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With the continuous development of network technology, the production and lifestyle of human beings are also quietly changing. People find that the network makes life faster and more convenient and also makes our life more “transparent.” The openness, sharing, and convenience of the network make it easier to infringe on the privacy rights of others, bringing an unprecedented impact on traditional privacy protection. This paper studied information security assurance-related algorithms and built an information security assurance model. Through this model, some privacy violation events existing in the network today were analyzed. Then, a corresponding questionnaire was constructed according to some of the problems of these events. The questionnaire is mainly used for research on people of all age groups, mainly to study their understanding of relevant legal knowledge and their views on the law. A total of 188 valid questionnaires were collected in this survey. Only 37.23% people knew a lot about the law. Most of them learned it from the Internet, and they rarely learned about it from relevant books. About 70% people believe that the law plays a big role in privacy protection, and they will choose legal help if they encounter privacy violations. However, this is inconsistent with some data obtained from the information security assurance model. Through analysis, it can be seen that although they want legal help, they lack the relevant knowledge of the law, and they do not know whether the privacy of individuals has been violated. Therefore, it is necessary to strengthen personal knowledge of privacy protection laws and improve the personal information legal protection and fair use system.

Polysaccharides are important biological macromolecules in all organisms, and have recently been studied as therapeutic agents for ulcerative colitis (UC). However, the effects of Pinus yunnanensis pollen polysaccharides on ulcerative colitis remains unknown. In this study, dextran sodium sulfate (DSS) was used to induce the UC model to investigate the effects of Pinus yunnanensis pollen polysaccharides (PPM60) and sulfated polysaccharides (SPPM60) on UC. We evaluated the improvement of polysaccharides on UC by analyzing the levels of intestinal cytokines, serum metabolites and metabolic pathways, intestinal flora species diversity, and beneficial and harmful bacteria. The results show that purified PPM60 and its sulfated form SPPM60 effectively alleviated the disease progression of weight loss, colon shortening and intestinal injury in UC mice. On the intestinal immunity level, PPM60 and SPPM60 increased the levels of anti-inflammatory cytokines (IL-2, IL-10, and IL-13) and decreased the levels of proinflammatory cytokines (IL-1β, IL-6, and TNF-α). On the serum metabolism level, PPM60 and SPPM60 mainly regulated the abnormal serum metabolism of UC mice by regulating the energy-related and lipid-related metabolism pathways, respectively. On the intestinal flora level, PPM60 and SPPM60 reduced the abundance of harmful bacteria (such as Akkermansia and Aerococcus) and induced the abundance of beneficial bacteria (such as lactobacillus). In summary, this study is the first to evaluate the effects of PPM60 and SPPM60 on UC from the joint perspectives of intestinal immunity, serum metabolomics, and intestinal flora, which may provide an experimental basis for plant polysaccharides as an adjuvant clinical treatment of UC.

The plastic behaviors’ description of a tungsten heavy alloy (95W-3.5Ni-1.5Fe) at temperatures of 298–773 K and strain rates of 0.001–11,000 s−1 is systematically studied based on four constitutive models, that is, Zerilli-Armstrong model, modified Zerilli-Armstrong model, Mechanical Threshold Stress model, and modified Mechanical Threshold Stress model. The quasi-static compression experiments using an electronic universal testing machine and the dynamic compression experiments using a split Hopkinson pressure bar apparatus are employed to obtain the true stress–strain curves at a total of three temperatures (298 K, 573 K, and 773 K) and a wide range of strain rates (0.001–11,000 s−1). The parameters of the four constitutive models are obtained by the above fundamental experimental data and Grey Wolf Optimizer. The correlation coefficient and average absolute relative error are used to evaluate the predicted performance of these models. Modified Mechanical Threshold Stress model is found to have the highest predicted performance in describing the flow stress of the 95W-3.5Ni-1.5Fe alloy. Eventually, two compression experiments whose loading conditions are not in the fundamental experiments are conducted to validate the four models.

The split Hopkinson pressure bar and universal testing machine are used to study the dynamic response and failure behavior of U71Mn using a hat-shaped specimen under the compression-shear stress state. The shear stress–strain curves are presented at the shear strain rates ranging from 0.001 to 19,200 s−1 and temperatures ranging from 25 to 600 °C. It is observed that the effects of strain rate hardening, strain hardening, and thermal softening are closely related to the changes of the shear stress–strain curves. The coupling effects are very significant in the process of deformation failure. The fracture morphology and longitudinal section microstructures of U71Mn are investigated by scanning electron microscope. According to the results, the shear strain rates and temperatures greatly influence the failure mechanisms of the material. Furthermore, the increase in temperature promotes the occurrence of dynamic recrystallization and reduces the tendency of the pearlite flowing toward the center of the shear zone. Based on the quasi-static tensile tests and finite element analysis, the Johnson–Cook damage model parameters are fitted and applied to the finite element analysis of the hat-shaped specimen.

