperbolic System with Localized Damping and Delay | 10.1007/s10883-023-09653-1 |
2023-09-01 | We investigate the stabilization of a multidimensional system of coupled wave equations with only one Kelvin–Voigt damping. Using a unique continuation result based on a Carleman estimate and a general criteria of Arendt–Batty, we prove the strong stability of the system in the absence of the compactness of the resolvent without any geometric condition. Then, using a spectral analysis, we prove the non uniform stability of the system. Further, using frequency domain approach combined with a multiplier technique, we establish some polynomial stability results by considering different geometric conditions on the coupling and damping domains. In addition, we establish two polynomial energy decay rates of the system on a square domain where the damping and the coupling are localized in a vertical strip. | A N-dimensional elastic
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viscoelastic transmission problem with Kelvin–Voigt damping and non smooth coefficient at the interface | 10.1007/s40324-022-00297-y |
2023-09-01 | The long-term chemo–thermo–hydro–mechanical behavior, the salt migration, and the salt attack on unstabilized rammed earth have been rarely investigated in the literature. The authors simulated the mechanical degradation of a typical unstabilized rammed earth (URE) wall under salts and rising damp attack effect by using the finite element method. The simulation results show that the water/salinity in a freshly built rammed earth wall decreases/increases significantly due to the water evaporation and capillary effects after construction, and these effects are stabilized in the following 3 years. Globally, the wall is wetter, cooler, and saltier in winter than in summer and has a lower strength. The strength in the upper part of the wall is higher than in the lower part. In the first 4 years after construction, the strength in the upper part increases and then reaches an equilibrium stage with time, while the strength in the lower part increases and then has the tendency to decrease in the latter 3 years due to the accumulation of salt. The strength inconsistency may exist in the wall due to the combined effects of salt accumulation and water evaporation, and the strength on the surface may be higher or lower than that of the inside due to the changes of surrounding conditions with time. The simulation results show that the wall has the best mechanical performance without damp and salt attacks. | Mechanical degradation of unstabilized rammed earth (URE) wall under salts and rising damp attack effect | 10.1007/s11440-023-01865-w |
2023-09-01 | In this paper, we consider the following nonlinear Petrovsky equation with variable exponents: $$\begin{aligned} u_{tt}+\Delta ^{2} u+a|u_{t}|^{m(.)-2}u_{t}=b|u|^{p(.)-2}u, \end{aligned}$$ u tt + Δ 2 u + a | u t | m ( . ) - 2 u t = b | u | p ( . ) - 2 u , where a , b are positive constants and the exponents m ( x ), p ( x ) are given functions. By using the Faedo-Galerkin method, the existence of a unique weak solution is established under suitable assumptions on the variable exponents m and p . We also prove a finite-time blow-up result for arbitrary negative initial energy. | Existence and blow up of solutions for a Petrovsky equation with variable-exponents | 10.1007/s40324-022-00302-4 |
2023-09-01 | This research is mainly dealt with determining the effectiveness of base isolation in multiple degree of freedom systems (MDOF) of different fundamental natural time periods (FNTP). Base isolation devices avert the detrimental ground shaking to maximum extends and mitigates the lateral forces caused by earthquakes. In this research, it is intended to study about under what circumstances the base isolation system will be effective in reducing the lateral forces caused by earthquakes. Every MDOF system will be having its own FNTP with respect to its mass, stiffness and damping matrices. To determine the effectiveness of base isolation, five numbers of five-storey buildings of different FNTP, i.e., 0.4 s, 0.8 s, 1.2 s, 1.6 s and 2.0 s had been selected. Different FNTP were obtained by maintaining constant mass as well as damping matrices while changing stiffness matrix for each building. Subsequently, comparison was made between the structural responses of buildings with and without providing base isolation. Finally, it was found out that a building of lower FNTP was performing well when it was provided with base isolation. | Effects of fundamental natural time periods on the seismic performance of base isolated multistorey buildings | 10.1007/s42107-023-00604-6 |
2023-09-01 | The results of an experimental investigation on a developed small-scale MR damper for seismic response reduction in buildings are presented in this article. The damper is intended to have a target capacity of 2 kN. The damper was designed and built using the flow mode principle. The MTS servo-hydraulic UTM was used for testing, and the results were obtained as force–velocity and force displacement plots based on real-time data collected by the MTS suite. From the force–displacement curve, energy dissipated by the MR damper for corresponding frequencies has also been determined. To compare the percentage increase in damping force, the force corresponding to all excitation frequencies is obtained and plotted as force velocity. The maximum force was 252.77 N at 1 Hz, and the minimum force was 175.55 N at 0.1 Hz, with the corresponding velocity of 31.22 mm/s at 1 Hz and 3.56 mm/s at 0.2 Hz. The experiment showed that the MR damper’s velocity varies with displacement control and variable excitation frequency. As the excitation frequency/velocity increases, so does the damping force. Furthermore, the energy dissipated by the MR damper increases significantly as the excitation frequency/velocity increases, ranging from 1.72 to 2.43 J, demonstrating that the developed small-scale MR damper is suitable for use as a vibration-control device in structures. | Small-scale MR damper: design, fabrication and evaluation | 10.1007/s42107-023-00582-9 |
2023-09-01 | Adding particles to mechanical elements can reduce their vibrations. Both the particles and the mechanical elements interrelate in a highly complex manner, thereby influencing the energy dissipation of the mechanical elements. The particle damping is extremely nonlinear, and the energy dissipation mechanism in such a granule–structure interaction system has scarcely been examined. This study aims to investigate the dynamic behavior and energy dissipation mechanism for a mass–spring–damper–slider system with a particle damper. A simple but robust energy method was first proposed to explore the energy dissipation mechanism, and a two-way coupled model of the discrete element method (DEM) and multi-body dynamics (MBD) was employed to analyze the complex interaction system. Three numerical benchmark tests and free vibration experiments for the system with a particle damper were conducted to validate the proposed energy method and the adopted coupled DEM–MBD model. Results show that the coupled DEM–MBD simulations reasonably agree with the corresponding experiments. The validated coupled model was subsequently employed to calculate the distribution of system energy, and to explore the effect of contact properties on the energy dissipation of the system during the free vibration process. In the mass–spring–damper–slider system with a particle damper, the damping effect resulting from particles is essentially caused by the contact forces generated when the particles make contact with the hollow box. The induced contact forces act as resistance forces to the hollow box, always do negative work, and suppress the motion of the hollow box. The energy loss of the particles primarily occurs through contact friction and contact damping when the particles are hit by the hollow box. Contact properties, such as friction and restitution coefficients, exhibit a negligible effect on the dynamic behavior of the hollow box, but substantially affect the distribution of energy dissipation in the particular system. | A study on the energy dissipation mechanism of dynamic mechanical systems with particle dampers by using the novel energy method | 10.1007/s11071-023-08698-y |
2023-09-01 | Based on finite element discretization, a new two-grid algorithm based on Newton iteration is proposed to solve the stationary Navier–Stokes equations with nonlinear damping term. The proposed new two-grid algorithm consists of three steps: in the first step, we solve one small nonlinear coarse grid problem, and then, in the second and third steps, we solve two linear fine grid problems based on Newton iteration which have the same stiffness matrices with only different right-hand sides. We analyze stability of the present algorithm and prove rate of convergence of the approximate solutions obtained from the algorithm. Numerical results are given to demonstrate the effectiveness of the present algorithm, showing that our algorithm greatly improves the accuracy of the approximate solutions comparable to that of the usual two-grid algorithm. | A New Two-grid Algorithm Based on Newton Iteration for the Stationary Navier–Stokes Equations with Damping | 10.1007/s11464-021-0018-6 |
