Archive of Applied Mechanics最新文献

This study presents a high-fidelity modelling and vibration analysis framework for a 600 MW turbo-generator stator end winding, integrating composite materials theory and discrete element methods. The double-layered winding is modelled as a conical shell model with ring and stringer stiffeners representing supporting components. Natural and forced vibration equations are derived using the Rayleigh–Ritz method with an enhanced Fourier series, enabling accurate simulation of complex elastic boundary conditions. The model is extended to optimize the stator-winding characteristic equation, yielding a semi-analytical solution for spring stiffness configuration. Key innovations include the analytical derivation of modal parameters, a rigorously formulated frequency response function, and the introduction of Rayleigh damping and excitation force potential energy. Multidimensional displacement response analysis demonstrates strong agreement with finite element results, validating the proposed equivalent digital mechanism model’s accuracy and robustness.

The design of metallic support towers for energy transmission and telecommunication networks increasingly demands efficiency and reliability. As these towers become more slender, they are highly susceptible to wind-induced vibrations, which can compromise structural stability. Conventional passive dampers are effective in controlling vibrations but often increase project costs, limiting practical implementation. This study investigates an alternative approach using connection dampers based on rubber rings installed in bolted joints. These dampers reduce connection stiffness while increasing damping, enhancing the structure’s energy dissipation capacity. Experimental tests characterized the mechanical properties of the rubber rings, and we implemented the results in a numerical optimization framework applied to a three-dimensional lattice steel tower under synoptic wind. The Whale Optimization Algorithm determined optimal stiffness and damping parameters. Comparisons between rigid and semi-rigid connections equipped with the proposed dampers demonstrate notable improvements: the structural damping ratio increased by approximately 173%, and the maximum displacement at the tower top decreased by around 28%. These results confirm the effectiveness of the proposed methodology in mitigating wind-induced vibrations and improving the dynamic response of slender lattice towers.

In this work, the inverse hyperbolic shear deformation theory (IHSDT) is used to examine the bending, buckling, and free vibration responses of functionally graded graphene nanoplatelets-reinforced composite (FG-GNPRC) plates. This theory ensures that there are no traction forces on both the top and bottom sides of the plate. It achieves this without needing to use a shear correction factor, and it allows for a nonlinear distribution of transverse shear stresses across the plate. The study utilizes a finite element approach incorporating a nonlinear function based on inverse hyperbolic sine function. A C⁰ finite element model is created for the GNPRC plate in the framework of IHSDT to determine the structural responses of the plate in MATLAB environment. It studies graphene nanoplatelets (GPLs) distributions, patterned as UD, FG-X, FG-O, and FG-A throughout the thickness in composite plate. The weight fraction (wt%) of GPLs varies along the thickness direction and is evenly distributed throughout the matrix of each layer, follows a specific distribution pattern. The Halpin–Tsai micromodel is used to estimate the effective Young’s modulus of the GNPRC plate, and the rule of mixtures is used to calculate the Poisson’s ratio and mass density. The plate domain is discretized using an eight-noded elements, each with 56 degrees of freedom. Further the analysis looks at the effects of a variety of factors, including the number of layers (N_L) of GNPRC plate, length/thickness, and length/width ratio of GPLs, wt% of GPLs, and dispersion patterns of GPLs on the structural responses of FG-GNPRC plate. The numerical results demonstrate that the rigidity of plates can be significantly enhances by incorporating GPLs and the outcomes were compared with prior findings in order to evaluate the performance and effectiveness of the suggested mathematical approach.

Bending fracture is a critical failure mechanism in many engineering structures such as rock beams, slabs and bridge components. This is particularly the case when prefabricated cracks are present. In order to accurately simulate such failure processes, a method is required that can capture both continuous deformation and the transition to discontinuous fracturing. The hybrid finite-discrete element method (HFDEM) is particularly well-suited for this purpose, as it integrates the advantages of continuum-based finite element methods with those of discontinuum-based discrete element methods. However, conventional HFDEM approaches are computationally intensive and often impractical for large-scale problems. This paper introduces a general-purpose graphic processing unit-parallelized HFDEM that is general-purpose and achieves execution speeds exceeding 128 times those of sequential code. The model is employed to simulate the bending fracture processes of sandstone specimens with prefabricated cracks under varying test configurations, revealing the mechanism by which loading rate influences fracture mechanics behavior. The results demonstrate good agreement with existing research findings, thereby validating the model. The core contribution, however, lies in revealing the intrinsic mechanisms behind the strongly rate-dependent fracture behavior. The simulations elucidate how higher loading rates weaken the guiding effect of prefabricated cracks and promote a transition to complex mixed-mode fracture, thereby establishing that the apparent toughness increase is primarily driven by inertial effects and exhibits fundamental divergence between different fracture modes.

This study presents a novel analytical framework to investigate the photothermal response of functionally graded semiconductor materials under laser pulse excitation, utilizing a nonlocal thermoelastic model. By integrating the single-phase-lagging (SPL) concept with a nonlocal thermal length-scale, the model captures finite thermal wave speeds critical for micro- and nanoscale transient phenomena. The analysis examines coupled thermal, elastic, and plasma wave interactions in materials with spatially varying properties. Numerical results show that increasing the nonlocal thermal length-scale significantly reduces temperature and carrier density, while material gradation enhances near-surface temperature but markedly suppresses displacement. Longer laser pulse durations lower peak temperatures but increase stresses, highlighting key trade-offs. By overcoming limitations of classical Fourier heat conduction and incorporating size-dependent effects, the model provides insights into thermoelastic wave propagation in nanostructured materials. These findings emphasize the importance of material design and pulse optimization for improving energy transfer and stress management, with applications in semiconductor device engineering, thermal management, and laser-based manufacturing in nanotechnology and optoelectronics.

