Reliability study for diesel engine cylinder head through fatigue failure analysis and structural optimization

Abstract

Crack and failure are often captured in the cylinder head of diesel engine during high cycle fatigue test. In order to study the cause and improve the fatigue resistance, tensile test, metallographic observation and fracture analysis were carried out. In addition, the finite element method was applied to simulate the stress distribution and fatigue strength of the cylinder head. Meanwhile, the influence of load factors on the fatigue strength was analyzed. The structure was optimized on the finite element analysis. The results show that the material properties are not the main cause of cylinder head failure. High cycle fatigue failure of cylinder head is identified by the reason of working loads. Among the causes affect fatigue strength, gas force was determined as the dominant factor by changing stress amplitude, while thermal load as the secondary factor by changing mean stress. Additionally, the structural optimization measures for the cylinder head were put forward according to the failure causes, and the safety coefficient of the vulnerable parts was increased from 0.88 to 1.04, meeting the design requirements. This study can provide a reference for the engine reliability analysis.