中文摘要：

为了对50^#车轴钢疲劳可靠性问题进行评估，本研究在室温大气环境下用四连式悬臂梁型旋转弯曲疲劳实验机对该材料开展了超长寿命疲劳问题的研究，并根据实验得到的数据提出使用小样本耐久强度疲劳实验数据推定50^#车轴钢的疲劳强度分布的统计方法。具体的方法如下：（1）假设在不同的应力循环周次下疲劳强度的分布近似相同；（2）确定均值孓Ⅳ曲线倾斜部向水平部转移点处的应力循环周次N0；（3）基于线性累计损伤原理，将耐久强度区的应力值换算为对应于Nn的一组应力值；（4）通过换算后的应力数据确定疲劳强度的概率分布。本方法推定的疲劳极限分布结果与本实验获得的疲劳极限区实验数据的分散程度基本一致。

英文摘要：

In order to evaluate the fatigue reliability of 50^# railway axle steel, in this study the very high cycle fatigue test was carried out a four-axis cantilever-type rotary bending fatigue machine using in open environment at room temperature. A statistical method for decision of fatigue strength distribution of 50^# railway axle steel is proposed based on the data obtained from the test. This method is based on endurance strength data of a small sample. The procedure of the proposed method is as follows ： （ 1 ） it is assumed that the distributions of fatigue strength at different number of cycles are approximately identical; （ 2 ） the number of cycles No corresponding to the keen point obtained from mean S-N curve is determined;（ 3 ）based on linear theory of cumulative damage, the stress data in endurance strength region are transformed into one group of stress corresponding to N0; （ 4 ） the fatigue strength distribution is estimated by the group of stress corresponding to N0. The result of the fatigue limit distribution obtained from the proposed method is in good accordance with the scatter degree of test data in fatigue limit region.