Acta Mechanica最新文献

In this work, the isogeometric analysis (IGA) is employed to study the dynamic instability characteristics of functionally graded (FG) multilayer graphene-reinforced composite plate with holes. The laminated nanocomposite plate is subjected to a periodic uniaxial in-plane load. The modified Halpin–Tsai scheme and rule of mixtures are utilized to evaluate the effective material properties of the nanocomposite plate. The third-order shear deformation theory (TSDT) of Reddy is used to describe the displacement field of the plate. Dynamic instability regions of graphene platelets reinforced composite (GPLRC) laminated plates with hole are approximated by applying the IGA and the Bolotin’s method. To demonstrate the capability of the developed formulation in predicting the dynamic instability behavior of GPLRC plates with central holes, several numerical examples are solved and compared with the existing solutions. Then, parametric studies are performed to examine the influences of significant parameters on instability zones of the functionally graded graphene platelet reinforced composite (FG-GPLRC) plates with circular/rectangular holes.

The present study develops an extended analytical framework for investigating Love-type wave propagation in multilayered magneto-electro-elastic (MEE) composites while accounting for nanoscale electrical, magnetic, and mechanical interfacial imperfections. The primary purpose is to establish a generalized dispersion relation that unifies classical Love-wave theory with coupled-field effects and imperfect interface conditions. The methodology employs the complex function approach in conjunction with the Helmholtz equation and wavefield superposition theory. Interfacial imperfection factors are introduced via a spring-type boundary model, leading to an infinite system of equations. A systematic truncation procedure ensures convergence of the analytical solution, and numerical simulations are performed to illustrate the influence of imperfections, thickness ratio, and coupling coefficients on dispersion, attenuation, and coupling efficiency. Findings reveal that imperfections significantly suppress phase velocity, with electrical defects producing stronger effects than magnetic ones, while mechanical bonding imperfections accelerate attenuation. Combined imperfections exhibit a synergistic nonlinear influence, producing dispersion shifts more severe than the sum of individual effects. Comparisons between EMO and EMS boundary conditions highlight that stress-driven EMS interfaces are more sensitive to imperfections than displacement-driven EMO boundaries. Additionally, increasing the guiding layer thickness enhances wave confinement, raising phase velocity and partially mitigating defect influence. Validation is achieved by demonstrating that the model naturally reduces to the classical Love-wave solution in the absence of coupling and imperfections, showing excellent agreement with previously published results. The novelty of the work lies in providing the first comprehensive formulation that integrates piezoelectric, piezomagnetic, and imperfection effects within a unified Love-wave framework. Limitations include restriction to anti-plane shear (SH) motion and idealized isotropic elastic half-space substrates, which may be extended in future studies to anisotropic or viscoelastic media. Practical applications include non-destructive evaluation of layered composites, defect detection, fatigue life prediction, energy harvesting, and the design of piezoelectric/piezomagnetic sensors.

This study develops a unified framework to analyze the random vibration of piezoelectric nanobeams on viscoelastic foundations. Using nonlocal elasticity and Hamilton’s principle, governing equations are derived within a unified shear deformation theory that includes Timoshenko, Reddy, sinusoidal, hyperbolic, and exponential models. A frequency response function is formulated for stationary white noise excitation and validated with literature results. Parametric results show that nonlocal effects increase vibration amplitudes, higher-order theories provide greater accuracy than the Timoshenko model, and voltage and temperature amplify responses due to electromechanical and thermal coupling. The framework offers a versatile tool for designing nanoresonators, sensors, and actuators under random loads requiring precise dynamic modeling.

In this study, the free vibrations of multiple-cracked nanostructures composed of functionally graded materials (FGMs) are investigated based on the nonlocal elastic theory (NET) and the dynamic stiffness method (DSM). The material properties of the FGMs vary nonlinearly along the height of the beam element. Cracks in the FGM nanostructures are modeled as two elastic springs connecting the intact segments at the cracked section. The differential equations of motion of a multiple-cracked FGM Timoshenko nanobeam element are derived using Hamilton’s principle and the NET with continuity conditions incorporated at the cracked sections. Exact closed-form solutions, which resolve the nonlocal paradox associated with the fundamental frequency of FGM cantilever beams, are proposed to construct the dynamic stiffness matrices for multiple-cracked FGM nanostructures under arbitrary boundary conditions. The proposed DSM model enables efficient and accurate computation of the free vibrations of multiple-cracked FGM nanostructures using a minimal number of elements. The reliability of the proposed DSM-based solutions is validated through comparisons with existing numerical results in the literature. Furthermore, the effects of the nonlocal parameters, material gradation, geometric properties, and elastic foundation on the vibration behavior of multiple-cracked FGM nanostructures are analyzed in detail.

