Acta Mechanica Solida Sinica最新文献

In the framework of elastoplastic theory, by introducing dissipative plastic energy (instead of cumulative plastic strain) and dissipative plastic energy rate (instead of cumulative plastic strain rate) into the ratchetting parameter evolution equation and isotropic evolution rules respectively, a cyclic elastoplastic constitutive model based on dissipative plastic energy is established. This model, termed the WDP model, describes the physical meaning and evolution rule of the unclosed stress–strain hysteresis loop using an energy method. A comparison of numerical implementation results with experimental data demonstrates the capability of the WDP model to predict the cyclic deformation of EA4T steel, effectively capturing the cyclic softening characteristics and ratchetting behaviors of axle steel EA4T.

The development of wearable electronics necessitates flexible and robust energy storage components to enhance comfort and battery longevity. The key to flexible batteries is improving electrochemical stability during deformation, which demands mechanical analysis for optimized design and manufacturing. This paper summarizes the progress of flexible batteries from a mechanical perspective, highlighting highly deformable structures such as fiber, wave, origami, and rigid-supple integrated designs. We discuss mechanical performance characterization and existing evaluation criteria for battery flexibility, along with simulation modeling and testing methods. Furthermore, we analyze mechano-electrochemical coupling, reviewing theoretical models that simulate mechanical and electrochemical behavior under various loads and introduce coupling tests that assess electrochemical performance during deformation. Finally, we suggest future research directions to advance flexible energy storage devices.

The strain transfer behavior of graphene and black phosphorus heterostructure on flexible substrates plays a crucial role in the functionality and regulation of the device. Specifically, it is imperative to investigate the anisotropy associated with strain transfer at the black phosphorus interface. In this study, a sample transfer method was proposed to prevent the contact of black phosphorus with water, achieving monolayer graphene and few-layer black phosphorus heterostructures on a PET film substrate. Micro-Raman spectroscopy was used to measure the strain of graphene and black phosphorus when the PET film substrate was under uniaxial tensile loading along the zigzag and armchair directions of black phosphorus, respectively. The Raman shift-strain relationship of black phosphorus was derived, and an interface transfer model was developed for the heterostructure. Based on the model, the strain transfer efficiency of each measuring spot was calculated and the strain transfer mechanism of each layer was analyzed. The results uncover the influence of the anisotropic interlayer properties inside the black phosphorus on the strain transfer behavior in the heterostructure on the flexible substrate.

The recently reported silicon/graphite (Si/Gr) composite electrode with a layered structure is a promising approach to achieve high capacity and stable cycling of Si-based electrodes in lithium-ion batteries. However, there is still a need to clarify why particular layered structures are effective and why others are ineffective or even detrimental. In this work, an unreported mechanism dominated by the porosity evolution of electrodes is proposed for the degradation behavior of layered Si/Gr electrodes. First, the effect of layering sequence on the overall electrode performance is investigated experimentally, and the results suggest that the cycling performance of the silicon-on-graphite (SG) electrode is much superior to that of the graphite-on-silicon electrode. To explain this phenomenon, a coupled mechanical–electrochemical porous electrode model is developed, in which the porosity is affected by the silicon expansion and the local constraints. The modeling results suggest that the weaker constraint of the silicon layer in the SG electrode leads to a more insignificant decrease in porosity, and consequently, the more stable cycling performance. The findings of this work provide new insights into the structural design of Si-based electrodes.

Honeycomb structures of shape memory alloy (SMA) have become one of the most promising materials for flexible skins of morphing aircraft due to their excellent mechanical properties. However, due to the nonlinear material and geometric large deformation, the SMA honeycomb exhibits significant and complex nonlinearity in the skin and there is a lack of relevant previous research. In this paper, the nonlinear properties of the SMA honeycomb structure with arbitrary geometry are investigated for the first time for large deformation flexible skin applications by theoretical and experimental analysis. Firstly, a novel theoretical model of SMA honeycomb structure considering both material and geometric nonlinearity is proposed, and the corresponding calculation method of nonlinear governing equations is given based upon the shooting method and Runge–Kutta method. Then, the tensile behaviors of four kinds of SMA honeycomb structures, i.e., U-type, V-type, cosine-type, and trapezoid-type, are analyzed and predicted by the proposed theoretical model and compared with the finite element analysis (FEA) results. Moreover, the tensile experiments were carried out by stretching U-type and V-type honeycomb structures to a global strain of 60% and 40%, respectively, to perform large deformation analysis and verify the theoretical model. Finally, experimental verification and finite element validation show that the curves of the theoretical model results, experimental results, and simulation results are in good agreement, illustrating the generalizability and accuracy of the proposed theoretical model. The theoretical model and experimental investigations in this paper are considered to provide an effective foundation for analyzing and predicting the mechanical behavior of SMA honeycomb flexible skins with large extensional deformations.

