INITIATION AND PROPAGATION OF SHORT FATIGUE CRACKS IN STEEL 45

The overall evolution for initiation and propagation of the short fatigue cracks in smooth specimen of the steel 45 was observed under optical microscope by using of the replication short crack initiation life is less than 10% of the failure one. According to the cracking rate. the growth of short cracks may separate into two stages. i.e., micro-crack and physical crack, of which the characteristic values of crack size and the equations of growth rate to identify them are given