Inorganic perovskites, a class of materials with the general formula ABX3, exhibit a wide range of electronic, dielectric, and structural properties, making them pivotal in energy, electronics, and catalysis applications. Accurate atomistic simulations of these materials require accurate interatomic potentials that capture both short-range and long-range interactions. While first-principles methods are of high accuracy, empirical and machine learning potentials remain essential for large-scale simulations. This survey categorizes and reviews the atomic potentials used in inorganic perovskite modeling based on how they treat electrostatic interactions: potentials without charges, potentials with constant charges, and potentials with variable charges. Given the ionic nature of perovskites, we emphasize the importance of charge treatment, and each class of potentials is discussed in detail with representative examples, functional forms, and application scenarios. For comparison, we perform molecular dynamics simulations to calculate the critical temperature for the phase transition of the perovskite CsPbI3 with available empirical potentials, highlighting their strengths and limitations in capturing structural evolution. Finally, we outline future directions for developing more accurate and transferable atomic potentials for inorganic perovskites. We hope that this review can serve as a guiding resource for researchers who are starting to perform simulations for inorganic perovskites.
The dynamic deformation behaviors of aluminum alloy sheets often differ from the quasi-static ones. Here, a dynamic biaxial tensile experiment of cruciform specimens has been proposed with electromagnetically actuated punch. A notched cruciform specimen was adopted to obtain heterogeneous deformation covering from equal-biaxial tensile to uniaxial tensile strain path. The inverse identification was used to determine the parameters of Hill48 and YLD2000-2D anisotropic yield functions for 5052-O aluminum alloy sheet. The YLD2000-2D anisotropic yield function was validated by comparison of the simulated and experimental principal strains. By comparison with the anisotropic yield functions under quasi-static loading conditions, the anisotropic yielding behaviors of 5052-O aluminum alloy sheet are alleviated under dynamic loading conditions.
The Hall effect of elastic waves has attracted much attention due to its unique properties. A hexagonal lattice phononic crystal plate model is designed in this paper. By changing the spatial symmetry of the unit cell, a band gap for the A(0) Lamb wave is opened. The existence of the edge state of the phononic crystal plate is obtained by finite element simulation. It is found that both zigzag-type edge and bridge edge are topological edge states by analysis of the band structure of the supercell. A rectangular model with a straight channel is designed and the simulation results show that the two types of channels are topologically protected only for the A(0) mode Lamb wave but not for the S-0 mode. In addition, the results of numerical simulation are verified by experimental data measured by a laser vibrometer. Finally, it is found that neither upside V-shaped channels nor channels with defects will affect the stable propagation of A(0) Lamb waves along the proposed route. This proposed model and method are helpful in broadening the means of regulating elastic waves in phononic crystal structures, and extending practical application of topological edge states in such structures.
The ablation behavior of ZrC-coated C/C composites is a complex coupling process involving thermal, mechanical, chemical interactions, formation and propagation of cracks. In the present study, we propose a peridynamic (PD) thermo-mechanical-oxidation-diffusion coupled model to describe such a phenomenon comprehensively. Firstly, motion and heat transfer equations are formulated, incorporating growth strain governed by the Clarke model. The oxidation rate of the material is evaluated using diffusion equilibrium and oxidation equations. In addition, the effects of oxidation on different materials are considered, such as growth strain in ZrC materials and material consumption caused by oxidation of C/C composites. To characterize the material failure caused by mechanical and chemical reactions in ablation, a porosity criterion is proposed and its effect on diffusion is considered. The reliability and accuracy of the proposed PD model are validated by analyzing the oxidation process of C/C composites and ZrC and comparing with experimental results. Further, the model effectively captured the crack propagation and oxidation of ZrC-coated C/C composites in an oxyacetylene environment.
