车钩铸造E级钢拉-拉载荷下威布尔分布P-S-N曲线及应用

Tension-tension Load of Grade E Steel for Coupler Cast and its Application

为了获得铁路货车车钩铸造E级钢的疲劳性能以及车钩疲劳寿命预测,首先开展了拉-拉脉动载荷下的高周疲劳试验,对疲劳试验结果进行统计分析,基于威布尔分布函数模型,获得该材料的概率疲劳P-S-N曲线;然后结合换算得到的应力谱和材料P-S-N曲线对车钩疲劳寿命进行了预测。研究结果表明:在分别对应于10^(5)次左右循环寿命和3×10^(5)次左右循环寿命的450 MPa和400 MPa应力水平下,铸造E级钢在同一应力水平下的疲劳寿命不符合正态分布;在10^(5)~10^(7)次循环范围内,铸造E级钢疲劳寿命较好地符合威布尔分布。利用最大相关系数优化法,确定了不同应力水平下的威布尔分布的参数,获得了铸造E级钢在拉-拉载荷下失效率为1%的P-S-N曲线和失效率为50%的中值S-N曲线。通过车钩台架试验载荷谱转换得到车钩危险部位应力谱,结合材料P-S-N曲线对车钩产生裂纹时的疲劳寿命进行了预测,预测结果与试验结果吻合良好。

The fatigue performance of grade E steel for railway freight car couplers and the life prediction of the coupler were obtained by conducting a high-cycle fatigue test under tension-tension pulsating load,analyzing the fatigue test results,and obtaining a probabilistic fatigue curve P-S-N of the material based on the Weibull distribution function model.Then,the fatigue life of coupler is predicted by combining the converted stress spectrum and P-S-N curve of the material.The results show that the fatigue life of grade E cast steel at the same stress level does not conform to the normal distribution at the stress levels of 450 MPa and 400 MPa corresponding to about 10^(5) cycle life and 3×10^(5) cycle life,respectively;the fatigue life of grade E cast steel conforms better to the Weibull distribution in the range of 10^(5) to 10^(7) cycles.Using the maximum correlation coefficient optimization method,the parameters of the Weibull distribution at different stress levels were determined,and the P-S-N curve with a failure rate of 1%and the median S-N curve with a failure rate of 50%were obtained for the grade E caste steel under tension-tension load.The stress spectrum of the dangerous part of the coupler was obtained by converting the load spectrum of the coupler bench test,and the fatigue life of the coupler in case of cracking was predicted by combining with the P-S-N curves of the material,and the prediction results were in line with the test results.