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开裂失效是发动机排气歧管典型的失效模式之一。为了找出失效原因并改进发动机排气歧管结构,研究了发动机排气歧管结构的优化设计。构建了发动机排气歧管热应力分析模型,研究了歧管在冷热冲击条件下开裂的失效机理,基于降低歧管关注位置的热应力和残余应力与塑性应变,提出了排气歧管结构的优化设计方案。仿真实验分析显示,在歧管“V”形位置处的各项指标在冷热冲击载荷作用下,其热应力、残余应力和塑性应变均高于设计极限值,是导致歧管开裂失效的主要原因。借助在“V”形位置加筋及外表面连接位置剖分等技术措施,可改善应力集中状况。实验结果验证了该排气歧管优化设计方案的合理性与有效性。
Cracking failure is one of the typical failure modes of engine exhaust manifold. In order to find out the cause of failure and improve the engine exhaust manifold structure, the optimal design of engine exhaust manifold structure was studied. The analysis model of engine exhaust manifold thermal stress is established. The failure mechanism of the manifold cracking under the condition of thermal shock is studied. Based on the reduction of thermal stress, residual stress and plastic strain of the manifold, the exhaust manifold structure The optimal design. The simulation analysis shows that the thermal stress, residual stress and plastic strain are all higher than the design limits under the impact of thermal shock load at the manifold “V” position, which is the cause of failure of the manifold cracking The main reason. With the “V ” shaped position reinforcement and the surface of the outer surface of the connection position and other technical measures to improve the stress concentration. The experimental results verify the rationality and effectiveness of the optimal design of the exhaust manifold.