含相似多细节结构的构件疲劳额定系数研究

相似多细节的存在显著影响结构的疲劳性能,细节模拟试件试验得到的结果需要通过构件疲劳额定系数RC进行修正才能正确反映结构的疲劳性能.基于各相似细节之间独立同分布的假设,分别建立疲劳寿命服从对数正态分布和双参数Weibull分布时,RC与相似细节数的函数关系以及RC与可靠度的关系;讨论对应疲劳寿命的RC与对应疲劳强度的RC之间的联系.给出典型细节数对应的RC以及铝合金材料2种可靠度水平下RC与相似细节数的关系曲线.     

高温多轴疲劳损伤与寿命预测研究进展

介绍国内外疲劳一蠕变交互作用研究的一些进展，其中包括微观裂纹萌生及扩展机理的研究、高温多轴疲劳一蠕变实验的发展。对四种具有代表性的疲劳一蠕变损伤累积模型及寿命预测方法，即线性损伤累积模型、损伤率法、延性耗竭法和过应力法进行较为详尽的描述，并对这几种方法在多轴领域的改进和推广进行重点介绍。     

Comparison of the fatigue life of F.F. shaft material according to various environmental temperatures

A rotary bending fatigue test was carried out with two kinds of materials, S43C and S50C, using the front engine and front driveshaft (F.F. shaft) of the vehicle. The specimens were heat-treated using the high frequency induction method (about 1 mm depth and HRC56∼60) and the test environment temperatures were -30 °C (-22 °F), +25 °C (+77 °F), and +80 °C (+176 °F) in order to determine the influence of the heat treatment and the temperatures. The fatigue life increased on the order of +80 °C, +25 °C, and -30 °C regardless of heat treatment. In comparison of the fatigue lives with the basis of the tested result at +25 °C, the fatigue lives of non-heated specimens decreased about 35%, but that of heat-treated specimens decreased by only about 5% at +80 °C, more than at +25 °C. And fatigue life of non-heated and heat-treated specimens were about 110% and 120% higher at -30 °C than that of +25 °C. The initiation of surface microcracks was observed at 0.2 fatigue life ratio in as-received S43C and S50C, but the average crack length in S50C was about 14% longer than that of S43C at the same fatigue life ratio.     

随机载荷下疲劳寿命的估算

复杂随机载荷下疲劳寿命的评估，一直是工程上所关心的问题之一。在设计阶段，通常难以确定详细的应力历程，因而也无从进行循环计数和累计损伤。本文基于传统的疲劳设计思想和概率分析方法，综合考虑平均应力的影响和疲劳寿命固有的分散性，研究了宽带随机载荷作用下疲劳寿命的估算问题     

铆钉搭接头疲劳强度曲线的研究

研究铆钉搭接头的疲劳寿命。通过在Saginamiya动态伺服液压疲劳机上用频率为5．0Hz的正弦波应力比R=0．05的拉一拉载荷，对不同环境条件和形状的铆钉搭接头试样进行测试，得到铆钉搭接头在空气和3．5％NaCl溶液中的疲劳强度曲线，并推导出描述铆钉搭接头疲劳寿命的数学表达式。     

润滑油添加剂对轴承钢球滚动接触疲劳寿命的影响

利用自制的球—棒疲劳试验机研究了4种添加剂对GCrl5钢球接触疲劳性能的影响，并借助于扫描电镜分析了不同添加剂对钢球接触疲劳的作用机理。结果表明，4种添加剂都不同程度地提高了GCrl5钢球的接触疲劳寿命，其中以含磷的极压添加剂T305和含有活性基团的降凝剂仍旧效果为佳。     

受疲劳损伤材料的持久极限的变化

基于材料的S－N曲线，对材料在交变应力作用下受损、承载能力下降的过程进行讨论，给出计算受损材料持久极限的公式。公式型简洁，可以方便地作出受损材料的S－N曲线，并进行疲劳强度计算。公式很好地揭示了应力水平略低于材料持久极限的应力循环对材料寿命的影响。     

