材料属性温度相关热弹塑性接触问题研究

应用有限元方法建立了可考虑屈服应力温度相关效应的粗糙表面热弹塑性接触模型.研究了摩擦力和不同热输入情况下圆柱体与弹塑性平面的接触力学特性.求解了考虑屈服应力温度相关效应的粗糙表面热弹塑性接触问题,探讨了摩擦热效应对表面温升、接触压力、平均间隙及接触体应力分布的影响.提出了考虑热膨胀系数温度相关效应的热弹塑性接触模型.通过刚性圆柱体与半无限大平面的热弹塑性接触研究了热膨胀系数温度相关效应对接触体应力分布的影响.     

粗糙表面热弹塑性接触自适应无网格分析

为了在较真实地模拟接触状态的同时节省计算耗费,采用自适应无网格法求解粗糙表面热弹塑性接触问题.计算中考虑了屈服强度温度相关因素,将基于应变能梯度的自适应无网格法与线性规划一增量初应力法相结合,构建了热弹塑性接触自适应无网格分析模型,并给出相应的程序流程.通过粗糙表面与弹塑性平面热弹塑性接触算例进行验证,分别对两种不同工程材料考虑切向摩擦力、材料应变硬化和材料屈服强度温度相关等情况进行了讨论.结果表明,采用自适应无网格法能有效求解粗糙表面热弹塑性接触问题,在保证计算精度与整体加密相当的情况下,自适应加密的计算耗费约为整体加密计算耗费的10%.     

粗糙表面热弹塑性接触自适应无网格分析

为了在较真实地模拟接触状态的同时节省计算耗费,采用自适应无网格法求解粗糙表面热弹塑性接触问题。计算中考虑了屈服强度温度相关因素,将基于应变能梯度的自适应无网格法与线性规划-增量初应力法相结合,构建了热弹塑性接触自适应无网格分析模型,并给出相应的程序流程。通过粗糙表面与弹塑性平面热弹塑性接触算例进行验证,分别对两种不同工程材料考虑切向摩擦力、材料应变硬化和材料屈服强度温度相关等情况进行了讨论。结果表明,采用自适应无网格法能有效求解粗糙表面热弹塑性接触问题,在保证计算精度与整体加密相当的情况下,自适应加密的计算耗费约为整体加密计算耗费的10%。     

材料属性温度相关热弹塑性接触问题研究

应用有限元方法建立了可考虑屈服应力温度相关效应的粗糙表面热弹塑性接触模型。研究了摩擦力和不同热输入情况下圆柱体与弹塑性平面的接触力学特性。求解了考虑屈服应力温度相关效应的粗糙表面热弹塑性接触问题,探讨了摩擦热效应对表面温升、接触压力、平均间隙及接触体应力分布的影响。提出了考虑热膨胀系数温度相关效应的热弹塑性接触模型。通过刚性圆柱体与半无限大平面的热弹塑性接触研究了热膨胀系数温度相关效应对接触体应力分布的影响。
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弹塑性粗糙表面实际接触面积演变规律研究

粗糙表面的实际接触面积直接影响精密机电设备配合表面的摩擦因数、热导/电导率、接触应力等.然而,针对弹塑性接触行为进行系统性地研究很少,弹塑性粗糙表面实际接触面积的演变规律尚不明确.针对这一问题,通过理论研究获得了弹塑性粗糙表面实际接触面积的影响因素,并引入弹塑性接触力学数值计算方法,对具有不同材料参数和表面形貌特征的弹塑性粗糙表面的接触行为进行数值仿真计算,得到各种情况下的表面实际接触面积随着平均接触压力的变化曲线,总结出了实际接触面积演变规律与这些影响因素之间的映射关系,并最终得到实际接触面积的计算公式,为弹塑性接触力学的相关工程应用奠定了基础.     

含涂层真实粗糙表面的弹塑性接触特性研究

运用有限元法、线性规划法和塑性增量理论对含涂层真实粗糙表面的弹塑性接触问题进行了分析。通过改变涂层材料的弹性模量、屈服极限及涂层厚度，研究了不同条件下接触面积与接触压力、平均间隙与接触压力的关系及变化规律，给出了3种数值方法的解与弹性解的比较，分析了各主要因素对接触压力、接触面积及平均间隙的影响。     

