Metals and alloys are widely used in industry due to their excellent mechanical properties. Researchers have been continuously searching new materials with better properties or mechanisms to enhance existing ones. In the metal and alloy forming process, hot deformation can effectively refine the grain and improve mechanical properties such as yield strength and tensile strength. Therefore, it is necessary to study the deformation behavior of metal and alloy materials at high temperatures. The hyperbolic-sinusoidal Arrhenius-type model has been widely used by researchers because of its good simulation effect at high temperatures. In this paper, the building process of the model is studied, and the modeling process is optimized with the help of a neural network model. A neural network model is constructed to efficiently determine the hyperbolic-sinusoidal Arrhenius-type equations, based on which the flow stress of high-entropy alloys (HEAs) for different high temperatures and strain rates can be well predicted. The reported hot deformation behaviors of Al_0.3CoCrFeNi HEAs are examined by current model. The results show that the coefficients obtained by the neural network method can better describe the experimental hot flow stress, especially at high strain rate or low temperature conditions. The root-mean-square error (RMSE) and the correlation coefficient R are used to assess the degree of difference between the results. The RMSE and R of the neural network method at total data are 27.7 and 0.985, respectively, which are better than 33.1 and 0.979 of the traditional method. To show the general applicability of the model, the hot deformation behaviors of (CoCrNi)₉₄Ti₃Al₃, FeCrCuNi₂Mn₂, and AlCrCuFeNi are analyzed by the model. The research work presented in this paper can improve the efficiency and accuracy of the hyperbolic-sinusoidal Arrhenius-type model and reduce the difficulty of establishing the model, and is of positive significance for the wide use of the model.

Anisotropic materials find widespread applications across various engineering domains. The investigation on vibrational properties of anisotropic materials holds significance for structural vibration mitigation and safety design. This paper introduces a novel approach, the peridynamic operator method (PDOM), to construct a non-local anisotropic model and applies it to the analysis of free vibrations in anisotropic plates. The model incorporates the unique feature of PDOM, which transforms local differentials and their products into non-local integrals, thereby reformulating the strain energy density from its local form to a non-local form within classical anisotropic theory. Additionally, the paper employs a variational principle and introduces the free vibration equation to develop a PDOM solution for anisotropic free vibration problems. Three numerical examples are provided, including the free vibrations of a thin anisotropic rectangular plate, an anisotropic rectangular plate with cracks, and an anisotropic rectangular plate with holes. The results are compared with finite element results, showcasing the model's convergence, stability, and high computational accuracy in dealing with free vibrations of anisotropic plates with defects and discontinuities.

This study investigates the mechanical behavior of binary Cu-Zr metallic glass under cyclic loading using the molecular dynamics simulation method. Firstly, simulations of single indentation are performed on metallic glasses with four different alloy ratios (Cu₅₀Zr₅₀, Cu₅₄Zr₄₆, Cu₆₀Zr₄₀, and Cu₆₄Zr₃₆), and their corresponding force-depth curves are obtained. The evolution of their microstructures is analyzed using Voronoi indices. To further reveal the hardening mechanism of the metallic glasses under cyclic loading with different alloy ratios and loading rates, the hardness, average atomic volume, residual indentation depth, local shear strain, and large-strain atoms involved in indentation are analyzed. The results indicate that the yield capacity of metallic glass increases with the Cu content under different alloy ratios, primarily due to a higher Cu content resulting in more short-range-ordered structures, thus enhancing the yield capacity. Simulation results also show that after cyclic loading, the average hardness at large-depth indentation of metallic glass with the four different alloy ratios increases by 1.86% to 3.17% compared to that of single indentation. The generation and accumulation of shear bands during the cyclic process, as well as the decrease in the average atomic volume in the region beneath the indenter, lead to a denser structure, effectively resisting further deformation and serving as the main factors contributing to the hardening effect. After cyclic indentation of Cu₅₀Zr₅₀ metallic glass at different loading speeds (80 m/s, 100 m/s, and 150 m/s), it is found that the higher the loading rate, the more micro-plastic deformation, residual indentation depth, and large-strain atoms in the matrix. This leads to a higher average hardness and a more pronounced hardening effect in the metallic glass. This work not only contributes to a better understanding of the plastic deformation mechanism of binary Cu-Zr metallic glass under cyclic loading, but also provides reference data for potential applications and the design of new nanostructured materials.

