Simulation Studies on the Settlement of Composite Foundation with Contact Element of Zero Thickness

The various factors influencing the settlement of composite foundation have been more completely studied through numerical simulation. The influence on the settlement of composite foundation of the geometry and mechanical properties of the pile, soil, cushion, and the interface between pile and soil have been investigated through computer simulation, in which the contact elements with zero thickness are used. Some valuable conclusions for the settlement of composite foundation have been obtained: (1) The method using the contact element of zero thickness is successful when used in the simulation of the settlement of composite foundation; (2) Among the factors influencing the settlement of composite foundation, the compression modulus of the soil is the largest, and the cohesion of the soil is the second largest; (3) The effects on settlement of the internal friction angle of the soil, the elastic modulus, the radius, and the length of the pile, and the elestic modulus of the cushion are also more obvious.

Experiment and finite element method analysis mass erosion and transfer of Ag/La_2NiO_4-based electrical contacts during operation

A uniform transient temperature field model of electrical contacts operation was found by analyzing the process of closing arc constriction resistance Joule heat ~ breaking arc. Essential parameters of Ag/La2NiO4 electrical contact material for transient temperature field calculation were obtained through tests of electrical contact experimental instrument under 18 V DC in different cur- rents, other correlation experiments, and calculation anal- ysis. The finite element method was applied to solve the transient temperature field, and the features and distribution of the transient temperature field were obtained. The condition of material erosion and mass transfer can be forecasted by those calculation results. It is beneficial to research about the lifetime of Ag/La2NiO4 electrical material.

BOUNDARY ELEMENT ANALYSIS OF CONTACT PROBLEMS USING ARTIFICIAL BOUNDARY NODE APPROACH

An improved version of the regular boundary element method, the artificial boundary node approach, is derived. A simple contact algorithm is designed and implemented into the direct boundary element, regular boundary element and artificial boundary node approaches. The exisiting and derived approaches are tested using some case studies. The results of the artificial boundary node approach are compared with those of the existing boundary element program, the regular element approach, ANSYS and analytical solution whenever possible. The results show the effectiveness of the artificial boundary node approach for a wider range of boundary offsets.

Analysis of Leakage in Bolted-Flanged Joints Using Contact Finite Element Analvsis

The evolution of leakage is studied using detailed contact finite element analysis. The distribution of stress at the gasket is analyzed using a contact condition based on slide-line elements using ABAQUS, a commercial finite element code, Slide-line elements also take into account pressure penetration as contact that is lost between flange and gasket. Results are presented for a particular flange, a raised face flange sealed by a mild steel gasket. A comparison of the results from the gasket contact analysis and the contact conditions specified by the ASME Boiler and Pressure Vessel Code, Sections VIII, Division 1 shows that the conditions specified in the ASME Code predict leakage relatively accurately.

BOUNDARY ELEMENT METHOD FOR MOVING AND ROLLING CONTACT OF 2D ELASTIC BODIES WITH DEFECTS

A scheme of boundary element method for moving contact of two-dimensional elastic bodies using conforming discretization is presented. Both the displacement and the traction boundary conditions are satisfied on the contacting region in the sense of discretization. An algorithm to deal with the moving of the contact boundary on a larger possible contact region is presented. The algorithm is generalized to rolling contact problem as well. Some numerical examples of moving and rolling contact of 2D elastic bodies with or without friction, including the bodies with a hole-type defect, are given to show the effectiveness and the accuracy of the presented schemes.

Finite Element Analysis of Elastic-Plastic Contact Mechanic Considering the Effect of Contact Geometry and Material Properties

Each surface of roughness has different shape of asperity which is modeled with various shapes of analytical models. In this paper, the differences among various models of shape of asperity investigate using the Finite Element Method (FEM) and various analytical models. The contact stresses in rough surfaces are calculated analytically using various asperity shape models. Finite element analysis is also carried out assuming three types of material properties namely, the linear, the elastic-perfect plastic and the elastic-nonlinear hardening. The analytical results are compared with the results obtained by the finite element method. The results illustrate for using a deterministic approach which the numerical models are suitable. In hertz model, the result of force is very big in interface of causing deformation plastic, while Model Zhao has almost same result with FEM nonlinear property model. It is observed that the results obtained from Zhao’s model are generally in a better agreement with the results obtained from various finite element models especially in elastic-plastic and plastic zones, hence it may be concluded that Zhao’s model can be used for analyzing the rough surfaces in contact mechanics.

