Acta Mechanica最新文献

The nonlinear bending and vibration behaviors of a variable-width piezoelectric nanoplate considering flexoelectric effect are investigated in this paper. The nonlinear Mindlin plate theory and finite element method are applied to derive the governing equations of variable-width piezoelectric nanoplate with flexoelectricity. The influences of geometric nonlinearity, flexoelectricity, and varying width on the bending deflection and natural frequency of the piezoelectric nanoplate with flexoelectricity under four kinds of boundary conditions are explored in detail. The numerical results show that the flexoelectric effect can strongly influence the maximum deflection, the morphology of deformation, and the natural frequency of the variable-width piezoelectric nanoplate. The consideration of geometric nonlinearity becomes necessary for nanoplate exhibiting strong flexoelectricity or subject to significant voltage loads. The boundary conditions not only affect the morphology of deformation but also influence the variation trend of natural frequency with the variable-width ratio of the piezoelectric nanoplate. While the variation trend of maximum deflection is jointly affected by the boundary conditions and flexoelectricity. The closer the shape of the piezoelectric nanoplate is to a triangle, the greater the combined effect of boundary conditions and flexoelectricity on the variation trend of maximum deflection. The results of this study can contribute to the optimization of piezoelectric nanostructures, and they are helpful in enhancing our comprehension of the mechanical behavior of piezoelectric nanostructures.

This study investigates the free vibration behavior of auxetic metamaterial plates using a refined plate theory. The research focuses on the integration of functionally graded graphene origami (GOri) into the plate structures, examining various content levels and folding patterns to enhance dynamic performance. The GOri-reinforced plates are analyzed within the context of a Winkler–Pasternak elastic substrate. Hamilton’s principle is applied to derive the kinetic equations governing the auxetic metamaterial plates, facilitating an analytical solution for the governing equations. A comprehensive comparison of numerous parameters is conducted, including graphene content and dispersion type, GOri folding degree and distribution pattern, temperature effects, and elastic foundation coefficients, all of which influence the vibrational characteristics of the plates. The findings identify critical factors affecting natural frequency, providing a thorough understanding of the relationship between the physical configuration of auxetic metamaterial plates and their dynamic response. This study ultimately aims to leverage these insights to optimize the design of auxetic metamaterials for improved vibrational performance in engineering applications.

Broadband vibration suppression is a major challenge in engineering applications. In this paper, two Bragg bandgaps of a piezoelectric metamaterial beam with a shunted circuit are bridged to form an ultrawide bandgap by using the genetic algorithm. Piezoelectric patches are periodically attached to the host beam. Inductive-capacitive-resistive (LCR) shunted circuits are connected to the piezoelectric patches. A supercell with different LCR shunted circuits is designed. To couple multiple locally resonant bandgaps to Bragg bandgaps, an optimized scheme based on genetic algorithm is designed. The imaginary part of the wavenumber is used as an optimization objective to achieve the maximum attenuation within the target frequency range. The results show that two Bragg bandgaps are bridged to form an ultrawide bandgap and maximum attenuation is achieved. The transmissibility shows that the metamaterial can achieve optimal vibration suppression in the ultrawide frequency range. The finite element results verify that the optimized metamaterial can bridge the two bandgaps into a wide bandgap and can realize optimal vibration suppression at ultrawide frequencies. The pseudo-stochastic vibration of 600–8100 Hz confirms that the optimized metamaterials are more suitable for broadband vibration suppression. This metamaterial has more advantages in complex engineering environments.

Polymers consist of many discrete chains, making them inherently discrete rather than continuous. To analyze polymers (and their composites) using continuum mechanics, it is necessary to establish a bridge between their discrete and continuum models. In this paper, the discrete microsphere model is employed to derive a physics-based strain gradient continuum, where the strain gradient term relies on the concrete geometric structure. This is achieved by connecting the stretch fluctuation field of polymer chains with the strain gradient field through an asymptotic homogenization method. This homogenization method first provides the construction of the Helmholtz free energy density for the microsphere model and then develops the transformation of the free energy density to that strain gradient continuum. Applying the proposed strain gradient continuum to the Euler–Bernoulli beam, the size-dependent effects of the free energy, the bending rigidity, and deflection are investigated in detail. This homogenization method bridges the gap between discrete and continuous polymer mediums. Furthermore, the continuum model retains high-order strain gradient information. This correlation facilitates the application of polymers in nanocomposites, enabling the creation of groundbreaking materials through artificial design.