The ratchetting-fatigue interaction of engineering materials has been extensively investigated in the recent decades. However, as an essential engineering problem, the fatigue failure of notched components with ratchetting has not yet been well touched. It is known that the local stress/strain field at the notch root is a prerequisite for further fatigue life assessment. Neuber's rule is a widely used semi-analytical method for predicting the local stress/strain at the notch root, but its feasibility is not verified when remarkable ratchetting occurs at the root. Therefore, in this work, the cyclic deformation of a notched bar made of U75V steel under asymmetrically uniaxial stress-controlled cyclic loading is simulated using the finite element method. A cyclic elasto-plastic constitutive model is selected and verified according to the experimental results of U75V steel. A UMAT subroutine is developed and implanted into the finite element software Abaqus. Based on the simulation, the stress/strain distributions and corresponding stress/strain concentration coefficients at the notch root, as well as their evolutions during cyclic deformation, are studied. Then, the applicability of Neuber's rule to analyze the local stress-strain response at the notch root of notched components is discussed, taking ratchetting into consideration. The results show that during cyclic deformation, the local stress at the notch root is relaxed, and the stress concentration coefficient decreases accordingly. Meanwhile, the ratchetting strain becomes concentrated at the notch root, and the strain concentration coefficient increases with the number of cycles. The geometric mean of stress and strain concentration coefficients also gradually increases with the number of cycles, significantly differing from the theoretical stress concentration coefficients. This suggests that Neuber's rule cannot accurately describe the stress-strain response at the notch root of notched components when significant ratchetting behavior occurs. Therefore, modifications should be made to Neuber's rule to expand its application scope.

Elastic wave metamaterials are artificial periodic structures that can control elastic waves. They can be used in aeronautics and astronautics, vehicle engineering, and other fields. This paper proposes a tunable metamaterial with two magnetic resonators. In this structure, a stainless steel plate connects the magnetic resonator to the external frame. Adjusting the distance between the magnets can affect the in-plane stress of the stainless steel plate and thus the internal stiffness. By adjusting the cell structure, a double-cell system with different internal stiffnesses can be formed to achieve a wider coupling band gap. First, the variations of the stiffness of the thin plate and the negative stiffness of the magnetic force with the distance between two magnetic resonators are determined. The dispersion relationship and the transmissibility of the single-cell metamaterial with double magnetic resonators and the double-cell metamaterial formed by adjusting the distance between magnets are obtained using a theoretical model. Then, the effect of the distance between two magnetic resonators on the metamaterial bandgap and double-cell coupled bandgap in a specific case is further studied. Finally, an experimental model is designed and manufactured using 3D printing technology. The transmissibility curves at different distances between two magnetic resonators are measured, and the bandgap coupling results of double-cell metamaterial structures are verified. The theoretical prediction of the bandgap of the metamaterial agrees well with the experimental results. This adjustment method can provide a new idea for the active control of restraining elastic wave transmission.

