齿轮涂层接触应力场分析及应用

涂层的机械力学性能对于涂层的应用尤为重要,涂层/基体系统的失效和破坏与涂层表面及界面接触应力密切相关.基于赫兹接触理论,应用有限元法对齿轮涂层接触应力场情况进行模拟.先在没有涂层的系统上对模型的精确性进行检验,然后通过改变涂层的弹性模量比和厚度,探究应力分布规律.结果表明:当涂层/基体弹性模量比Ec/Es＜2、涂层厚度/接触半径对t/a=0.05齿轮涂层应力分布最为有利 ;研究结果为齿轮涂层技术的应用提供了科学的理论依据.     

固体润滑滚子轴承的接触表面应力分析研究

为获得固体润滑滚动轴承滚动体与滚道处的接触应力,通过固体润滑滚子轴承拟动力学分析并考虑涂层的影响,获得了滚子轴承稳定运行过程中滚动体的力载分布。通过建立带涂层接触的平面应变问题的力学模型,将涂层与基底两种材料的特性等效为一种材料来求解滚子与接滚道触应力分布情况,并与轴承的拟动力学分析相结合,获得了滚子轴承中滚动体与固体润滑膜接触表面的接触变形、接触半径与外加载荷之间的关系,讨论了不同涂层的弹性模量以及不同涂层厚度对接触界面应力分布的影响。当涂层弹性模量比基底大时,涂层的存在使得接触半宽减少,最大名义接触应力增加;涂层弹性模量比基底小时,则与之相反。当涂层的厚度<0.01mm时,涂层的存在对固体润滑滚子轴承的接触表面应力分布影响较小;在一定范围内,当涂层的厚度逐渐增大时,涂层对轴承接触表面应力分布的影响增大。     

涂层材料特性对滚子轴承润滑性能的影响*

涂层材料被广泛应用于滚子轴承中以改善界面性能和提高疲劳寿命,为了探讨涂层材料性能对滚子轴承润滑性能的影响,基于流体力学与接触力学理论,建立带涂层的有限长线接触弹流润滑模型,探讨不同载荷、速度以及涂层材料特性对油膜压力、油膜厚度的影响。研究表明：随着涂层厚度的增加,硬涂层使得最小油膜厚度先增加后减小,而软涂层轻载时使得最小油膜厚度先减小后增加,重载时最小油膜厚度一直减小;随着速度的增加,出口区二次压力峰值增加,硬涂层尤为明显,并且油膜厚度也增加,油膜平坦区域减小,出口区油膜紧缩值增加。为提高润滑性能,当使用较厚软涂层时应考虑增加滚子凸度量,而使用较厚硬涂层时应考虑减小滚子凸度量。     

带有硬涂层的球轴承应力场分析

在建立名义点接触问题有限元模型的基础上，计算了不同涂层厚度下6309深沟球轴承的亚表层应力场，首次提出了一个涂层膜厚的无量纲参数ξ。结果表明，当涂层厚度参数ξ小于0．035时，接触区内的Mises应力和最大剪应力的最大值及其所在深度较之无涂层时无显著变化；与无涂层的情况不同，涂层体系表面接触中心处的Mises应力不为零；涂层／基体界面上的Mises应力的最大值出现在接触中心处，最大剪应力在偏离接触中心处出现。     

超硬涂层轴承的滚动接触疲劳试验

介绍了超硬涂层轴承滚动接触疲劳试验机的原理及功能,并对表面涂层的51306型轴承滚动接触疲劳失效进行了试验分析。通过对影响涂层接触疲劳破坏的几个重要参数的动态检测与控制,试验成功捕捉到了超硬涂层轴承表面疲劳裂纹的初始形态,分析了涂层轴承接触疲劳失效机理,为涂层轴承疲劳寿命评估提供了依据。     

滚动轴承疲劳破坏机理和疲劳寿命模型综述

延长轴承疲劳寿命,尤其是滚动轴承的接触疲劳寿命.一直是轴承工作者十分重视的研究课题.本文概括了滚动轴承接触疲劳破坏机理的主要形式和形成原因,总结了不同阶段的滚动轴承接触疲劳寿命计算公式,分析了不同滚动轴承接触疲劳寿命模型的区别.介绍了表面涂层的摩擦学性能在滚动轴承中的应用.     

