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中文摘要：
研究中国铁路货车转向架B级铸钢的概率疲劳极限。研究中采用小子样升降法疲劳试验,揭示出该材料的疲劳裂纹主要萌生于铸造缺陷;在较低应力幅范围,裂纹扩展韧性有所降低,但仍呈现典型疲劳河流与阶梯状花纹及辉纹,并伴随有二次裂纹,属于韧性疲劳特征。视疲劳极限定义为期望寿命下服从正态分布的疲劳强度,应用极大似然法测定概率疲劳极限。与现有常规法、DIXON-MOOD法和ZHANG-KECECIOGLU法比较,证明极大似然法是唯一满足给定寿命的疲劳强度定义,效果良好的方法。针对其他方法,尤其是ZHANG-KECECIOGLU法,给出分散性与偏差较大的预测。
英文摘要：
Fatigue limits and damage are investigated experimentally on the grade B cast steel for Chinese railway freight car bogie frame.Small sample up-and-down test method is employed for the study.Results reveal that fatigue cracks are initiated mostly from the cast flaws and shrinkage cavities.The fatigue cracks grow with river like flowers and many sub-cracks.Distinct tough eddies are distributed on the fracture surface.Maximum likelihood method is applied for the probabilistic measurement of the fatigue limits,in which the limits are defined as the fatigue strengths following normal distribution at an expected fatigue life.The statistical parameters are estimated by the likelihood function meeting the definition.A comparison analysis is carried out to the existing conventional,DIXON-MOOD and ZHANG-KECECIOGLU methods.The maximum likelihood method is verified to be only approach meeting the definition.Others,especially the Zhang-Kececioglu approach,have bigger deviational predictions.
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