The shear failure behaviors of U71Mn rail steel are investigated by quasi-static and dynamic compression tests utilizing two different hat-shaped specimens: S1 which combines shear and compressive stress states and S2 which combines shear and tensile stress states. A split Hopkinson pressure bar is used to acquire shear stress–strain curves at various initial temperatures and shear strain rates, and it is found that a lower shear strain rate is observed in hat-shaped specimen S1 than that in hat-shaped specimen S2 under the same impact pressure. Scanning electron microscopy is employed for observing the microstructures of specimens. The results indicate that the hat-shaped specimen S1 is difficult to form voids and dimples. Moreover, as far as the hat-shaped specimen S2 is concerned, the number of voids reduces with the rising shear strain rate, and no voids appear on the fracture surface at the shear strain rate of 36,000 s−1. Furthermore, the creation of voids is aided by a rise in initial temperature. The factors affecting the formation of adiabatic shear bands are explored based on the numerical simulation, which suggests that the magnitude of the temperature gradient plays a crucial role in the generation of adiabatic shear bands.

This work is a supplement to the work of Sneddon on axisymmetric Boussinesq problem in 1965 in which the distributions of interior-stress fields are derived here for a punch with general profile. A novel set of mathematical procedures is introduced to process the basic elastic solutions (obtained by the method of Hankel transform, which was pioneered by Sneddon) and the solution of the dual integral equations. These processes then enable us to not only derive the general relationship of indentation depth D and total load P that acts on the punch but also explicitly obtain the general analytical expressions of the stress fields beneath the surface of an isotropic elastic half-space. The usually known cases of punch profiles are reconsidered according to the general formulas derived in this study, and the deduced results are verified by comparing them with the classical results. Finally, these general formulas are also applied to evaluate the von Mises stresses for several new punch profiles.

The paper presents a new method to study the dynamic mechanical properties of concrete under low pressure and a high strain rate via the inversion of spherical wave propagation. The dynamic parameters of rate-dependent constitutive relation of elastic concrete are determined by measured velocity histories of spherical waves. Firstly, the particle velocity time history profiles in the low stress elastic region at the radii of 100.6 mm, 120.6 mm, 140.6 mm, 160 mm, and 180.6 mm are measured in the semi-infinite space of concrete by using the mini-explosive ball and electromagnetic velocity measurement technology. Then, based on the universal spherical wave conservation equation and the fact that the accommodation relationship in state equation satisfies linear elastic law, the inverse problem analysis of spherical waves in concrete (called “NV + T0/SW”) is proposed, which can obtain the dynamic numerical constitutive behavior of concrete in three-dimensional stress by measuring the velocity histories. The numerical constitutive relation is expressed in the form of distortion, and it is found that the distortion law has an obvious rate effect. Finally, the rate-dependent dynamic parameters in concrete are determined by the standard linear solid model. The results show that the strain rate effect of concrete cannot be ignored with the strain rate range of 102 1/s. This study can provide a feasible method to determine the dynamic parameters of rate-dependent constitutive relation of concretes. This method has good applicability, especially in the study of the dynamic behavior of multicomponent composite materials with large-size particle filler.

The present study is on the analytical solution for the elastic field due to a cuboidal inclusion of uniform eigenstrain within a transversely isotropic full-space material, and a numerical method to model inclusions of any arbitrary shapes and with any eigenstrain distributions as the integration of a set of such cuboidal inclusions. The fast Fourier transform (FFT) is applied for efficient computation. The developed method and results are implemented to analyze the elastic field in a transversely isotropic full-space material containing inclusions of different shapes, different eigenstrain distributions, and multiple cuboids of different densities. Furthermore, the effect of material anisotropy on the stress field subjected to a spherical inclusion with pure dilatant eigenstrains is explored by comparing the behavior of a transversely isotropic material with that of a corresponding isotropic one. The numerical results show that the induced stresses are drastically influenced by the Young’s moduli of transversely isotropic materials, and that material constant C 33 has a large influence on normal stress σ 33 .

