气缸盖螺栓断裂失效分析

某型号柴油发动机气缸盖螺栓安装过程中发生批量性断裂。通过宏观形貌分析、扫描电镜分析、金相组织检测、力学性能检测、安装工艺模拟、化学成分检测等手段对螺栓断裂原因进行分析。结果表明: 螺栓断裂模式为扭拉应力作用下的过载断裂。引起螺栓过载断裂的主要原因是螺栓安装工艺不合理，导致安装过程中螺栓承受轴向载荷过大，超过其强度极限。结合实验室模拟安装结果与现场装配条件对气缸盖螺栓的安装工艺进行改进，制定合理的安装工艺。

Fracture failure analysis of cylinder head bolt

Batch fracture of cylinder head bolts for a certain type of diesel engine occurred during the installation. The causes of bolt fracture were analyzed by macroscopic morphology analysis, scanning electron microscope analysis, metallographic structure detection, mechanical properties detection, installation process simulation, and chemical composition detection. The results showed that the bolt fracture mode belonged to the overload fracture under torsional load, and the main reason for the bolt overload fracture was the unreasonable installation process of bolt. It led to too much axial load, which exceeded the strength limit of bolt. Combined with laboratory simulation installation results and field assembly conditions, the installation process of cylinder head bolts was improved, and a reasonable installation process was established.