GENERALIZED EQUATION FOR EVALUATING THE EFFECT OF CRACKS ON THE ENDURANCE LIMIT OF MATERIALS

On the basis of small-crack mechanics a generalized equation is derive d that describes by a single curve the effect of cracks of arbitrary l ength on the endurance limit of various materials and makes it possibl e to establish a link between the endurance limit of smooth specimens and other characteristics of the material. The endurance limit of low- strength steels is shown to be virtually independent of the initial de fects of the material and to be determined only by the yield limit, wh ereas the endurance limit of high-strength steels depends weakly on th e yield limit and is determined mainly by the length of the initial cr acks and the threshold value of the stress intensity coefficient.