疲劳失效预测的研究现状和发展趋势

综述了国内外有关疲劳失效的判断、疲劳强度理论及其应用、疲劳失效预测方面的研究现状。分别对常用的理论和方法进行了介绍,指出了不同理论和方法的优缺点。重点介绍了疲劳裂纹形成的失效预测方法,按疲劳裂纹形成失效预测的基本假定和控制参数大致分为名义应力法、局部应力应变法、场强法和能量法等。根据断裂力学的相关理论所建立的疲劳裂纹扩展寿命的相关预测方法在寿命预测中具有越来越重要的地位,对疲劳失效预测进一步的发展方向进行了展望。     

变幅载荷下的有限寿命疲劳设计方法和设计数据

本文论述了变幅载荷下的有限寿命疲劳强度评价方法与寿命估算方法,给出了用Ｍｉｎｅｒ法则、修正Ｍｉｎｅｒ法则和Ｃｏｒｔｅｎ－Ｄｏｌａｎ理论进行疲劳强度评价和寿命估算的方法和计算公式。最后,还用４种零构件进行随机疲劳试验对三种累积损伤理论的疲劳强度评价和寿命估算精度和这生进行了验证和对比。     

Study on Rolling Contact Fatigue in Hydrogen Environment at a Contact Pressure below Basic Static Load Capacity

A method to determine the shoulder height in an angular contact ball bearing using a 3D contact analysis is proposed. The load analysis was performed by calculating the distributions of internal loads and contact angles for each rolling element. From the results of the bearing load analysis and the contact geometry between the ball and raceways, 3D contact analyses using an influence function were conducted. The algorithm developed was applied to an angular contact ball bearing for an automotive wheel. The effects of axial load on contact pressure at the inner and outer raceways were evaluated and the critical axial loads in the present shoulder height were calculated. The critical shoulder heights were also determined when the bearing was subjected to a practical load for a steel ball bearing. The proposed methodology is generally applicable for the purpose of reducing the material cost and improving the efficiency of the bearing design process.     

Experimental Study of Cyclic Rolling-Contact Fatigue of Silicon Nitride Balls

A newly developed pure-rolling fatigue test rig with three contact points for bearing balls was used to perform rolling-contact fatigue (RCF) tests. The fatigue properties of GCr ₁₅ steel balls and two kinds of Si ₃ N ₄ ceramic balls (GSN-200 and NBD-200) produced with different technologies were compared. Life test data, summarized in accordance with the Weibull theory, showed that the life of the GSN-200 balls was close to that of the GCr ₁₅ balls, whereas the life of the NBD-200 balls was much longer than those of GSN-200 and GCr ₁₅ . Under the same working condition, the temperature rise of all the ceramic balls was lower than that of the steel balls. Ball surfaces were examined after failure with optical microscopy and scanning electron microscopy. It was identified by test that the failure mode of ceramic balls was surface spall. The research shows that subsurface cracks play a dominant role in spalling failure. These cracks originated from volume defects of the material and propagate to form elliptical fatigue spalls.     

铁路轴承试验机主轴疲劳强度有限元分析

某型号铁路轴承试验机接连发生3根主轴断裂事故,为了分析主轴断裂原因,建立了主轴有限元分析模型,计算出了主轴静应力分布情况.在有限元静力学分析基础上,根据给定的载荷,用“轴不动、载荷旋转”来模拟实际的“轴旋转、载荷不变”情况,采用专业疲劳分析软件Fe- Safe计算了主轴的疲劳强度.计算结果表明,主轴疲劳强度安全系数小于...     

单轴载荷下的无限寿命疲劳设计方法与设计数据

本文提供了作者在单轴载荷下的无限寿命疲劳设计方法和设计数据研究方面的试验研究结果。它们包括：单轴载荷下的无限寿命疲劳设计公式,疲劳缺口系数和尺寸系数的设计公式,表面加工系数线图,平均应力影响系数数据和计算公式,许用安全系数数据和６７种国产机械材料的疲劳极限数据．     