Finite Element Analysis of the Contact Mechanics of Ceramic-on-Ceramic Hip Resurfacing Prostheses

Ceramics are good alternative to metal as bearing couple materials because of their better wear resistance. A Finite Element(FE) study was performed to investigate the contact mechanics and stress distribution of Ceramic-on-Ceramic (COC) hip resurfacingprostheses. It was focused in particular on a parametric study to examine the effects of radial clearance, loading,alumina coating on the implants, bone quality, and fixation of cup-bone interface. It was found that a reduction in the radialclearance had the most significant effect on the predicted contact pressure distribution among all of the parameters considered inthis study. It was determined that there was a significant influence of non-metallic materials, such as the bone underneath thebearing components, on the predicted contact mechanics. Stress shielding within the bone tissue was found to be a major concernwhen regarding the use of ceramic as an alternative to metallic resurfacing prostheses. Therefore, using alumina implantswith a metal backing was found to be the best design for ceramic resurfacing prostheses in this study. The loading, bone quality,and acetabular cup fixation conditions were found to have only minor effects on the predicted contact pressure distribution alongthe bearing surfaces.

CALCULATION OF MILL RIGIDITY BY THREE DIMENSION CONTACT BOUNDARY ELEMENT METHOD

Vertical rigidity of the space self adaptive 530 high rigidity mill is calculated by applying the boundary element method (BEM) of three dimension elastic contact problem,which can update the existed deforming separation calculating theory and corresponding methods of material mechanics,elastic mechanics and finite element method.The method has less hypotheses and stronger synthesis in contact type calculating model.The advantages of the method are high calculating rate,high calculating accuracy,etc..

Influence of particle contact models on soil response of poorly graded sand during cavity expansion in discrete element simulation

The discrete element method(DEM) has been extensively adopted to investigate many complex geotechnical related problems due to its capability to incorporate the discontinuous nature of granular materials. In particular, when simulating large deformations or distortion of soil(e.g. cavity expansion),DEM can be very effective as other numerical solutions may experience convergence problems. Cavity expansion theory has widespread applications in geotechnical engineering, particularly to the problems concerning in situ testing, pile installation and so forth. In addition, the behaviour of geomaterials in a macro-level is utterly determined by microscopic properties, highlighting the importance of contact models. Despite the fact that there are numerous contact models proposed to mimic the realistic behaviour of granular materials, there are lack of studies on the effects of these contact models on the soil response.Hence, in this study, a series of three-dimensional numerical simulations with different contact constitutive models was conducted to simulate the response of sandy soils during cylindrical cavity expansion. In this numerical investigation, three contact models, i.e. linear contact model, rolling resistance contact model,and Hertz contact model, are considered. It should be noted that the former two models are linear based models, providing linearly elastic and frictional plasticity behaviours, whereas the latter one consists of nonlinear formulation based on an approximation of the theory of Mindlin and Deresiewicz. To examine the effects of these contact models, several cylindrical cavities were created and expanded gradually from an initial radius of 0.055 m to a final radius of 0.1 m. The numerical predictions confirm that the calibrated contact models produced similar results regarding the variations of cavity pressure, radial stress, deviatoric stress, volumetric strain, as well as the soil radial displacement. However, the linear contact model may result in inaccurate predictions when highly angular soil particles are involved. In addition, considering the excessive soil displacement induced by the pile installation(i.e. cavity expansion), a minimum distance of11 a(a is the cavity radius) is recommend for practicing engineers to avoid the potential damages to the existing piles and adjacent structures.

Major elements and lithostratigraphic study of the contact rocks of the Togo and the Dahomeyan formations in Ghana

The thrust contact between the Togo and the Dahomeyan formations in Ghana is a lithotectonic boundary that exists between two major Precambrian formations which are of importance to geologists owing to the fact that Precambrian rocks in Ghana host almost all economic minerals and metals. The lithostratigraphy of the Togo-Dahomyan thrust contact rocks from a borehole in Kwabenya near Accra (the Capital of Ghana) has been studied and major crustal chemical elements assayed using Instrumental Neutron Activation Analysis (INAA) techniques. The results have revealed elemental compositions and the mineralogical make up of the lithostratigraphic units of these contact rocks and the general geology of the Togo and the Dahomeyan formations. The profile shows a thrust contact that exists between the Togo formations which are underlying the Dahomeyan formations. The Togo formations here are made mainly of quartzite in fresh schist and the Dahomeyan made of gneisses. In between these two major geologic formations are the rocks of the contact which are intercalation of quartzite and schist. The rocks are felsic with an average felsic index (F) of 85.74 and feldspar rich with K- (orthoclase) feldspars dominating the Dahomeyan rocks. Iron and titanium oxides are depleted with depth from 52 m depth below surface downward and potassium oxide was enriched with depth from 42 m below surface downward. Major mineral forming elements such as aluminum and calcium had varied levels in the Togo and in the Dahomeyan rocks.