2023-09-01 | A magnetorheological (MR) damper is effective and economical for miscellaneous applications in automotive, mechanical, civil, and relative fields. A parameter tuning methodology independent of manual trial-and-error has received much technical interest for controlling vibrations. The present work contributes mathematical and Simulink modeling followed by MR damper design and development for vibration optimization of the single degree of freedom system. A Simulink model of an MR damper is performed on the mathematical model for vibration control, and the MR damper’s tuning parameters are experimentally investigated to control the resonance frequency. Theoretical simulated results and its experimental verification show that increasing current raises the force to control the resonance frequency in an MR damper. The present approach provides a concise and improved platform for dynamic vibration absorber in the current potential market and the highly interested control community for the development of the distinctive attributes of the MR Damper. | Dynamic Characterization of MR Fluid-Based Dynamic Vibration Absorber | 10.1007/s13369-022-07410-3 |
2023-09-01 | With the aim to model the self-excited oscillations of a body, a hypothesis is proposed for the formation of periodic bottom-wake vortex structures whose frequency coincides with the natural frequency of oscillations of the body, and the force effect of the oscillations on the body is mathematically described with a harmonic function of time. Analytical formulas for aerodynamic derivatives and equivalent aerodynamic derivatives are obtained. It is shown that the mathematical model satisfactorily describes the dependence of the pitch angle on time and the dependence of the equivalent aerodynamic derivatives on the amplitude of oscillations for two moments of inertia of the body. The mathematical model predicts a hyperbolic law for the dependence of the amplitude of self-excited oscillations on the reduced frequency. | Mathematical modeling of self-excited oscillations over the pitch of a conical-spherical body at Mach number M = 1.75 using the forced-oscillation hypothesis | 10.1134/S0869864323050086 |
2023-09-01 | This research tries to render an unconventional model for thermoelastic dissipation or thermoelastic damping (TED) in circular microplates by accommodating small-scale effect into both structure and heat transfer fields. To accomplish this purpose, the modified couple stress theory (MCST) and Guyer−Krumhansl (GK) heat conduction model are utilized for providing the coupled thermoelastic equations of motion and heat conduction. The equation of heat conduction is then solved to acquire the closed-form of temperature profile in the circular microplate. By placing the extracted temperature profile in the equation of motion, the size-dependent frequency equation influenced by thermoelastic coupling is established. By conducting some mathematical manipulations, the real and imaginary parts of damped frequency are obtained. In the next stage, with the help of the description of TED based upon the complex frequency (CF) approach, an explicit single-term relation consisting of structural and thermal scale parameters is derived for making a size-dependent estimation of TED value in circular microplates. For evaluating the precision and veracity of the proposed model, the results obtained through the presented solution are compared with the ones available from the literature. In addition, by way of several examples, the pivotal role of length scale parameter of MCST and thermal nonlocal parameter of GK model in the magnitude of TED is assessed. Various numerical results are also given to place emphasis on the impact of some parameters such as boundary conditions, geometrical features, material and ambient temperature on TED value. The formulation and results provided in this study can be used as a benchmark for optimal design of microelectromechanical systems (MEMS). | A non-Fourier and couple stress-based model for thermoelastic dissipation in circular microplates according to complex frequency approach | 10.1007/s10999-022-09633-6 |
2023-09-01 | The proposed method solves the difficulty of unstable sliding rock (USR) adjustment. The study provides a judgment criterion for the quantitative identification of USR. The improved method can provide a practical reference for engineers engaged in rapidly identifying USR. | Experimental Study on the Real-Time Stability Assessment Method for Unstable Sliding Rock | 10.1007/s00603-023-03419-8 |
2023-09-01 | Electromagnetic shock absorbers with mechanical motion rectifier have two operating conditions: engagement and disengagement. The alternation of two operating conditions occurs the nonlinear phenomena. In this paper, the nonlinear dynamic property of an electromagnetic shock absorber with mechanical motion rectifier is investigated in experiment and simulation. The characteristic of the electromagnetic shock absorber is quantified by the disengagement ratio in time domain and phase-plane. The effects of excitation frequency, amplitude and load resistance on the damping properties are analyzed. The results show that the disengagement of the damping force is caused by the reverse of the inertial force during the deceleration. Large amplitude will approximately amplify the damping curve equally. Large frequencies make the damping curve steeper. The lower resistance will result in a fuller damping curve. Meanwhile, the disengagement is most sensitive to changes in the excitation frequency. The results of adjustment interval determine the disengagement intervals that can be improved. This sets the stage for the disengagement of the damping force to restrain. | Damping Characterization of Electromagnetic Shock Absorbers by Considering Engagement and Disengagement | 10.1007/s40997-022-00578-x |
2023-09-01 | We use the three-phase sphere model or the generalized self-consistent scheme (GSCS) to study the mechanical damping of a particulate composite with concurrent interface slip and diffusion under a time-harmonic deviatoric far-field load. In particular, we determine the specific damping capacity characterizing the effective damping behavior in the particulate composite. Our results indicate that both interface slip and interface diffusion contribute to the specific damping capacity and effective storage shear modulus. Two peaks of the specific damping capacity can appear. The co-existence of interface slip and diffusion will enhance the maximum value of the specific damping capacity. | Damping behavior of a particulate composite with interface slip and diffusion under a deviatoric far-field load | 10.1007/s00161-023-01226-8 |
2023-09-01 | Abstract The instability of an incompressible boundary layer on a compliant plate with respect to inviscid perturbations in the limit of high Reynolds numbers is analyzed using triple-deck theory. It is shown that unstable inviscid perturbations can exist only if the inertia and/or damping of the plate are taken into account. A twofold role of damping is revealed: it suppresses instability under certain conditions, while leading to its generation under other conditions. | Influence of Damping of a Compliant Surface on Inviscid Instability of Overlying Incompressible Boundary Layer | 10.1134/S0965542523090130 |
2023-09-01 | Metals are indispensable raw materials for industry and have strategic importance in economic development. The price forecasting of metals is crucial for the production sector and production policies of countries. The paper presents the application of various exponential smoothing methods to metal spot price forecasting. Aluminum, copper, lead, iron, nickel, tin, and zinc prices were analyzed by using yearly data from 1990 to 2021. The root mean square error (RMSE), mean absolute percentage error (MAPE), and mean absolute error (MAE) values of the models were obtained and their performances were compared to determine the appropriate model for each metal price. These metal prices were forecasted up to 2030 by using the best-fitted models. | Comparison of exponential smoothing methods in forecasting global prices of main metals | 10.1007/s13563-022-00354-y |