Fluid-conveying pipes have been widely used in diverse engineering fields, particularly in aerospace systems, nuclear power plants, oil transportation infrastructure, and biomedical devices. The recent advancements in 3D printing and materials science have increased research interest in the stability and vibration characteristics of slender pipes fabricated from hard magnetic soft (HMS) materials for magnetic control applications. Although several theoretical investigations have been conducted on magnetically controlled cantilevered fluid-conveying pipes, the understanding of their dynamical behavior in vascular environments remains incomplete. In this study, we investigate the buckling and dynamical behaviors of an HMS pipe under the combined effects of an applied magnetic field and nonlinear distributed spring constraints. By solving the nonlinear governing equation, natural frequencies, critical flow velocities, buckling displacements, and dynamic responses of the HMS pipe conveying fluid are obtained. The analysis reveals that the addition of distributed spring constraints leads to a substantial reduction in both buckling and dynamic displacements of the pipe system. Under constant magnetic field conditions, the pipe exhibits static deformation characteristics even when exposed to flow velocities exceeding the critical threshold for buckling instability. When subjected to an alternating magnetic field, the pipe system exhibits periodic oscillatory behavior across a wide range of flow velocities. This periodic response is characterized by displacement variations that show direct correlation with changes in the magnetic declination angle. Notably, nonlinear resonance phenomena associated with the first-mode natural frequency can occur even when the flow velocity is below the threshold for buckling instability. These results demonstrate that both magnetic field strength and declination angle offer a possible means for adjusting the stability, buckling behavior, and dynamic response of an HMS pipe.
Acoustic metamaterials (AMs) exhibit outstanding sound absorption performance due to their customizable design. In this work, a low-frequency sound-absorbing metamaterial plate, which combines a fractal-based labyrinth acoustic metamaterial (FLAM) and a micro-perforation panel, is proposed. The theoretical, simulation, and experimental methods are used to comprehensively examine the sound absorption performance. A triangular fractal curve is first introduced, and the combined FLAM model is constructed. An equivalent straight channel model is developed to study the effects of the structural parameters on the sound absorption coefficients. The finite element analysis (FEA) is further conducted to validate the theoretical results. All the findings indicate that the proposed combined FLAM exhibits excellent sound absorption performance at a deep sub-wavelength scale, with absorption coefficients of 0.89, 0.98, and 1.00 for the first three fractal orders, respectively. Finally, the prototypes are fabricated, and the impedance tube experiments are conducted, yielding results that align closely with both analytical and FEA results. Notably, the sound absorption performance of large-area sound-absorbing plates is also investigated by splicing two/four FLAMs together, demonstrating a relative absorption bandwidth exceeding 35%. This work offers a viable alternative to low-frequency sound-absorbing materials for potential engineering applications.
Polyethersulfone (PES) can be widely used in extreme environments due to its exceptional strength and stability. In this study, molecular dynamics (MD) simulations were used to construct tribological models of PES under varying pressures. The variations of PES molecular chains and frictional interface properties were explored for understanding microscopic tribological mechanism. The simulation results show that high pressure and high vacuum conditions reduce the coefficient of friction and wear rate. The variations in radial distribution function (RDF), relative concentration of atoms, friction interface temperature, and atomic motion velocity were analyzed. It was found that high pressure and high vacuum promote PES molecular chains moving away from the surface of the iron atomic layer, decreasing interaction energy, RDF, temperature, and velocity at the friction interface. This work offers novel methodologies and theoretical insights for studying the friction and wear of polymer composites in complex environments.
Fretting fatigue in bolted joints within aero-engine fan and compressor structures, characterized by multi-layered, thin-walled components and high preload, poses a significant structural safety challenge. This study investigates fretting fatigue in a bolted joint configuration simulating compressor axis contact with sealing disk ends, analyzing hysteresis loops, fretting scars, and fracture surfaces. Numerical simulation, incorporating a UMESHMOTION subroutine, and a critical plane approach utilizing the Smith-Watson-Thorpe parameter and Miner's law, alongside wear morphology simulation, were employed to evaluate fretting fatigue life. Results revealed a non-monotonic relationship between surface quality and fretting fatigue life, demonstrating an initial life decrease followed by an increase, primarily due to a transition from partial to gross slip. The study highlights the significant impact of fretting on the life prediction of aero-engine bolted joints, demonstrating that improved surface quality does not always guarantee enhanced fatigue performance. The accuracy of the life prediction approach was validated through experimental correlation with wear-aware simulation results.