The angle of repose in particle systems is a fundamental scientific problem in particle science. A deep understanding of its influencing factors and patterns of variation is of great significance for optimization in fields such as civil and chemical engineering. However, existing research based on experiments is limited by available types of particles and measurement methods, making it difficult to comprehensively reveal the impact regulations of various physical parameters on the angle of repose. This paper conducts a high-precision numerical study on the angle of repose in particle systems using the discrete element method (DEM), uncovering the most important particle property parameters that affect the angle of repose. DEM is a numerical method that directly simulates the motion of complex particle systems. Specifically, this study adopts a rolling friction coefficient to characterize the influence of non-sphericity on the simulation and validates the established model with existing experimental data. In addition, binary images of the heap projection in the vertical plane are utilized to calculate the angle of repose reasonably. Simulation results show that both sliding and rolling friction coefficients are positively correlated with the angle of repose. Increasing the sliding friction coefficient can double the angle of repose, while increasing the angle of repose caused by the rolling friction coefficient will reach an upper threshold. Once reaching this value, the angle of repose cannot be further increased. The particle's Young's modulus and restitution coefficient have a relatively small impact on the angle of repose. At the same time, this study employs the DEM to investigate the heat transfer characteristics of granular heaps. It is observed that during heating, the region with the highest heat flux within granular heaps migrates from the bottom to the top. These results reveal the most important factors affecting the angle of repose and can guide engineering optimization.

Fatigue failure is the most common form of failure in engineering. Under the interaction betweenthe corrosive environment and fatigue load, the fatigue life of a structure is significantly reduced. It often consumes a lot of time and economic costs to evaluate the fatigue properties of materials or structures through corrosion fatigue experiments. Therefore, it is crucial to establish a reliable numerical prediction model for scientific research and engineering design. In this study, we develop a peridynamic corrosion fatigue model, which combines the peridynamic fatigue crack model and the peridynamic stress-corrosion model, according to the superposition model of corrosion fatigue. In this model, corrosion fatigue damage is a linear superposition of corrosion damage and fatigue damage, and the coupling between stress and corrosion is considered. Consequently, the effect of structural deformation on the corrosion rate, the heterogeneity of the products, and the geometry of the corrosion front can be considered simultaneously in the model. The new model is then applied to simulate the corrosion fatigue failure process (including crack initiation and crack growth phases) of stainless steel compact tensile specimens. The simulation results show that the model can accurately describe the complete corrosion fatigue failure process of the compact tensile specimen, with the corrosion fatigue crack initiating randomly but consistently around the expected high-stress region. The decrease in fatigue life due to the interaction between the corrosion environment and fatigue load is captured, and prolonged corrosion time exacerbates the reduction in fatigue life when a lower load is applied. The influence of loading frequency on corrosion fatigue behavior is investigated by calculating the crack initiation life and comparing crack length curves. The model can also capture the significant influence of loading frequency on the fatigue life in corrosion fatigue processes. Reducing the loading frequency extends the corrosion time between each cyclic load, intensifying corrosion damage and ultimately reducing the crack initiation life while accelerating crack growth. The numerical results demonstrate that the introduced mechano-chemical damage model can capture the loading frequency sensitivity.

The minimal surface structure is a continuous and smooth porous structure. It has the advantages of low density, high intensity, and excellent energy absorption capability. This paper has studied the mechanical properties and energy absorption characteristics of the minimal surface prepared by additive manufacturing process using nylon PA12. First, using the parametric modelling method, three kinds of minimal surface porous structures (G-surface, P-surface, and D-surface) with the same volume fraction of 20% are designed. The corresponding minimal surface structures are manufactured with Multi Jet Fusion (MJF) additive manufacturing technology. The mechanical response and energy absorption characteristics of different minimal surface structures are then analyzed by combining quasi-static compression tests and numerical simulations. For the mechanical response, it is found that the three kinds of minimal surface structures show better load-bearing capacities compared with the traditional BCC lattice structure. In detail, the nominal stresses of the three minimal surface structures (G-surface, P-surface, and D-surface) are 4.0 MPa, 2.1 MPa, and 4.75 MPa, respectively. The nominal stress value of the BCC lattice structure under the same volume is 2.0 MPa. It is clear that all values of the three minimal surface structures are significantly higher than that of the BCC lattice structure. For the study of energy absorption, the energy absorption per unit volume is used as one of key parameter to evaluate the energy absorption characteristic of the porous structure. The results indicate that the values of the energy absorption per unit volume for the three minimal surface structures (G-surface, P-surface, and D-surface) are all higher than that of the BCC lattice structure. The energy absorption per unit volume for the three minimal surface structures can approximately reach 7, 4, and 8 times that of the BCC lattice structure. In conclusion, the minimal surface structure can show excellent characteristics of mechanical property and energy absorption and has extensive application prospects in the fields of aerospace, automotive industry, and machinery.