2023-09-01 | With the vigorous construction of intercity railways, the environmental vibrations along the railways, especially in buildings with precision instruments (PI), have been deteriorating, and the internal instruments are affected by repeated vibrations. The train-induced vibrations will be more severe when two trains meet at a high speed. In this study, numerical simulation analysis of PI in adjacent buildings was carried out. A coupling model of high-speed trains meeting was developed, and a method for predicting vibration superposition was proposed. The existing vibration data were collected and used for model verification. Based on this, the vibrations of PI were evaluated, and corresponding measures were proposed. The prediction results show that the dominant frequency of the existing vibrations is 10–20 Hz, and there is a risk of excessive vibrations in this frequency range. PI can be affected by high-speed trains meeting, resulting in abnormal operation. The high-frequency train-induced vibrations (40–80 Hz) are effectively alleviated by the damping pad. After the superposition of train-induced vibrations and existing vibrations, the vibrations on higher floors are mainly in the 10–20 Hz range, which requires attention and implementation of reduction measures for PI. 随着城际铁路的大力建设, 铁路沿线特别是一些放置精密仪器的建筑因振动环境恶化, 内部仪器受到反复振动的影响, 且当列车高速会车时, 引起的振动更为剧烈. 本文对邻近线路建筑物内的精密仪器进行数值仿真分析, 建立了高速列车会车的耦合模型, 提出一种振动叠加的预测方法. 对既有振动数据进行采集, 用于模型验证. 在此基础上, 对精密仪器的振动进行评估并提出相应的减振措施. 结果表明, 既有振动主频在 10~20 Hz, 在该频段存在振动超限风险; 列车高速会车会导致精密仪器无法正常工作. 加装减振垫可以有效缓解列车引起的高频振动(40~80 Hz)影响. 列车振动与既有振动叠加后, 高层振动以 10~20 Hz 为主, 建议在精密仪器处采取减振措施. | Vibration impact and reduction measures of high-speed trains meeting on precision instruments in adjacent buildings | 10.1007/s11771-023-5441-2 |
2023-09-01 | As a main source of energy dissipation, thermoelastic damping (TED) cannot be ignored in designing resonators with high-quality factor. However, due to the size-dependent effect and the thermal relaxation, the TED models formulated in the classical theory are no longer able to accurately estimate the energy dissipation in the micro-/nano-resonators. To fill theses gaps, the present work aims at developing a new TED model for micro-plate resonators based on the modified couple stress theory incorporating memory-dependent derivative heat conduction model. The corresponding governing equations are derived, and the analytical solution for the TED is obtained. In order to discover the variation law of TED of micro-plate resonators, the numerical results corresponding to different materials and different theories are illustrated and compared. In calculation, the effects of the material parameters, the boundary conditions, the length scale parameters and the length on the peak value as well as the critical thickness of TED are further studied. It is expected that this novel model may provide a theoretical basis for designing high-performance micro-plate resonators under complex working conditions. | Investigation on thermoelastic damping of micro-plate resonators based on the modified couple stress theory incorporating the memory-dependent derivative heat transfer model | 10.1007/s00419-023-02450-z |
2023-09-01 | This paper aims to explore a theoretical analysis method, quasi-conservative stochastic averaging, to study the stochastic response and harvesting performance of a class of bistable vibration energy harvesting (VEH) systems with inelastic bilateral stoppers subject to colored noise excitation. The Hertz-damp impact model describes the local deformation and dissipation of the energy as the system collides with obstacles. The first step is to give the variable transformation according to the equilibrium point of the bistable VEH system to transform the proposed system into two first-order stochastic differential equations. After that, by analyzing the relationship between the system’s total energy and the potential energy of the obstacle position, we derive the piecewise smooth average It $$\hat{\textrm{o}}$$ o ^ equation using the quasi-conservative stochastic averaging method. The analytical expressions of the system response, mean square output voltage, root mean square voltage, average output power and power conversion efficiency are theoretically revealed by solving the corresponding Fokker–Planck–Kolmogorov equation. Finally, an illustrated example is given, and the effects of the physical parameters on the system response and energy harvesting performance are analysed. In addition, we also obtain the relationship between noise intensity and optimal power conversion efficiency. All results are verified using Monte Carlo simulations. | Stochastic analysis of vibro-impact bistable energy harvester system under colored noise | 10.1007/s11071-023-08773-4 |
2023-09-01 | An additively manufactured particle damper (AMPD) is a novel particle damper fabricated by deliberately leaving unfused powder inside the structure during the laser powder bed fusion (LPBF) process. It retains the advantages of a conventional particle damper, while yielding unique merits. However, the damping mechanism and performance of AMPD are still unclear owing to insufficient experimental and simulation analyses. This work focused on experimentally and numerically exploring the damping capacity of AMPDs at three different frequencies (200, 350, and 500 Hz) and an acceleration range of 150–300 m/s^2. Two AMPDs with different numbers of unit-cells (64 and 27) were manufactured using LPBF with 316 L stainless steel. The complex power method is used to measure the energy dissipation of the AMPD in a straightforward manner. A numerical method based on the discrete element model of a previous study was proposed to predict energy dissipation in the simulation model. The developed numerical method was validated by comparing it with experimental data which showed good agreement. The influence of excitation frequency, excitation amplitude, and cavity size on the damping mechanism and performance of the AMPD was investigated using experimental and simulation methods. The results showed that the AMPDs had the highest damping performance at an excitation frequency of 500 Hz, and the motion mode of the internal particles was affected by the excitation intensity and cavity size, which play an essential role in the damping performance of AMPDs. | Numerical and experimental analysis in the energy dissipation of additively-manufactured particle dampers based on complex power method | 10.1007/s40571-022-00540-3 |
2023-08-31 | The focus of the present work is the (theoretical) approximation of a solution of the p ( x )-Poisson equation. To devise an iterative solver with guaranteed convergence, we will consider a relaxation of the original problem in terms of a truncation of the nonlinearity from below and from above by using a pair of positive cut-off parameters. We will then verify that, for any such pair, a damped Kačanov scheme generates a sequence converging to a solution of the relaxed equation. Subsequently, it will be shown that the solutions of the relaxed problems converge to the solution of the original problem in the discrete setting. Finally, the discrete solutions of the unrelaxed problem converge to the continuous solution. Our work will finally be rounded up with some numerical experiments that underline the analytical findings. | A damped Kačanov scheme for the numerical solution of a relaxed p(x)-Poisson equation | 10.1007/s42985-023-00259-7 |
2023-08-26 | The reproducing kernel particle method (RKPM) is a widely used meshless method that has been extensively applied in numerical analysis. The drawback of RKPM is that when different kernel functions are chosen during the computation process, there are different calculation accuracy, and significant discreteness. To address this issue, the radial basis function is introduced to RKPM, and the radial basis reproducing kernel particle method (RB-RKPM) is proposed. The negative impacts of different kernel functions on calculation accuracy can be eliminated by RB-RKPM, which possesses some advantages, such as good convergence, high computational accuracy and efficiency. Furthermore, the RB-RKPM is applied to the damped elastic dynamics problems (DEDPs), the governing equations for the DEDPs are derived based on the weak integral formulation, and the time is integrated by using the Newmark-linear acceleration method. Finally, the correctness of the proposed method in analyzing the DEDPs is verified through numerical examples. | Radial Basis Reproducing Kernel Particle Method for Damped Elastic Dynamics Problems | 10.1007/s40997-023-00701-6 |