The high strain rate in metal cutting significantly affects the mechanical properties of the work piece by altering its properties. This study outlines the material strain rates during elliptical vibration cutting. The finite element analysis, Taguchi method, and analysis of variance (ANOVA) were employed to analyze the effects and contributions of cutting and vibration process parameters (feed rate, rake angle, tangential amplitude, and frequency of vibration) on the variation of strain rates during machining of Inconel 718. Taguchi signal-to-noise analysis on an L18 (21 × 33) orthogonal array was used to determine the optimum parametric combination for the maximum strain rate, and ANOVA was applied to evaluate the significance of control parameter factors on the strain rate. The results of the finite element analysis under different conditions illustrated that the feed rate and rake angle were negatively related to the strain rate, whereas the tangential amplitude and frequency had a positive response. Furthermore, ANOVA results indicated that the effect of the feed rate, tool rake angle, vibration frequency, and tangential amplitude on the strain rate were all statistically significant, with a reliability level of 95%. Of these, the dominant parameter affecting the strain rate was the feed rate, with a percentage contribution of 40.36%. The estimation of the optimum strain rate and confirmation tests proved that the Taguchi method could successfully optimize the working conditions to obtain the desired maximum strain rate.

In this study, the finite element (FE) analysis, analysis of variance (ANOVA), and the back propagation neural network (BPNN) were employed to evaluate and predict the cutting forces of titanium alloy Ti-6Al-4V depending on vibration frequency, tangential amplitude, and thrust amplitude, as well as cutting speed during elliptical vibration cutting (EVC). A series of EVC simulations were conducted based on the verified FE model to evaluate the impacts of different EVC parameters on cutting forces. The results show that the tangential force decreases with increasing vibration frequency, tangential amplitude, and thrust amplitude, but with decreasing cutting speed. The positive and negative thrust forces decrease with increasing frequency and tangential amplitude, but with decreasing thrust amplitude and cutting speed. In addition, ANOVA results clearly indicated that the tangential amplitude is the dominant parameter affecting the cutting forces, and the percent contributions to cutting forces are 69.56%, 66.03%, and 62.83%, respectively. Further, the BPNN models with three different activation functions and different architectures are utilized to predict the cutting forces, and the best performance, in terms of agreement with the target outputs, can be achieved by the network using logarithmic sigmoid activation function and architecture with 15 neurons in one hidden layer. The correlation coefficients for training and testing the selected network are 0.99993 and 0.99916, and the mean square errors are 0.1963 and 2.6070, respectively, and these reveal that BPNN is fairly successful in predicting the cutting forces.

Semi-analytical models (SAMs) have been developed to analyze contact problems efficiently, including those of inhomogeneous materials, based on the equivalent inclusion method. However, understanding the behavior of microscopic inhomogeneities requires SAMs of even higher efficiency. This study builds a new semi-analytical model for high-speed simulations of contacts of materials containing distributed particles of sizes orders of magnitude smaller than that of the contact radius. The domain decomposition method is applied to construct a two-level mesh set to implement multiscale computation. The macroscopic mesh uses homogenized elements that ensure a high computing efficiency in obtaining the contact pressure distribution as a boundary condition, whereas the material microstructures are modeled using the microscopic mesh, and thus the microscopic stress and strain are obtained. New influence coefficients are derived for eigenstress and eigenstrain calculations in both mesh levels and are used to calculate the eigenstress and equivalent eigenstrains. The new model is implemented to investigate the effects of particle clustering on the contact performances of composites.

Team innovation is related to the long-term survival of the organization. In today's open innovation environment, the cross-border activities of the team and its members are increasingly frequent. The topic of cross-border behavior and team innovation performance has attracted the attention of scholars. The purpose of this paper is to explore the relationship between cross-border behavior, team trust, and corporate innovation performance. In this paper, a sample of 78 teams and their superiors are used as samples, and the hierarchical regression method is used for data analysis. This paper introduces team trust into the relationship between cross-border behavior and team innovation performance, constructs and demonstrates the relationship model between “cross-border behavior, team trust and team innovation performance”, and finds the boundary conditions of this relationship model. The conclusion that cross-border behavior (coordination and detection) has a positive impact on team innovation performance is achieved through the intermediary role of team trust,the standardized regression coefficients were 0.253 (P

