Evaluation of quenching process on low cycle fatigue life for cylinder head

Due to the complex geometry and thermos-mechanical loading, cylinder heads are the most challenging parts among all parts engines. They must endure cyclic thermal and mechanical loading throughout their lifetime. Cast aluminum alloys are normally quenched after solution treatment process to increase mechanical properties which can create high residual stress. Residual stress is one of the dominant elements for failure of cylinder heads. The impact of residual stress on the thermal stress and low cycle fatigue life (LCF) of cylinder heads was studied. For this goal, Solidworks software was used to model the cylinder heads. Then the thermo-mechanical analysis was performed to determine the temperature and stress field in ANSYS software. Finally, the fatigue life analysis that considers residual stress effect was done. The thermo mechanical analysis showed that the maximum temperature and stress happen in the valves bridge between the two exhaust valves. The results of finite element analysis (FEA) proved that the impact of residual tress in LCF is considerable. Thus, residual stress must be investigated in the thermo-mechanical fatigue analysis of the cylinder heads.