This study investigates the buckling behavior of sandwich plates under various in-plane compressive loads (uniform, linear, and exponential). The plates consist of bidirectional functionally graded (BDFG) face sheets, with material properties graded along both axial and thickness directions, and a porosity-graded metal foam core, all partially supported by an elastic foundation. A quasi-3D shear deformation theory is employed to formulate a high-fidelity model, with governing equations derived via the principle of virtual work and solved analytically. After validation of results of the present study, a comprehensive parametric study is presented to evaluate the effect of foam porosity, gradient index, load distribution and foundation stiffness of the buckling stability. Numerical analysis reveals that the critical buckling load is contingent upon a multitude of factors: the plate typology, its geometric slenderness (a/h ratio), the characteristics of the imposed loading, and the underlying elastic medium. The comprehensive parametric analysis confirms that the proposed model provides an efficient and reliable predictive tool for the optimal design of advanced sandwich structures in demanding aerospace, civil, and marine engineering applications.

Cylindrical shells can vibrate in three distinct modes: shell modes, beam modes, and breathing modes. Understanding breathing modes is crucial, especially when shells are subjected to internal pressure or explosive loads in spacecraft and pressure vessel applications. This study focuses on the breathing mode of simply supported thin-walled cylindrical hyperelastic shells made from Mooney–Rivlin material, subjected to radial harmonic excitation. By analyzing the shell’s spatial deflections, the coupled equations of motion are derived using the Lagrangian in terms of generalized coordinates and substituting it into the Euler–Lagrange equations. Assuming radial motion is dominant, the system simplifies to a single governing equation, which unlike asymmetric modes, contains both quadratic and cubic nonlinearities. The quadratic nonlinearity poses a softening behavior to the shell for some parametric values. Introducing dimensionless parameters, this equation is solved using the method of multiple scales to examine nonlinear frequency responses and numerically to explore nonlinear dynamics. The frequency response curves reveal that, unlike shell modes, which typically show hardening behavior, breathing modes of hyperelastic shells can display either softening or hardening characteristics depending on the shell’s radius-to-length ratio. Softening for low and hardening for high radius-to-length ratios. Additionally, the presence of damping is shown to transform the shell’s quasi-periodic motion into asymptotically stable.

In this study, the vibration and flutter behaviors of a sandwich microbeam with a functionally graded porous (FGP) core and carbon nanotube (CNT)-reinforced face sheets resting on a visco-Pasternak foundation are thoroughly investigated. The different dispersion patterns of CNTs are compared to each other and the properties of the porous cores are derived based on the symmetric porosity distribution patterns. The governing equations are formulated according to the Reddy beam theory (RBT) and Hamilton’s principle. For the numerical solution, the harmonic differential quadrature method (HDQM) is employed, and a comprehensive numerical analysis is carried out within the framework of the modified couple stress theory (MCST). The aerodynamic loading is modeled using the classical piston theory, and aerodynamic damping is neglected due to its relatively minor influence in the supersonic regime considered in this study. Furthermore, the effects of various parameters, such as the CNT volume fraction, CNT agglomeration, and pore distribution pattern, are examined to provide a detailed and accurate insight into the instability behavior of such structures. The obtained results can serve as valuable guidelines for the optimal design of lightweight and high-strength structures in aerospace and advanced engineering applications.

Rotor-bearing modeling is essential for the safe operation of rotating machinery. Typically, in practice, bearings can be loosely fitted to the housing to allow axial thermal elongation of the rotor which can cause misalignment of the bearing. This phenomenon is investigated in this study using a full ball bearing stiffness matrix including cross-coupling terms with a three-dimensional solid finite element rotor model. The effect of misalignment on bearing stiffness and rotordynamics is studied. The results show a significant drop in stiffness due to drastic changes in the contact forces and their distribution between the balls and the raceway. Consequently, there are changes in the rotor’s critical speeds and mode shapes as a result of bearing arrangement and misalignment.

This paper proposes an innovative horizontal fall-arrest system with steel strand track (HFAS-SS) for structural construction and maintenance such as power transmission towers, which is mainly used to prevent falling injuries for high-altitude workers. A total of 72 sets of fall impact tests were conducted under different fall heights, track spans, and initial preload. The mechanism of change of fall impact load, track tension and strain of HFAS-SS was studied and the dynamic response during the falling process was revealed. Then, a finite element dynamic analysis model that was verified through tests was established to further study the impact of steel strand specifications on the performance of HFAS-SS. The results show that the HFAS-SS has sufficient safety, can effectively brake and be used for high-altitude operations on the transmission line. The larger the falling height, the greater the impact load and track tension. The larger the track span, the smaller the impact load, the greater the track tension. Reducing initial preload is an effective way to reduce track tension, but this will also increase the worker’s falling height and load. When the fall factor is greater than 1, the impact load will exceed the human safety limit of 6 kN. While ensuring structural safety, the use of steel strands with small diameters ad 1 × 7 strands can better provide protection to the worker. Finally, the design process of HFAS-SS was established based on the energy balance method.