An important influence that distinguishes the dynamic response of tunnels embedded in saturated frozen soil from that of unfrozen soil is the freezing of liquid-phase water in the pores, and the formation of ice alters the propagation of loads through the frozen soil. The dynamic response of the tunnel embedded in saturated frozen half-space when loads are applied to the lining invert is addressed by the wave function method. The saturated frozen soil is regarded as a poroelastic medium, the lining is regarded as a hollow cylinder, and the total wave field in the surrounding medium consists of outgoing cylindrical waves and down-going plane waves. The plane wave function and cylindrical wave function could be converted to obtain the boundary conditions that are convenient for solving the ground surface and soil-lining interface in the rectangular and cylindrical coordinate systems. The parametric analysis demonstrates that the dynamic response of a tunnel embedded in a saturated frozen half-space and the surrounding medium could be influenced by the permeability, porosity, ice content of frozen soil and the change of the tunnel depth. This method provides a novel approach to the safety and stability of tunnels in cold regions and serves as a reference for predicting the vibration of tunnels embedded in saturated frozen half-spaces.

This study investigates the dispersion characteristics of Lamb waves in porous functionally graded materials (FGM) with free boundaries, with a focus on the influence of porosity. The material properties of porous FGM are characterized by a mixed power-law model. Based on elastic wave theory, the wave equations for an infinite porous FGM plate are derived, and the dispersion equations of Lamb waves are obtained using the Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) method. To validate the proposed approach, the porous FGM layer is reduced to an isotropic material, and the results are compared with existing literature, demonstrating the method’s accuracy. Numerical solutions of the dispersion equations are implemented via MATLAB to analyze the effects of porosity, layer thickness and gradient index on dispersion curves. The results indicate that porosity, layer thickness and gradient index significantly affect Lamb wave dispersion. This study provides both theoretical and numerical foundations for understanding and utilizing Lamb waves in porous FGM structures, with potential applications in structural health monitoring and nondestructive testing for aerospace and civil engineering.

The plane strain problem for an interface crack between two different piezoelectric materials with an arbitrary polarization direction under remote mechanical loading is analyzed. Mechanically frictionless and electrically permeable contact zones are assumed at the crack tips, and the remaining part of the crack is considered as electrically permeable. An analytical method is used based upon the presentations of the field variables via sectionally analytic vector functions with the resulting formulation and the solution of the combined Dirichlet–Riemann boundary value problem. Clear analytical expressions for crack opening and stresses along the bimaterial interface as well as for stress intensity factors are derived. Furthermore, a system of the transcendental equations for the determination of the contact zones lengths in the sense of Comninou is obtained. The numerical analysis performed for a certain piezoelectric bimaterial showed an essential influence of the changing poling direction on the stress intensity factors and the contact zones lengths as well as on the crack opening displacement and the variations in the stress at the bimaterial interface.

This study tackles the problem of wall thickness nonuniformity in the automated fiber placement (AFP) of composite conical shells by introducing a layer-wise control strategy grounded in a fiber accumulation model. A mathematical model for the single-layer fiber placement path is constructed, and the equivalent area method is utilized to quantitatively describe the overlap ratio of prepreg tows, from which the axial ply thickness distribution function is derived. To achieve uniform thickness, a multi-layer placement strategy with decreasing placement heights is introduced, establishing a mapping relationship between layer termination positions and cumulative thickness. A parametric analysis reveals that achieving a target thickness of 4 mm necessitates 28 layers, with fiber placement lengths decreasing beyond the 15th layer. The optimized scheme results in a mean squared error (MSE) of 0.021 mm in the total thickness. Based on the Tsai-Wu failure criterion, the predicted ultimate internal pressure is 4.2 MPa, slightly lower than the pre-optimization value of 4.8 MPa. This indicates that the optimized conical shell experiences only a marginal decline in failure performance while achieving a 22.35% reduction in material usage and still satisfying the strength requirements. Finite element analysis using Abaqus shows that under an internal pressure load of 4 MPa, the maximum displacement magnitude is 4.1 × 10^–2 mm. This method effectively alleviates fiber accumulation induced by curvature gradients and offers a theoretical foundation for the high-precision manufacturing of thin-walled composite structures in aerospace applications.

The parametric vibrations of the flexible beams with account of the geometrically nonlinear deformations and breathing crack are studied. The crack breathing is described by using contact parameter and crack function. The nonlinear integro-differential equation, which describes geometrically nonlinear parametric vibrations of the beams with breathing cracks, is derived from the variational principal of Hu–Washizu. The nonlinear integro-differential equation is transformed into the system of piecewise—nonlinear ordinary differential equations by using the weighted residuals method. Arc length continuation technique and shooting technique are used jointly to study numerically nonlinear oscillations, their stability and bifurcations. The Neimark–Sacker and the saddle-nodes bifurcations are observed due to numerical analysis. Quasi-periodic and chaotic oscillations are studied numerically.