CVD多层沉积的使用性能试验

使用CVD涂层对9Cr18不锈轴承钢的摩擦磨损性能和流动接触疲劳性能进行了对比试验，试验结果表明：9Cr18不锈轴承钢经CVD多层沉积TIC-TiCn…TiN后，相对耐磨性提高22倍，摩擦系数降低至0．15，滚动接触疲劳寿命明显的提高，额定寿命L10提高4倍，中值寿命L50提高2倍以上，寿命离散性也小。附图12幅，表2个，参考文献5篇。     

摩擦因数对单排球转盘轴承接触次表层的影响

利用ABAQUS有限元软件建立单排四点接触转盘轴承球与沟道接触的局部模型,通过对比Hertz理论计算的最大接触应力验证模型的正确性,以接触次表层的正交剪应力和等效应力作为疲劳损伤的评价依据,分析不同摩擦因数对滚动接触次表层正交剪应力幅值、到沟道表面的深度以及等效应力变化的影响。结果表明:随着摩擦因数的增大,最大正交剪应力交变幅值有所增加,疲劳损伤萌生位置的深度减小,转盘轴承的寿命减小。     

超硬涂层材料滚动接触疲劳试验机的研制

在总结分析目前国内外表面超硬涂层零件接触疲劳失效行为评估技术的基础上，依据超硬涂层零件接触疲劳失效机制模型，自主研制了一种超硬涂层材料滚动接触疲劳试验机。介绍了该试验机的设计原理和特殊功能，采用该试验机对51306纳米超硬材料涂层轴承滚动接触疲劳失效行为进行了试验评定。试验证明所研制的超硬涂层材料滚动接触疲劳试验机智能检测控制系统能够动态探测诊断涂层轴承表面初始疲劳裂纹并实现急停，可捕捉试验轴承表面疲劳初始状态，为超硬涂层零件接触疲劳失效机制分析提供可靠的试验依据。     

电弧离子镀制备TiN/TiSiN多层涂层及其性能研究

为提高单一TiN涂层的性能，采用AS600DMTXBE型阳极层离子源辅助电弧离子镀系统制备TiN层和TiSiN层厚度比分别为1∶2、2∶2、3∶1的TiN/TiSiN多层涂层。研究不同厚度比的TiN/TiSiN多层涂层的形貌、结构以及性能，并与TiN涂层性能进行比较。结果表明：TiN/TiSiN多层涂层为TiN面心立方结构，其中厚度比为2∶2的TiN/TiSiN多层涂层的TiN(111)衍射峰较强；厚度比为1∶2的TiN/TiSiN多层涂层摩擦因数最低，表明掺入Si的含量越大，涂层减摩性能越好；TiN/TiSiN多层涂层的减摩作用、硬度和结合强度都优于TiN涂层，且厚度比为2∶2的TiN/TiSiN多层涂层的硬度和结合强度均最大；厚度比为2∶2的TiN/TiSiN多层涂层的耐腐蚀性最高，表明Si元素的掺入能够提升涂层的耐腐蚀性能。     

Method and surface roughness aspects for the design of DLC coatings

The design of coatings for highly loaded component contacts, such as bearings, gears and valve train components involves several important factors, including load, friction, lubrication, surface characteristics and material parameters. This paper presents an investigation of the influence of the material, coating thickness and surface roughness on tensional stress levels for coatings that are more compliant than the substrate material. Specifically the effect of multiple asperity contact is studied in three dimensions. The simulation is based on a finite element model where the load is applied as several interacting Hertzian pressure distributions.The results show that the surface structure, in combination with the elastic properties of the coating, has a large influence on the tensional stress level in the coating. The highest tensional stress level in the coating occurs when contact spots almost overlap neighbouring cells and at the same time the size of the contact spots is in the same order of magnitude as the coating thickness.     

含多粗糙峰涂层等效应力的有限元分析

研究刚性平面与含粗糙峰涂层在二维与三维模型下的弹性接触问题,采用有限元法分析涂层弹性模量比、涂层厚度、粗糙峰间距、刚性平面压下深度对涂层粗糙峰表面、涂层/基体界面分布及基体等效应力分布的影响。计算结果表明压下深度对三维涂层粗糙峰表面最大应力的影响最大,涂层厚度、涂层/基体弹性模量比、粗糙峰间距的变化对应力值影响逐渐减小;增大涂层厚度、减小压下深度和粗糙峰间距、降低弹性模量比会使得三维接触模型最大等效应力值显著降低;增加涂层粗糙峰数和涂层厚度、同时降低涂层弹性模量有助于提高涂层/基体界面结合强度。相对于二维接触模型来说三维接触模型在粗糙峰表面的等效应力增大,造成这种变化的主要原因是由于涂层表面粗糙峰之间的等效应力叠加引起的。该研究为涂层粗糙峰及涂层/基体界面强度的应力分析提供依据。     

功能梯度材料圆柱滚子轴承轴向材料性能优化

为了解决轴承"边缘效应"问题,采用有限元法针对功能梯度材料圆柱滚子轴承滚动体的轴向材料性能对轴承最大等效应力和最大接触应力的影响进行了研究,结果表明:当滚动体轴向材料性能分布合理时,在一定程度上可以降低轴承滚动体的最大等效应力和最大接触应力,降低或避免轴承滚动体"边缘效应",提高轴承承载能力。     

The maximum tensile stres on a hard coating under sliding friction

In the friction of a hard coating the maximum tensile stress in the sliding direction generated at the friction surface is important for predicting crack propagation in the coating. The finite element method is employed to evaluate the stress field in the hard coating and the substrate under frictional loads, and the ratio between the values of maximum tensile stress and the maximum contact pressure is calculated under various contact conditions. Finally, a simple equation is introduced for the calculation of the maximum tensile stress at the friction surface. This equation is a function of friction coefficient, maximum contact pressure, coating thickness, contact width and elastic moduli of coating and substrate, and gives the value of the maximum tensile stress which is affected by the existence of the substrate.     

