Ultrasonic measurement of fatigue damage of nodular cast iron

Abstract

According to the principles of damage mechanics, the evolutional law of fatigue damage of pearlite nodular cast iron under uni-axial stress control was studied by measuring the ultrasonic speed and attenuation. The results show that the fatigue damage variable D of pearlite nodular cast iron as a function of fatigue cycle ratio varies according to the index law. The critical fatigue damage variable was obtained. By comparing with ultrasonic speed, the attenuation is more sensitive to fatigue damage of ductile cast iron. At the early stage of fatigue, the variation of ultrasonic speed and attenuation comes from the movement and proliferation of dislocation in matrix. This is not a real reflection to fatigue damage in ductile cast iron.