2023-08-24 | Purpose This paper presents the design, development, and performance analysis of a Two-Degree-of-Freedom Vibration-Based Electromagnetic Energy Harvester (TDOF VBEEH). The purpose is to enhance power output and widen the operational frequency band of the harvester. In the literature, various techniques such as mechanical amplification, resonance tuning, and nonlinear oscillations etc., have been explored. The proposed TDOF VBEEH incorporates a mechanical amplifier in series with a traditional Single-Degree-of-Freedom (SDOF) VBEEH. Methods The paper derives an analytical expression for the average power output of the TDOF VBEEH based on the principles established by Tang and Zuo. The effects of mass ratio, electrical damping ratio, and tuning ratio on the power output and effective operational frequency band of TDOF VBEEH have been studied to provide design guidelines for TDOF VBEEH. Also, the experimental analysis is conducted to examine the effects of a purely resistive load and mass ratio on the average harvested power of the TDOF VBEEH. The study utilizes a specially designed setup for TDOF VBEEH. Furthermore, by employing the method of surface plots and contour diagrams, the global optimum values of power output for the TDOF VBEEH under various electrical damping ratios and normalized excitation frequencies have been determined. Results The results demonstrate that the appropriate selection of mass ratio, tuning ratio, and electrical damping ratio can enhance the power output and widen the effective operational frequency band of the TDOF VBEEH. Notably, the maximum harvested power is achieved when the electrical circuit connected to the harvester has a resistive load of approximately 1500 Ω, which aligns with the internal resistance of the copper coil. The results show that the increased power output is attainable over a widened operational excitation frequency band compared to the traditional Single-Degree-of-Freedom (SDOF) VBEEH. From the comparison of the experimental and analytical results, it is seen that the TDOF VBEEH performs better than the SDOF VBEEH when the parameters are properly chosen. Conclusion These findings highlight the superior performance and potential of TDOF VBEEHs over SDOF VBEEHs, emphasizing the importance of parameter selection in maximizing power output and widening the operational frequency band. Also, the findings offer valuable design guidelines for selecting system parameters when developing TDOF VBEEHs to power small electronic devices. | Means of Enhancing the Power Output and Widening the Operational Frequency Band of Vibration-Based Electromagnetic Energy Harvester | 10.1007/s42417-023-01101-5 |
2023-08-17 | In this paper, we study the long-time dynamics for the nonautonomous wave equation with nonlocal weak damping and super-cubic nonlinearity in a bounded smooth domain of $$\mathbb {R}^3.$$ R 3 . Based on the Strichartz estimates for the case of bounded domains, we first prove the global well-posedness of the Shatah–Struwe solutions. Then we establish the the concept of uniform $$\varphi $$ φ -attractor and verify that the family of Shatah–Struwe solution processes has a uniform polynomial attractor, which is a compact uniformly attracting set and attracts any bounded subsets at a polynomial speed. | Long-Time Dynamics of the Wave Equation with Nonlocal Weak Damping and Super-Cubic Nonlinearity in 3-D Domains, Part II: Nonautonomous Case | 10.1007/s00245-023-10043-z |
2023-08-14 | Of concern is the energy decay property of solutions to wave equations with time-dependent damping. A reasonable class of damping coefficients for the framework of weighted energy methods is proposed, which contains not only the model of “effective” damping $$(1+t)^{-\beta }$$ ( 1 + t ) - β $$(-1\le \beta <1)$$ ( - 1 ≤ β < 1 ) , but also non-differentiable functions with a suitable behavior at $$t\rightarrow \infty $$ t → ∞ . As an application of the weighted energy estimate, global existence for the corresponding semilinear wave equation is discussed. | Weighted energy method for semilinear wave equations with time-dependent damping | 10.1007/s00028-023-00908-9 |
2023-08-12 | This article discusses an alternative way of evaluating the roll damping coefficient and natural frequency of a floating body. Experimental values are required for the data assimilation process. In this study rather than performing an actual experiment, pseudo-experimental values were derived through computational fluid dynamics (CFD). An extended Kalman filtering (EKF) technique with CFD for estimation of the equivalent linear damping coefficient and natural frequency of free roll decay motion was determined. For the free roll decay motion, the roll angle values obtained from the CFD simulations were given as input to the EKF, and the parameter estimation was performed. CFD analyses were performed to simulate free roll decay by using the Unsteady Reynolds-Averaged Navier–Stokes (URANS) approach with success. Using calculated data of roll response inverse analyses were carried out to identify roll damping and natural frequency for the 3-D floating body. The effects of uncertainty in the process and measurement noise statistics on performance were examined. The measured residual was compared to the theoretical estimate for filtering correctness. It is found that the variation of the damping coefficient and natural frequency with time was determined by EKF within very small error limits. | Estimation of ship roll damping and natural frequency using an extended Kalman filter applied to URANS output | 10.1007/s12046-023-02232-x |
2023-08-12 | In the vehicle suspension system field, smart materials are contributing their top-notch characteristics in building up magneto-rheological (MR) dampers. Though MR fluid has good characteristics to absorb shock, sedimentation problem is a significant issue while performing an MR damper. MR grease eliminates the sedimentation problem and can be used a MR damper in vehicle suspensions system, in vibration control of large structures, biomedical, etc. This paper aims to conduct a numerical study based on coupled FEA and CFD and evaluate the damping force induced in the MR grease gap region for a different input current ranging from 0.1A to 0.4A at frequencies 1 Hz and 2 Hz. ANSYS CFX solver has been used with SST k-ω turbulence model and ‘Herschel-Bulkley’ model for the numerical simulation. At first the simulation approach/model was validated with the experimental results. Initially, the simulation was assumed to be a laminar flow, but as the piston of the damper moves for the stroke, the flow becomes turbulent. Without Shear Stress Transport (SST) turbulence model the simulation was unable to capture laminar to turbulent transition and suddenly stopped when the transition occurred without writing any result. Also, a comparison analysis between ‘Herschel-Bulkley’ fluid model and ‘Bingham’ model was done to prove that only the ‘Herschel-Bulkley’ fluid model can capture the rectangular curve of the damping force for MR Grease as it is stated by the authors who validated the experimental results for MR Grease. No numerical simulation has been found for characterizing MR Grease damper. The FEA has been used to determine the fluid properties due to various currents and frequencies, which were input for the CFD analysis to determine the damping forces and Quasi-static analysis. This simulation model could capture the hysteresis behavior correctly also. | An FEA and CFD coupled numerical analysis approach for characterizing magneto-rheological (MR) grease damper | 10.1007/s12046-023-02196-y |
2023-08-11 | In the context of damped second order linear dynamical systems, we study the asymptotic behavior of a time discretization of a slowly damped differential equation. We prove that this discretization can be constructed by means of a variable time step that gives rise to the same asymptotic behaviour as for the system in continuous time. | Asymptotic Behavior of an Adapted Implicit Discretization of Slowly Damped Second Order Dynamical Systems | 10.1007/s00245-023-10027-z |
2023-08-02 | In this study, an outdoor automated guided vehicle (AGV) with an absorbent vibration system was designed, and a 7-degrees of freedom (DOF) model was established for this system. We built a simulation model in Simulink software that serves as the 7-DOF model. The three indicators for evaluating the stability of the AGV are simulated and analyzed in the simulation model when one side of the AGV crosses a sloping obstacle. A vibration absorptive property experiment of the AGV was performed, and the average maximum displacement of the AGV sprung mass was 13.42 mm. The maximum predicted amplitude of sprung mass in the Simulink simulation model is 12.8 mm, and its prediction error is about 4.6%. The prediction accuracy of the Simulink model is higher than that of the Adams simulation method. According to the efficiency comparison experiment of the AGV obstacle crossing simulation method, the obstacle crossing simulation method based on Simulink designed in this paper saves about 28% of the working time of the designer compared with the traditional Adams simulation method, which provides a new idea for the simulation method of outdoor AGV obstacle crossing before the 3D model is established. | Dynamics model and simulation of outdoor AGV obstacle crossing without 3D model | 10.1007/s00170-023-12056-y |