CONTACT FRICTION ANALYSIS AND STRESS OSCILLATION SUPPRESSION WITH A SIMPLE INTERFACE ELEMENT

A simple interface element for analyzing contact friction problems is developed. Taking nodal displacements and contact stresses as unknowns, this element can simulate frictional slippage, decoupling and re-bonding of two bodies initially mating or having gaps at a common interface. The method is based on the Finite Element Method and load incremental theory. The geometric and static constraint conditions on contact surfaces are treated as additional conditions and are included in stiffness equations. This simple element has the advantages of easy implementation into standard finite element programs and fast speed for convergence as well as high accuracy for stress distribution in interface. Undesirable stress oscillations are also investigated whenever large stress gradients exist over the contact surfaces. Exact integration or the conventional Gauss integration scheme used to evaluate the interpolation function matrix of the interface element is found to be the source of the oscillations. Eigenmode analysis demonstrates that the stress behavior of an interface element can be improved by using the Newton-Cotes integration scheme. Finally, the test example of a strip footing problem is presented.

Contact position controlling for two-dimensional motion bodies by the boundary element method

An algorithm is presented for controlling two-dimensional motion contact bodies with conforming discretization. Since a kind of special boundary element is utilized in the algorithm, the displacement compatibility and traction equilibrium conditions at nodes can be satisfied simultaneously in arbitrary locations of the contact interface. In addition, a method is also proposed in which the contact boundary location can be moved flexibly on the possible contact boundary. This method is effective to deal with moving and rolling contact problems on a possible larger moving or rolling contact region. Numerical examples show effectiveness of the presented scheme.

Study of adaptive finite element techniques for contact problem in elastic bodies

The adaptive element techniques of contact problem are studied by means of penalty method, and the error estimators are discussed. Based on error estimators, algorithm of the adaptive element techniques is developed, then the Gauss - Newton iterations are used which allow the nonlinear problem to be transformed into a sequence of linear sub- problems then easily solved. In addition, the algorithm can be applied into the simulation of de -bonding of fiber - reinforced composites.

THREE DIMENSIONAL ELASTO-PLASTIC CONTACT BOUNDARY ELEMENT ANALYSIS FOR ROLLING WITH CONSIDERATION OF FRICTION

The boundary element method in framework is given to evaluate three dimensional frictional contact problems. Elasto plastic material behavior is taken into account by mean of an initial stress formulation and Von Mises yield criterion. The amount of tangential traction at contact surface is limited by Coulomb's friction law and constant shear rule. From some numerical results of a plate rolling problem, it is demonstrated here that the BEM can be used to efficiently and accurately analyze this class of forming problems.

Mathematical Description and Finite Element Equation of 3D Coupled Thermo-elastic Contact Problem

Through defining slide yield function and floating potential function of thermo-contact surface, the complementary equation of thermo-contact boundary has been reached, the fundamental equations to solve 3D thermo-contact coupled problem have been listed. On this foundation, the finite element equation and definite solution condition of contact heat transfer have been given out. Based on virtual work principle and contact element technology, the finite element equation of 3D elastic contact system has been deduced under the effect of thermal stress. The pseudo load brought by contact gap have been introduced into this equation in order to reflect the contact state change. During iteration, once contact rigidity matrix is formed, it won’t change, which will make calculation reduce greatly.

SOLVING CONTACT PROBLEM WITH FRICTION BY A NEW FAST BOUNDARY ELEMENT METHOD

The formulation of boundary element method for handling contact problems with friction and the technique for high speed contact analysis are presented. This formulation is based on the idea of modifying the length of contact elements without altering the total number of elements. The high precision of solution and high speed analysis are verified according to the results of conventional method and analysis method.