Stress distributions and plastic deformation zones are factors directly influencing the fatigue life of components under cyclic contact. An effective approach to improving the resistance of a steel to contact fatigue failure is surface hardening, which builds gradient yield strength from the surface of the steel to the bulk. When using the distortion energy theory as the criterion to identify failure initiation for a case-hardened steel, contact yield starts in the subsurface wherever the von Mises stress reaches the local material strength, rather than at the point of the maximum von Mises stress in the subsurface. If the yield strength changes from the surface to the bulk following a straight line, the location of yield initiation should occur at the tangency of the strength line and the von Mises stress curve. Analyses on circular, rectangular, and elliptical contacts are presented to reveal the locations of contact yield initiation for such case-hardened steels subjected to rolling contact stresses, for which the influence of friction can be ignored. A group of formulas relating contact yield initiation, in terms of the critical pressure, location of the first yield, and plasticity index (transition to plasticity) to case-hardening parameters, such as the case slope, the minimum case depth, and surface and bulk strengths, are derived to facilitate contact element designs using case-hardened materials. The results are applied to examine the rolling contact behaviors of several case-hardened steels, and the data correlation suggests that their rolling contact fatigue lives are related to a nondimensional case-hardening slope besides external loading.

The paper generalizes the analytical solutions for the thermal-eigenstrain-induced elastic field in two joined half-space solids or a bimaterial with an interface of coupled dislocation-like and force-like imperfects. The present model permits quantitative jumps in displacements and/or stresses from one medium to the other. The model also leads to a set of explicit closed-form expressions for the dilatation-induced elastic fields in half-spaces I and II joined by such an imperfect interface. Cases for the elastic fields subjected to an ellipsoidal, a spherical, a spherical shell, and a cylindrical thermal inclusion are analyzed, and key results are validated by comparison with existing experimental results. The influences of several types of interfaces, such as the perfectly bonded, dislocation-like, and force-like interfaces, on the stress and displacement transmissions are further discussed.

This paper reported a size-dependent semi-analytical model (SAM) on the contact involving a functionally graded elastic film indented by a rigid frictionless cylinder, where Chen-Yao's surface elastic theory is employed to account for the effects of surface energy and surface strain. The model assumes that the film is perfectly bonded to a rigid substrate, and that the shear modulus of the film varies along the thickness direction following a simple exponential form. The core fundamental solutions of the elastic displacements and stresses for such an elastic thin film with respect to the unit applied force are derived firstly, incorporating the surface effects by means of Chen-Yao's surface elastic theory. Then the frequency response functions (FRFs) and their conversion into the corresponding influence coefficients (ICs), are analytical obtained. Efficient numerical techniques, supported by the conjugate gradient method (CGM) and the fast Fourier transform (FFT), are applied to obtain the unknown pressure and stress distributions. The combined effects of shear modulus ratio, film thickness, and surface energy on the contact behavior of the thin film are explored, and a schematic map is constructed to reveal the influences of film thickness and material characteristic length, which correlates the geometric configuration (i.e. a film or a half-space) and surface behaviors (i.e. with or without considering the surface effects).

This paper reports a semi-analytical model (SAM) for simulating the dynamic contact of a rigid sphere and the surface of a multiferroic magnetoelectroelastic (MEE) film under an increasing applied force. The frequency response functions (FRFs) and their conversion into influence coefficients (ICs) for the MEE film are analytically derived, incorporating the loading velocity in a dynamic process. Fast numerical techniques, including the conjugate gradient method (CGM) and the fast Fourier transform (FFT), are employed for efficient numerical solutions to the dynamic contact behaviors, including the distributions and variations of contact pressure and electric/magnetic potentials, as well as subsurface stresses. The proposed model is implemented to analyze the influences of loading velocity, film thickness, and sphere radius on the dynamic MEE responses, including pressure/stresses and electric/magnetic potentials. An energy conversion factor is selected to evaluate the performance of MEE energy conversion. Furthermore, a sensitivity analysis is conducted to evaluate the influence of material properties and their coupling on the efficiency of mechanical–electric/magnetic energy conversion.

This paper presents the derivation of a set of the novel closed-form solutions for the eigenstrain-induced elastic fields in two joined half-space solids with an interface of coupled dislocation-like and force-like imperfects. A model is proposed to characterize the interfacial discontinuity properties concerning displacements and stresses, which permits quantitative jumps of either the displacements or the stresses from one medium to the other. Basic Galerkin vectors in these two imperfectly joined half-spaces are derived based on the boundary conditions, and thus the elastic responses are obtained in explicit expressions. Taking advantage of the three-dimensional fast Fourier Transform algorithms for the convolution and correlation, the elastic fields subjected to one arbitrarily shaped inclusion or more can be efficiently and accurately evaluated. The influences of several types of interfaces, such as the perfectly bonded interface, the dislocation-like interface, and the force-like interface, on the stress and displacement transmissions are discussed. Cases for the elastic fields due to a cuboidal, a spherical, and an array of multiple cuboidal inclusions, are investigated.