In this study, the effect of width ratio (branch channel width/main channel width) on droplet breakup dynamics in a horizontal microfluidic T-junction using oil–water volume fraction contours, pressure profile, and velocity profile has been investigated using 2D simulation. Simulations have been also conducted to reveal the effect of branch arm length ratio (right arm length/left arm length) on droplet breakup dynamics. The numerical simulation is validated with experimental results taken from the literature. Two types of breakup regimes, along with a non-breakup regime, have been found. The breakup regimes are tunnel breakup, and obstructed breakup, and the non-breakup regime is the alternate movement of droplets. The tunnel breakup and the obstructed breakup are mainly due to the pressure difference in the branch channel and the direction of the velocity vectors which are towards the branch’s exit and the pressure swing phenomenon is the reason behind the alternate movement of the droplets. Breakup with tunnel is found in WR (width ratio) = 0.75, 0.5, breakup with obstruction is found in WR (width ratio) = 0.25 and alternate movement is found in WR (width ratio) = 1 for V_w (velocity of water) = 0.01 m/s, V_o (velocity of oil) = 0.18 m/s. It has been found that breakup tendency increases as we decrease the width ratio (1, 0.75, 0.5, and 0.25) and increase the arm length ratio (0.4, 0.6, and 0.9). Some 3D simulations have been performed regarding these and the 3D simulations confirm the accuracy of the 2D simulations. Droplet breakup conditions have been studied. Various mixed flow regimes have been identified and illustrated. Mixed flow patterns have been displayed with the help of a flow pattern map for the width ratio = 1, 0.75, 0.5, and 0.25. Prediction of simulated pressure gradient have also been done with the help of the Dimensional analysis for width ratio = 1 and 17% of average error is found between predicted and simulated pressure gradient. This quantitative analysis of the pressure drop evidenced that the solver correctly captures viscous dissipation and interfacial forces and the design of bifurcated channel geometry is optimal.

This article presents a study on the dynamical response of FG (functionally graded)-CNTRC (carbon nanotube-reinforced composite) curved pipes subjected to a moving load in thermal field. The effect of Winkler elastic foundation as well as the effect of Pasternak shear foundation is taken into consideration. The distribution pattern of carbon nanotubes is designed through the pipe’s thickness using five various profiles. The kinematic equations are obtained and implemented for the nanocomposite curved pipe based on the higher-order shear deformation theory considering the von Karman type of geometric nonlinearity. The time-dependent governing equations are formulated for the nanocomposite curved pipe via the Hamilton’s principle. The Ritz solution method is implemented to obtain the matrix representation for governing differential equations with three different types of boundary conditions. The obtained time-dependent equations are traced in time by considering the Newmark time marching method. Finally, several numerical examples are discussed to explore the influences of the important parameters on the dynamical response of the FG-CNTRC curved pipes subjected to a moving load.

In this work, we will study, from the analytical point of view, two problems arising in second-gradient thermoelasticity. The first one involves the Lord–Shulman second-gradient theory. An existence and uniqueness result is shown by using the theory of linear semigroups. Then, we prove that the energy decay is of exponential type and that the semigroup associated to the differential operator is not differentiable, which implies that this is not analytic neither. The second problem includes the so-called Moore–Gibson–Thompson second-gradient theory. Two cases will be considered if we assume that the thermal law includes (or not) fourth-order spatial derivatives. In the case of second-order spatial derivatives, we recall that the problem has a unique solution but the energy decay is slow; meanwhile, if fourth-order spatial derivatives are present, the decay is of exponential type. For this last problem, we study the analyticity of the semigroups depending on a constitutive coefficient.

With the development of aerospace industry, the complexity and large size of spacecraft bring huge time cost for simulation. The damping characteristics of materials and the influence of solar heat flux will further lead to a decrease in computational efficiency. In this study, a model order reduction method for viscoelasticity-thermal coupled multibody systems is proposed. The Absolute Nodal Coordinate Formulation (ANCF) and the Kelvin–Voigt viscosity model are used to build the system equation of motion. The Proper Orthogonal Decomposition (POD) method is introduced to reduce the system degrees of freedom. The computational efficiency is further improved by dividing the system motion process into multiple linearized intervals based on the first-order Taylor expansion. To improve the robustness of the reduced-order model, a multi-parameterized reduced-order model is constructed based on Grassmann manifold interpolation theory. Three numerical examples are presented as verification and validation. Results show that the proposed method is able to quickly predict the response of the viscoelasticity-thermal coupled systems with uncertain parameters.

We investigate the expansion or growth of an internally pressurized pre-existing small spherical cavity in soft solid blocks made of compressible isotropic Blatz–Ko materials by accounting for cavity surface effects. We seek to study the influence of the dimensionless elastocapillary parameter called (gamma ^*) and Poisson’s ratio, i.e., (nu _0), on the cavitation phenomenon. In doing so, we revisit the standard approach by transforming the balance equations into a one-dimensional second-order nonlinear ordinary differential equation (ODE). It turns out that the ODE can be solved only numerically when varying the Poisson’s ratio, i.e., (nu _0). Firstly, we focus on the classical case in order to validate our numerical findings, that is, for a specific Poisson’s ratio (nu _0=0.25), the shape factor (eta =) 1.5–100 and zero surface effects. Secondly, we analyze the influence of Poisson’s ratio (nu _0=) 0.25–0.40 on the cavity critical state when (eta =3.5). Thirdly, we study the effects of varying both the Poisson’s ratio and the dimensionless elastocapillary parameter (gamma ^*) on the cavitation phenomenon.

A mechanical model was developed to investigate the effects of micro-morphology and macro-geometry on the bearing capacity of two contacting spheres. First, the influence of the frequency index on the elastoplastic deformation stage was analyzed. Next, by correlating the curvature radii of the two spherical surfaces with the contact area distribution function, an improved asperity contact area distribution function was derived. Finally, a fractal contact model for interacting spherical surfaces was established. The results indicate that internal contact provides a higher load-bearing capacity than external contact. Furthermore, when the radii of the two spheres are equal, internal contact approximates plane contact, and the load-bearing capacity reaches its maximum value. This study provides a theoretical foundation for enhancing the load-carrying capacity of mechanical components such as bearings.