Mechanics of Solids最新文献

This study investigates the effects of rotational fields on the propagation of thermo-elastic and optical waves in a hydrodynamic semiconductor medium, using normal mode analysis to explore the dynamic interactions in this environment. Our analysis highlights the complex interplay between rotational fields and wave propagation. The photo-thermoelasticity theory is applied to solve the coupled thermo-poro-opto-mechanical equations. The model applies hydrodynamic principles to a rotationally influenced semiconductor, treating it as a homogeneous medium responsive to combined optical and acoustic wave excitations under specific boundary conditions of poroelastic semiconductors. Using normal mode analysis, we solve the non-dimensionalized field equations to obtain analytical expressions for the main physical fields. Our findings reveal that the rotational field significantly alters the amplitude and phase of wave propagation in all physical fields, amplifying oscillatory behavior due to Coriolis and centrifugal effects. Numerical simulations using porous silicon parameters demonstrate that both rotation and porosity enhance wave coupling and dispersion characteristics. The results provide crucial insights into the dynamic behavior of advanced semiconductor materials under rotational and thermal excitation, with potential applications in optoelectronics, plasma devices, and rotating microelectromechanical systems (MEMS).

Towed wheel shimmy is a common nonlinear vibration in the landing gear of aircrafts, which can pose serious safety hazards to aircrafts. In order to analyze and predict the vibration amplitude of the towed wheel shimmy, a two degrees-of-freedom (DOF) mathematical model is established. Then, the Newton interpolation method is used to modify the incremental harmonic balance (IHB) method. On this basis, the amplitude of the towed wheel shimmy is semi-analytically solved and predicted for different speeds and lateral damping of the suspension, the results are verified with the help of numerical integrations. In addition, the three-dimensional diagram of the system response for different speeds and lateral damping is obtained by using the modified IHB method, the influence of the lateral damping of the towed wheel is studied. The results indicate the modified IHB method can accurately predict the vibration amplitude of the towed wheel shimmy for different parameters, and the increase of the lateral damping of the suspension is effective for suppressing shimmy.

The interporosity fluid flow between the matrix pores and fractures is a major cause of strong wave dispersion and attenuation in the seismic frequency range. A modified interporosity flow equation using fractional derivative is introduced for wave propagation in fluid-saturated double-porosity media. The effects of the interporosity flow on wave dispersion and attenuation are investigated. The reflection and transmission behaviors of elastic waves at the loosely bonded interface between an elastic solid and a fluid-saturated double-porosity solid are investigated. The bonding parameter describing the degrees of bonding between the two media is used in the boundary conditions. The energy ratios are derived by satisfying the interfacial conditions of tractions and displacements. Based on the numerical results, the influences of the interporosity flow and degrees of bonding at the interface on reflection and transmission behaviors are mainly studied. It is observed that the energy ratios are affected noticeably by the interporosity flow and loosely bonded interface.

The pipeline bridge is a common structure in water transfer project. The external wind loads play an important role in the case of the flexible pipeline with large aspect ratio. In this paper, we investigate the dynamic response of cross-flow(CF) vortex-induced vibration(VIV) of pipeline bridge under external linearly sheared flow. Firstly, we apply the distributed van der Pol oscillator model to describe the location-dependent hydrodynamic loads on pipeline due to external sheared wind flow. And the dynamic equation of pipe with internal flow is deduced with the consideration of internal flow velocity, inner pressure and external tension. Secondly, the numerical analysis is conducted by central difference scheme. Finally, the lock-in response property and the effects of several factor, i.e. internal flow velocity, inner pressure, external tension and shear parameter, on the dynamic response are discussed in detailed. The results indicate that the multi-mode response always occurs in external sheared flow exhibits more complexity than single-mode response in external uniform flow. Among the above factors, the external tension has the greatest impact on dynamic response of pipeline bridge.

In order to clarify the influence of interfacial bonding properties on the anti-penetration performance of UHMWPE rigid target plates, this study was carried out using a combination of experiments and numerical simulations. In the experiments, 1.1 g wedge-shaped broken pieces were used to conduct multiple penetration tests on UHMWPE laminated target plates with two different adhesives, and the internal damage morphology after penetration was observed by CT scanning technology. In the numerical analysis, a finite element model corresponding to the experimental conditions is established based on LS-DYNA, and different interfacial bond strengths are simulated by changing the bond coefficients, so as to obtain the penetration process, ballistic limit velocity and energy absorption characteristics of the target plate. The results show that the interfacial bonding strength has a significant effect on the anti-invasive performance of the target plate, which shows a trend of increasing and then decreasing. When the bonding coefficient is in the moderate range, the target plate has the highest ballistic limit velocity, the optimal energy absorption efficiency, and the interfacial damage extension is more homogeneous; while too low or too high bonding strength will reduce the anti-penetration capability of the target plate, too low bonding leads to serious delamination damage, and too high bonding leads to local load concentration and accelerated failure. The results of the study can provide an effective reference basis for the structural design and interface optimization of UHMWPE rigid target plates.