The shear behaviors of U71Mn rail steel are investigated during different impact loadings using hat-shaped specimens, where the dynamic shear stress-strain responses of the specimens can be obtained by utilizing a split Hopkinson pressure bar apparatus. The maximum shear tractions are determined through the shear stress-strain curves of the experiments, and cohesive energies are obtained by trial and error method, i.e., the strain waves of the simulations are compared with those of the experiments. It is found that the maximum shear tractions and shear cohesive energies of U71Mn steel are sensitive to strain rates. Further, a strain rate-dependent cohesive zone model is developed to describe the dynamic fracture behaviors. Finally, the crack velocities are acquired under different impact loadings, and the dynamic stress intensity factor and dynamic energy release rates vary with the crack velocity.

Semi-analytical models have been developed to analyze the contact of inhomogeneous materials based on the equivalent inclusion method. It is important to pursue a higher efficiency in numerical implementation of the semi-analytical models. This paper reports the development of a dual-grid computational scheme for further improving the efficiency of the current semi-analytical modeling. Parametric studies show that the new method can save at least 50% of the execution time with respect to the original algorithm in a considerably wide range of conditions. The new method is applied to investigate the influence of inhomogeneities on contact pressure distributions. Data regression is performed to obtain the amplitudes of contact pressure disturbances as a function of inhomogeneitys elastic modulus, size and location. Then, a criterion is developed based on the values of contact pressure disturbances to determine the circumstances in which the coupling between inhomogeneities and surface contact be ignored.

This paper presents a semi-analytical model (SAM) for three-dimensional frictional magnetoelectroelastic (MEE) contact of two multiferroic bodies, together with a set of effective solution methods. The frequency response functions (FRFs) for the MEE fields in a multiferroic half-space are analytically derived with respect to a unit concentrated normal force, a unit concentrated tangential force, a unit electric charge, and/or a unit magnetic charge, which are then converted into the results of continuous Fourier transforms of the influence coefficients (ICs), followed by the discrete Fourier transforms with a proper aliasing treatment. The conjugate gradient method (CGM) is used to obtain the unknown distributed pressure. Furthermore, the discrete convolution-fast Fourier transform (DC-FFT) algorithm is implemented to calculate the in-plane electric/magnetic potentials and subsurface stresses. The model is implemented to analyze the frictional sliding contact between a half-space and a sphere, and to study the coupled effects of surface electric/magnetic charges and friction on contact behaviors, including pressure, stresses, and electric/magnetic potentials. A sensitivity analysis is also conducted to evaluate the influences of friction and material properties on the contact-induced multifield coupling behaviors. A number of case studies are committed, and the results indicate that electric/magnetic charge densities and the friction coefficient strongly influence the contact pressure, stress, and electric potential.

Semi-circular bend specimens are used to measure the brittle materials' fracture toughness, such as brittle metals, rocks, and ceramic materials. The quasi-static and dynamic model I fracture toughness of tungsten heavy alloy, a typical brittle metal material, are measured using the semi-circular bend specimens under quasi-static compression and dynamic impact loadings. For quasi-static cases, the specimens are loaded on a universal testing machine with a constant loading speed. While for dynamic cases, the specimens are executed on a modified split Hopkinson pressure bar system with the impact pressures from 0.2 to 0.4 MPa. The results show that the dynamic fracture toughness of tungsten alloy increases with the increase of the loading rate. Further, a rate-dependent bilinear traction-separation law is introduced to explain the dynamic fracture behaviors of tungsten alloy. The parameters of the rate-dependent law are obtained from the experiments and the finite element simulations. Finally, the dynamic simi-circular bend simulations using the cohesive element with rate-dependent cohesive law are established to simulate the crack propagation, and the simulation results are in good agreement with the test data.

The stiffness and failure properties of the materials are a pair of opposing physical quantities, which are often mutually constrained and fettered. Therefore, it is extraordinary meaningful and essential to explore the failure behavior of the lightweight porous materials under the design strategy of the optimal stiffness. In this paper, the failure modes of a stiffness-guided lattice specimen, which is designed by the topology optimization method and manufactured by the 3D printing technique, are investigated under quasi-static and dynamic compressions. The results illustrate that the failure behavior of the stiffness-guided lattices is strongly dependent on the non-optimized structural parameter and the loading strain-rates when the base material for 3D printing is polyamide 12 (PA12). The failure modes are mainly manifested as three categories: the unstable collapse mode, the bending collapse mode and the brittle collapse mode. In addition, the Young's modulus , initial crushing stress, and energy absorption behavior of the stiffness-guided lattices have been studied. The results indicate that the lattices' crush behavior and energy absorption behavior are highly dependent on the failure modes. Remarkably, the stiffness-guided lattices exhibit superior specific energy absorption , stable deformation mode , and a high compressive modulus in the bending collapse mode.

