Abstract:

For three kinds of materials, a family of equivalent damage curve was measured on various stress levels using toughness degradation fatigue tests by fixing a group of cyclic numbers. It displays the materials damage in all the damage field. The mathematical function of the equivalent damage curve family is well fitted with the test data. The damage cumulative model and fatigue life prediction in complex loading were derived from the damage curve family function. The comparison of fatigue test data of two stage loading with prediction of the equivalent damage curve method for three kinds of materials shows good agreement.The fatigue life prediction with the model of the equivalent damage curve is more straight and reasonable if the assumption of equivalent damage exists.

Key words: equivalent damage, damage cumulation, life prediction, toughness degradation