The study of disturbance propagating as waves across a transversely isotropic medium is the focus of this article. In addition to macroscopic translational deformation, the particles in the considered medium also exhibit small-scale internal rotation. The medium is micropolar by nature as a result of this additional translational flexibility. In addition, the medium is incompressible, and given particular plan-strain conditions, the dispersion relation of waves propagating through the media is obtained. We may infer from the dispersion relation that three transverse waves propagate across the medium due to incompressibility. Non free boundary conditions are employed to find out the reflection coefficients. Effect of different values of nonlocal parameter is studied. For a certain media, the findings are visually displayed. The suggested model is used to simulate the mechanical properties of complex materials, such biological tissues and composites that include microstructural heterogeneity. A comparison is made with the results obtained by others when the external parameters neglected that indicate to the strong impact for the new parameters. The results applicable to a variety of domains, including acoustics, engineering, geophysics, and astronomy.

This study investigates vibration phenomenon including thermocoupling effects in nanoscale resonators exposed to a fluctuating heat source. Mathematical model of the problem is established by employing the Atangana-Baleanu (A-B) fractional derivative within a two-temperature, three-phase-lag thermoelastic heat transfer model. The approach incorporates the non-singular Mittag-Leffler kernel associated with the A-B operator to account for memory-dependent effects, providing an enhanced representation of thermal and mechanical wave propagation in microscale systems. The governing equations for a clamped nano-resonator beam are solved analytically by using the Laplace transform technique, with numerical inversions carried out via the Riemann-sum approximation to determine the distributions of displacement, conductive and thermodynamic temperatures, and axial stress. Analysis of the significant parameters depicted through the graphical representations, highlights the crucial impacts of the A-B fractional parameter, two-temperature phenomena, and the angular frequency of the heat source on the thermophysical fields. The results align with trends observed in previous theoretical and computational studies, thereby confirming the model’s accuracy and its effectiveness in elucidating complex interactions within nanoscale resonators. These findings establish a solid foundation for optimizing the design and functionality of micro- and nano-electromechanical systems subjected to dynamic thermal loads.

This paper aims at the free vibration of a rotating truncated conical shell with meridional variable thickness and elastic boundary conditions. Based on Donnell’s shell theory, the governing equations of the truncated conical shell with variable thickness are derived first. Then the artificial spring technique is used to model the elastic boundary conditions at both edges. Finally, a new solution formula for rotation is proposed. The present theoretical modeling based on the generalized differential quadrature (GDQ) method is validated through comparison with both finite element method (FEM) and existing studies. This study examines the individual and coupled effects of meridional variable thickness, elastic boundary conditions, and various rotational forces (e.g., Coriolis force, centrifugal force, and initial hoop tension) on the system’s frequency characteristics. The results demonstrate that the standing wave frequencies of low-wavenumber circumferential modes (LCM) are predominantly influenced by both thickness variations and boundary conditions. In contrast, the frequencies of high-wavenumber circumferential modes (HCM) are primarily governed by the shell’s average thickness. Furthermore, the effects of different spring types (e.g., meridional springs, circumferential springs, transverse springs, and rotational springs) and rotational forces on the frequency characteristics differ significantly. Finally, the slope of the frequencies with respect to the speed is also found to depend on both thickness variations and boundary conditions.

This paper provides a systematic summary of the development of an explosive reactive armor (ERA). It details the structural characteristics and protective performance of typical ERA from the first to fourth generation, along with an in-depth analysis of how the ERA interferes with the shape charge jet (SCJ). This study also reviews current research on anti-ERA technology, particularly focusing on tandem-charge warhead penetrating without detonation technology. Finally, it forecasts the future trends of ERA and anti-ERA technologies, in conjunction with existing advancements to enhance armor protection and ammunition damage capabilities.

Generalized wave impedance theory, used to simplify stress wave analysis, has practical limitations. This study examines its applicability under non-ideal conditions, specifically the influence of coupling factors on wave propagation at variable cross-sections via simulations. Based on the generalized wave impedance theory, this study investigates the influence of coupling factors in generalized wave impedance on stress wave propagation characteristics at variable cross-sections through simulation analysis. The research reveals that under constant generalized impedance, a larger cross-sectional area ratio reduces the error between theory and simulation for reflected waves but increases it for transmitted waves. Analyzing the influence of the area ratio, wave impedance ratio, density, Young’s modulus, and sound speed on transmitted and reflected waves showed that the area ratio is the primary factor affecting the accuracy of the generalized wave impedance. Maintaining the same area ratio while altering the density and Young’s modulus ratios (changing wave impedance) revealed that accuracy improves with increasing amplification coefficients. Sound speed, as a coupling factor of density and Young’s modulus, had minimal impact on accuracy. The findings not only contribute to improving the theoretical foundation of Split Hopkinson Pressure Bar (SHPB) experiments but also offer new perspectives for enhancing the accuracy of material parameter measurements.