考虑粗糙度效应的微孔化机械密封摩擦副接触特性分析

针对机械密封装置在启停阶段或某些特定工况下出现高温以及摩擦磨损严重等问题，探究考虑粗糙度效应的微孔化机械密封端面接触压力及温升的变化规律，以揭示机械密封端面的真实接触状态。基于分形理论建立机械密封静环粗糙表面和动环微孔接触模型，采用数值计算方法，研究微孔对机械密封端面接触压力和温升的影响，以及表面粗糙度对机械密封端面接触面积、接触压力、温升的影响。结果表明：微凸体经过微孔时，微凸体嵌入微孔边缘使得接触压力峰值增大，导致切削发生；摩擦过程中，压力最高点位置因为微凸体的弹塑性变形而不固定，改善了微凸体的受力情况；微孔降低了密封端面的接触面积，从而使得微凸体的接触减少、压力极值点减少，降低了密封端面摩擦副的温度，改善了密封端面的磨损状况；表面粗糙度越小，接触面积越大，接触压力、端面温度更加均匀，表面粗糙度越大，端面磨损风险更加严重。     

微动接触中分形粗糙表面的接触应力研究

表面粗糙度对微动状态下接触面的接触压力和剪切摩擦力有着显著影响.在这项研究中,创建Python脚本将Matlab中利用Weierstrass-Mandelbrot函数构造的分形表面轮廓坐标导入ABAQUS中,并使用样条曲线拟合轮廓坐标,从而构建包含粗糙表面的二维柱面/平面接触模型.采用有限元方法研究考虑粗糙表面接触的接触压力和剪切摩擦力分布,并讨论材料弹性、弹-塑性和载荷幅值对剪切摩擦力的影响.结果表明,粗糙表面的存在导致接触压力分布为非光滑曲线,局部应力集中程度高;当表面粗糙度较大时,接触面上接触压力的分布是离散的.同时发现,不同材料接触副下,剪切摩擦力沿粗糙表面的分布差异明显.     

列车制动闸片接触界面接触压力分布研究

以列车盘式制动器为研究对象,建立一个三维瞬态热-结构耦合模型,利用有限元软件ABAQUS非线性多物理场耦合方法,数值模拟了制动过程,发现制动闸片上的温度场和接触应力场在接触界面呈不均匀分布,并且在每个闸块上二者存在着相互耦合的关系,温度高的区域由于热变形大、接触面积小,导致接触压力较高。此外,接触压力在制动过程中的变化还与摩擦力、减速移动热源有关。     

自旋对角接触球轴承弹流润滑与油膜刚度的影响

根据角接触球轴承自旋运动特征,同时考虑弹流润滑效应,建立角接触球轴承考虑自旋运动的弹流润滑模型;采用多重网格法求解弹性变形,利用有限差分法迭代求解雷诺方程,得到较为精确的数值解;分析不同赫兹接触压力、滚道表面粗糙度下自旋对角接触球轴承弹流润滑和油膜刚度的影响。结果表明：考虑自旋时随着Hertz接触压力、自旋角速度增大,油膜厚度减小,油膜压力增大,油膜承压区域呈细长状,并向接触中心靠近;随着滚道表面粗糙度幅值增大,油膜压力和膜厚均出现了波动,且考虑自旋运动时,轴承油膜厚度明显减小,油膜局部压力峰值更大;随着卷吸速度、润滑油黏度增大,油膜刚度减小,而考虑自旋运动时油膜刚度值更大;随着自旋角速度增大,油膜刚度逐渐增大。     

ANALYSIS ON THERMAL ELASTO-PLASTIC ASPERITY CONTACTS OF LAYERED MEDIA

A thermal elasto-plastic asperity contact model is investigated, which takes into account the steady-state heat transfer and the asperity distortion due to thermal elasto-plastic deformations. A hard coating and a soft coating are applied to study the correlations between contact area and contact pressure, average gap and contact pressure, coating thickness and contours of the contact stress distribution, etc. The effects of material properties, coating thickness, frictional coefficient, and the heat input combinations on the stress distribution are investigated and discussed. The frictional heat input increases the maximum value of yon Mises stress. Finally, the appropriate thickness of the hard coating is also discussed. To protect the substrate, one can choose hard coating and the thickness of that is suggested that can be hc=70 Rm.     

An analysis of three-dimensional elasto-plastic sinusoidal contact

Researchers have developed many models to simulate the elasto-plastic contact of spheres. However, there does not appear to exist a closed-form analytical model for elasto-plastic three-dimensional sinusoidal contact. This work uses a finite element model (FEM) to characterize elasto-plastic sinusoidal contact. Although at initial contact the sphere and sinusoidal case are very similar and can both be described by the classic elastic Hertz contact case, once the contact is pressed past a certain range of deformation the two cases are very different. The model produces equations which can be used to approximately relate the area of contact to the contact pressure for elasto-plastic sinusoidal contact. The equations are fit to the FEM results and existing elastic solutions of sinusoidal contact. An empirical expression for the average pressure which causes complete contact between elasto-plastic sinusoidal contacts is also provided.     

