Abstract
The cylinder head of large commercial vehicle has generally been developed by high strength gray cast iron. The residual stress developed during casting process is also considered as an important contributor to the endurance. Considering the importance of the residual stress, the correlation between stress and performances has not evaluated enough. To increase the understanding the relationship, the cylinder heads were subjected into several heat treatment conditions and the residual stress was evaluated qualitatively by X-Ray diffraction and drilling method and finally, rotating bending fatigue evaluation was conducted to evaluate the effect of the residual stress on fatigue property and the optimized heat treatment condition to release the harmful stress from cylinder head was proposed. After releasing the residual stress, the fatigue property was enhanced about 30% due to improvement of the stress distribution of cylinder head.