不同损伤参量对橡胶隔振器疲劳寿命预测结果影响的研究

基于橡胶哑铃形试件的疲劳试验结果,分别以最大主工程应变、最大主对数应变、最大主Green-Lagrange应变、八面体切应变、应变能密度、Luo等效应力、Saintier等效应力为损伤参量建立七种橡胶疲劳寿命预测模型。应用此七种模型预测某汽车动力总成橡胶悬置的疲劳寿命,对比不同寿命模型的预测效果。研究结果表明,以最大主工程应变、最大主对数应变、最大主Green-Lagrange应变、八面体切应变、应变能密度为损伤参量建立的寿命模型预测的疲劳寿命均在实测寿命的4倍分散线之内;以Luo应力、Saintiter应力为损伤参量建立的寿命预测模型的预测寿命落在实测寿命的2倍分散线之内。因此,以Luo应力、Saintiter应力为损伤参量建立的寿命预测模型预测效果更好,Luo应力、Saintier应力更适合作为疲劳损伤参量来预测橡胶隔振器的疲劳寿命。     

氮化硅陶瓷球滚动接触疲劳寿命模型

针对球与圆柱接触模型中的陶瓷球,利用WEIBULL断裂统计方法导出球疲劳失效概率与寿命之间的关系方程,在相关额定寿命与最大接触应力的数值解基础上,基于最大主拉应力,构建氮化硅陶瓷球的滚动接触疲劳寿命与接触应力的数学模型.经与不同接触应力水平下的滚动接触疲劳寿命试验结果验证,表明该拉应力一寿命模型的正确性,从而验证了氮化硅陶瓷球的滚动接触疲劳失效源于最大主拉应力,而非基于最大切应力的设想.通过与L.P切应力一寿命模型预测结果的比较,表明拉应力一寿命模型适合于陶瓷球的接触疲劳寿命预测.     

汽车钢圈轮辐裂纹成因分析及优化设计

钢圈对汽车行驶的安全性起着重要的作用。某新型钢圈在弯曲疲劳试验中,在未达到设计使用寿命要求时,轮辐表面就出现了裂纹。为找出裂纹形成原因,在有限元软件中建立钢圈弯曲疲劳试验有限元模型,并分析了钢圈的应力状态及其对疲劳强度的影响。在控制应力幅和最大切应力不超过许用值的条件下,采用正交试验的方法优化轮辐横截面的几何参数。改进后钢圈的疲劳寿命分析表明,借助正交试验可有效改进钢圈的结构,从而增加钢圈的疲劳寿命。     

复合应力对接触疲劳的影响

作者采用统计学的实验和数据处理方法,研究复合应力对接触疲劳的影响。实验结果表明,附加拉伸弯曲应力显著地缩短接触疲劳寿命。而压缩弯曲应力的影响,则取决于它的数值大小。较小的附加压缩应力能够增加疲劳寿命,而大的压缩应力将促进疲劳发生。存在一个临界压缩弯曲应力值,此时疲劳寿命为最大值。根据实验结果,作者就通常计算接触疲劳强度所采用的几种决定应力的适用性提出分析和评价。以最大的表面剪切应力作为决定应力更适合于接触疲劳问题,复合应力作用下的接触疲劳裂纹可能发源于金属表面。     

钻、铰工艺对铝合金紧固孔件疲劳寿命的影响

为研究钻、铰工艺对紧固孔件疲劳寿命的影响,分别对LY12CZ硬铝合金疲劳试样采用钻、铰两种工艺加工出孔并进行了疲劳试验,对钻、铰工艺下孔壁的表面形貌和粗糙度、切向残余应力以及试样的疲劳断口特征进行了测定和分析。结果表明:钻削后孔壁的表面较粗糙,其表面粗糙度为12.92μm,而铰削后孔壁表面非常光滑,其表面粗糙度为1.57μm;钻削孔壁表层的应力为残余拉应力,幅值为165MPa,而铰削孔壁表层的应力为残余压应力,幅值为78MPa;相比于钻孔试样,铰孔试样的疲劳条带间距较窄,裂纹扩展速率较低,其疲劳寿命是钻孔试样寿命的1.81倍。     

轴向和法向应力对DD3和DZ125镍基合金微动疲劳性能的影响

在自行设计的微动疲劳试验装置上进行了各向异性镍基合金DD3和DZ125与粉末高温镍基合金FGH95配对接触的微动疲劳试验,对接触区域萌生裂纹的断口形貌进行了观察,分析了轴向和法向应力对微动疲劳寿命以及微动接触区最大等效应力(Von-Mises等效应力)、滑移幅值、法向应变幅值等微动疲劳参数的影响。结果表明:保持法向应力不变,增大轴向应力将会降低DD3和DZ125合金的微动疲劳寿命;保持轴向应力不变,法向应力对微动疲劳寿命的影响不如轴向应力的显著;微动接触区域的最大等效应力和法向应变幅值受法向应力和轴向应力的共同影响,而滑移幅值仅受轴向应力的影响。     

