机车抱轴箱随机应力谱下的疲劳寿命预估研究

针对机车铸钢抱轴箱在运行中产生疲劳裂纹的现象，笔者对机务段检修和返厂检修的抱轴箱进行了调研，认为裂纹长度服从正态分布。对抱轴箱及其改进结构进行了有限元分析，其应力最大部位与发生裂纹部位一致。通过动应力实测获取抱轴箱危险部位的应力谱，用局部应力一应变法结合断裂力学方法估算了抱轴箱的疲劳总寿命，并与名义应力法计算结果进行了比较。结果表明，2种方法所得的疲劳总寿命基本是一致的，用局部应力-应变法计算机车抱轴箱裂纹萌生寿命是一种合理的方法，而大的铸造缺陷是抱轴箱产生裂纹的最主要原因。最后采用统计方法得到了裂纹扩展破坏的累积失效概率函数。

Research on Forecasting the Fatigue Life of the Axial Suspending Tube on the Locomotive under the Random Stress Spectrum

Aiming at the phenomenon that there occur fatigue cracks in the cast-steel axial suspending tubes on locomotives, and in order to find out the reasons that cause the cracks, the axial suspending tubes were investigated and analyzed. The lengths of fatigue cracks obey normal distribution. Finite Element Analysis of the axial suspending tubes was done under limited load cases. The result shows that the maximum stress acts where cracking appear. Dynamic stress tests on sites between Xi-an and Zheng-zhou helped to obtain the stress spectrum. The fatigue life was estimated by the combined local stress-strain method and fracture mechanics method. It was compared with the resuet of the nominal stress method. The two methods yield basically the same fatigue life. The local stress-strain method is a reasonable method to calculate the initiation life of the fatigue cracks of axial suspending tubes. Maior casting defects are considered the most important reason to produce cracks. The fatigue life provides the reliable basis for determining the repair cycle. Finally, the cumulative invalid probability function of the crack propagation was got by the statistical method.