某机车柴油机进气门失效分析

Failure Analysis of Intake Valve for A Locomotive Diesel Engine

针对某型重载机车柴油机进气门服役过程中盘部掉块的失效事故,通过对失效进气门的宏观形态、断口形貌、化学成分、组织及力学性能的检验及分析,查明了进气门失效的原因,并阐述了失效机理。结果发现,裂纹起始于气门盘锥面,在落座应力及热应力的综合作用下扩展直至断裂;进气门的化学成分、金相组织及锻造流线均不符合技术要求,降低了进气门的热强性和承载能力。有限元分析结果表明:应力峰值在气门盘锥面;由于进气门综合力学性能的下降,在循环交变应力的作用下,气门盘锥面产生掉块。

Aiming at the failure accident of dropping blocks of a heavy-duty locomotive diesel engine intake valve during service,the cause of the intake valve failure was found out through the inspection and analysis of the macroscopic shape,fracture morphology,chemical composition,microstructure and mechanical properties of the failed intake valve,and the failure mechanism was also elaborated.The results show that the crack starts from the conical surface of the valve disc and propagates to fracture under the combined action of seating stress and thermal stress;the chemical composition,metallographic structure and forging streamline of the inlet valve do not meet the technical requirements,which reduces the thermal strength and bearing capacity of the inlet valve.The results of finite element analysis show that the peak stress is on the valve cone;due to the decline of the comprehensive mechanical properties of the intake valve,dropping blocks occur at the valve cone under the action of cyclic alternating stress.