连杆螺栓二次装配断裂分析

通过对螺栓断口宏观和微观形貌的观察，结合加工方法和装配工艺，发现过度酸洗引起螺栓表面渗氢，一次装配后，在静拉伸应力作用下，氢向螺栓头部与杆部连接部位的应力集中处聚集，萌生氢致裂纹并缓慢扩展，二次装配预紧时，在扭距作用下，裂纹快速扩展，产生脆性断裂。

Analysis on the Fracture of Connecting Rod Bolt in Second Assembling

Analysis on the macroscopic and microscopic features of the fracture,reference to process of machining and assembling suggested that hydrogen spread into material during acid pickling and under the pulling stress after first assembling,the hydrogen accumulate at the position where the head and the rod connected and stress concentrated,so cracks produced and expanded till the stress stops.In second assembling,torque impelled cracks expands with high speed,then brittle fracture occurs.