某发动机总管支架销轴在使用过程中出现脱落和裂纹。通过断口的宏微观分析、金相检验与结构分析等，对销轴脱落和产生裂纹的原因进行了分析。结果表明：在发动机工作振动应力的作用下，销轴与支架连接的焊点产生疲劳裂纹，进而引起总管支架销轴脱落，脱落原因为支架组件的设计结构和连接工艺不合理、焊接强度低。

Falling off and cracks occurred to the pin roll of a engine manifold bracket during use. The fracture reasons for peeling off and cracks of the pin roll were analyzed by means of macroscopic and microscopic fracture analysis, metallographic examination and structural analysis. The results indicate that:under the vibration stress of the engine, fatigue cracks appeared at the welding spot of the bracket and the pin roll, and then resulted in the falling off of the pin roll of the manifold bracket; the reason of the falling off was the unreasonable structural design and joint technology and the low welding strength.