Stress triaxiality is a parameter that expresses the stress state and can be used as a variable to characterize the plasticity and fracture damage model of materials. It plays an important role in structural strength and failure analysis. The round bar tensile test with a notch can be used to calibrate the parameters in the plastic and damage models. However, there are two different formulas in the literature to calculate the triaxiality of the minimum cross-sectional axis of a notched round bar under tensile loading, which were proposed by internationally renowned scholars Bridgman and Wierzbicki, respectively. Their differences often cause confusion in application. Through refined finite element numerical analysis, this article attempts to clarify the validity and applicability of the two formulas. The results show that the Bridgman formula is more accurate only in the elastic stage and in a specific a/R range. The Bao-Wierzbicki formula, on the other hand, is in good agreement with the experimental data and simulation results, which can be used to calculate the arithmetic mean value of triaxiality during the entire tensile process. Based on further analysis, a new revised stress triaxiality formula in the plastic stage under elastic-perfectly-plastic condition is proposed, and the notch geometry effect and strain-hardening effect are further discussed. It is pointed out that notch ratio can affect the neck stress field. The smaller is the notch ratio, the closer is the stress triaxiality value in the elastic stage to 1/3. When the notch ratio is too small, it can also affect the change of stress triaxiality throughout the entire tensile process. The strain-hardening effect can change the trend of stress triaxiality during the stretching process, and an increase in the strengthening modulus will lead to a decrease in the peak value of the plastic stage. The higher is the strengthening modulus, the faster is the decrease of stress triaxiality after entering the plastic stage.

The emergence of graphene nanoplatelets (GPLs) has enabled the development of lightweight and high-strength plates, making it a prominent area of research in science and engineering. Therefore, it is essential to study the buckling performance of functionally graded graphene-reinforced composite (FG-GRC) plates. This paper presents a new meshless model to solve the buckling behavior problem of FG-GRC plates. The model is based on an improved Reddy-type third-order shear deformation theory (TSDT) with seven degrees of freedom and a moving Kriging (MK) interpolation method, which can overcome the challenge of implementing the second-type boundary conditions in meshless methods and eliminate the need for shear correction factors. The model is applicable to thin/medium/thick plate problems and has high computational accuracy. The Halpin-Tsai model is used to predict the effective Young's modulus of the FG-GRC plate, and the effective Poisson's ratio is determined using the mixture law. The meshless governing equation for the buckling of the FG-GRC plate with seven unknowns is derived based on the principle of minimum potential energy. The convergence and effectiveness of the proposed method are verified by comparing it with literature results. The numerical results demonstrate that when the total number of layers (N_L) of the FG-GRC plate is less than 10-15, the critical buckling load of the FG-O-type and FG-X-type plates changes more drastically than that of the epoxy pure plate, indicating that the stiffness of the graphene-reinforced plate decreases (or increases) rapidly in this stage, as opposed to the epoxy pure plate. However, when N_L exceeds 10-15, the change rate of the critical buckling load for the FG-GRC plate becomes smoother. Furthermore, the critical buckling load of the FG-GRC plate increases sharply when the length-thickness ratio of the GPLs reaches around 1000. Once the length-thickness ratio of GPLs surpasses 2000, the critical buckling load of the FG-GRC plate tends to stabilize, and the length-width ratio and length-thickness ratio of the GPLs have no significant effect on it. Overall, the research findings of this study not only contribute to the understanding of FG-GRC plates but also offer practical and insightful recommendations for their design and theoretical research.