Acta Mechanica最新文献

Graphene-reinforced composites are increasingly employed as core layers in smart microplates due to their exceptional mechanical and functional properties. Although graphene or graphene platelets (GPLs) are typically used to reinforce homogeneous matrices, integrating GPLs into conventional functionally graded materials (FGMs) represents a novel approach. This study proposed a new material model comprising a GPL-reinforced FGM core with piezoelectric coating layers. The composite matrix is continuously graded through the thickness following a power-law distribution, and five distinct GPL dispersion patterns are examined. The core’s material properties are determined using the modified Halpin–Tsai model in conjunction with the rule of mixtures. Based on variants of a four-unknown refined plate theory (RPT4) combined with the modified couple stress theory (MCST), governing equations for smart GPL-reinforced FGM microplates with two piezoelectric layers resting on a Winkler–Pasternak foundation are derived. A Navier-based analytical solution is then employed to compute the natural frequencies of the piezoelectric microplate. The performance of the proposed model and the different RPT4 variants is assessed, and the influences of material parameters, piezoelectric layer thickness, length scale, and foundation parameters on the natural frequency are thoroughly investigated.

A geometrically nonlinear framework is constructed for modeling material failure by adiabatic shear. Mechanisms encompassed include nonlinear thermoelasticity pertinent for high-pressure and high-temperature states, dynamic plasticity from combined actions of dislocation glide and twinning, initial and evolving porosity, rotational dynamic recrystallization (DRX), and localized material degradation from softening and ductile fracture. An order parameter of phase-field type accounts for softening mechanisms at a microstructure length scale too small to be resolved in structural mechanics applications. Phase-field regularization sets the finite width of a shear band or ductile crack, analogous to application of phase-field theory for regularizing sharp cracks in brittle fracture. The framework depicts the reduction in resistance to shear banding with (initial) defects or pores, and DRX, in a physically motivated scheme different from prior theory. Model calculations reproduce experimental observations on shear localization and fracture in steel and titanium, the latter with and without initial pores and DRX, under dynamic shear-dominant loading. Further results predict decreased shear stability from void growth under tensile pressure. Compressive pressure increases flow strength, leading to higher temperature and earlier localization in some cases, but later localization in others due to suppressed thermoelastic expansion. Higher loading rates can increase stability due to rate dependence of flow stress, transient phase-field kinetics, and possible inertial effects.

This research focuses on developing a numerical model for predicting time-varying displacement responses of damaged fibre-metal laminate (FML) hybrid structural components using a higher-order mathematical model, including pre-damage. The numerical solution accuracy obtained using a customized computational code (MATLAB) through the mathematical model is verified with experimental dynamic deflection data. The numerical transient responses are computed through Newmark’s (average acceleration) integration technique in association with the isoparametric finite element approach. Additionally, the pre-damage (crack) is introduced through a variable crack closure technique (VCCT) in a simulation tool (ABAQUS), and the mesh details, including the nodal information, are imported to the MATLAB platform using the compatibility code. For experimental validation purposes, a few hybrid FML (glass fibre epoxy panels joined with aluminium plates) are fabricated and utilized for experimentation, including the experimental material properties. The numerical model accuracies are initially verified with previously published transient values of the laminated composite. After fulfilling the necessary convergence criteria and the validation, the computational model is extended to work out a few parametric analyses to understand the significance of damage and limiting factors (curvature ratio, geometric shapes, and modular ratios) in designing such FML components. It can be concluded from the numerical experimentation that the geometrical parameters (curvature ratio, stacking sequence, and aspect ratio) largely influence the dynamic deflections, i.e. the responses vary from 4–8% (increase in peak displacement). Meanwhile, the values upsurge by 32%, while the structural end-restrained conditions are less (for a cantilever case: CFFF). Finally, a set of recommendations is listed to understand the advantages of the proposed model for the analysis of FML structure, including the damage effects.

Considering the increasing demand for vibration and noise control in fluid-conveying pipeline systems, this study presents the wave-based analytical model for investigating the vibration behavior of periodic pipe structures filled with internal fluids. The model is formulated by integrating Timoshenko beam theory with the wave-based method. Governing differential equations are derived, considering both cross-sectional deformation and shear effects. A fluctuation-type solution is employed to obtain the displacement fields. Based on the displacement and force continuity conditions at the interfaces of adjacent units, together with the appropriate boundary conditions, the global dynamic equations of the periodic fluid-filled pipe structure are derived.The model’s accuracy is validated through comparison with finite element method (FEM) results. Subsequently, a parametric analysis is performed to examine the effects of fluid velocity, structural geometry, and material properties on the bandgap characteristics. The proposed framework offers theoretical insights and practical guidance for the design and vibration control of fluid-filled periodic pipeline systems.