Fluid-conveying pipes generally face combined excitations caused by periodic loads and random noises. Gaussian white noise is a common random noise excitation. This study investigates the random vibration response of a simply-supported pipe conveying fluid under combined harmonic and Gaussian white noise excitations. According to the generalized Hamilton’s principle, the dynamic model of the pipe conveying fluid under combined harmonic and Gaussian white noise excitations is established. Subsequently, the averaged stochastic differential equations and Fokker–Planck–Kolmogorov (FPK) equations of the pipe conveying fluid subjected to combined excitations are acquired by the modified stochastic averaging method. The effectiveness of the analysis results is verified through the Monte Carlo method. The effects of fluid speed, noise intensity, amplitude of harmonic excitation, and damping factor on the probability density functions of amplitude, displacement, as well as velocity are discussed in detail. The results show that with an increase in fluid speed or noise intensity, the possible greatest amplitude for the fluid-conveying pipe increases, and the possible greatest displacement and velocity also increase. With an increase in the amplitude of harmonic excitation or damping factor, the possible greatest amplitude for the pipe decreases, and the possible greatest displacement and velocity also decrease.

Anode-free lithium metal batteries are prone to capacity degradation and safety hazards due to the formation and growth of lithium dendrites. The interface between the current collector and deposited lithium plays a critical role in preventing dendrite formation by regulating the thermodynamics and kinetics of lithium deposition. In this study, we develop a phase field model to investigate the influence of the current collector’s surface energy on lithium deposition morphology and its effect on the quality of the lithium metal film. It is demonstrated that a higher surface energy of the current collector promotes the growth of lithium metal along the surface of the current collector. Further, our simulation results show that a higher surface energy accelerates the formation of the lithium metal film while simultaneously reducing its surface roughness. By examining different contact angles and applied potentials, we construct a phase diagram of deposition morphology, illustrating that increased surface energy facilitates the dense and uniform deposition of lithium metal by preventing the formation of lithium filaments and voids. These findings provide new insights into the development and application of anode-free lithium metal batteries.

Based on the Timoshenko beam theory, this paper proposes a nonlocal bi-gyroscopic model for spinning functionally graded (FG) nanotubes conveying fluid, and the thermal–mechanical vibration and stability of such composite nanostructures under small scale, rotor, and temperature coupling effects are investigated. The nanotube is composed of functionally graded materials (FGMs), and different volume fraction functions are utilized to control the distribution of material properties. Eringen’s nonlocal elasticity theory and Hamilton’s principle are applied for dynamical modeling, and the forward and backward precession frequencies as well as 3D mode configurations of the nanotube are obtained. By conducting dimensionless analysis, it is found that compared to the Timoshenko nano-beam model, the conventional Euler–Bernoulli (E-B) model holds the same flutter frequency in the supercritical region, while it usually overestimates the higher-order precession frequencies. The nonlocal, thermal, and flowing effects all can lead to buckling or different kinds of coupled flutter in the system. The material distribution of the P-type FGM nanotube can also induce coupled flutter, while that of the S-type FGM nanotube has no impact on the stability of the system. This paper is expected to provide a theoretical foundation for the design of motional composite nanodevices.

A modified inner-element edge-based smoothed finite element method (IES-FEM) is developed and integrated with ABAQUS using a user-defined element (UEL) in this study. Initially, the smoothing domain discretization of IES-FEM is described and compared with ES-FEM. A practical modification of IES-FEM is then introduced that used the technique employed by ES-FEM for the nodal strain calculation. The differences in the strain computation among ES-FEM, IES-FEM, and FEM are then discussed. The modified IES-FEM exhibited superior performance in displacement and a slight advantage in stress compared to FEM using the same mesh according to the results obtained from both the regular and irregular elements. The robustness of the IES-FEM to severely deformed meshes was also verified.

A partial-periodic model is proposed for predicting structural properties of composite laminate structures. The partial-periodic model contains periodic boundary conditions in one direction or two directions, and free boundary condition in other directions. In the present study, partial-periodic model for composite laminate beam structures is particularly studied. Three-point bending experiments for laminate beam specimens with different laying parameters are firstly used to verify the present partial-periodic model. In addition, a detailed finite element method (FEM) model is also used to further quantitatively compare with the present partial-periodic model for composite laminate beams with different laying parameters. The results indicate that the proposed partial-periodic model is capable of providing accurate predictions in most cases. The computational time cost of the proposed partial-periodic model is much lower than that of the detailed FEM model as well. Convergence studies are also conducted for the present partial-periodic model with different model sizes and element sizes. It is suggested that the proposed partial-periodic model has the potential to be used as an accurate and time-saving tool for predicting the structural properties of composite laminate beam structures.