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。     

热障涂层粗糙表面弹塑性接触应力分析

含热障涂层的发动机零部件能有效提高抗热性能,但微接触作用下的部件涂层表面的应力分布规律及失效形式直接影响发动机可靠性。以热障涂层与榫头接触作用为背景,将其抽象为含规则粗糙峰的刚性表面与热障涂层微接触模式,利用弹塑性接触有限元方法分析涂层表面下的压力及应力分布,研究压入深度、涂层厚度、弹性模量和屈服强度对于涂层压力及残余应力分布的影响。     

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-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%.     

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。     

模具钢表面多弧离子镀CrAlN涂层的制备及其摩擦性能研究

为了改善模具钢表面质量,采用多弧离子镀技术在H13模具钢表面沉积CrAlN薄膜,探讨H13钢基体表面渗氮处理后对薄膜表面形貌、硬度、结合力、抗氧化性和摩擦磨损性能的影响。结果表明：基体表面渗氮处理前后制备的CrAlN涂层表面均匀致密,都有少量的大颗粒,涂层表面均呈CrN（200）面择优取向,而渗氮后制备的涂层CrN（200）面择优取向更强;基体H13钢经过表面渗氮后,硬度显著提高,对制备的涂层具有支撑作用,降低了裂纹产生倾向,提高了涂层产生裂纹的临界载荷,提高了涂层的膜基结合力;相较于基体表面未渗氮处理制备的CrAlN涂层,基体表面渗氮后制备的CrAlN涂层具有更高的硬度和结合力,更为优异的摩擦磨损性能,且抗高温氧化性能显著增强。     

一种结合部法向刚度的预估方法

提出一种结合部法向刚度的预估方法.通过表面形貌测量仪获取粗糙表面的轮廓数据,拟合生成粗糙表面轮廓曲线,在此基础上建立考虑摩擦的二维粗糙表面的有限元弹塑性接触模型,用罚函数法计算压力在0～0.8 MPa的加载过程中接触层的应力、位移和接触面积.计算结果表明,粗糙表面真实的接触面积在低载荷下快速增大,高载荷下的增大速度很缓...     

基于ANSYS的真实粗糙表面微观接触分析

基于材料弹塑性变形理论,采用激光测量仪测取零件表面微观形貌数据,使用小波对测量数据进行处理,提取不同层次的粗糙度,利用有限元分析软件ANSYS及其APDL工具,建立真实粗糙表面不同尺度上的微观接触参数化有限元模型,仿真分析了粗糙表面接触的弹塑性变形全过程。提出了基于ANSYS重启动分析、网格重划的多载荷步求解算法,以解决有限元微观接触分析过程中的网格畸变问题。通过通用后处理模块/POST1,提取了有限元分析结果文件中的真实接触面积、接触载荷、接触微凸体个数等接触参数,分析了多种不同粗糙度表面相互接触时接触参数的关系,以及不同尺度的粗糙面对接触参数的影响,为研究结合面的接触机理和连接性能提供了方法。     

深沟球轴承非赫兹接触及失效机理分析

考虑轴向载荷、弹塑性本构、协调接触、轴承游隙等因素的影响,对某汽车变速器中所采用的深沟球轴承在服役过程中出现的失效问题通过非赫兹有限元数值模型进行了求解,并据此分析了该轴承在工作过程中的失效机理。进一步研究了轴承材料本构、交变载荷等因素对接触状态的影响。结果表明:弹性本构承载体积小于弹塑性本构,应力水平高于弹塑性本构;载荷按一定角度作用可以降低轴承内部应力极值;载荷增加使应力极值和初始屈服深度增加,但当载荷过大时,初始屈服深度会急剧减小。     

限制淬透性轴承钢在大型滚子制造中的应用

对大型滚子制造用GCr4与GCr15SiMn、G20Cr2Ni4A材料的接触疲劳寿命、冲击韧度、压碎载荷等进行了对比试验，经过优化热处理工艺处理的GCr4滚子具有表面硬，心部软、韧且表面残余压应力较高的特点。利用该钢制造的大型滚子，质优价廉，材料热处理的成本可大幅度降低。     

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.     

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.     

Enhancement of a simplified model for maximum stress prediction

A simplified model for rapid estimation of maximum subsurface stress was previously reported by the authors. That model was found to predict the upper bound of the maximum von Mises stress in each layer below any surface with good accuracy. In this work, the model is enhanced by quantifying the difference between the predicted upper bound and the maximum stress for a specific rough surface. This is done by evaluating stress predictions for real rough surfaces, sinusoidal surfaces, ideal textured surfaces, and real rough surfaces with imposed computer generated texture. The difference between the predicted upper bound and the surface-specific maximum stress is found to be related to that surface’s roughness. The origin of this relationship is investigated in terms of apparent contact area. The enhanced simplified model provides an efficient means of estimating maximum stress in rough surface contact.     