Optimization Analysis of Sliding Electrical Contact Interface Based on Electromechanical Coupling

This work addresses the critical issue of current density distribution in the sliding electrical contact interface based on electromechanical coupling, which is essential for minimizing damage and enhancing performance. Using electromechanical coupling analysis and finite element analysis (FEA), the effects of initial contact pressure, pulse current input, and armature speed on current density are examined. Key findings indicate that optimizing the convex rail and armature structures significantly reduces peak current density, improving uniformity and reducing damage. These optimizations enhance the efficiency, accuracy, and service life of sliding electrical contact interfaces, providing a theoretical foundation for designing more durable and efficient high-current-density applications.

影响砂砾土堆积角形成的离散元关键参数

【目的】明确影响砂砾土堆积角形成的关键因素,分析Johnson-Kendall-Roberts(JKR)表面能、碰撞恢复系数、静摩擦、滚动摩擦系数等因素对砂砾土堆积角的影响,实现对砂砾土堆积角的精确预测。【方法】使用Box-Behnken中心组合设计试验方案,采用Generic EDEM material model database(GEMM)数据库获取仿真试验关键参数;基于Hertz-Mindlin with JKR接触模型对砂砾土进行堆积角仿真试验;利用MATLAB函数曲线读取堆积形态轮廓线的边界颗粒坐标,拟合堆积斜面轮廓线。【结果】实际最优因素参数组合为砂砾土颗粒间JKR表面能、滚动摩擦系数、静摩擦系数和恢复系数,分别为0.05 J/m2、0.1、0.39、0.45;EDEM仿真试验所得砂砾土堆积角为35.41°,与堆积角测量值(35.11°)误差为0.854%,且颗粒堆积形态无明显差异。【结论】砂砾土颗粒的JKR表面能和滚动摩擦系数是影响堆积角的重要因素。

下颌All-on-4种植固定义齿不同咬合接触应力分布的有限元分析

背景:All-on-4种植固定义齿的长期修复效果与生物力学问题密切相关,其中咬合设计影响修复体各部位的应力分布,然而,国内外目前有关All-on-4种植固定义齿的生物力学研究较少且无定论。目的:分析不同咬合接触对下颌All-on-4种植固定义齿应力分布的影响。方法:建立下颌All-on-4种植固定义齿的模型,通过改变加载力的大小、方向和加载部位,设置了10种加载工况,模拟正中咬合、侧方咬合和前伸咬合,通过在不同牙位上加载模拟不同的咬合接触类型,分析比较各组模型不同加载工况中模型各部分的应力分布和最大应力值。结果与结论:①各组模型的应力分布云图基本相似,种植体应力主要集中在种植体颈部,周围骨组织的应力主要集中在种植体颈部周围,并且皮质骨的应力明显高于松质骨;基台的应力主要集中在基台与种植体和基台与上部修复体连接的部位,上部修复体中钛支架的应力主要集中在基台与钛支架连接部位,上部修复体中树脂面的应力主要集中在各加载点上;②模拟正中咬合中,末端悬臂不加载时种植体的最大Von-Mises应力值明显增大,说明下颌All-on-4种植固定义齿在正中咬合时末端悬臂区可有咬合接触;③模拟侧方咬合中,在模拟尖牙保护[牙合]工况中模型各部分的最大Von-Mises应力值明显增大;模拟平衡[牙合]工况中模型各部分的最大Von-Mises应力值较组牙功能[牙合]工况略低,说明下颌All-on-4种植固定修复在完成骨整合永久修复时,为了提高咀嚼效率,可选择组牙功能[牙合],种植术后即刻修复时可选择平衡[牙合];④模拟前伸咬合中,只在前牙区加载时模型各部分的最大Von-Mises应力值明显增大;模拟平衡[牙合]工况中,后牙区加载点在悬臂区和在悬壁区前方时模型各部分的最大Von-Mises应力值较小,说明下颌All-on-4种植固定修复义齿前伸运动的咬合接触可选择前伸平衡[牙合]。

Plate Contact问题的混合有限元逼近

论文考虑了Plate Contact问题的混合有限元逼近,其变分问题为第二类四阶椭圆变分不等问题.首先,根据正则化方法,得到原问题的正则化问题.再根据网格依赖范数技巧,考虑了正则化问题的Ciarlet-Raviart混合有限元逼近,并证明了真解与逼近解之间的误差估计.最后通过数值算例验证了理论分析的结果.