2023-08-01 | Previous earthquakes have been shown that the direction of the bridge relative to the direction of the faulting might have a significant effect on its vulnerability. So, in some cases it is necessary to pay special attention to control the behavior of the bridge at least in one direction. In this study, the reduction of the longitudinal displacement in a suspension bridge was investigated using a tuned mass damper (TMD). At first, the performance of TMD for reducing the longitudinal response of Vincent Thomas suspension bridge against the near- and far-field earthquake records were examined. Then, optimum parameters for TMD were determined while various span lengths for the bridge were considered and different earthquake records were induced to the analytical models. Regression analysis was performed on the results to obtain simple formulas to facilitate the determination of optimum TMD parameters for different bridges with different proportions of lateral spans to mid span lengths. The efficiency of the formulations was confirmed by evaluating the seismic response of three sample bridges. The formulas indicated that the optimum angular frequency and damping ratio of TMD relatively increases as the span lengths ratio is increased. The results also showed that TMD damper is more efficient against the near-field records than the far-field ones so that the longitudinal displacement has decreased by over 40% against near-field records and 27% against far-field records. It was observed that the optimum damping ratio of TMD against the near field earthquakes varies from 0.042 to 0.092. | Optimal design of TMDs to reduce the longitudinal seismic response of the suspension bridges | 10.1007/s40435-022-01062-9 |
2023-08-01 | Abstract The worst disturbance problem for an oscillator with quadratic-law damping is stated. The role of the disturbance is played by an external force applied to the oscillator. It is assumed that this force acts in one direction, that the integral of this force with respect to time is given, and that at the initial instant of time the oscillator is resting in the equilibrium position. It is required to find a time history of the disturbing force that maximizes the maximum (with respect to time) of the absolute value of the displacement of the oscillator’s body from the equilibrium position. The worst disturbance from among rectangular pulses under which the disturbing force is constant on the initial time interval and is equal to zero outside of this interval is found and investigated. | The Worst Disturbance of an Oscillator with Quadratic-Law Damping by Means of a Force with a Given Integral | 10.1134/S1028335823080013 |
2023-08-01 | Abstract The task of angular orientation and stabilization of a space structure during its assembly in orbit is solved. The structure includes elastic elements that are installed during the assembly process. The elastic elements of the structure have no sensors to obtain information about their deformation parameters. Control algorithms are proposed to ensure the stability of the angular motion of the structure. A nonlinear extended Kalman filter is used to obtain the necessary information. A joint estimation algorithm for the coordinates of the angular motion of the considered mechanical system and the coordinates of the elastic vibration tones, as well as an algorithm for the identification of their unobservable parameters are developed. The results of mathematical modeling of a variant of the mechanical system of a space structure are presented, which confirm the operability and efficiency of the developed algorithms for estimating coordinates and parameters. | Angular Motion Control of a Large Space Structure with Elastic Elements | 10.1134/S0005117923080076 |
2023-08-01 | We show that the damping of plasmons in metallic nanoparticles highly exceeds that caused by scattering of electrons on defects, phonons, and other electrons and on boundaries of particles. The radiation losses in far-field zone due to the Lorentz friction is especially high at nanometre scale of metal confinement (e.g. attains the maximum at ca. 100 nm diameter of particle, Au in vacuum). This causes a different e-m response of such size structures in comparison to conventional solution of Maxwell-Fresnel equations using the bulk dielectric function for metal. The strong discrepancy occurs also if plasmons are coupled in near-field zone to nearby-located absorbing medium, e.g. semiconductor substrate. This coupling cannot be accounted for by classical electrodynamic treatment (e.g. by numerical solution of Maxwell equations by finite element method for differential equation solution) and needs the application of quantum Fermi golden rule to estimate plasmon damping and related modifications of dielectric functions both of metallic nanoparticles and of absorbing medium. Similarly, the perfect cancellation of radiative losses of plasmon-polaritons in metallic nano-chains is beyond classical Maxwell equation modelling, as it reveals the perfect vanishing of Lorentz friction losses in chain segments by radiative contribution from other segments in near-, medium- and far-field zones. This demonstrates that nano-plasmonic effects cannot be reliably numerically modelled using material parameters from conventional packets referred to optical constants measured in bulk. | On Damping of Plasmons and Plasmon-Polaritons in Metallic Nanostructures and Its Influence onto Numerical Simulations | 10.1007/s11468-023-01838-5 |
2023-08-01 | The open viscous damper installation configuration is a novel configuration that compensates for the vision obstruction present in conventional configurations and meets the artistic and serviceability requirements of buildings. The additional damping ratio of a structure is an important parameter in the design of viscous dampers; therefore, when it is calculated using the strain energy method, its results are directly affected by the calculation accuracy of the displacement amplification factor. However, the existing calculation formula for the displacement magnification factor of open viscous damper installation configurations is derived based on the structural shear deformation, whereas the deformation mode of multi-rise and high-rise buildings is generally of the shear-bending type, resulting in inaccurate calculation results. To address this problem, the calculation formulas for the displacement magnification factor of an open viscous damper installation configuration involving a single-story structure in the middle story of a multi-rise structure were derived considering the structural shear-bending deformation. Parametric analysis was performed based on the formula for the middle story of the multi-rise structure. In addition, the applicability of the formula for calculating the displacement magnification factor of general multi-rise and high-rise structures was verified by calculating the additional damping ratio of the structure using SAP2000. This study indicates that the displacement magnification factor acquired based on the shear-bending deformation formula exhibits better calculation accuracy for multi-rise and high-rise structures. | Calculation of the Displacement Magnification Factor for Open Viscous Damper Installation Configurations Considering the Structural Shear-Bending Deformation | 10.1007/s40996-023-01038-5 |
2023-08-01 | Clarifying how radial gap affects the vibration characteristic of a disc-like structure is of importance in engineering applications, such as in evaluating the operational stability of a runner of a pump turbine. In the present investigation, the runner is simplified as a disc, and a physical experiment is designed on it with variable radial gaps to measure the vibration characteristics, especially by considering rotation. Two frequency peaks for the diametrical mode are generated due to the rotation, and those with lower and higher frequencies are defined as positive and negative modes, respectively. The frequency difference between positive and negative modes increases linearly with the increasing rotating speed, and a linear function is captured to describe the relationship between natural frequency and rotating speed. Regarding the radial gap, its increase causes a slight increase in the natural frequencies but results in a significant reduction in the hydrodynamic damping ratio. Especially in the smaller radial gap conditions, such as when the relative radial gap increases from 0.67% to 3.3%, the reduction in hydrodynamic damping ratio reaches 31.52%. From the perspective of suppressing the resonance amplitude, reducing the radial gap of a runner is recommended due to the mechanism of increasing hydrodynamic damping. | How the radial gap affects the runner’s hydrodynamic damping characteristic of a pump-turbine: A physical experiment on a rotating disc | 10.1007/s42241-023-0058-3 |
2023-08-01 | One of the major challenges that countries all over the world are dealing with is their generated waste. Most of the research in the past few decades also focuses on the bulk utilization of this existing waste for different applications. This study focuses on the utilization of a part of municipal solid waste, i.e., MSW fines (particle size < 4.75 mm) reinforced with segregated fibers from the waste itself. The research investigates the influence of waste fiber content (FC) (0, 0.5, 1, 2, 4, 8, and 10%) on the dynamic parameters of MSW fines. The results revealed that the fiber inclusion remarkably influenced the shear strength parameters under monotonic loading and attained their optimum values when 8% of fiber content was applied. This study shows no significant improvements in dynamic shear modulus (G) of fiber-reinforced MSW fines under cyclic loading in the case of both unconsolidated undrained and consolidated undrained tests conducted on a cyclic triaxial test system. However, a significant improvement was noticed in the case of damping ratio (D) with FC. Further, a r_u (excess pore water pressure ratio) model for fiber-reinforced MSW fines is suggested to predict the behavior of r_u, which depends on two parameters, namely FC and γ (shear strain). | Study on cyclic strength and pore water pressure response of fiber-reinforced municipal solid waste (MSW) fines | 10.1007/s11440-023-01818-3 |
