Archive of Applied Mechanics最新文献

This study presents a semi-analytical approach for analyzing the bending and free vibration behavior of three-phase bi-directional functionally graded porous sandwich plates (2D-FGPSW). The sandwich plates considered feature face sheets with biaxial material gradation composed of three distinct constituents and a thickness-varying functionally graded porous core. Such structural configurations are relevant to advanced engineering applications requiring high strength-to-weight ratios and tailored mechanical performance. The analysis is based on Reddy’s third-order shear deformation theory and employs the pb2-Ritz method to obtain accurate solutions under various boundary conditions, with convergence checked through appropriate term selection. The model is validated through comparison with available benchmark solutions. A comprehensive parametric study is conducted to evaluate the effects of material gradation, geometric parameters, sandwich configurations, and boundary conditions on the structural response. The results contribute to a deeper understanding of the mechanical behavior of complex sandwich structures and support the design of efficient and lightweight composite systems.

The study of nonstationary vibrations and wave propagation in deformable waveguides is of considerable interest in many fields of science and engineering. This work addresses wave processes in extended multilayer cylindrical bodies. The aim of the study is to investigate the problems of wave propagation in an elastic hollow three-layered cylinder and to develop efficient analytical methods for solving the problem of nonstationary wave propagation in layered cylindrical structures. The problem is formulated and solved in a cylindrical coordinate system. Normal (radial) loads are applied at the free boundaries (either inner or outer) of the cylinder. The solution is constructed using the Laplace integral transform with respect to time, followed by its inversion. The solution in the original (time) domain is presented in a form that is convenient for numerical implementation. This formulation makes it possible to analyze wave propagation in a multilayer cylinder with an arbitrary number of coaxial layers. A spectral boundary value problem is derived for a system consisting of ordinary differential equations and partial differential equations, which is reduced to a system of ordinary differential equations with complex coefficients. The solution in the Laplace domain is expressed in terms of modified Bessel and Neumann functions of arbitrary order. The inverse transformation is carried out in a form free from contour integrals and is represented as a rapidly converging double series of cylindrical functions. It is established that, for large wave numbers, the limiting phase velocity of this mode coincides with the Rayleigh wave speed.

To improve stress–strain prediction accuracy for dense vulcanized rubber, this study develops a constitutive modeling fitting framework incorporating bulk modulus (K) effects (i.e., a nearly incompressible formulation). Six classical phenomenological hyperelastic models—Three-Term Mooney-Rivlin (MR_T), Yeoh, Yeoh_Revised (Yeoh_R), Gent-Gent (GGent), Ogden, and Lopez-Pamies—are comparatively evaluated within this framework. Systematic assessment via the goodness-of-fit (R²) metric quantifies model performance across three deformation modes (simple tension, planar tension, and equibiaxial tension) for multiple rubber materials, including HNBR, FPM, silicone rubber, and the Treloar dataset. The framework is further extended to highly compressible rubber-like materials (e.g., foams/hydrogels). Key results demonstrate: (i) Significant R² improvement for comprehensive tensile stress predictions in dense vulcanized rubber; (ii) Pronounced enhancement of equibiaxial tensile stress accuracy for generalized Mooney-Rivlin models (e.g., MR_T, Yeoh_R); (iii) Critical dependence of the Ogden model on parameter initialization to ensure physical relevance and mitigate sensitivity; (iv) Limited applicability to highly compressible materials with strong model-specific performance variation; (v) Essential requirement for comprehensive experimental validation, particularly high-precision bulk modulus (K) characterization. This work provides quantitative selection criteria for phenomenological constitutive models in FEA, incorporating the calculation of shear modulus (G) to enable more reliable assessment of rubber material behavior in engineering applications.

The Theory of Porous Media (TPM) with an embedded phase-field approach to fracture provides an elegant opportunity to study complex flow phenomena in fractured porous materials in a unified single-domain approach. On this basis, the interactive flow behaviour between free flow and porous-media flow is studied using the example of flow through a thin porous plate containing a rectangular channel. By considering different boundary conditions and investigating the flow behaviour for a range of hydraulic conductivities, our study is designed to reveal insights into phenomena which are relevant for various sub-surface geo-engineered applications. Furthermore, we show that the applied macroscopic single-domain approach is able to reveal local flow effects near the porous interface (channel walls), namely the so-called velocity profile inversion phenomenon. Moreover, we introduce a geometrically motivated estimation of the length-scale parameter (epsilon ) used in phase-field approaches, which is directly related to the roughness of the fracture surface. Thus, values for (epsilon ) are proposed for microfluidic devices and different rock types. Furthermore, we apply fully three-dimensional simulations to evaluate the influence of the thickness of thin porous plates on the overall flow resistance, which is typically relevant in microfluidic devices. In a combined numerical–experimental study, we compare results from representative microfluidic experiments and simulations and confirmed the choice of (epsilon ) to correctly predict the flow transition across the porous interface.

In recent years, extensive studies on carbon nanotubes-reinforced composites (CNTRC) focus on the uniform-thickness structures and free vibration. However, there is few researches on the vibro-acoustic behaviors of CNTRC structures with variable thickness. Accordingly, this paper constructs a variable thickness double-functionally graded (DFG) sandwich curved plates reinforced by CNTs. The Mori–Tanaka model and mixture rule are used to evaluate the effective elastic modulus of the composite structures. The thermal–mechanical dynamic equation is established using the Hamilton’s principle and solved via Navier’s method combined with the fluid–solid coupling conditions to determine the natural frequency and sound insulation. In calculation, the variable thickness parameters, gradient indices of FG materials, CNT distribution forms, curvature and temperature variations on the vibro-acoustic behaviors are examined. The obtained results show that the curvature of curved plates can significantly increase the vibration frequency and optimize sound insulation characteristics. The coupling effect of material softening and thermal stress under temperature field has a strong suppression effect on vibration frequency, while the nonuniform parameters of variable thickness and the change rate of thickness positively correlate with the vibro-acoustic performances.

