Creep-fatigue Damage Analysis Of Cylinder Head Based On Thermal-mechanical Coupling Load

In recent years, diesel engine’s maximal combustion pressure and gas temperature increased significantly with the increasing power density and rotating speed, which aggravates the loading situation of cylinder head. Cylinder head which has to endure high temperature and pressure is a key component in diesel engine, its reliability directly affects the reliability of the engine. The effect of load region, structure, constraint, and the cooling medium, will finally influence the rate of thermal load and mechanical load on fatigue damage behavior.In the present paper, AVL-Fire software is used to simulate different operating conditions of the engine. Heat transfer coefficient, temperature, and pressure values at different crank angles can be obtained through performance simulation.Finite element software is used to acquire cylinder head temperature, stress, strain distribution under different operating conditions. Later, the stress under thermal, mechanical load and thermal-mechanical load are obtained latterly. Finally, the regular of stress distribution can be obtained.Through comprehensive comparison of various characteristics of fatigue damage calculation method, combined with load characters that thermal load low frequency changes, mechanical load high frequency changes. Based on the continuum damage mechanics, the creep and fatigue damage are accumulated and the creep-fatigue model is constructed. According to the creep-fatigue damage model, the contribute rate of thermal load in fatigue damage is calculated.