2023-08-01 | Abstract The In this paper, we study the forced flexural vibrations caused by time-harmonic concentrated loads on a transversely isotropic thin rectangular plate (TRP) with a memory-dependent derivative (MDD).This study not only considered the size effect but also studied the memory, mechanical, and thermal field effects. If only one of them is studied, one-sided conclusions may result. we develop a closed-form mathematical model for the thin plate based on the Green–Naghdi (GN) III theory and non-local generalized Kirchhoff’s love plate theory of thermoelasticity using MDD. With the double finite Fourier transform technique, 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. We have demonstrated the effectiveness of the MDD kernel function on the resultant quantities. | Forced Flexural Vibrations due to Time-Harmonic Source in a Thin Nonlocal Rectangular Plate with Memory-Dependent Derivative | 10.3103/S0025654423600538 |
2023-08-01 | Powder Bed Fusion (PBF) enables the production of complex geometries which offer the opportunity to manufacture lightweight, stiffness-optimised or integrally designed components. Although these properties are usually advantageous for the performance in many applications, they pose disadvantages under vibration as they lead to low damped components. These are prone to high vibration amplitudes which result in higher sound radiation and a reduced lifetime. Particle damping can counteract these disadvantages. By including cavities during the design process, unmelted powder remains inside the component after its production. This powder dissipates energy under vibration by inelastic impacts and friction in particle-particle or particle-wall-interactions, increasing the damping characteristics of the component. In this work, additively manufactured AlSi10Mg specimens with cavities are investigated with respect to their damping characteristics by experimental modal analysis. The focus of the investigation is on thin and flat cavities that can be easily integrated into components without adapting the external geometry. The damping characteristics in dependence on excitation amplitude and mode are quantified. The extent to which settling effects of the powder during shaking influence the damping is analysed. The vibration of the specimens is forced by an electrodynamic shaker and their response is measured contactlessly via Scanning Laser Doppler Vibrometry (SLDV). A damping effect of up to 564% depending on the mode, excitation amplitude and specimen can be achieved. In addition, a significant settling effect of the powder which hampers the damping effect is identified by CT scans and modal analysis. | Forced-response characterization of PBF-LB/AlSi10Mg particle dampers with thin and flat cavities | 10.1007/s40964-023-00428-5 |
2023-08-01 | Abstract We designed and tested experimentally an acoustooptical modulator on a TeO_2 crystal for the frequency range 200–570 MHz with acoustic mode conversion upon reflection from the skew face of the acoustooptical cell. The modulator operated with a collimated light beam of diameter ~ 0.8 mm without beam focusing. We observed a sharp (by several times) reversible decrease of diffraction efficiency for a sequence of control signal pulses for f > 250 MHz in time T _1 = 3–20 μs after the beginning of diffraction. The temporal decay front was shorter than 0.5 μs. The value of T _1 depends on the control signal parameters. We determined the upper boundaries of the modulator frequency range in CW mode and in the regime of control signal pulse sequence at 360 and 570 MHz, respectively. We measured damping coefficients of the transverse slow acoustic mode in TeO_2 along the direction of its wavevector with a slope of 16.80° to the [110] axis: σ(360 MHz) = 1.8 ± 0.4 Np/cm and σ(570 MHz) = 5.5 ± 0.8 Np/cm. According to estimate, the exponent in frequency dependence σ( f ) ~ f ^ n was 2.4 ± 0.4. The results were used for investigating the potentialities and peculiarities of experiment on backscattering in TeO_2. | High-Frequency Acoustooptical Modulator with Acoustic Mode Conversion | 10.3103/S1068335623140051 |
2023-08-01 | Torsional vibration is prevalent in rotating mechanical systems such as powertrain transmission. It is a hot spot in current torsional vibration control research to effectively suppress torsional vibration of the system by implementing adaptive torsional dampers with adjustable parameters. The current research focuses on the variable damping torsional vibration absorber, while the investigation on variable stiffness torsional vibration absorber remains at the theoretical stage. With this premise, a transmission system with a novel magneto-rheological variable stiffness and damping torsional vibration absorber (MR-VSDTVB) is proposed. MR-VSDTVB with sequential adjustment of torsional damping and stiffness parameters is developed. Its aggregate dynamic output characteristics of stiffness and damping are tested. To describe the nonlinear output characteristics with coupled multiple control parameters of MR-VSDTVB and the subsequent control, a GA-BP neural network model and a hierarchical inverse model are adopted. To validate the feasibility of the transmission system with MR-VSDTVB, a dynamic model of the transmission system with MR-VSDTVB is constructed and simplified, and then the numerical simulation analysis and experimental tests are carried out. The output performances of the MR semi-active system with various traditional semi-active control strategies show that the transmission system with the proposed MR-VSDTVB can suppress torsional vibration effectively. | Magneto-rheological variable damping and variable stiffness torsional vibration control of powertrain transmission | 10.1007/s12206-023-0705-1 |
2023-08-01 | A vehicle’s solenoid valve-actuated shock (SVSA) absorber is of wide interest because of its adjustable damping characteristics. The proportional solenoid valve is a pivotal component for commanding damping force, but the research on its model principle still needs to be improved. Therefore, this research aimed to establish an accurate model of the proportional solenoid valve composed of the pilot valve and relief valve. In the pilot valve, we proposed a valve spool structure using a two-stage combined throttling groove to control flow accurately. Then, the dynamic equation of the spool was established, and it is also considered that the magnetic saturation of soft magnetic materials impacts electromagnetic force. The flow force in the dynamic equation was numerically solved by the CFD method. The flow rate in the relief valve was analyzed from the deformation of the lamination valves and main valve plate through the small deflections thin plate theory. Then, the SVSA bench test was carried out. The results show good agreement between the test and calculation, and the maximum error is within 9 %. It is indicated that the model of the SVSA equipped with the proportional solenoid valve has high accuracy. | Modeling and testing for continuously adjustable damping shock absorber equipped with proportional solenoid valve | 10.1007/s12206-023-0701-5 |
2023-08-01 | The characteristics of a dissipative dust ion acoustic soliton in a collisional dusty plasma consisting of ions, superthermal electrons, and negatively charged static dust particles are analyzed. The damped Korteweg-de Vries (DKdV) equation is obtained by applying the reductive perturbation technique to the fluid equations of the considered plasma model. The DKdV equation is not integrable; therefore, the homotopy analysis method is used to obtain its numerical solution, using the solution of the standard KdV equation at time zero as an initial approximation. The obtained solution is compared with one of the existing solutions, which was obtained considering the weakness of the collisional frequency. It is noticed that there is a good match between both solutions for small values of the collisional frequency, and a significant difference is observed for higher values of the collisional frequency. The effects of the ion-to-electron temperature ratio ( $$\sigma$$ σ ), dust concentration ( $$\mu$$ μ ), superthermality index ( $$\kappa$$ κ ), and ion-neutral collisional frequency ( $$\nu _{in0}$$ ν i n 0 ) on the obtained solitons solution are also investigated. | Managing strong ion-neutral collision in dusty plasmas | 10.1007/s12648-023-02635-w |
