粗糙金属表面接触性能研究

计算粗糙金属表面接触性能时，通常忽略凸体之间的相互影响和应力场、特别是热应力场的影响，这给高副接触性能的计算带来误差。本文在考虑微凸体之间相互影响的基础上，计算了线接触金属摩擦副接触表层中的压力场、温度场及应力场（包括等温应力和热应力场）。结果表明：表面粗糙度对压力分布、温度分布及应力分布均有重要影响；热应力使最大总Ｍｉｓｅｓ应力移向表面，且随βｔ值的增大，总Ｍｉｓｅｓ应力迅速上升。这对研究胶合失效机理和边界膜成膜机理具有重要意义。     

纯滚动状态下氮化硅陶瓷球临界应力分析

氮化硅陶瓷球临界应力在很大程度上决定其滚动接触疲劳和磨损寿命.由于陶瓷材料的抗拉能力较弱,所以设想其滚动接触疲劳失效的临界应力为最大主拉应力.应用弹性接触力学和赫兹理论分析纯滚动条件下陶瓷球表面层接触应力,得到表面层最大主拉应力.针对理论计算值,设计相应的纯滚动接触疲劳实验.分析表明,理论值与实验结果趋于一致,从而证实最大主拉应力为氮化硅陶瓷球滚动接触疲劳失效的临界应力.计算结果为陶瓷球的滚动接触疲劳寿命分析提供理论基础.     

不完全接触端微动疲劳强度界面力学评估

采用ABAQUS有限元软件对微动桥平面/平面试样接触状态进行三维有限元分析,详细计算了接触边缘应力变化,分析了不完全接触区应力场,讨论了不同半径R(0.3mm,0.6mm,0.9mm)和不同的摩擦系数f(0.3,0.6,0.8)对微动区接触应力集中的影响,分析其应力奇异性的变化。根据界面力学接触界面奇异应力场和应力强度参数来计算应力奇异性特征值λ,进而计算微动疲劳强度系数K,对微动疲劳强度进行评估。从理论计算出发,研究分析接触边缘的微动疲劳强度,以及各参数对微动疲劳强度系数K的影响。     

磨削表面层残余应力的三维试验研究

用X射线法对磨削表面层残余应力进行了三维空间的测定和研究。结果表明，摩削表面层的残余应力呈三维空间分布，并且残余应力的主应力方向不平行或不垂直于摩削表面。     

机械零件常规疲劳强度设计方法的研究

受变荷载影响,多数机械零件容易疲劳破坏,使得使用寿命大大缩短,一定程度上影响机械设备性能的充分发挥。因此,加强机械零件常规疲劳强度设计,对提高其抗疲劳性能具有重要意义。本文明确机械强度设计的步骤,阐述常规疲劳设计方法及疲劳强度的计算方法,提出了提升机械零件疲劳强度的有效设计对策,以供参考。     

铝合金铆接件疲劳损伤的影响因素分析

铆接在航空等结构中的应用非常广泛,而疲劳损伤是影响其使用寿命的主要因素。在铆接件疲劳试验基础上,以有限元软件ANSYS Workbench为平台,分析了铆接件模型的应力状态,研究了铆钉排列位置、接触面摩擦系数、过盈量对构件应力场分布的影响,预测了疲劳裂纹可能萌生的位置;其研究结果为铆接件的抗疲劳设计提供参考。     

考虑残余应力的螺旋锥齿轮接触疲劳裂纹萌生-扩展寿命计算方法研究

考虑渗碳、磨齿、喷丸等工艺产生的齿面残余应力,建立齿面接触应力与残余应力的复合应力场,提出一种螺旋锥齿轮接触疲劳裂纹萌生-扩展寿命计算方法。构建齿轮有限元接触分析模型,计算多轴交变接触应力场。考虑空间螺旋曲面残余应力分布的复杂性,将变曲率齿面离散为网状节点;测量各节点表面与次表面的残余应力,建立齿面残余应力场。基于Dang Van多轴疲劳准则,构建齿面裂纹萌生模型;计及残余应力与裂纹闭合效应,构建齿面裂纹扩展模型。计算复合应力场下齿轮接触疲劳寿命,研究残余应力对齿面裂纹萌生-扩展寿命的影响规律。结果发现：复杂齿面空间变曲率会影响喷丸等工艺产生的残余应力分布,中心区域的残余压应力高出齿面边缘区域约20%;复合应力场下齿面裂纹萌生位置与寿命主要取决于接触应力,残余应力会改变齿面节点平均应力进而影响疲劳寿命;齿面裂纹扩展寿命约占全寿命的10%,表征齿轮接触疲劳快速失效至迅速断裂。上述研究对于高性能齿轮传动的长寿命、高可靠性设计具有一定的参考价值。     