Glass fiber-reinforced polymer (GFRP) composites exhibit restricted mechanical performance, notably in terms of interlaminar shear strength and fracture toughness, as a consequence of the propensity for fiber/matrix fracturing and delamination when subjected to exterior loading. This study elucidates the enhancement of GFRP composites' mechanical characteristics through the integration of multi-walled carbon nanotubes (MWCNTs). A solution dip coating method was used to deposit 0.3 wt% MWCNTs on the glass fiber fabrics to manufacture the MWCNT-modified GFRP composites. A comprehensive experimental investigation was undertaken to evaluate the impact of MWCNTs on the mechanical attributes of GFRP composites across varying thicknesses and layups. Flexural strength, interlaminar shear strength and fracture toughness were investigated through three-point bending, short beam shear and end notch flexural (ENF) tests, respectively. To further decipher the microstructural enhancement mechanisms of MWCNTs in GFRP composites, fractured surfaces post-ENF testing underwent examination using a field-emission scanning electron microscope. The results revealed that MWCNT-modified GFRP composites with a 4-mm thickness and unidirectional orientation displayed optimal mechanical properties, and the MWCNT-modified GFRP composites with a certain layering angle surpassed the mechanical performance of their unmodified, thinnest unidirectional GFRP counterparts. This research thereby presents engineers with a novel design strategy to address the challenges posed by intricate application scenarios, enhancing the versatility and resilience of GFRP composites in advanced applications.

Mechanical connection is a common method used for joining composite materials, but it is bound to open holes in the composite material structure. These open holes may cause stress concentration at the hole edge, impacting the overall mechanical properties of the component. In this paper, a machine learning-based method for predicting the mechanical properties of open-hole composite laminates is proposed based on generalized regression neural network. In detail, by using the Hashin failure criterion, the finite element models of composite laminates with single holes of different diameters have been established. Their load–displacement curves, maximum failure stresses and maximum failure strains are calculated numerically. Then, the different hole diameters and corresponding load–displacements can be used as the input and output variables of the generalized regression neural network to train the neural network model. Based on the optimal generalized regression neural network model, the mechanical properties of the composite laminates with a certain single hole diameter can be predicted. Compared with the uniaxial tensile experiment of open-hole composite laminates, the effectiveness of this machine learning method is verified. Furthermore, the changes in mechanical properties of double-hole composite laminates under different hole diameters and positions are analyzed. This study holds significant practical implications for enhancing the understanding of the mechanical properties of composite materials and the influence of defects on their performance.

In this review paper, we provide a brief overview of the recent advances in the continuum modeling of gas–particle flows. First, we focus on the kinetic theory-based two-fluid models, which have become a valuable tool to investigate small-scale moderately dense turbulent gas–particle flows. Second, the continuum description is quite restrictive with respect to the maximum grid spacing, and large-scale simulations usually employ coarse mesh resolutions to keep the analyses practicable. Such coarse-graining inevitably neglects the small unresolved scales, which requires additional modeling. Here, filtered two-fluid models have been applied successfully to a variety gas–solid flow problems. Finally, we give a condensed outline about future research challenges for the continuum modeling of gas–particle flows.

The vibration response and stability of functionally graded porous (FGP) sandwich plates under moving mass are explored. The self-weight of the FGP sandwich plate is taken into account in this study. A four-variable equivalent-single-layer (ESL) plate theory is applied to this problem. Three different forms of porous cores are considered: symmetric porosity distribution (SPD), asymmetric porosity distribution (APD) and uniform porosity distribution (UPD). The governing equations of motion are derived based on Hamilton’s principle and then solved by using the eigenfunction expansion method in combination with the differential quadrature method (DQM). The stability analysis is conducted using the complex eigenvalue method. Convergence study and verification study are performed to show the reliability and accuracy of the proposed method. The effects of some key parameters such as moving mass’s weight and velocity, porosity coefficient, porosity distribution pattern, etc. on the vibration response and stability of the FGP sandwich plates are investigated.

This paper investigates the dynamic responses of spinning FG GPLs reinforced with a nanocomposite sandwich cylindrical shell based on a magnetorheological elastomer (MRE) core subjected to thermomechanical loading and residual stress. The sandwich cylindrical shell is considered using the Donnell–Moshtari theory based on metal matrix nanocomposites; furthermore, GPLs are used with uniform and FG distribution in the thickness direction to reinforce these layers. The MRE core layer is modeled based on FSDT. The effect of temperature on the mechanical properties of MRE, GPLs, and metal matrix nanocomposites is considered. The mechanical properties of the nanocomposite sandwich shell are obtained based on the Halpin–Tsai micromechanics model and the rule of mixture. The equations of motion for a spinning sandwich shell are obtained by considering the rotary inertia and shear effect. The frequencies of a spinning shell are derived using the Differential Quadrature Method. The effect of parameters such as weight fraction and distribution of GPLs, MRE core, spinning speed, residual stresses, and thermomechanical loading on the dynamic behavior of spinning nanocomposite sandwich shells are studied.

This study proposes a coupled hydro-thermo-mechanical scheme for freeze–thaw fracture of concrete based on the intermediately-homogenized peridynamic model. The strain of three-dimensional concrete prisms predicted by the present scheme is closer to the experimental measurements, and the predicted temperature and pore water pressure are in acceptable agreement with the finite element results. In addition, the effects of permeability and aggregate volume fraction on the mechanical properties and fractures of concrete during the freeze–thaw process are investigated. The results indicate that higher permeability decreases pore water pressure, crystallization pressure, and freezing strain, leading to fewer cracks and less overall damage in the specimens. Moreover, the higher the aggregate volume fraction, the higher the maximum temperature and maximum strain, and the greater the number of cracks and overall damage of the specimen. Numerical examples show the model has a good performance in analyzing the fracture process and mechanism of concrete under freeze–thaw cycles.