This work develops a rigorous analytical framework to examine the scattering behavior and dynamic stress response of semi-elliptical notches in piezoelectric half-planes subjected to anti-plane shear (SH) waves. The framework unifies the treatment of cracks, circular holes, and notches within a consistent wave–defect interaction model, while explicitly incorporating piezoelectric coupling and nanoscale surface/interface effects. The analysis employs the complex function method in combination with the Helmholtz equation and wavefield superposition theory, resulting in an infinite system of equations that rigorously enforces continuity and boundary conditions. A systematic truncation scheme is then applied to ensure stable and convergent solutions. The results reveal that surface/interface effects play a crucial role in suppressing the dynamic stress concentration factor (DSCF), particularly under vertical SH-wave excitation, while sharper resonance peaks emerge at low modulus ratios and higher piezoelectric constants, such as PZT-5H and BaTiO₃. In the absence of piezoelectric coupling, the formulation seamlessly reduces to classical elasticity, ensuring strong theoretical consistency. Validation is achieved through recovery of benchmark solutions (semicircular notch and edge crack), graphical comparisons with prior results, and the rapid convergence of the truncated system, confirming the model’s accuracy and robustness. The findings hold significant implications for structural health monitoring, non-destructive evaluation, and the design of advanced piezoelectric composites, where accurate prediction of stress amplification and defect evolution is essential. Although the present study focuses on semi-elliptical notches in half-plane geometries under SH-wave loading, the approach can be readily extended to more general defect shapes and mixed-mode disturbances. The novelty of this work lies in capturing piezoelectric surface/interface effects within an exact analytical framework, thereby enhancing predictive capability for defect-induced stress concentrations and providing a reliable basis for the design and durability assessment of high-performance piezoelectric materials.

In this study, the thermal post-buckling behavior of a truncated composite conical shell with a lattice core and two composite layers is investigated. The shell is subjected to a uniform and linear temperature rise in thickness direction with simply supported boundary conditions at both ends. The shell is assumed to have an initial geometric imperfection and a lattice core composed of three stiffeners types: longitudinal (stringer), radial (ring), and helical with constant helical angles. The governing equations are derived based on the classical shell theory, incorporating nonlinear stress–strain relations under thermal loading. The compatibility equations are solved using the Galerkin method and the method of undetermined coefficients to predict the thermal buckling loads and post-buckling response. Numerical results validate the proposed model by comparison with previous studies and show that the reinforcement pattern significantly affects the thermal buckling performance. Among the configurations, the helical stiffeners yield the highest thermal resistance.

The reflection behavior of a multiple physical fields coupled waves for four kinds of possible surface conditions of piezoelectric solid with void is studied in this paper. First, the dispersion equation for multiple physical fields coupled waves propagation in the piezoelectric porous media is derived through inserting the multiple physical fields coupled constitutive equations into the general governing equation. Different from the classic piezoelectric medium, there are four coupled elastic waves in the piezoelectric material with void. Due to the consideration of porous effects of the piezoelectric material, the surface conditions can be proposed in different forms. These surface conditions, which include the free surface and elastic surface, electrical short circuit and electrical open circuit, as well as zero volume fraction disturbance surface and zero equivalent force surface, are then used to determine the reflection coefficients of reflection waves. The numerical results are provided for incident QP wave and incident QSV wave, respectively, and are validated by the energy conservation law. Based on these numerical results, the influences of the four kinds of surface conditions on the reflection behavior of multiple physical fields coupled waves are discussed.

The buckling behavior of sandwich annular plates comprising a honeycomb core and graphene platelet-reinforced top and bottom layers is studied in this paper using the high-order deformation theory. The structure is in hygrothermal environment with assuming the foundation with spring and shear layer assuming frictional effects. This modeling framework also captures a wider range of deformation behavior that is often missed by lower-order models. Considering this complicated problem, the numerical highly accurate technique of diffrential quadrature method (DQM) is used which efficiently manages the complicated boundary conditions. Finally, extensive numerical simulations are performed in order to analyze the buckling response in depth, focusing on major design parameters like the annular plates inner radius, temperature, moisture, foundation, boundary conditions, friction coefficient and GPL’s volume fraction in the nanocomposite layers. The results highlight the sensitivity of buckling behavior to these changes in design and provide greater insight into the mechanics that controls composite sandwich structures under compressive loads. A larger volume fraction of GPL will increase the buckling load. Increasing temperature from 30 to 45 °C decreases the buckling load by about 14%. and moisture content up to 40% lowers the buckling load by approximately 23%. In addition, changing boundary conditions from C–F to C–C raises the buckling load by up to 70%.

Piezoelectric beams are widely used as energy harvesting from mechanical vibration. For nanoscale beams, the flexoelectric effect is remarkable. This paper investigates the vibration of a clamped–clamped nanobeam with flexoelectric and piezoelectric effects carrying a concentrated nanoparticle. A governing equation and associated boundary conditions are derived from Hamilton’s principle. An exact frequency equation is obtained. Further, through the integral equation method, an explicit expression for the fundamental resonance frequency can be given with satisfactory accuracy. A comparison between the exact and approximate resonance frequency is made. Numerical results show the influence of flexoelectricity, piezoelectricity, and attached mass on the resonance frequencies of a vibrating beam-mass system, in particular for nanoscale beams.

A thermo-magneto-vibrational model is developed for sandwich nanoplates composed of composite metallic–ceramic face sheets and a hexachiral auxetic core. The formulation integrates higher-order shear deformation theory with nonlocal strain gradient theory to incorporate shear–flexural coupling and nanoscale size effects. Present research simultaneously addresses the influence of hexachiral geometry, elastic foundation parameters, magnetic field, and face-sheet composition within a unified framework. The governing equations are derived using Hamilton’s principle and solved through the Navier approach under simply supported boundary conditions. A systematic parametric study is carried out to assess the role of geometric ratios, material gradation, and scale-dependent parameters on vibration and thermal stability. Combining composite layers and core hexachiral auxetic lattice structure with multiphysics fields and nanoscale elasticity, offering a generalized formulation that captures interactions not previously considered together. The outcomes provide a basis for the design of thermally and magnetically durable sandwich nanoplates in aerospace, automotive, acoustic, and protective structural applications.