排气阀杆早期断裂失效分析
Failure Analysis on Early Fracture of Exhaust Valve Rod
戴乐阳1, 林少芬1, 陈清林1, 段 振2
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作者单位：(1. 集美大学 轮机工程学院, 福建 厦门 361021; 2. 沪东中华造船(集团)有限公司, 上海 200129)
中文关键字：排气阀杆； 锁槽； 断裂； 表面粗晶； 夹杂
英文关键字：exhaust valve rod; slot; fracture; surface coarse grain; inclusion
中文摘要：对某批早期断裂的排气阀杆进行了成分分析和金相观察，对其断口也进行了宏观和微观观察分析。结果表明：该批排气阀杆锁槽早期断裂主要是由于阀杆组织存在表面粗晶层，在高频率冲击应力作用下，阀杆的锁槽处形成严重的能量集中和表面应力集中，从而在锁槽圆周产生多个裂纹源。 同时，阀杆内部大量分散的夹杂物又形成内部应力集中源，加速排气阀杆的断裂，导致阀杆早期断裂。
英文摘要：The chemical composition and microstructure of an early fracture exhaust valve rod was examined. The macroscopic and microscopic appearances of the fracture were observed. The results show that the main reason for the early fracture is the coarse grain layer in the surface microstructure, which endangers the slot neck particularly. Under a high frequency impact stress, a serious energy and surface stress concentration is formed at the shrinkage neck, which induces multi-crack fountains in slot circle. The cracks of the slots are accelerated to cause the early breaking by dispersive inclusions which form interior stress concentrations.