Impact force identification (ImFoId), which involves impact localization and force reconstruction, is recognized as a doubly ill-posed inverse problem in structural dynamics, where even slight measurement noise or modeling inaccuracies can lead to completely erroneous results. To tackle it, a novel hierarchical ImFoId methodology using truncated impact response (TIR) is proposed in this paper, which significantly improves the accuracy and robustness of ImFoId. The proposed method initiates by utilizing variational mode decomposition (VMD) to decompose the complete impact response (CIR), which encompasses the full spectrum of the vibration signal, into several modal impact responses (MIRs). Then, by superimposing these MIRs, the so-called TIR is obtained. The utilization of TIR facilitates the establishment of a high-fidelity forward transfer model, as it excludes frequency components beyond the natural frequencies of structures and eliminates modal truncation errors induced by higher-order modal responses. In the phase of impact localization, an impulse model is employed to approximate the impact force, and the localization is efficiently realized by maximizing the collinearity between the estimated impact response (EIR) and TIR. Following the localization result, the forward transfer matrix between time histories of the impact force and TIR is established, and the unknown impact force is accurately reconstructed by solving the invers problem through truncated singular value decomposition (TSVD) based Tikhonov regularization technique. Numerical simulations conducted on a spring-mass-damper system, along with experimental validations performed on a clamped–clamped beam and a cantilevered metal plate, demonstrate that the proposed method yields both remarked robustness and accurate identification results.

A mechanical model and finite element method for the simultaneous solution of Stokes and incompressible Navier–Stokes flows on multiple curved surfaces over a bulk domain are proposed. The two-dimensional surfaces are defined implicitly by all level sets of a scalar function, bounded by the three-dimensional bulk domain. This bulk domain is discretized with hexahedral finite elements which do not necessarily conform with the level sets but with the boundary.The resulting numerical method is a hybrid between conforming and non-conforming finite element methods. Taylor–Hood elements or equal-order element pairs for velocity and pressure, together with stabilization techniques, are applied to fulfil the inf-sup conditions resulting from the mixed-type formulation of the governing equations. Numerical studies confirm good agreement with independently obtained solutions on selected, individual surfaces. Furthermore, higher-order convergence rates are obtained for sufficiently smooth solutions.

This study focuses on the vibrational analysis of functionally graded material saturated porous annular sector plate reinforced with multi-walled carbon nanotubes (MWCNTs) on a Winkler foundation. The analysis takes into account the coupled effect of CNT waviness and agglomeration, as well as the influence of pressure in the closed cell on the vibrational properties of the composite plate. In order to assess the mechanical properties of the nanocomposite, a modified Halpin–Tsai micromechanical model incorporating orientation, waviness, and agglomeration factors of MWCNT is utilized. Also, the Biot constitutive law is used instead of the simple Hooke’s law to obtain realistic and practical conclusions. The principle of minimum potential energy and the Rayleigh–Ritz method are employed to solve the governing equations. A comprehensive investigation is conducted considering multiple parameters that can influence the natural frequency of the annular sector plate. These parameters include the CNT weight fraction, CNT distribution pattern, CNT dimension, and porosity parameters such as the porosity coefficient, Skempton coefficient, and porosity distribution. The effect of CNT waviness and agglomeration, as well as the Winkler elastic foundation coefficient, is also taken into consideration. Additionally, the dimension of the sector plate is explored through variations in the inner-to-outer radius ratio, inner-to-thickness ratio, and sector angle.

304 stainless austenitic steel (AISI 304) is renowned for its high temperature resistance and has been the subject of considerable research. To explore its rheological behavior at high temperature, isothermal hot compression experiments were conducted on the Gleeble-3800 thermal simulator at temperatures of 800–1200 °C, strain rates of 0.011–11 ({s}^{-1}), and a total strain of 60%. From the experimental data, a Johnson–Cook (JC) constitutive model was formulated and further optimized. The optimized model considers the combined effect of strain, strain rate, and temperature, resulting in a more precise constitutive equation. The enhanced JC model had excellent predictive power, with a correlation coefficient (Rco) of 0.9884 and an average absolute relative error (AARE) of 8.42%. ABAQUS simulations for verification confirmed the model to be valid. This study offers valuable theoretical information for the hot working of SS 304, enabling more precise predictions of stress behavior at high temperature and easier optimization of processing parameters and overall material behavior. Also, deformation of metastable austenitic stainless steel at temperatures below the Md point leads to the transformation of austenite into martensite. This study investigates how prior deformation, conducted at temperatures both below and above Md, affects the dynamic tensile behavior of AISI 304 stainless steel. Pre-deformation at 25 °C (below Md), as well as at elevated temperatures of 200 °C and 300 °C (above Md), enhances both the yield strength and ultimate tensile strength of the material. Notably, prior deformation at 25 °C to a small equivalent strain (< 0.03) results in significant improvements in strength (22%) and ductility (21–37%) during subsequent high strain-rate tensile loading at 200 and 300 s⁻¹. The evolution of local strain fields and strain rates is analyzed using digital image correlation. Additionally, the development of localized necking is investigated through in-situ high-speed camera imaging.