Thermo-mechanical analysis of magnesium alloy cylinder heads using a two-layer viscoplasticity model

Loading conditions and complex geometry have led the cylinder heads to become the most challenging parts of diesel engines. The aim of this study is to compare the distribution of temperature and stress in the aluminum and magnesium cylinder heads under thermo-mechanical loads. The three-dimensional model of the cylinder heads was simulated in abaqus software and a two-layer viscoplasticity model was utilized to investigate the elastic, plastic and viscous behavior of the cylinder heads. The temperature and stress results of magnesium alloy was compared to aluminum alloy results. The results of finite element analysis (FEA) showed that surface temperature of the magnesium cylinder heads is about 23°C lower than the aluminum cylinder heads. As a result, the fatigue lifetime of the magnesium cylinder heads can be improved in comparison to the aluminum cylinder heads. The thermo-mechanical analysis showed that the magnesium cylinder heads tolerate less tensile and compressive cyclic stress compared to the aluminum cylinder heads. The stress reduction value in the magnesium cylinder heads was about 10 MPa which can lead to higher fatigue lifetimes in comparison to the aluminum cylinder heads.