Failure analysis of a diesel engine cylinder head based on finite element method

• Fatigue failures are all located in the valve bridges of the cylinder head.
• Temperature and stress of the cylinder head are evaluated by finite element method.
• Temperature dependency of material mechanical properties is used in analysis.
• Both temperature and stress contribute to the failures of the cylinder head.

Macro fatigue cracks are expected to occur in valve bridges of cylinder head when engine is operating in normal working condition. In order to determine the causes of these failures, stress analysis is carried out using finite element method with a concern of temperature dependency of material properties. Mechanical and thermal properties of material tested at high temperatures are applied to the finite element analysis. Furthermore, temperatures of the cylinder head in actual working condition are measured to validate the simulation results of finite element analysis. After that, stress computation is performed and the regions of stress concentration on the flame deck surface are obtained. The analysis results of stress show that the regions of stress concentration are in agreement with the actual failure regions of the cylinder head. When analyzing the failures on the flame deck surface of a cylinder head by evaluating stress concentration, temperature’s effect on mechanical strength of material should not be ignored. The methodology of failure analysis proposed in this paper is time-saving and also relatively accurate and predictive in actual engineering practice.