阀杆断裂分析

Stem Fracture Analysis

对阀杆进行宏观检查、金相显微组织观察、化学成分分析、硬度测试试验和拉伸试验,结果表明:该阀杆因为同时受到交变应力和附加弯曲应力的共同作用,在阀杆外表面处产生微裂纹,微裂纹逐渐扩展,致使阀杆的有效承载面积逐步缩小,直至发生断裂。阀杆断裂的主要原因是:阀杆的硬度偏高,强度偏低,力学性能不符合要求,而且长期在高应力的交替作用下导致其发生疲劳断裂。

The macroscopic examination, microstructure observation, chemical composition analysis, hardness testing test and tensile test of stem were carried out. The results show that： because of the stem suffering from the alternating bending stress and additional stress, the micro-cracks exist in the outer surface of the stem, and the micro-cracks gradually extend, resulting in the reduction of the effective bearing area of the stem gradually, until the fracture occurs. The stem fracture is mainly due to：higher hardness of stem, lower strength, poor mechanical properties, and under the action of higher alternating stress in long term leading to fatigue fracture of the stem.