基于冲击功离散性的曲轴早期疲劳失效评估方法  

Assessment Method for Early Fatigue Failure of Crankshaft Based on Dispersion of Impact Energy

作　　者：李向哲 梁刚 郑小梅[3] 徐聪聪 许金泉 LI Xiangzhe;LIANG Gang;ZHENG Xiaomei;XU Congcong;XU Jinquan(State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Shanghai Marine Diesel Engine Research Institute,CSSC,Shanghai 201108,China;Beijing Aeronautical Engineering Technical Research Center,Beijing 100076,China)

机构地区：[1]上海交通大学海洋工程国家重点实验室,上海200240 [2]中国船舶集团有限公司第七一一研究所,上海201108 [3]北京航空工程技术研究中心,北京100076

出　　处：《上海交通大学学报》2025年第1期111-120,共10页Journal of Shanghai Jiaotong University

基　　金：国家自然科学基金(11772189);国家重大科技专项(J2019-IV-0008-0076)资助项目。

摘　　要：考虑实际材料强度寿命特性的离散性,提出了一种用于评估曲轴早期疲劳失效的方法.材料强度寿命离散性的微观机理在于材料内部的微观组织结构(包括微观缺陷)分布的不均匀性,这可以用初始损伤的概率分布来统一表征.同种牌号的合金,其强度寿命特性的中值基本一致,但离散范围则会有很大差别,必须通过足够的取样试验才能确定.对于由34CrNi3MoA合金制成的某柴油发动机曲轴锻件,由冲击取样试验的冲击功离散性估算了疲劳极限的离散性,由结构疲劳试验确定了疲劳极限概率分布的均值.传统设计手册所推荐的安全系数只是暗中假定了材料的某种离散性,本研究给出考虑材料实际离散性的安全系数与可靠性间的定量关系.当实际使用的材料不满足规定的可靠性要求时,曲轴就易发生早期疲劳失效.Considering scattering behaviors of strength and fatigue life characteristics of actual materials,a method for evaluating the early fatigue failure of crankshafts has been proposed.The micro-mechanism of the scatter of strength and life characteristics is the nonuniform distribution of microstructures(including micro-defects)inside the material,which can be uniformly characterized by the probability distribution of initial damage.For the same grade of alloy,the median values of strength and fatigue life can be basically the same,but the dispersion can be significantly different,which must be determined by sufficient sampling tests.For a diesel engine crankshaft forging made of the 34CrNi3MoA alloy,the dispersion of fatigue limit was estimated based on the scatter of impact sampling test data,while the mean value of probability distribution of fatigue limit was determined by structural fatigue tests.The safety factor recommended in the conventional design manual only implicitly assumes material dispersion.Considering the actual dispersion of the tested material,the quantitative relationship between safety factor and reliability has been established.Early fatigue failure of the crankshaft can easily occur when the actual dispersion of material fails to meet the specified reliability requirement.

关 键 词：早期疲劳失效 离散性 冲击功 疲劳极限 可靠性 

分 类 号：O346.2[理学—固体力学]