Elasto-Plastic Contact of Rough Surfaces

An isothermal elasto-plastic asperity contact model is developed and presented in this paper, which deals with micro plastic flows of materials and the influence of the elasto-plastic deformation of materials on the behavior of contacting surfaces. The model is solved with the incremental form of a simplex-type algorithm. The von Mises yield criterion is used to determine the onset of the plastic deformation. The effectiveness and validity of the model are studied through analyzing a Hertzian contact problem. Substrate stresses are calculated and differences are observed. Furthermore, the contact pressure, real area of contact, and average gap of real rough surfaces under the elastic, elastic-perfectly-plastic, and the elasto-plastic contact conditions are numerically investigated and the results are compared.     

The Effect of Scale-Dependent Hardness on Elasto-Plastic Asperity Contact between Rough Surfaces

Statistical methods are used to model elasto-plastic contact between two rough surfaces using a recent finite element model of elasto-plastic hemispherical contact and also recent advances in strain gradient modeling. The elasto-plastic hemispherical contact model used to model individual asperities accounts for a varying hardness effect due to deformation of the contact geometry that has been documented by other works. The strain gradient model accounts for changes in hardness due to scaling effects. The contact between surfaces with hypothetical material and surface properties, such as the elastic modulus, yield strength, and roughness are modeled. A model is also constructed to consider a variable asperity contact radius to evaluate if the strain gradient model will affect it differently. The models produce predictions for contact area, contact force, and surface separation. The strain gradient effects decrease the real area of contact and increase the average contact load in comparison to the model without these effects. The strain gradient model seems to have a larger influence on the predictions of contact load and area than does considering a variable asperity contact radius for the cases considered in this work.     

Thermo-mechanical finite element analysis of a rail wheel

The rail wheel, which is acted upon by mechanical forces also experiences thermal stresses due to braking, during service. The coupled nature of these forces is analysed using a three-dimensional elasto-plastic finite element model. Contact stresses at the rail–wheel interaction location are analysed using a global–local approach on a three-dimensional elasto-plastic finite element model. The paper also brings out the size and shape of the plastic zone at the contact region. Commercial finite element code ABAQUS has been used for the analysis and SDRC’s I-DEAS has been used for modelling. American Association of Railroad’s standards, available for the purpose of analytical evaluation of the rail wheel, has also been critically evaluated in this work.     

A Finite Element Study of an Elasto-Plastic Disk or Cylindrical Contact Against a Rigid Flat in Plane Stress with Bilinear Hardening

This work presents a finite element study of elasto-plastic cylindrical contact. The geometry could also be described as a vertically aligned disk whose axis of symmetry is parallel to the contact surface. The cylinder is considered to be in the plane stress state. The material of the cylinder is modeled as elasto-plastic with bilinear hardening (also known as linear hardening). Simulations for a range of material properties and deflections typical to engineering applications are carried out. A mesh convergence study has also been performed. By employing symmetry, the cylinder has been modeled as a quarter circle and a straight line is used to model the opposing rigid flat surface. The finite element results for the elastic and fully plastic cylindrical contact cases are compared to other existing models such as Hertz contact and spherical elasto-plastic models. Since the case considered is plane stress, the stress distribution is significantly different from elasto-plastic spherical contacts, which would be closer to a plane strain case. An empirical relationship is fit to the results to allow for prediction of the contact width as a function of displacement and force.     

A statistical model of elasto-plastic asperity contact between rough surfaces

This work models statistically elasto-plastic contact between two rough surfaces using the results of a previous finite element analysis of an elasto-plastic sphere in contact with a rigid flat. The individual asperity contact model used accounts for a varying geometrical hardness effect that has recently been documented in previous works (where geometrical hardness is defined as the uniform pressure found during fully plastic contact). The contact between real surfaces with known material and surface properties, such as the elastic modulus, yield strength, and roughness are modeled. The asperity is modeled as an elastic-perfectly plastic material. The model produces predictions for contact area, contact force, and surface separation. The results of this model are compared to other existing models of asperity contact. Agreement exists in some cases and in other cases it corrects flaws, especially at large deformations. The model developed by Chang, Etsion and Bogy is also shown to have serious flaws when compared to the others. This work also identifies significant limitations of the statistical models (including that of Greenwood and Williamson).     

二维多粗糙峰涂层表面的弹塑性接触力学分析

应用有限元方法对二维多粗糙峰涂层表面的弹塑性接触力学行为进行了分析。对不同涂层材料弹性模量、不同屈服极限、不同涂层厚度及不同表面形貌的粗糙表面与刚性平面的弹塑性接触问题进行了模拟,分析了这几种因素对接触压力、接触面积、表面轮廓变形及应力场分布的影响。