Rolling/sliding contact fatigue life prediction of sintered and hardened steels

Among the several competing mass production methods, powder metallurgy (PM) techniques give much contribution as a means of saving material and energy. It also delivers the material with good fatigue properties that are good substitute for the conventional materials. Application of PM parts is getting wider in many areas such as automotive parts, agricultural equipment, business machine, electrical and electronics, hardware and industrial applications, etc. Many structural machine components made of PM route like gears and bearings experiences rolling–sliding contact fatigue conditions (RSCF). Contact fatigue is a type of failure commonly found in the surface of bearings, gears etc., and this type of failures decide the useful life of these structural parts. Presence of friction between the bodies normally encountered in service, many influence the contact fatigue behavior. The use of new materials and in particular sintered materials requires a thorough understanding of contact fatigue behavior for better product design and development. RSCF on sintered and hardened of 7 gm/cc density (FLC 4608-110HT, Fe–Ni PM steel) were carried out in a specially designed test rig for different contact parameters such as contact stress and slide to roll ratio. Twin-disc type rolling/sliding experimental set-up has been developed in laboratory to simulate the sliding and rolling between two rollers. Contact stress distribution and RSCF life prediction models suitable for sintered and hardened steel were also developed. The predicted life was compared with the experimental RSCF life for sintered and hardened steel.     

滚子偏斜对圆锥滚子与内圈接触的影响

滚子偏斜对高速滚子轴承的寿命有显著影响。文中分析了在直母线和对数修形母线两种母线形式下,GCr15圆锥滚子和Si3N4圆锥滚子无偏斜、向小端偏斜及向大端偏斜三种情况时与GCr15滚道接触的应力分布情况。结果表明,对GCr15滚子或Si3N4滚子,一旦出现滚子偏斜,其接触应力和Mises应力值将显著增加,疲劳寿命大大降低,但修形后偏斜时的应力值要小于修形前。由于Si3N4的弹性模量大于GCr15的弹性模量,同时泊松比小于GCr15的泊松比,修形前后Si3N4滚子的应力值都高于GCr15滚子的应力值,疲劳源的深度也比GCr15滚子的大。     

基于接触应力的圆柱滚子轴承疲劳寿命分析

首先介绍了圆柱滚子轴承疲劳寿命的经典理论计算方法.然后运用Hertz接触应力理论计算出圆柱滚子轴承的最大接触应力,结合三参数幂函数公式确立疲劳寿命曲线方程计算出轴承的疲劳寿命值.通过改变轴承滚子数目、径向力大小以及径向游隙等参数,将基于接触应力得到的疲劳寿命结果与经典理论结果进行比较,证明了该方法的合理性.并分析了在考虑离心力作用下高速圆柱滚子轴承疲劳寿命与转速之间的关系.     

Finite element analysis of coating adhesion failure in pre-existing crack field

Abstract

The influence of a pre-existing crack field on coating adhesion failure in a steel surface coated with a 2 μm thick titanium nitride (TiN) coating was investigated by finite element method modelling and simulation. The stress and strain fields were determined in contact conditions with a spherical diamond tip sliding over the coated surface at a loading of 8 N. One crack in or at the coating increased the maximum tensile stresses with six times from 82 to 540 MPa when the crack was vertical through the coating or L shaped and with nine times when the crack was horizontal at the coating/substrate interface. A simulated multicrack pattern relaxed the tensile stresses compared to single cracks. The results indicate that a cracked coated surface needs to have about five to nine times higher adhesive and cohesive bonds to resist the same loading without crack growth compared to a crack free surface. For optimal coated surface design, the strength of the adhesive bonds between the coating and the substrate in the vertical direction needs to be 50% higher than the cohesive bonds within the coating and the substrate in the horizontal direction. The first crack is prone to start at the top of the coating and grows vertically down to coating/substrate interface, and there it stops due to the bigger cohesion within the steel material. After this, there are two effects influencing that the crack will grow in the lateral direction. One is that steel cohesion is normally bigger than the coating/interface adhesion, and the second is that there are higher tensile stresses in the horizontal than in the vertical cracks. Several vertical cracks can stop the horizontal crack growth due to stress relaxation.     

滚动轴承疲劳寿命的影响因素

对影响滚动轴承疲劳寿命的各种因素进行了综述，包括各种疲劳诱导应力(最大切应力、最大动态切应力、Von Mises应力和八面切应力)，切向力、残余应力和环向应力疲劳极限应力、表面粗糙度、弹流润滑、表面处理、润滑油中污染颗粒、温度、速度、不失效寿命和钢材纯净度(氧含量)的影响，为轴承寿命的准确预测提供参考。