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采用直读光谱仪、显微硬度机、光学显微镜和扫描电子显微镜等分析手段,对失效的汽车发动机活塞连杆总成断裂原因进行了分析。断裂首先发生于连接大盖,裂纹源位于凹槽端面底部应力集中严重的过渡R处,该处还存在加工刀痕,更加剧了应力集中程度。连杆总成在承受了多次反复冲击载荷后,在该处首先产生了裂纹源,发生了疲劳断裂,之后连杆总成正常运动状态受到破坏,连接螺栓接着发生了一次性韧性断裂。
The causes of the failure of the piston rod assembly of automobile engine were analyzed by direct reading spectrometer, microhardness tester, optical microscope and scanning electron microscope. Fracture first occurred in the connection of large cover, crack source is located at the bottom of the groove end of the stress concentration of serious transition R Department, there are still processing marks, more intensified the degree of stress concentration. After multiple repeated impact loads, the connecting rod assembly firstly produced the crack source and fatigue fracture occurred there. After that, the normal movement of the connecting rod assembly was damaged, and the connecting bolt followed by a one-time tough fracture.