Understanding the friction behavior between hexagonal boron nitride (h-BN) and water is critical for the potential applications of h-BN in liquid-related functional devices. By using a density-functional-theory (DFT)-based machine learning (ML) technique combined with long-time ML-parameterized molecular dynamics simulations, we have systematically investigated charge transfer and friction at the interfaces between h-BN and water. The introduction of defects (including Stone-Wales, B-vacancy, N-vacancy, and B-vacancy/N-vacancy defects) into h-BN significantly enhances heterogeneous charge polarization and distribution at h-BN layers, as well as increases the friction coefficients at water/h-BN interfaces compared to perfect h-BN. The observed increase in interfacial friction of defected h-BN can be attributed to stronger charge transfer and higher charge density at the defected h-BN layers induced by interactions with water molecules. Our results offer deeper insights into the role of defects in modulating charge exchange and transfer between water and h-BN, as well as their impact on interfacial friction.
Bidirectional functionally graded (BDFG) beams are a promising solution for spacecraft structures subjected to extreme thermal and vibrational environments due to their superior thermal performance and design flexibility. Therefore, developing an efficient and highly convergent thermal vibration analysis method for BDFG beams under complex temperature fields is of paramount importance. This paper proposes a Chebyshev spectral method based on Reddy's higher-order shear deformation theory (HSDT) to investigate the thermoelastic vibrations of BDFG beams. The material properties are temperature-dependent and vary with both thickness and length. The proposed method is validated by comparing the results with those in the existing literature. The analysis reveals that the critical buckling temperature rise is primarily influenced by the ceramic content, but thermal buckling can be mitigated by adjusting the material distribution. A trade-off exists between suppressing thermal buckling and relaxing thermal stresses, necessitating a balanced approach. The titanium alloy BDFG beam offers a broader design envelope compared to the metal-ceramic BDFG beam. The method presented in this study will provide theoretical support and guidance for the design of BDFG beams.
Based on the linear elasticity theory of quasicrystals, this study addresses two defect problems in two-dimensional piezoelectric quasicrystals: rigid inclusions and holes. Using the Stroh formalism, Green's function solutions are obtained for these defects under concentrated and uniformly distributed forces. Numerical examples are presented to analyze the mechanical behavior when loads are applied at various positions, including the center, outside, on the boundary, and at infinity of the elliptical defect. The study emphasizes the significant impact of the phonon line force on the distribution of key physical quantities. Results show that elliptical defects significantly disrupt multiple physical fields, leading to substantial variations in displacement and potential at the hole boundaries and pronounced stress concentrations. The stress in the phason field near the elliptical defect boundary exhibits complex variations under loading conditions, and the piezoelectric effect becomes more pronounced. These findings provide critical guidance for designing quasicrystal-based smart materials with controlled defect responses.
FeMnSi-based shape memory alloys (SMAs) have great applied potential to large-scale structures in civil engineering, especially as an aseismic structural material. Low-cycle fatigue performance is one of the most important properties of FeMnSi-based SMA aseismic materials. However, the low-cycle fatigue behavior of such SMAs, especially the stress-controlled low-cycle fatigue behavior (with ratchetting effect), has not been clearly understood. In this work, the low-cycle fatigue behavior of the FeMnSiCrNi SMAs subjected to stress-controlled cyclic tension-compression loads is investigated, and the effects of temperature, loading frequency, stress amplitude, and stress ratio are addressed. By analyzing the cyclic stress-strain response, fatigue fracture surface morphology, dissipation energy, ratchetting strain, and equivalent damping ratio, the mechanisms behind the temperature-, loading frequency-, stress amplitude-, and stress ratio-dependent low-cycle fatigue behavior are discussed. The results show that the plasticity, martensitic transformation, and/or the ratchetting strain caused by their tension-compression asymmetry are the decisive factors affecting the low-cycle fatigue behavior of FeMnSiCrNi SMAs.
