Archive of Applied Mechanics最新文献

This study introduces an innovative methodology for simulating anguilliform swimming by combining a finite volume method with a coupled overset mesh and radial basis mesh (RBF) deformation technique. The overset mesh technology efficiently handles domain alterations resulting from forward motion, while the RBF mesh deformation method accommodates boundary deformations. Our approach’s robustness and accuracy are rigorously validated through comprehensive comparisons with both numerical and experimental results for self-propelled fish-like swimming. These comparisons unequivocally establish the precision and effectiveness of our methodology, highlighting its potential as a valuable tool for simulating and comprehending complex fluid dynamics in anguilliform swimming and other related fields.

This work aims to optimize the topology and fiber orientations of symmetric laminated composite plates. The goal is to maximize their stability under thermal loading while meeting volume fraction constraints. First, lamination parameters and densities are set as design variables to determine fiber orientations and topological shapes. A composite optimization model is established based on penalty theory. The method of moving asymptotes (MMA) algorithm is used to obtain the optimum lamination parameters and topological shapes. Next, leveraging the relationship between lamination parameters and fiber orientations, the solution of nonlinear equations is reformulated as a least-squares optimization problem. The Levenberg–Marquardt algorithm is then applied to determine the fiber orientations. Finally, the effectiveness of the proposed method is verified through optimization examples of four-sided and opposite-sided clamped laminate plates.

Green’s functions are essential analytical tools in physics, providing key insights into the behavior of complex multiphase systems. This study examines poroelastic effects in infinite orthotropic materials with smooth contact interfaces using Green’s functions, which play a significant role in flotation mattresses and rock–soil systems. By employing strict differential operator theory and potential theory, we present compact mono-harmonic general solutions to the governing equations that satisfy sixth-order homogeneous partial differential equations. Based on the obtained compact general solution, the 2D fundamental solution for a steady line fluid source in an infinite orthotropic poroelastic plane with smooth interfaces is derived using six newly introduced harmonic functions.functions, ensuring their ease of use in practical applications. Numerical simulations, presented through non-dimensional contours and spatial visualization, reveal elliptical behavior, high-density levels near the fluid source, decay at a distance, higher-order singularities, zero-common tangents, and adherence to interface continuity conditions.

Forming-induced residual stresses highly influence the performance of metallic engineering components. They offer great potential particularly for increasing fatigue life by targeted introduction of compressive residual stresses in failure-critical areas. However, this only holds true if one can understand and predict the change of residual stresses under cyclic mechanical loading and thus ensure their stability. In the present paper, we introduce a combined experimental and numerical approach for the investigation of residual stress evolution under cyclic mechanical loading. Therefore, a suitable experiment is conceptualized and realized using a 4-point bending setup. The initial plastic deformation of each specimen is followed by a certain number of load cycles and experimental residual stress analyses. From this, a course of residual stresses over the fatigue life is constructed. In order to simulate the determined change in residual stresses, a cyclic plasticity model is proposed that takes into account the nonlinear kinematics due to the large deflection of the beam. A parametrization algorithm is presented, which employs a global optimization strategy using uniaxial stress–strain data from various parametrization experiments. The final comparison of experimental and numerical results shows a qualitative agreement. Their stabilization level after a few thousand load cycles can be predicted.

The nonlinear aeroelastic dynamic responses and bifurcation behaviors of the ferromagnetic panel in steady/harmonic magnetic field under the supersonic airflow environment are investigated. The geometrical nonlinear effect of the ferromagnetic panel is depicted through the Von-Karman strain and the aerodynamic load is incorporated by the classical piston theory. Then, the reduced equations of motion are obtained and the Newmark method is used to determine the dynamic response with the Newton–Raphson iterative procedure for the nonlinear equilibrium equation at each time step. After examining the accuracy of the established mechanical model through numerical comparisons with experiment results and literature solutions, the main parametric studies focusing on the steady magnetic field strength, harmonic magnetic amplitude and frequency, dynamic pressure on nonlinear dynamic response are studied and the global bifurcation diagrams are given. Results show that the steady magnetic field leads to enhancement of the critical flutter dynamic pressure and a delaying of chaotic motion for the ferromagnetic panel. However, the harmonic magnetic field will complicate the motion type of the ferromagnetic panel and bring a chaotic state earlier.