喷砂工艺对双金属带锯条锯切性能和疲劳寿命的影响

用快速高压喷砂和慢速低压喷砂两种喷砂工艺对双金属带锯条进行处理,通过锯切GCr15和空转疲劳测试,分别对比两种工艺处理后带锯条的锯切寿命和疲劳寿命。通过影像测量仪和扫描电镜观察带锯条锯刃和锯条体表面形貌,通过X射线衍射检测带锯条锯条体表面的残余应力。结果表明:与快速高压喷砂相比,慢速低压喷砂能够优化锯齿齿尖形貌,减少锯切过程中的崩刃,从而提高带锯条的锯切性能;同时还能增加锯条体表面残余压应力,并使表面形貌均匀,从而提高带锯条的疲劳寿命。     

裂纹源位置对6005A铝合金挤压型材高周疲劳寿命的影响

通过高周疲劳试验研究了裂纹源位置对6005A-T6铝合金挤压型材高周疲劳寿命的影响。结果表明:6005A-T6铝合金挤压型材在应力比0.1下的中值疲劳强度为164.5 MPa,疲劳强度较高,但疲劳寿命分布较分散;在最大应力200 MPa条件下,具有不同疲劳寿命试样的疲劳裂纹源区的面积较小,疲劳裂纹扩展区均由疲劳条带和二次裂纹组成,瞬断区的面积较大,均由孔洞和韧窝组成;在相同最大应力下疲劳寿命存在差异的原因在于疲劳裂纹源位置的不同,在最大应力为200 MPa条件下,疲劳裂纹源位于孔洞缺陷处试样的疲劳寿命最长,比疲劳裂纹源位于氧化夹杂物处试样的疲劳寿命延长一个数量级,疲劳裂纹源位于Al7(Cr Fe)第二相颗粒处试样的疲劳寿命居于二者之间。     

影响弹簧疲劳寿命的表面缺陷

汽车发动机气门弹簧的表面裂纹是一项关键性因素，它同有害的非金属夹杂物及表面脱碳一起影响到气门弹簧的疲劳寿命。通过对高应力弹簧及经氮化处理的弹簧做人工纵向裂纹后进行疲劳试验，以解读表面裂纹对疲劳寿命的影响。通常认为：所有弹簧的疲劳寿命随裂纹深度增加而减少，在这项试验中，进一步证实了当裂纹深度小于0.05mm时，疲劳寿命不会下降。因此我们认为处于表层大量的残余应力有效地遏制了疲劳开裂的扩展。     

基于最大切应变幅和修正SWT参数的多轴疲劳寿命预测模型

工程中的大多构件承受着复杂的载荷形式,将单轴疲劳模型应用到多轴载荷情况已不能满足工程精度的要求,多轴载荷下的疲劳寿命计算日益引起人们的重视。基于临界平面的思想,结合Fatemi-Socie(FS)模型和Smith-Watson-Topper(SWT)参数各自的优点,提出一种新的多轴疲劳寿命预测模型。该模型以最大切应变幅与最大切应变幅平面上修正SWT参数的和作为多轴疲劳损伤控制参量,此参量可以同时考虑非比例附加循环硬化和平均应力对材料多轴疲劳寿命的影响,能同时适用于比例和非比例加载下的多轴疲劳问题。采用纯钛Ti、BT9钛合金、304不锈钢、S45C钢和1045HR钢5种材料多轴疲劳试验数据对提出的模型进行评估和验证,对几种材料比例和非比例加载下的多轴疲劳寿命预测结果大都分布在试验结果的2倍分散带之内,结果表明提出的多轴疲劳寿命模型具有较高的预测精度。     

New Stress-Based Fatigue Life Models for Ball and Roller Bearings

New stress-based life models are introduced to define “dynamic stress capacity” in rolling bearings for the first time. The generalized stress capacity equations are formulated, for both point and line contacts, in terms of distinct geometrical and materials parameters while the empirical constants are now material independent. Life equations are first developed for individual rolling element to race contacts and then statistically combined to estimate lives of both races, rolling elements, and, finally, the whole bearings for both ball and roller bearings. An estimate of the empirical constant for the ball bearing equation is derived by regression analysis of available experimental data. The applicable constant for roller bearings is then derived by relating the ball and roller bearing constants to the fundamental subsurface fatigue hypothesis applicable to both point and line contacts. For AISI 52100 bearing steel at room temperature, life predictions with the new stress-based equations are in complete agreement with those currently provided by widely used load-based formulations, where the empirical constant contains the elastic properties of AISI 52100 bearing steel. In addition to these life equations based on the magnitude and depth of maximum orthogonal subsurface shear stress and the volume of material stressed, a new model that eliminates life dependence on the depth of maximum orthogonal shear stress and relates life to only the subsurface maximum shear stress and the stressed volume is presented. Though the predicted life estimates with the currently used and newly introduced life models are comparable in the contact stress range of 2 to 3 GPa, the new model provides significantly higher lives at low contact stresses.     

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.     