Materials having two or more constituents of different mechanical properties are often seen in engineering practice. These constituents are connected through their interfaces where the material displacements and tractions are most likely discontinuous, subjected to one, or more, of the five general interface conditions, i.e., perfectly bonded, dislocation-like, force-like, spring-like, and frictionless contact. This paper focus on the contact problem of a rigid sphere sliding on a layered half-space with a spring-like interface between the layer and the substrate. The frequency-domain analytical solutions for the elastic field caused by surface pressure and shear traction are derived. Three stiffness coefficients are introduced to reflect the relationship between tractions and the difference in displacements at both sides of the interface. Further, a sliding contact problem of a rigid sphere and a layered half-space with the spring-like interface is numerically investigated, and the effects of stiffness coefficients on the contact behaviors are explored. Finally, the two-layer model for a coated surface with an inner layer is compared to the spring-like model. When the inner layer is thin and soft, the pressures, as well as stresses, obtained by both models are similar to each other, and the two models are equivalent.

Double-layered inhomogeneities consist of enclosed, or layered, inhomogeneities of different material properties, embedded in a matrix material. They are found in engineering materials used for components under contact and relative motion. Currently, most theoretical investigations on the double-layered inhomogeneities are limited to elastic or plane-strain problems. This work proposes a novel model, based on the numerical equivalent inclusion method, for the elasto-plastic contact of materials with double-layered inhomogeneities. The current analysis is focused on such inhomogeneities as a stiff core enclosed by a compliant outer layer. A group of in-depth parametric studies is performed to reveal the effects of this type of double-layered inhomogeneities on the contact plasticity of the matrix material. The results indicate that the plastic strain distribution in the matrix material is related to the Young's modulus and geometric eccentricity of the inner and outer inhomogeneities, as well as the location and shape of the inhomogeneities. For the cases of individual double-layered inhomogeneity embedded at different locations, the maximum equivalent plastic strain in the matrix appears in the vicinity of the double-layered inhomogeneity, wherever is the closest to the location of the theoretical maximum elastic stress from the homogeneous solution. For the cases of multiple double-layered inhomogeneities, the overlap of the plastic strain concentration regions amplifies the disturbance caused by these inhomogeneities, and the amplification effect is related to the inhomogeneity layout. If the stiff core is completely encircled in the outer inhomogeneity layer, plastic strains would initiate from the outer layer and then permeate to the matrix material.

This paper reports a size-dependent semi-analytical model (SAM) on the frictional magnetoelectroelastic (MEE) contact of a multiferroic thin film and a rigid insulating sphere subjected to surface MEE effects. The Huang-Yu and Gurtin–Murdoch theories are extended to account for the effects of surface MEE. The frequency response functions (FRFs) for the MEE film are analytically derived, which incorporate the surface effects and are consequently converted to the corresponding influence coefficients (ICs). The conjugate gradient method (CGM) is used to obtain the unknown pressure distribution and the fast Fourier transform (FFT) is involved to calculate the surface electric/magnetic potentials and subsurface stresses. The proposed model is implemented to analyze the influences of surface MEE, multiferroic film thickness, and friction coefficient on the contact behaviors, including pressure/stresses and electric/magnetic potentials. A sensitivity analysis is conducted to evaluate the influence of surface parameters and their coupling on the contact behaviors. A set of behavior maps for the pressure and electric/magnetic potentials are constructed to reveal the influences of film thickness and material characteristic length, which can be used to determine the appropriateness of the geometry configuration (i.e. film or half-space) and surface behaviors (i.e. with or without considering the surface MEE effects).

A layer-substrate, or coating-substrate, interface can be mathematically formed by jointing a homogeneous half-space and a layer of another material or even the same material. The physical formation of the interface may be complex due to coating processing and material mismatching properties. In general, the coating and substrate may be imperfectly bonded to each other, and the their interface can be described by models of imperfect interfaces subjected to the dislocation-like, force-like, spring-like, and frictionlessly interfacial conditions. This paper presents a coupled dislocation-like and force-like interface model for the elastic fields caused by pressure and shear tractions applied on the surface of such a layer-substrate system. The model is solved analytically by employing the Papkovich–Neuber potentials, where six displacement and stress jumping coefficients are utilized to reflect the discontinuity at the interface. The derived analytical equations can be used as the basic solutions for solving contact problems involving a layer-substrate material system and an arbitrarily shaped indenter. The sliding contact of a spherical indenter and a layered flat is further investigated. The pressure, loading curve, as well as the stresses, for the system with different layers are analyzed with respect to different jumping coefficients.