疲劳损伤演化的机理及损伤演化律

疲劳是由材料内部的损伤演化导致的,但损伤演化的机理目前尚不清楚。根据原子运动的热扰动,当原子的活性能大于某一临界值时,原子将从原平衡位置逃逸并产生空穴。当材料受循环应力作用时,因原子平衡位置的变化而导致热扰动所产生的空穴不能完全相互湮灭,从而形成缺陷或导致其发展。这一观点不仅可以说明疲劳损伤演化的机理,而且可以把损伤演化速率与原子逃逸过程的速率联系起来,从而可以提出一种具有机理性依据的疲劳损伤演化律的一般形式。这种形式的损伤演化律,是与已知的金属材料损伤寿命关系相一致的。讨论并给出对称循环下损伤演化律的具体形式,并依据该演化律讨论损伤的累加方式。     

W6Mo5Cr4V2高速钢传动轴疲劳寿命分析

详细介绍了结合有限元软件ANSYS和疲劳分析软件MSC.Fatigue对传动轴进行疲劳寿命预测的流程。分析了W6Mo5Cr4V2高速钢材料性能参数对传动轴疲劳寿命的影响。结果表明:材料弹性模量对传动轴疲劳寿命影响很小,抗拉强度对其影响较大,传动轴疲劳寿命随着抗拉强度的增加而增加。     

运用MSC.Fatigue进行塔式起重机疲劳寿命预测

基于Miner线性损伤理论和有限元分析,用名义应力法并结合一定可靠度和置信度,利用疲劳分析软件进行起重机的寿命计算。该算法结果精度高,且非常接近实际工况。为疲劳寿命估算提供了1种简单实用、可靠的方法,也对于确定维修周期、预防事故发生具有十分重要的意义。算例结果表明该方法是可行的。     

AZ31B镁合金激光喷丸强化后疲劳裂纹扩展的数值模拟研究

激光喷丸(LSP)是一种先进的材料表面强化工艺,能有效提高零件的机械性能及其使角寿命.建立了以有限元软件ABAQUS和MSC.Fatigue为平台,面向抗疲劳制造的激光喷丸工艺有限元分析模型.结果表日月激光喷丸可以有效抑制疲劳裂纹扩展,延长疲劳寿命,喷丸次数的增加在一定程度上增大残余应力及疲劳寿命.残余应力抑制疲劳裂纹扩展的原因归结为最终断裂尺寸的增大以及裂纹扩展速度的减小.研究结果为LSP抗疲劳效果的预测提供了有效的方法,对于优化工艺参数,减少试验次数,降低成本具有指导意义.     

Characteristics of fatigue crack initiation and fatigue strength of nitrided lCr-lMo-0.25V turbine rotor steels

To investigate the effect of nitriding layer on both fatigue crack initiation and fatigue life, turbine rotor steel (lCr-IMo-0.25V steel) specimens were nitrided by the nitemper method and then put to a rotary bending fatigue test at room and elevated temperatures. In nitriding, temperature and time were controlled to obtain a different nitrided thickness. Microstructure analysis, micro-Vickers hardness test, and scanning electron microscope observation were carried out for evaluating experiments. In results, the fatigue cracks of nitrided specimens were initiated at inclusion near the interface between nitrided layer and substrate, which showed fish-eye type appearance in fractograph. The fatigue life of nitrided specimens at every temperature was prolonged compared to that of the non-nitrided. However, there was not observable improvement in fatigue characteristics with the increase of a nitrided thickness.     

钛合金断口反推疲劳应力的实验与工程应用研究

对钛合金在实验和工程应用条件下的构件进行断口定量反推，研究疲劳条带间距反推疲劳应力在钛合金应用的可行性。结果表明，实验条件下应力水平较低时，钛合金断口反推计算的疲劳应力的误差较小，随着应力水平的提高，误差逐渐增大，采用无量纲数a/D在0．45～0．55范围内的疲劳条带间距进行反推的误差在10％以下；而对钛合金实际构件的疲劳断裂，可采用疲劳条带间距进行反推其疲劳振动应力，该方法简单易行，且误差较小。     

汽车后桥疲劳试验时裂纹扩展与应变变化的试验研究

在汽车后桥疲劳试验时监测记录了应变的变化过程,并测得了疲劳裂纹扩展的长度。通过分析研究,得到裂纹扩展与应变变化的关系,提出一种应用计算机实时监测应变变化来分析疲劳裂纹产生、扩展的方法。