Study on Stress and Plastic Deformation of Scaled Cylinder Head Specimens under Thermal Shock

Thermal fatigue properties of several scaled cylinder head specimens (SCHS) are evaluated. The plastic deformation of the intake holes (ITH) and exhaust holes (EXH) during the experiment was recorded. The results show that the plastic deformation mainly occurred in the early stage of the thermal shock. The increment of the plastic deformation decreases with an increase in the number of fatigue test cycles. Additionally, the thermal stress distribution indicates that the nose bridges of the SCHS suffers greater thermal stresses than other areas. In particular, nose bridges between the ITH and EXH suffer the largest thermal stress than the other nose bridges. Furthermore, nose bridges with lower thermal stress, reduced initial surface roughness and deformation have better performance in terms of thermal fatigue life. This study provides a basis for exploring the thermal fatigue failure mechanism of cylinder head and is beneficial for the cylinder head design.