高速列车锻钢制动盘热疲劳裂纹耦合扩展特性研究

Research on Coupled Extension Characteristic of Thermal Fatigue Cracks at Forged Brake Disc for High Speed Train

据制动盘裂纹剖面的宏观形貌,发现盘面长裂纹的形成以多条半椭圆表面裂纹连通为主。针对制动盘在运行过程中的典型运用工况,采用有限元法计算制动盘在300 km/h紧急制动后的热应力,发现周向残余应力较大,并以此推测周向残余应力是驱动制动盘热疲劳裂纹扩展的主要原因。在此基础上,建立制动盘盘面的裂纹网格,研究了裂纹扩展过程中的应力强度因子和多裂纹耦合扩展规律。通过研究发现对于给定的载荷条件,不同初始形状比时,裂纹前缘应力强度因子的分布规律存在一定的规律性,随着裂纹的扩展,裂纹形状趋于扁平化;多裂纹扩展时,裂纹间距越小,裂纹间的相互作用越明显,扩展速度越快;但受制动盘结构和尺寸限制,共线裂纹数越多,每条裂纹扩展到临界值时的应力强度因子越小。

According to the profile of brake disc crack macro-morphology, the main forms of long crack are approximately its own expansion and multiple cracks connectivity. Regarding the brake disk typical conditions during operation, the circumferential residual stress are considerable by calculated the thermal stress in 300 km/h emergency braking using the finite element method. Thereafter, the thermal fatigue crack growth of brake disc is drove through circumferential residual stress. Based on the conclusion, the brake disc grid with crack is established, and then the distribution of the stress intensity factor and the coupled propagation law between multi-cracks in the crack propagation process are researched. The results show that, the stress intensity factor of crack tip have regularity for different initial crack size and the crack shape tends to flatten with crack propagation under same load; When multiple crack are propagated, crack spacing smaller, the faster expansion and the interaction are more obvious; however, considering the structure and size limits, the more the number of cracks, the smaller the stress intensity factor when crack extended to critical value.