In this paper, the free vibration and stationary stochastic response of functionally graded (FG) rectangular plates with varying thickness in supersonic flow and thermal environment are analyzed. Two types of material property variations of FG plates with varying thickness are considered: the variation along the direction perpendicular to the mid-surface and that along the direction perpendicular to the bottom surface. Considering the effects of aerodynamic pressure and thermal load, the governing equations of motion of FG plates with varying thickness are derived using Hamilton's principle within the framework of first-order shear deformation theory. A meshfree Jacobi radial point interpolation (Jacobi-RPI) shape function is constructed by combining the Jacobi polynomials and radial basis to approximate the displacement components of the plate. The accuracy and reliability of the present approach are confirmed through sufficient comparisons with numerical results from the published literature and the finite element software ABAQUS. Finally, the effects of different parameters on the free vibration and stationary stochastic response of FG plates are investigated.
Long-duration vehicles in near space have achieved great success; however, the non-destructive testing (NDT) methods for the envelope materials of such long-duration vehicles remain blank. In this paper, we propose the air-coupled ultrasonic NDT method theoretically. In the theoretical analysis process, the envelope material is simplified as an orthogonal sandwich structure. To calculate the displacement and stress fields of each medium, the state vectors are established and the transfer matrices of the material from the upper interface to the lower interface are obtained by using boundary conditions. Then, linear equations about the amplitude of reflected and transmitted waves are derived by combining the coupling boundary conditions of air and solid. The effects of incident angles, inflation of the envelope material, and debonding of the interfaces on the transmission coefficients are considered. The results show that the air-coupled ultrasonic NDT of the envelope material can be carried out in the pre-inflated state. Finally, a method for identifying interface debonding is proposed based on judging transmission coefficients within a certain frequency range.
Grinding technology is widely applied in the manufacturing and mechanical processing sectors. Different from conventional three-dimensional rough surface friction models, ground metals exhibit a striated surface morphology, which can be simplified as a two-dimensional plane strain friction issue. Due to surface morphology diversity and loading condition complexity, numerical modeling and experimental approaches have difficulty achieving rapid prediction of line-contact surface friction behavior. Therefore, this study innovatively proposes a hybrid physics-data-driven model integrating finite element analysis (FEA) with machine learning (ML), enabling efficient and accurate prediction of line-contact friction behavior on two-dimensional rough surfaces. An extensive friction behavior database was generated through finite element simulations. Based on this dataset, the random forest (RF) algorithm was used to achieve high-precision prediction of the friction coefficient. Furthermore, a comprehensive analysis was performed on the effects of surface roughness, normal load, yield strength, and local friction coefficient on friction behavior. The RF model exhibits excellent performance in predicting friction coefficients and also accurately identifies the most influential features governing friction behavior. Residual analysis further verifies our model's reliability, as the RF predictions agree with the FEA results, demonstrating remarkable adaptability and accuracy. Feature importance analysis results reveal that the local friction coefficient and normal load are the main factors influencing friction behavior, but the surface roughness and yield strength exhibit a relatively minor influence. The study innovatively identifies the coupling effects of key parameters through contour maps. Namely, the influence of local friction coefficient decreases with increasing normal load but becomes significantly more pronounced with elevated material yield strength. By integrating ML, our proposed model maintains the high accuracy of FEA while capturing the complexity of interfacial responses through data-driven approaches. Our study advances traditional tribological research from "experience-driven" to "data-intelligence-driven," thus providing novel insights for understanding and predicting complex friction behaviors, as well as for optimizing frictional design in engineering applications.
This paper proposes a state-of-the-art three-dimensional Voronoi cell finite element method (3D VCFEM) aimed at investigating the mechanical properties of particle-reinforced composites (PRCs) in space under different microstructural properties. Firstly, the modified residual energy generalized function of 3D VCFEM was proposed by applying the hybrid stress element method, and the element format of the 3D Voronoi element was constructed. On this basis, the interaction between the matrix and the inclusions was considered, and the higher-order stress function including the interaction stress term was constructed. Secondly, to solve the difficulty of integrating easily due to the complexity and irregularity of the integration region in space, Delaunay tetrahedra were introduced within the 3D Voronoi element for mesh refinement. It simplified the integration process. Finally, to verify the accuracy and efficiency of the 3D VCFEM model, comparative models of 3D VCFENM and FEM were established for analysis and discussion. The stress field and strain field were compared and analyzed for the first time. An example was also given for the presence of a large number of randomly distributed inclusion particles. The results showed that under the same accuracy, 3D VCFEM had the advantages of convenient mesh delineation and high computational efficiency compared with FEM, which provided a new way of thinking to analyze the actual PCRs.
