排气歧管紧固螺栓失效分析与设计改进

Failure Analysis and Improvement Design of an Engine Exhaust Manifold Fastening Bolt

某发动机的排气歧管紧固螺栓在耐久试验中出现失效。本文采用不同试验手段,从产品性能、预紧力校核、装配工艺等角度,对失效件进行了详细分析,认定是其预紧力过小而导致出现疲劳断裂。另外,在分析过程中还发现了设计上的诸多问题,如材料选择不当、产品摩擦系数未作规定等。通过有针对性的改进,重新交样于客户。经反馈,耐久试验顺利通过。

The fastening bolts of the exhaust manifold are failed during the endurance test.In this paper,different test methods are used to analyze the failure parts in detail from the aspects of product performance,pre-tightening force check and assembly process.It is determined that the pre-tightening force is too small to cause fatigue fracture.In addition,many problems in the design are also found in the analysis process,such as improper material selection and no requirement for the friction coefficient of the bolts.After the corresponding improvements,the new samples are resubmitted to the customer.Then the customer′s feedback is that the endurance test passed successfully.