X-Ray Investigation on the Residual Stress in the Process of Fatigue in Cast Iron

In view of the fact that the residual stress, affecting the fatigue phenomena of materials, varies with repeated strain, it is not considered to be altogether proper to evaluate fatigue strength solely on the value of the residual stress in the virgin materials, but it is necessary to study the process of changes in the residual stress under cyclic loading, which is also an important process in making nondestructive prediction of fatigue life.In this papers reported the experimental study made on this problem about cast iron, particularly malleable cast iron.The following conclusions have been obtained:(1) If there is residual stress in the virgin materials, the changes in the stress are in three stages.(2) If there is no residual stress in the virgin materials, the changes in the stress are in two stages.(3) These changes correspond to the fatigue behaviour of the materials.(4) These relationships will be utilized in making nondestructive prediction of fatigue life of cast iron.