2023-07-28 | The stochastic resonance (SR) phenomenon for a second-order fractional-damping nonlinear system driven by multiplicative colored noise and additive white noise is investigated. Applying generalized harmonic function technique, based on detailed balance condition and two-state theory, the output spectral amplification (SPA) for the system is obtained. It is found that double SR phenomenon takes place when the SPA varies with the fractional exponent and with the damping coefficient. One resonance peak appears when the SPA changes with the correlation time of the multiplicative noise. Traditional SR can be observed on the curves of the SPA versus the strength of the multiplicative noise and that of the additive noise. | Effect of fractional-damping and multiplicative colored noise on stochastic resonance for a second-order nonlinear system | 10.1007/s10773-023-05430-9 |
2023-07-22 | Cementitious coarse-grained soils are widely used as filling materials in infrastructure projects such as high-speed railway subgrades, earth dams, and highway bases, due to their excellent strength, stiffness, and stability performances. This study conducted unconfined compression tests on fine-grained soils first to investigate the optimal mixing ratio of the raw material (metakaolin) and alkali activator (composed of quicklime (CaO) and sodium bicarbonate (NaHCO_3)) for comprising the geopolymer binder. Then, the dynamic characteristics of geopolymer-stabilized coarse-grained soils with a relatively fixed dosage of the geopolymer binder were studied by large-scale dynamic triaxial tests. The influences of rock-block content and confining pressure on the dynamic parameters of the geopolymer-stabilized coarse-grained soils were further discussed. The results indicated that the ideal mixing ratio of metakaolin, CaO, and NaHCO_3 for preparing the geopolymer binder was 4:1:1, and their optimal mixing ratio for fine-grained soil stabilization was 15% by the weight of dry soil. The maximum dynamic shear modulus of geopolymer-stabilized coarse-grained soils had an approximately linear relationship with the rock-block content and a nonlinear relationship with the effective confining pressure. With the shear strain being normalized, the dynamic shear modulus ratios of geopolymer-stabilized coarse-grained soils were distributed in a narrow band with low dispersion, while the damping ratio increased with the shear strain and showed a relatively high dispersion in values. The dynamic shear modulus ratio and normalized damping ratio of geopolymer-stabilized coarse-grained soils could be described by functions of the normalized shear strain amplitude. The results of this study could provide a design parameter basis for the application and popularization of similar geopolymer-stabilized coarse-grained soils in engineering practices. | Experimental study on static and dynamic characteristics of geopolymer-stabilized coarse-grained soils | 10.1007/s11440-023-01876-7 |
2023-07-19 | Purpose In response to the difficulty of dynamic vibration absorber (DVA) to realize the broadband vibration reduction of large marine mechanical equipment, an air spring dynamic vibration absorber (ASDVA) was proposed, then its damping and vibration absorption performance were studied. Methods A piecewise integral method was used to identify the damping, and the modal tests were carried out to determine the vibration absorption frequency. Subsequently, the effects of the air pressure and the orifice opening on the vibration absorption frequency and damping were analyzed. A single-degree-of-freedom (SDOF) system model was established to analyze the influence of the damping on the vibration absorption performance, and then relevant vibration absorption performance tests were carried out. Results The piecewise integral method is accurate in identifying the damping. The changes of the air pressure and the orifice opening affect not only the vibration absorption frequency, but also the damping. In particular, the damping reaches a maximum value at a certain orifice opening, and the vibration absorption frequency will jump from the low frequency to the higher frequency. The increase of the damping reduces the vibration absorption effect, but broadens the vibration absorption bandwidth. Conclusion By properly adjusting the air pressure and the orifice opening, the ASDVA can obtain appropriate vibration absorption frequency and damping, thus achieving good broadband vibration reduction effect. | Research on Damping and Vibration Absorption Performance of Air Spring Dynamic Vibration Absorber | 10.1007/s42417-023-01083-4 |
2023-07-19 | The dispersion relation and Landau damping rate of dust-acoustic waves (DAWs) are studied by the incorporation of Poison–Vlasov model of the kinetic theory of plasmas. The real and imaginary frequencies of DAWs are obtained in a three-component plasma i.e., electrons, ions and dust grains. The electrons are taken as hybrid non-thermal Vasyliunas–Cairns distributed and in limiting cases as kappa and Cairns distributed as well, while the ions and dust are kept Maxwellian. The findings reveal that the simultaneous presence of two non-thermality parameters (i.e., $$\alpha $$ α and $$\kappa $$ κ ) have a remarkable impact on the dispersion and damping rates of DAWs as compared to the sole presence of any non-thermality parameter and also in the case of thermal electrons. It is also presented that the real and imaginary frequencies of DAWs are significantly influenced by the other important parameters, such as electron to ion temperature and density ratios. This work has notable significance in the understanding of important constituents of space plasmas i.e., thermal and non-thermal dusty plasmas in various environments of space plasmas, where the mixed particle distributions are observed. | On dispersion and damping rates of dust-acoustic waves in hybrid non-thermal Vasyliunas–Cairns distributed plasmas | 10.1007/s12036-023-09963-7 |
2023-07-17 | Purpose One of the key challenges in the research of phononic crystals is achieving small-size control of large wavelengths, which means obtaining low-frequency band gaps with relatively small lattice dimensions. Previous studies have mostly been unsatisfactory in this regard. To obtain lower starting frequencies and more satisfactory band gap widths, this work presents a novel design for a phononic crystal structure. Design Approach The proposed phononic crystal consists of a silicon rubber connecting plate, an epoxy resin substrate, and tungsten metal cone scatterers. Through finite element method (FEM) calculations and analysis, we have successfully achieved an ultrawide band gap. To delve further into the origin of the ultra-wideband gap in a newly conceived phononic crystal, the vibrational modes of this crystal were carefully studied. Findings This work has successfully achieved an ultrawide band gap with a width ranging from 122.47 to 4360.2 in the case of a lattice constant of a = 8.5 mm. It was found that the low-frequency ultra-wideband gap cannot be obtained without the presence of silicone rubber. Furthermore, an equivalent spring model was developed, and the accuracy of this model was successfully validated through meticulous calculations. At last, It is found that d1, d4, h1, and h3 have the most pronounced effect on the ultrawide bandgap, and the intrinsic reason is the fact that they determine the geometric structure of the silicone rubber connection plate. Research Limitations/implications Due to the chosen research method of finite element analysis, the study results may vary depending on the different mesh discretizations, but this type of error is small and can be ignored. Practical Implications This work provides a new design solution for phononic crystal miniaturization. Originality/value Compared with previous reports, the new phonon crystals designed in this paper have smaller size, lower starting frequency, and wider band gap. | Low-Frequency Ultrawide Band Gap Study of Symmetric Conical Scatterer Phononic Crystal | 10.1007/s42417-023-01077-2 |
2023-07-17 | In this paper, a multi-objective optimization process is used to design and optimize a semi-active hybrid electromagnetic suspension system. To control the performance of the vehicle, the magnetorheological (MR) damper modeled by Bouc–Wen model is utilized in semi-active suspension that its energy is supplied from harvested energy by electromagnetic generator. The performance of the suspension system is evaluated by ride comfort, road holding and absolute regenerated power criteria. A two-degree of freedom (2-DOF) quarter car model included semi-active suspension system and electromagnetic generator is used to analyze the system. To improve the performance of the vehicle, the genetic algorithm (GA) is used to solve the multi-parameter optimization problem. The Pareto front results obtained from GA show that the ride comfort and handling stability are two conflicting design criteria. To compare the optimized cases with the not-optimized suspension system the response of the system in time and frequency domains is employed. The results show that for the overall optimized case the absolute regenerative power and ride comfort can be improved significantly compared with the not-optimized case. Also, according to the frequency responses, only about the first natural frequency of the vehicle body, the ride comfort quality decreases for the overall optimized case. | Multiobjective optimization for semi-active electromagnetic vehicle suspensions | 10.1007/s40430-023-04347-y |