We describe an algorithm to be used for the numerical integration of plasticity models in finite element or finite difference codes. The algorithm is simple to code and implement. It is presented here for a generic form of plasticity model encompassing both single and multiple yield surfaces, and it is readily adaptable to more complex models. Three examples are given to demonstrate the efficacy of the algorithm in controlling integration errors.

The scaled boundary finite element method (SBFEM) is further extended to compute the natural frequencies of laminated composite beams. In the proposed method, the beam is simplified into a one-dimensional model. Only the displacement components along x and z directions are selected as the fundamental unknowns. Starting with the fundamental equations of elasticity and built on the scaled boundary coordinate, the principle of virtual work and the dual vector technique, the first-order ordinary differential scaled boundary finite element dynamic equation for composite beams is obtained, whose general solution is the analytical matrix exponential function. The Padé expansion is utilized to solve the matrix exponential function, and the dynamic matrix of each beam lamina can be acquired. According to the principle of matching degrees of freedom, the global stiffness and mass matrices of the laminated beam are gained. Solving the eigenvalue equation results in the vibration frequencies of laminated composite beams. This method is widely applicable, and there is no limitation on the layer number and boundary conditions. Comparisons with natural frequencies of three-, four- and ten-layered beams as well as the stepped beam, the accuracy, high efficiency and fast convergence of the introduced SBFEM are validated.

In this paper, we propose a modified permeable model to analyze the fracture behavior of two collinear cracks under a thermo-electro-elastic load that is described by a cubic function. By employing this modified model and Fourier transformation, the mixed boundary value problem is firstly reduced to a set of singular integral equations. Then, based on using the Cauchy kernel theory, we derive analytical solutions for these equations, with a focus on key crack-tip physical quantities and intensity factors. Numerical results demonstrate that the crack size, initial unit heat flux adjustment parameters, and initial electric displacement adjustment parameter, accounting for the effects of initial heat flux, electric displacement, and irregular crack surfaces, significantly influence the temperature gradients and intensity factors.

Linear piezoelectric energy harvesters exhibit coupled vibration phenomena under external excitation. This study proposes a novel semi-analytical method for examining the vibration response of linear piezoelectric energy harvesters in vortex-induced vibration environments. In this study, the governing equations of a vortex-induced piezoelectric energy harvester, derived with the help of Euler–Lagrange equation, are solved using the multi-step differential transform-Padé approximation method. The accuracy of this method is validated against the fourth-order Runge–Kutta method. Furthermore, the influences of the bluff body’s diameter and the length of piezoelectric beam on the system’s output power are examined. Finally, optimization of the model is conducted using the non-dominated sorting genetic algorithm II with the objectives of maximizing output power and minimizing system mass, in which response surface methodology is employed to tackle with the time-consuming problem in computation process. The results indicate that the output power at the turning points calculated through idealized points is 13.37% greater than that of the initial design point, while the total system mass is reduced by 3.06%.

The dynamic responses of a railway bridge subject to a moving train are randomly affected by track irregularities. With particular attention on track random irregularities, an in-depth analysis is performed in this study to achieve the uncertainty quantification of train-track-bridge interactions. In the method, a 3D train-bridge dynamic model is constructed, in which the ballastless tracks and the bridge girders are integrated as an integral system, and the nonlinear wheel-rail interactions are considered. The track-bridge time-varying coupled method is introduced to improve the modeling and solution efficiency. As the main system excitation, a method for characterizing the ergodic wavelength and amplitude properties of track irregularities is introduced, through which the train-track-bridge system responses can be fully revealed. By introducing a probability density evolution method, an accurate and efficient probabilistic assessment of the influence of track random irregularities on system responses can be achieved. In comparison with the generally used methods, this present work is capable of conducting more complete and accurate evaluation for random vibrations of train-track-bridge systems. Furthermore, the stability of train operation and ride comfort are evaluated for different running speeds and different track geometric conditions. The results show that considering the impact of full probability irregularities is crucial in the random analysis of the train-track-bridge system.