离散磁道式磁盘与磁头动力学接触有限元分析

基于Hertz冲击理论,采用有限元仿真方法,建立了无摩擦条件下离散磁道式磁盘与磁头接触的动力学模型,研究了磁头径向寻道速度固定、法向冲击速度变化时,磁道材料力学特性对磁盘接触力场特性的影响规律,研究结果表明:随弹性模量增大,最大接触面积减小,最大接触力、最大VonMises应力和最大等效塑性应变均增大;屈服强度对力场特性的影响与接触力场Von Mises应力大小有关,只有当磁盘最大Von Mises应力达到磁道材料屈服强度时,屈服强度变化才会影响磁盘的接触力场特性。     

Analyzing Elastic-Plastic Real Rough Surface Contact in Running-in

A numerical method is presented for evaluating the elastic-elastic contact of real rough surface contacts during running-in. For the surface contact, an elastic-plastic model based on the variational method is applied to analyze the pressure distribution and contact area of worn surfaces during running-in. In conjunction with the classical statistic model of Greenwood and Williamson, the numerical result showed that the plasticity index Ψ was decreased to one in the elastic range as running-in proceeded. In comparison with the Hertzian solution, the influence of the asperities is very significant on the pressure distribution, thereafter causing a higher peak value of contact pressure. For the subsurface, the interior stress from the von Mises criterion was calculated to evaluate the subsurface stress field subject to both normal and tangential forces. In the calculated of the interior stress, the total stress is decomposed into a fluctuating component and a smooth component. The fluctuating part is solved by using FFT from the concept of the convolution theorem while the smooth part is obtained directly by analytical solution. Calculations of contact area and subsurface stress on experimentally produced surfaces whose topography has been determined using an atomic force microscope and friction coefficient front sliding have been carried out. The results showed that asperities and friction coefficient gave rise to stress increase in the near-surface stress field and produced a high stress zone towards the surface. As a result, transverse asperity cracking was produced. The calculations and supporting experimental evidence clearly confirmed that the reduction of peak pressure during running-in decreased the plastic deformation of contact.     

基于ABAQUS的变截面橡胶密封条热应力与密封性分析

研究用于发动机油气分离器的乙烯丙烯酸酯橡胶密封胶条在不同温度下的强度和密封性能。借助于大型有限元分析软件ABAQUS建立橡胶密封胶条与配合壳体的有限元模型,采用Mooney-Rivlin模型,对不同温度下的密封胶条进行热应力计算分析,得到橡胶密封胶条在不同温度下的Von Mises应力、压缩率、接触应力和接触宽度。结果表明:随着温度的升高,密封胶条的Von Mises应力和密封胶条与壳体连续接触面上的接触应力逐渐增加,接触宽度基本不变,密封条的压缩率逐渐减小;密封胶条的Von Mises应力远小于橡胶材料的拉伸强度,满足强度要求;密封胶条连续接触面上的接触应力始终大于油气分离器的工作压力且接触宽度符合要求,橡胶密封胶条满足密封条件。     

An Engineering Model for Three-Dimensional Elastic-Plastic Rolling Contact Analyses

Fatigue life of heavily loaded rolling bearings is strongly dependent on elastic-plastic material properties. For bearing steels these elastic-plastic properties can be accurately obtained by performing monotonic or half-compressive tests. A three-dimensional strain deformation analysis based on the incremental theory of plasticity and the use of Prandtl-Reuss relations in conjunction with the von Mises yield criterion was developed in order to evaluate the permanent deformation in dry contacts loaded above the elastic limit in case of normal loading. The Ramberg-Osgood stress-strain relation for two martensitically hardened variants of SAE 52100 bearing steel considered the nonlinear kinematic and/or isotropic material behavior. Parameters describing the influence of retained austenite are modeled by using a nonlinear isotropic law. Pressure distribution and contact surface displacements during incremental loading are evaluated by using a conjugate gradient method and the internal stress field is derived by using the superposition principle. Further, a fast analysis of smooth surfaces in elastic-plastic static and rolling contact is developed based on analytical relations for the internal stress field. Cyclic evaluation of plastic strains and residual stresses is carried out until shakedown. In order to verify the theoretical model, rolling contact tests under high normal load were performed. Residual stresses and residual profiles measurements show excellent agreement between numerical and measured cyclic values.     

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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Prediction of microgeometrical influences on micropitting fatigue damage on 32CrMoV13 steel

Micropitting is a form of surface fatigue damage that occurs in the gear teeth. It is due to the effect of variation in the mechanical loading in the contact zone between the two teeth, induced especially by flank roughness. In this study, generic roughness profiles were built with geometrical parameters to simulate the contact between two rough surfaces. Using elastohydrodynamic lubrication code and Crossland's fatigue criteria, the influence on fatigue lifetime was analysed for changes in each parameter. The relevant parameters were determined that influence (i) the conventional pitting, (ii) the extent to which the von Mises equivalent stress exceeds the material yield stress in the zone where micropitting occurs, and (iii) the fatigue lifetime for steel teeth. With nitriding benefits, the same trends were shown with weaker effects.