高碳铬轴承钢超长寿命S-N关系的概率特性

Probabilistic character for S-N relations of high carbon-chromium bearing steel in super-long cycle life region

为了对高碳铬轴承钢疲劳S-N(应力-寿命)试验数据做出正确评估,采用广义极大似然法对全部S-N数据和区分裂纹萌生机制下的S-N数据分别进行了拟合,建立了概率S-N曲线模型。结果表明,在区分裂纹萌生机制下,能较好地拟合试验数据和描述S-N曲线形式;在疲劳极限(大约1 200 MPa)以上的部分要选用裂纹萌生于表面的S-N曲线形式,对于疲劳极限以下的要选用裂纹萌生于内部的S-N曲线形式;同时验证了广义极大似然法能较好地测定该材料的概率S-N曲线(由P-S-N曲线、C-S-N曲线和P-C-S-N曲线组成)和表征该材料超长寿命S-N关系的概率特性。

In order to accurately evaluate the fatigue S-N （stress-life） test data of high carbonchromium bearing steel in super-long cycle life region, the entire S-N data and the S-N data based on differentiating fatigue crack initiation mechanisms were fitted by general maximum likelihood method respectively, its probabilistic S-N curve models were established. Analysis result shows that the test data can be well fitted and the S-N curve can be well depicted with differentiating fatigue crack initiation mechanisms. It is discovered that when load level is above the fatigue limit （about 1 200 MPa）, the S-N curve that fatigue crack initiates from surface should be chosen, on the contrary, the S-N curve that fatigue crack initiates from subsurface should be chosen. It is proved that the material＇s probabilistic S-N curves, including survival probability-stress-life curves, confidence stress-life curves and survival probability-confidence-stress-life curves, can be determined, and the probabilistic characters for the S-N relations in super-long cycle life region can be depicted by general maximum likelihood method. 2 tabs, 5 figs, 8 refs.