A thermal elastohydrodynamic lubrication model is proposed for a coated gear pair in which the influence coefficients for the elastic deformation and the subsurface stress components are obtained through the frequency response functions. The generalized Reynolds equation is utilized to represent the non-Newtonian effect. Energy equations of the contacting solids and the oil film are derived and solved based upon the marching method. The discrete convolute, fast Fourier transform method is used for fast calculation of the tooth surface displacement and the stress components underneath the surface. Variations of the slide-to-roll ratio, rolling speed, and the tooth load during gear meshing are considered and the film squeeze effect is taken into account. Effects of the coating thickness on the tribological performance, i.e. the film thickness, the pressure, the frictional behavior as well as the stress components are investigated under both the smooth and rough surface assumptions. Effects of the root mean square value of the tooth surface roughness on the pressure and stresses are discussed.

An integrated finite element and artificial neural network method is used to analyze the impact of scratch process parameters on some variables related to elastoplastic deformation of titanium alloy. The elastoplastic constitutive parameters applied for scratch simulations are obtained from the nanoindentation experiments and finite element analysis. The validity of the finite element model of scratch is confirmed by comparing the friction forces from simulations to those from experiments. The input parameters of the artificial neural network are three scratch process parameters: tip normal force, tip radius, and shear friction coefficient. The outputs are four variables related to material deformation measured during scratch: scratch depth, elastic recovery height, plowing height, and plowing friction coefficient. The network is trained with pairs of input and output datasets generated by scratch simulations. The prediction results of the neural network are in agreement with the finite element results. The model provides assistance for the prediction and analysis of complex relationships between scratch process parameters and variables related to material deformation, and between the plowing friction coefficient and the relevant parameters. The results show the independence of scratch depth and the shear friction coefficient, and the positive relationships between the shear friction coefficient and plowing friction coefficient.

An elastohydrodynamic lubrication model for a rigid ball in contact with a transversely isotropic half-space is constructed. Reynolds equation, film thickness equation, and load balance equation are solved using the finite difference method, where the surface vertical displacement or deformation of transversely isotropic half-space is considered through the film thickness equation. The numerical methods are verified by comparing the displacements and stresses with those from Hertzian analytical solutions. Furthermore, the effects of elastic moduli, entertainment velocities, and lubricants on fluid pressure, film thickness, and von Mises stress are analyzed and discussed under a constant load. Finally, the modified Hamrock–Dowson equations for transversely isotropic materials to calculate central film thickness and minimum film thickness are proposed and validated.

The tangential fretting is explored in the present study when one of the contacting bodies distributed with multiple inhomogeneities. The tangential fretting contact of an elastic sphere with an inhomogeneous material is considered. A new numerical model based on a semi-analytical method is developed by using Eshelby’s equivalent inclusion method and fast Fourier transform algorithms. The coupling between the contact loading and inhomogeneities is fully considered. The influence of multiple inhomogeneities on tangential contact is investigated. Parametric studies are conducted for the effects of randomly distributed inhomogeneities on the contact pressure, tangential displacement, subsurface stress, etc., revealing the significance of the influences of inhomogeneity distribution parameters on tangential fretting performance.

Analytical solutions to the elastic fields induced by eigenstrains, such as plastic strains, in materials subjected to different types of joints are important for developing numerical simulations of advanced materials. This paper reports the derivation of a set of explicit integral kernels for the eigenstrain-induced elastic fields in two frictionlessly joined half-space solids or bi-materials. The elastic responses caused by arbitrary inclusions inside one of the two joined half-spaces are solved for the cases of known Galerkin vectors for the inclusion in the half-space solid. By discretizing the arbitrarily shaped single or multiple inclusions into a number of small elementary cuboids, the entire elastic response to the inclusions can be obtained through summation of the contributions from all elements with the assistance of the fast Fourier transform algorithms for convolution or correlation involved in the solutions. Cases for the elastic fields which subjected to a cuboidal, and a spherical, as well as multiple cuboidal inclusions are analyzed; and key results compared with the corresponding results for perfectly bonded half spaces. The phenomenon of probable interface separation associated with frictionless interfacial condition is further discussed.