偏斜工况下向心关节轴承应力场分析

利用非线性接触有限元方法对向心关节轴承进行应力场分析,在有限元模型中将心轴和轴承座作为柔性体处理,分别考察内、外圈相对偏斜工况下的应力场分布。结果表明:在极限静载荷工况下,内、外圈相对偏斜对关节轴承的应力场分布产生明显影响;由于偏斜工况下应力分布不对称,在内、外圈的端面接触处产生应力集中现象,其应力值明显高于无偏斜工况下的最大应力值,且在偏斜角达到1.5°时,出现峰值应力。     

冻结砂土层中埋地管道管土界面应力分析

寒区埋地管道管土相互作用对压力输送管道受力分析和安全防护设计具有较大影响。利用试验研究与有限元模型分析相结合的方法,对冻结砂土与管道间的界面应力问题进行了研究。考虑管土间摩阻力、粘结力、冻结力及管土弹塑性变形等耦合作用影响,利用层间界面双线性接触模型,建立有限元分析模型,进行了相应的试验验证。结果表明,寒区砂土层中管土间界面应力的有限元分析结果与试验结果误差为3.97%,该有限元模型可用于分析管土相互作用下的界面应力问题,为进一步研究埋地管道局部损失、腐蚀坑应力集中致损问题奠定了基础。     

高承载铸铁气缸盖火力面结构抗疲劳设计

疲劳损坏是柴油机失效的主要形式,随着现在柴油机向高功率密度方向的发展,对结构的抗疲劳设计也提出了新的挑战,通过对气缸盖火力面的载荷特征及应力分布进行分析,确定了火力面的疲劳类型,根据疲劳类型及特点提出了3种抗疲劳结构方案,通过应力和疲劳寿命对比分析,得到1种综合可靠性更高的结构,并通过热疲劳试验验证了该结构的合理性,为铸铁气缸盖火力面的结构抗疲劳设计提供了基础技术支撑和依据。     

弹流润滑条件下织构表面亚表层特性研究

为研究在弹流润滑状态下表面形貌对亚表层特性的影响，利用激光加工方法获得2种微凹坑型织构表面形貌，通过将实测的表面形貌坐标输入弹流润滑数值计算程序得到油膜压力和膜厚分布；以对应工况的油膜压力作为表面法向压应力，利用Rabinowicz经验公式算出剪切应力；将表面法向压应力和切向剪应力叠加后对弹流润滑界面亚表层特性进行仿真研究。结果表明：表面织构使亚表层应力分布发生显著改变；微凹坑直径、卷吸速度对亚表层应力的大小与分布有不同的影响；亚表层变形在摩擦过程中呈现随深度增加先缓慢减小后快速下降的规律，研究结果将为通过表面形貌设计改善轴承等零件受力状况提供理论支持。     

弹流润滑在摩擦无级变速器疲劳分析中的应用

本文在摩擦传动弹流润滑理论分析与牵引机理试验研究的基础上，进行零件表面牵引力和表层内应力场的研究，而且利用这一方法来分析零件的抗疲劳强度。分析多种设计参数对零件疲劳寿命的影响，研究了壁面附近的滑动对摩擦传动的影响。     

Molecular dynamics simulations of elastohydrodynamic lubrication oil film

This paper reviews recent research in molecular dynamics studies of the traction properties of hydrocarbon fluids under elastohydrodynamic lubrication, focusing on the technical problems that arise on making predictions of the traction properties of an oil film with a submicron thickness at the actual sliding contacts of the machine elements by at a nanoscale molecular simulation. The effect of the oil film thickness and shear rate are examined including the result of a submicron thickness simulation of the oil film using a tera‐flops computer. The mechanism of the phase transition of the fluids under high pressure, the boundary slip, and the momentum transfer related to the molecular structure of the fluids are also presented. Copyright © 2010 John Wiley & Sons, Ltd.     