The purpose of this paper is to make an assessment on the performance of a fiber reinforced plastic (FRP) helmet-head system subjected to ballistic impact. Firstly, a finite element (FE) model for the human head is developed. Constitutive models for each component of the head are determined and, in particular, strain rate effects of the compact bone of the skull and the hyperelastic property of the scalp are taken into account for the first time. Secondly, an FE model for Kevlar fiber reinforced plastic (KFRP) helmet is constructed based on the personal armor system for ground troops (PASGT) helmet. Recently developed dynamic constitutive models for metals and FRP laminates are employed for full metal jacketed (FMJ) bullet and the KFRP helmet. Finally, both the head and the helmet models are validated against available test data. Furthermore, the effects of various factors such as padding system, impact position, and projectile type on the ballistic performance of the helmet-head system have been systematically investigated with special attention being paid to the severity of head injury. It is found that the performance of the helmet with OA foam is advantageous over that of the helmet with strap-netting in head injury prevention. It is also found that a lower velocity (358 m/s) FMJ bullet poses more threats to head injury than a higher velocity (610 m/s) fragment-simulating projectile for the PASGT helmet-head system.
This paper presents a novel fully edge-based smoothed finite element method for free vibration analysis of functionally graded plates, incorporating a quasi-weak form of smoothed integral within an edge-based finite element method framework. Employing first-order shear deformation plate theory, the present method accounts for transverse shear strain and rotary inertia effects while addressing exponentially graded material properties along the plate thickness. The formulation integrates a three-node Mindlin plate element (MIN3) with a shear stabilization technique to prevent shear locking. The quasi-weak form of smoothed integral necessitates the evaluation of indefinite integrals for shape functions, effectively tacking domain integrals related to the shape functions without partial derivatives. By applying both quasi-weak form of smoothed integral and strain smoothing technique, all domain integrals in stiffness and mass matrices are converted into boundary integrals over smoothing domains. Therefore, isoparametric mapping and computing of Jacobian matrix are completely eliminated throughout the solution process. The natural frequencies obtained using the present method are in good agreement with those reported in the literature, highlighting the versatility of the present method for free vibration analysis of functionally graded plates. Notably, the present method demonstrates advantages in eliminating shear locking and reducing sensitivity to mesh distortion.
The recovery stress of materials has a great potential application in the field of road crack self-repair, composite material self-repair, and so on. Taking into account the diversity of practical application environments, the recovery stresses of constrained shape memory alloy (SMA) materials in the initial state of austenite and twinned martensite are given respectively in this paper. As for the experimental research, the austenitic SMA is loaded and constrained. The recovery stresses at different stages are observed by increasing the temperature. In terms of the theoretical research, constitutive models with the initial state of austenite and martensite are established respectively based on the one-dimensional macroscopic phenomenon theoretical model and constraints of SMA. These constitutive models can describe the relationship between recovery stress and volume fraction of martensite under temperature loading with different pre-strains. The theoretical model and experimental data in this paper can provide specific support for the practical engineering application of SMA recovery stress.
In order to realize the automatic recognition and classification of cracks with different depths, in this study, several deep convolutional neural networks including AlexNet, ResNet, and DenseNet were employed to identify and classify cracks at different depths and in various materials. An analysis process for the automatic classification of crack damage was presented. The image dataset used for model training was obtained from scanning experiments on aluminum and titanium alloy plates using an ultrasonic phased-array flaw detector. All models were trained and validated with the dataset; the proposed models were compared using classification precision and loss values. The results show that the automatic recognition and classification of crack depth can be realized by using the deep learning algorithm to analyze the ultrasonic phased array images, and the classification precision of DenseNet is the highest. The problem that ultrasonic damage identification relies on manual experience is solved.