A numerical thermal elastohydrodynamic lubrication model is developed for a coated gear pair, in which the elastic deformation is calculated through the frequency response function of Green function and the discrete-convolute fast Fourier transform. Tribological performance of the gear pair is evaluated in terms of the pressure, the film thickness, the coefficient of friction, the frictional power loss, as well as the temperature rise during meshing. Effects of the elastic modulus and the coating thickness of the coating material are studied under various working conditions. Results provide tribological guidance for engineering practice of gear coating design.

This research explores the influence of inhomogeneities on the torsional fretting via a newly developed semi-analytical method with considering the load history. The disturbances of elastic fields caused by inhomogeneities are modeled based on Eshelby’s equivalent inclusion method. Solutions are achieved iteratively through considering the coupling of surface tractions and subsurface inhomogeneities. The influences of a single inhomogeneity are investigated, revealing that the presence of an inhomogeneity causes significant surface effects on the torsional fretting. Further, the influences of inhomogeneity distribution parameters on the torsional fretting performance are quantified, demonstrating the capability of the proposed method.

This study presents a generalized model of mixed elastohydrodynamic lubrication, in which the dimensional Reynolds equation is discretized according to a modified differential scheme based on the full analysis of the pressure balance within the lubrication region. The model is capable of a wide range of lubrication regimes from fully hydrodynamic down to boundary lubrication, and both the steady-state and the time-dependent conditions can be considered. A simplified computational procedure is proposed for elliptical contacts without the ellipticity parameters specified. The evolution of lubrication behavior at startup and shutdown conditions is investigated and the transient effect of surface waviness is discussed. The model application is then extended to contacts of multilayered materials, and the effects of the layer stiffness and the fabrication methods on the stress fields and lubrication performance are analyzed. The conclusions may potentially provide some insightful information for the design and analysis of functional materials and their engineering structures.

Rolling contact experiments of (TiB + TiC)/Ti–6Al–4V composites reveal that inhomogeneous reinforcements reduce the materials’ rolling-contact fatigue (RCF) lives. The composite microstructures are examined and reconstructed based on the dual-beam focus ion beam scanning electron microscopy (FIB/SEM) technique. Integration of the microstructure-based stress analysis approach and Zaretsky’s RCF life prediction methodology leads to a new numerical RCF life modeling method. The newly developed mesh differential refinement scheme, together with the fast Fourier Transform techniques, is utilized to improve the efficiency and versatility of the proposed method. The RCF lives of the composites predicted by the new model are then compared with the experimental data, illustrating the effectiveness of the proposed method.

This paper reports the derivation of the explicit integral kernels for the elastic fields due to eigenstrains in two joined and perfectly bonded half-space solids or bimaterials. The domain integrations of these kernels result in the analytical solutions to displacements and stresses. When the eigenstrains are all in solid I, the kernel for the elastic fields has four groups in this solid and two groups in the other joined solid. Explicit closed-form solutions for a cuboidal inclusion with uniform eigenstrains are derived as the basic solutions, i.e., the influence coefficients. When the computational domain is meshed into cuboidal elements of the same sizes, the total elastic fields can be quickly obtained by implementing three-dimensional fast Fourier transform-based algorithms. The results for the fields due to a cuboidal, a spherical, and a cylindrical inclusion, as well as multiple cuboidal inclusions are presented and discussed. Residual stresses in an elasto-plastic contact involved a coated substrate is further analyzed with the new solution approach.

This paper presents a numerical solution approach of solving smooth- and rough-surface contact problems involving distributed inhomogeneities with arbitrary shapes and different material properties, based on the numerical equivalent inclusion method (EIM). Full 3D FFT techniques and a mesh differential refinement scheme are incorporated into the proposed solution method to enhance the efficiency and flexibility. Comparative studies referencing the FEM and a simplified method demonstrate the efficiency and accuracy of the present method. Computations of several heterogeneous contact cases verify the capability of the method in solving complicated and rough-surface contact problems involving materials with distributed inhomogeneities.

This work quantitatively explores the dependence of the truncation errors on computational mesh settings for image-inclusion approaches and proposes a corresponding amendment. The new method is based on FFT algorithms and involves four individual portions. A mesh differential refinement scheme, consisting of independent and flexible selections-combinations of the surface, source, and target domains, is conceived to assist the proposed method. Comparisons of the results produced by the new and conventional mesh schemes demonstrate the significant improvements in computational performances. The new method can facilitate the numerical evaluation of local elastic characteristics caused by distributed inclusions or defects in contacting components.