三维非牛顿体椭圆接触弹流润滑应力分布及其图示

对机械系统中常见滚滑点接触摩擦润滑问题进行了三维弹性润滑的数值模拟分析,在分析了弹流中的各种流变模型之后,提出了粘塑性四次方型本构关系式。对弹流润滑中热效应和润滑剂的非牛顿体效应的耦合作用进行了分析,得到提示润滑接触区内牵引力机理的三维切应力分布。由数值模拟研究了对疲劳分析有意义的接触体表层内应力场,得到了椭圆接触三维Mises应力分布。     

Lubricant Effects on White Etching Cracking Failures in Thrust Bearing Rig Tests

Abstract

White etching cracking (WEC) is a subsurface bearing failure mechanism influenced by a number of factors, including lubricant composition. Certain metal-containing lubricants have been reported to promote WEC-induced failure; however, the exact mechanisms linking lubricant effects on WEC propensity are still not fully understood. An interesting field that has not been elucidated is the influence of additive concentration and tribofilm growth on WEC initiation, propagation, and failure. The investigations conducted in this work involved two series of oil formulations: one with additives that give rise to WEC (WEC oils) in different combinations and concentrations and another with additives that do not cause WEC (non-WEC oils). A mini traction machine (MTM) in combination with a spacer layer imaging machine (SLIM) was employed to study the growth of tribofilms and their influence on friction response. Insights from the MTM-SLIM study allowed for better interpretation of FE8 bearing tests. When using oils that contribute to WEC formation, the tribofilm-induced WEC mechanism was confirmed, with cracks initiating as early as after 20 h of FE8 testing. Metal-containing additives were found to favor the formation of WECs by generating a high-friction tribofilm and increasing the water content in the lubricant. Furthermore, the source of subsurface H associated with WEC failure is investigated using heavy water (D2O)-saturated oil. A mechanism of water dissociation induced in tribofilm growth (incubation period) is proposed in this article.     

Stress Analysis on Layered Materials in Point Elastohydrodynamic-Lubricated Contacts

For multilayered or coated substrates in elastohydrodynamic-lubricated (EHL) contacts, the subsurface stress distributions under a normal load combined with shear traction have been analyzed in this article through computer simulations. The Papkovich-Neuber potentials and Fourier transform are adopted to deduce the pressure–displacement, pressure–stress, and shear traction–stress response functions in frequency domain for the coated substrates, and to calculate distributions of pressure and subsurface stress. The results from the analysis of EHL contacts on coated substrates are compared with those from dry contact model in which shear traction is assumed to obey Coulomb’s law. Effects of the Young’s modulus of coatings, the properties of lubricants, and the magnitude of traction are discussed. Similar to the results in dry contacts, hard coatings in lubricated cases tend to increase the von Mises stress, whereas soft coatings decrease the stress. Shear traction makes the max von Mises stress increasing and moving closer to surface. However, the changes in subsurface stress due to shear traction are less obvious in lubricated contacts. Comparison between EHL and dry contact models reveals that lubrication can reduce the von Mises stress in the coating layer due to smaller shear traction. The analyses show that pressure, film thickness, and subsurface stress distributions are influenced by surface coatings, sliding velocity, rheological models, and pressure–viscosity behaviors.     

乏油工况下斜齿轮热弹流润滑特性研究*

建立斜齿轮的乏油热弹流润滑模型,并讨论供油量、转速和齿面粗糙度对润滑性能的影响。结果表明:乏油工况下增大入口区供油量,润滑区的膜厚增大而摩擦因数、温升和次表面应力幅值降低;随着供油量增大,乏油润滑特性逐步趋于全膜润滑状态下特性;随着转速升高,润滑膜厚增大但幅度有限,相应温度场增大和次表面应力场增大;齿面粗糙度会使油膜压力出现剧烈的波动,在油膜压力峰位置的次表面会出现应力集中。     

Experimental measuring set‐up and procedure for the traction coefficient on roller‐on‐disc contact

A pin‐on‐disc machine was modified to measure traction coefficient and the potential of contact difference under controlled conditions of slide‐to‐roll ratio, temperature, contact pressure and entrainment speed; oil, grease, grease's base oil and bleed‐oil were tested. This new arrangement proved to be efficient to characterise lubricants traction behaviour, film separation and tribofilm generation. Copyright © 2016 John Wiley & Sons, Ltd.     

面接触形式下牵引油拖动特性的研究

牵引传动是利用牵引油膜在传动接触区产生的剪切力来传递运动和动力的,所以油品本身牵引特性的高低直接影响牵引传动的牵引效率,因而对各种油品特性的研究也较多。在HZS-1型动压滑动轴承试验台上对8号液力传动油面接触形式下的拖动特性进行了实验研究,并运用Matlab软件对实验结果进行了处理,分析比较得出结论。     

极限剪切状态下的线接触Reynolds方程

本文导出了考虑极限剪切状态的线接触流变热弹流Reynolds方程,该方程以Evans—Johnson流变模型为基础,可用于求解线接触流变热弹流润滑问题的油膜厚度、压力分布、剪应力分布和牵曳系数曲线。计算实例表明,润滑油的流变特性对弹流润滑的油膜形状和压力分布影响不大,但对Hertz接触区的剪应力分布有显著影响。