In the practical application of multi-link mechanism, lubricating oil has been widely used in kinematic pairs to reduce the influence of clearance on the accuracy and stability of the mechanism. However, the operation of the press is still inevitably affected by the impact loads. Impact loads will also reduce dynamic response characteristics of the mechanism and affect its accuracy and reliability. At present, the research on dynamic response characteristics of mechanisms mainly focuses on the effect of lubrication clearances. Theoretical research on dynamic of mechanisms with lubrication clearances under impact loads is rare. Experimental studies involving impact loads are uncommon. Therefore, an effective approach for dynamic characteristics of multi-link mechanism with lubrication clearances under impact loads was proposed, and the dynamic response of multi-link presses with lubrication clearances under impact loads was studied in the article. Taking a seven-link press mechanism as an example, a dynamic equation of the mechanism with lubricating clearance was derived based on the Lagrange multiplier method. The dynamic model of the seven-link press mechanism with lubrication clearance under impact load was developed. Then the effects of lubrication conditions, dynamic viscosity, driving speeds, and impact loads on dynamic characteristics of press mechanisms were analyzed, respectively. Finally, an experimental platform consistent with the theoretical model was built. Through the experimental research and the analysis of experimental results, the rationality of models and the validity of theoretical analysis were verified. The study provides a method for understanding dynamic characteristics of presses during impact loads, and provides an important reference for dynamic optimization design of multi-link press mechanism.

Currently, asymmetric thin-walled U-shaped girders in urban rail transit are widely applied, and triply coupled spatial torsional-flexural forced vibrations of asymmetric thin-walled beam bridges can be induced by moving train loads, which further endangers structural or driving safety. However, no such work on the corresponding theoretical analytical solutions is reported. Thus, taking the simply supported asymmetric thin-walled U-shaped girders in the urban rail transit line 1 project of Chongqing City as an example, this study focuses on the theoretical approach for triply coupled spatial torsional-flexural vibration of asymmetric thin-walled beam bridge under moving train loads. The moving trains can be modeled as concentrated moving loads, and the triply coupled spatial dynamic governing equations under concentrated moving loads are firstly developed considering the effects of rotary inertia and warping resistance. The equations are then decoupled and resolved using the mode superposition method, Laplace integral transformation, and the relationship between the three roots and constant coefficients of a cubic equation. The analytical vibration response expressions in vertical, lateral and torsional directions are derived from this approach, and the resonance conditions are further explored. The results conclude that the vertical, lateral and torsional responses will be simultaneously set in resonance if the parameter related to velocity Ω cn approaches the natural frequency ωni . Subsequently, a novel numerical approach that combines the Galerkin approach and a precise integration method is employed to verify the validity of the above analytical solutions. On this basis, an extensive parametric study is performed. As per the results, the asymmetry, warping effect and eccentricity of the concentrated moving load to the shear center along the Y axis all have a significant impact on the vibration responses in lateral and torsional directions. Specifically, for this asymmetric thin-walled U-shaped girder in urban rail transit bridges, the peak lateral and torsional vibration responses are approximately 3.12 and 2.13 times that of the corresponding monosymmetric one, respectively. The lateral and torsional vibration responses with the warping effect are 28.46% and 14.83% higher than those without the warping effect, respectively.

With the rapid development of intercity railways in China, issues such as wheel rail wear and excessive lateral forces during the negotiation of small-radius curved tracks have emerged. This paper proposed a method of integrating Electro-Hydrostatic Actuator (EHA)-based active radial steering dynamic modeling. The method integrates vehicle dynamic modeling, fractional-order Proportional-Integral (PI) control, and wear analysis. An EHA model integrating permanent magnet synchronous motors, gear pumps, and hydraulic cylinders was developed in Simulink. To address the poor curve-negotiation performance of conventional passive bogies, two EHA configuration schemes (longitudinal and lateral arrangements) were proposed based on theoretical analysis. Parameter analysis has been conducted, and the longitudinal EHA configuration has been demonstrated to be superior in the simulation environment. The results show that active radial steering technology significantly improves curve-negotiation performance through optimized wheelset alignment, with the longitudinal EHA configuration achieving superior reductions in attack angles, wear, and lateral forces. The longitudinal EHA arrangement demonstrates superior performance in suppressing wheelset attack angle and comprehensive wear control. Under standard conditions, it reduces wheelset attack angle by 35% and wear number by 30% in a small radius curved track. This technology enhances operational safety and reduces maintenance costs, providing critical technical support for efficient intercity railway operations.

Purpose Headland turning is a crucial maneuver in steep, sloped vineyard cultivation. This work investigates whether performing row-changing maneuvers under high-slope conditions is safe. Methods Three common ground-robot architectures are considered, and their dynamic models are evaluated. Potentially hazardous turning conditions during headland maneuvers are analyzed to identify the critical forward speed that marks the transition to unsafe operation. Results Results show that braking during headland turning on a slope is the most hazardous condition, potentially causing instability. Dynamic stability parameters are proposed accordingly. Conclusion The analysis provides quantitative criteria and safe operating velocities to support motion-planning and control strategies for field deployment.

This study develops a nonlinear elasto–plastic–damage material model to simulate the mechanical response of adhesive-free lapped scarf timber joints with inclined faces and hardwood dowels. The formulation integrates plasticity and continuum damage to capture progressive stiffness degradation and irreversible deformation in anisotropic wood. A three-dimensional finite element model was implemented in Abaqus through a user-defined UMAT subroutine, employing the Hoffman yield criterion to describe the onset of plastic flow and a damage evolution law to govern stiffness reduction under tensile and compressive loading. The joint configuration, consisting of English oak dowels connecting Norway spruce beams, was analyzed as a representative hybrid arrangement. Calibration and validation against experimental bending tests demonstrate that the model accurately predicts the nonlinear load–displacement response and reproduces key failure mechanisms. The results confirm the effectiveness of the proposed framework in providing reliable numerical analysis for adhesive-free timber joints.