A Critique of Rolling Contact Fatigue Criteria for Bearing Rings with Hoop Stresses

Tensile residual and interference fit stresses not treated in classical bearing formulations are known to reduce bearing rolling contact fatigue (RCF) life. Recent modifications of such theory to account for these stresses have simply included them in the computation of a single yield stress type criterion—either maximum shear or equivalent stress. An alternative modification is proposed and demonstrated for fatigue crack initiation that recognizes the primary influence of the maximum range of shear stress but includes the effect of normal stress on the critical planes, as in other successful bulk fatigue criteria for multiaxial nonproportional stress cycle fatigue.     

交叉滚子转盘轴承的有限元分析

通过分析交叉滚子转盘轴承两组滚子的载荷分布情况,确定受载最大滚子,计算接触表面及次表面应力值,利用Pro/E和ANSYS Workbench之间的无缝连接,将在Pro/E中建立的三维几何模型导入ANSYS Work-bench中进行有限元分析,并与传统的理论分析计算结果进行比较,证明有限元分析的正确性,为转盘轴承的设计优化和疲劳寿命分析提供了科学依据。     

Effect of Rolling Bearing Refurbishment and Restoration on Bearing Life and Reliability

For nearly four decades it has been a practice in commercial and military aircraft application that rolling-element bearings removed at maintenance or overhaul be reworked and returned to service. The work presented extends previously reported bearing life analysis to consider the depth (Z₄₅) to maximum shear stress (τ₄₅) on stressed volume removal and the effect of replacing the rolling elements with a new set. A simple algebraic relationship was established to determine the L₁₀ life of bearing races subject to bearing rework. Depending on the extent of rework and based on theoretical analysis, representative life factors for bearings subject to rework ranged from 0.87 to 0.99% of the lives of new bearings. Based on bearing endurance data, 92% of the bearing sets that would be subject to rework would result in L₁₀ lives equaling and/or exceeding that predicted for new bearings, with the remaining 8% having the potential to achieve the analytically predicted life of new bearings when one of the rings is replaced at rework. The potential savings from bearing rework varies from 53 to 82% that of new bearings depending on the cost, size, and complexity of the bearing.     

Effect of Silicon Nitride Balls and Rollers on Rolling Bearing Life

Three decades have passed since the introduction of silicon nitride rollers and balls into conventional rolling-element bearings. For a given applied load, the contact (Hertz) stress in a hybrid bearing will be higher than that of an all-steel rolling element bearing. The silicon nitride rolling-element life as well as the lives of the steel races were used to determine the resultant bearing life of both hybrid and all-steel bearings. Life factors were determined and reported for hybrid bearings. Under nominal operating speeds, the resultant calculated lives of the deep-groove, angular-contact, and cylindrical roller hybrid bearings with races made of post-1960 bearing steel increased by factors of 3.7, 3.2, and 5.5, respectively, from those calculated using the Lundberg-Palmgren equations. An all-steel bearing under the same load will have a longer life than the equivalent hybrid bearing under the same conditions. Under these conditions, hybrid bearings are predicted to have a lower fatigue life than all-steel bearings by 58% for deep-groove bearings, 41% for angular contact bearings, and 28% for cylindrical roller bearings.     

风电偏航轴承接触力分布与疲劳寿命分析

根据风电偏航轴承的结构和受载特点,建立轴承的整体有限元模型并求解联合载荷下的接触力分布.为降低模型复杂性和减小计算规模,通过赫兹接触理论获取滚动钢球与滚道的接触力和变形关系;将这些变形特征赋予非线性的弹簧单元,使弹簧单元与钢球的接触变形特征一致,从而模拟钢球与滚道的接触,并通过经验公式和实验验证了模型的正确性.建立轴承...     

单层涂层最佳厚度的有限元分析

采用有限元数值计算的方法对TiN、TiC、Si3 N4及SiC四种材料的硬涂层体系表面下的应力分布进行了模拟分析。结果表明 ,对于TiN材料 ,当涂层厚度与接触半宽之比t/a <0 .3时 ,表面下的最大剪应力分布对提高轴承疲劳寿命较为有利 ;t/a =0 .5时 ,涂层系统的摩擦力学性能最差。涂层厚度较薄时 ,位于赫兹接触中心附近的涂层表层上的最大剪应力要远大于基体内的最大静态剪应力 ;当t/a >0 .1时 ,涂层表面上的最大剪应力对提高轴承疲劳寿命较为有利 ;涂层材料与基体材料的弹性模量之比小于 2 .0时 ,有利于提高涂层系统的疲劳寿命     

考虑温度影响的角接触球轴承疲劳寿命仿真研究

针对承受热应力和结构应力共同作用下的角接触球轴承,利用ANSYS Workbench软件对其进行疲劳寿命分析。在三维软件Pro/E中建立轴承模型,导入有限元软件ANSYS Workbench中得到轴承的有限元模型,进行热-应力耦合分析,得到轴承温度分布和应力分布;根据零件的材料属性,利用ANSYS Workbench的Fatigue模块分析了轴承的疲劳寿命。根据软件模拟计算得到轴承寿命情况,为机床主轴轴承寿命的预测奠定基础。     

高速铁路轴承疲劳寿命浅析

通过对影响高速铁路轴承疲劳寿命主要因素的理论分析,对如何提高疲劳寿命及以疲劳寿命不足为主要失效形式的轴承提供一种分析参考。