2023-07-17 | Purpose In the present research paper, a dual annular duct (DAD) MR damper is considered, which is having a primary flow duct between the cylinder-piston head and the second one through the piston head. DAD damper is a combined mode model consisting of two annular gaps where the outer one experiences relative shearing motion and the inner one behaves as a fixed wall flow type. Methods An analytical model is derived for DAD MR Damper. A computational approach has been adopted to compute the dynamic characteristics of the damper. The analytical approach is done by interconnecting CFD and FEA. The magnitude and profile of magnetic flux force have been investigated through magnetostatic analysis in ANSYS. These values are employed in determining the dynamic viscosity of the MR fluid using an empirical model of the MR fluid. Results The credibility of the results is examined by comparing them with the experimental values of the first case of MR damper. Also, the computational results are verified with analytical results for all models. On examining the results from the simulations of all the models, it can be concluded that higher damping can be achieved by combining more than one mode of operation. | Characterization of Dual Annular Duct MR Damper with Numerical and Computational Approach | 10.1007/s42417-023-01073-6 |
2023-07-17 | Introduction The impact of vibrations excited by incident sound fields has become a major concern today, due to its influence on the performance of systems and installations. Vibrations have the potential to cause considerable dynamic disturbances and instabilities, which can lead to significant structural and functional damage. Consequently, it is crucial to control vibration phenomena right from the system design phase. To solve the problem of vibration, it is sometimes possible to increase the damping level of the structure by incorporating a damping treatment. Objective The aim of this paper is to present a simplified numerical approach to study the vibro-acoustic responses of structures with PCLD “Passive Constrained Layer Damping” treatment in the thermal environment, taking into account the frequency and temperature dependence of the different viscoelastic behavior laws. Material and Methods The modal stability procedure MSP is based on the finite element method in order to discretize and formulate the equation of motion. The asymptotic numerical method “ANM” is applied to approximate the solution of complex eigenvalue problems and construct the modal basis. The variability of the frequency responses is evaluated by a Monte Carlo simulation (MCS) combined with MSP and ANM to evaluate the stochastic behavior of a sandwich beam with random properties. Results The comparison with the direct frequency responses (DFR) demonstrates that the results are highly satisfactory in terms of the validity of the present MSP approach. A comparative study of viscoelastic behavior models was carried out to evaluate their damping properties provided to the structure. The viscoelastic materials provide significant damping particularly for amplitudes corresponding to the high frequencies. This is in contrast to the responses obtained without the viscoelastic layer. Conclusion The obtained results show the importance of viscoelastic damping, which has a significant effect on the vibro-acoustic behavior, implying the improvement of the damping of the structure, especially for large frequencies and high temperatures. | Vibroacoustic Analysis in the Thermal Environment of PCLD Sandwich Beams with Frequency and Temperature Dependent Viscoelastic Cores | 10.1007/s42417-023-01065-6 |
2023-07-13 | In this paper, we investigate the initial boundary value problem of the following nonlinear extensible beam equation with nonlinear damping term $$\begin{aligned} u_{t t}+\Delta ^2 u-M\left( \Vert \nabla u\Vert ^2\right) \Delta u-\Delta u_t+\left| u_t\right| ^{r-1} u_t=|u|^{p-1} u \end{aligned}$$ u tt + Δ 2 u - M ‖ ∇ u ‖ 2 Δ u - Δ u t + u t r - 1 u t = | u | p - 1 u which was considered by Yang et al. (Adv Nonlinear Stud 22:436–468, 2022). We consider the problem with the nonlinear damping and establish the finite time blow-up of the solution for the initial data at arbitrary high energy level, including the estimate lower and upper bounds of the blow-up time. The result provides some affirmative answer to the open problems given in Yang et al. (2022). | Blow-Up Phenomena for a Class of Extensible Beam Equations | 10.1007/s00009-023-02469-0 |
2023-07-10 | This paper presents the issue of the Sub-synchronous resonance (SSR) phenomenon in a series compensated DFIG-based wind power plant and its alleviation using a Battery Energy Storage-based Damping Controller (BESSDC_L). A supplementary damping signal is developed considering the angular speed deviation and is incorporated into the BESS control system. Wide-area Measurement System data is used to determine the angular speed deviation. A linearized system model is developed to perform eigenvalue analysis, and to detect and examine unstable SSR modes. The variation of wind speed and three-phase fault are also taken into consideration to validate the robustness of the controller. To further verify the efficacy of the proposed damping controller, time-domain simulations are performed using MATLAB/Simulink. The application of the proposed BESSDC_L stabilizes all the unstable system modes effectively at wind speeds of 7 m/s, 9 m/s, and 11 m/s, and at 40%, 50%, and 60% series compensation levels, as well three-phase fault conditions. | Battery energy storage-based system damping controller for alleviating sub-synchronous oscillations in a DFIG-based wind power plant | 10.1186/s41601-023-00309-7 |
2023-07-07 | Anti-seismic devices are employed to implement the best performance of the structures under earthquakes. In this paper, semi-active tuned mass dampers (SA-TMDs) are studied by considering several combinations of variable friction forces and external disturbances. The variable damping model is used, where the goal consists in estimating the external actions to find the best friction force for system dampening. In particular, general, sinusoidal, and Gaussian dynamic loadings are considered. To obtain the response of the structure and dampers, several numerical solutions have been implemented. Probabilistic and determines analyses have been also developed to study different damper characteristics. Results show that a SA-TMD can reduce the structure displacements up to ~ 70.0% indicating a good performance in controlling different oscillations. This technology not only preserves the integrity of a structure mitigating its vibrations but also improves the life of occupants and their safety and comfort. This is beneficial from the perspective of practical application, and it is an advancement with respect to this theme. | Semi-active tuned mass dampers under combined variable actions of friction forces and external disturbances | 10.1007/s12517-023-11567-y |
2023-07-05 | This paper analyzes the influence of three different shape memory alloy (SMA) wires (i.e., Ni-Ti, Cu-Al-Ni, and Cu-Zn wires) for mitigating model cable vibration. Shape memory alloy (SMA) wires because of their superelasticity or shape memory properties can promise to be one of the effective damping materials in suppressing stay cable oscillations. The investigation explores through experimental works, the capabilities of three Ni-Ti, Cu-Al-Ni, and Cu-Zn SMA wires by estimating the vibration amplitude suppression of the model stay cable. The effective location of the SMA wires on the model cable for vibration suppression was estimated in free as well as forced vibration cases. To impart free and forced vibration, respectively, in the cable, a transducer-based hammer and exciter were used. An accelerometer and data acquisition system was used to record and acquire vibration data. It is also very appropriate to ascertain which wire among one of the three SMA wires performs well. It is found that the Ni-Ti SMA wire has a better performance in vibration suppression as compared to Cu-Al-Ni and Cu-Zn wires. It is also established that the attachment of the SMA wire at the mid-length of the cable gives better vibration suppression for the first mode. | Efficacy of SMA Wire in Vibration Suppression of a Stay Cable: An Experimental Investigation | 10.1007/s11665-023-08472-6 |
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