Copyright © 2010 SciRes. ENG The Fatigue Fracture Criterion Based on the Latent Energy Approach

The extensive literature on the fatigue problem, published for more than one hundred years, is reviewed by the known scientists [1,2]. As it follows from these investigations, the fundamental amount of failures in en-gineering practice connected with the fatigue fractures of materials and structure elements. The fatigue prob-lem is complicated one and it is not solved yet. So the theoretical and experimental investigations of this problem will be continued. In our paper the energy approach to formulate the fatigue strength criterion is proposed. The criterion is based on the conception of the latent energy [3-7]. This conception was not ap-plied previously to the fatigue problem. The latent energy is consumed to generate the irreversible deforma-tion and to damage and fracture of metallic materials. So the fatigue fracture criterion can be formulated us-ing the results of latent energy measurements in the macro experiments. This is most impotent advantage of the proposed approach. The logistic function is used to describe the dependence of latent energy from the value of irreversible deformation. It is assumed that the cyclic strength of metals is defined by the latent en-ergy, stored in specimen, when it is reached the critical value in accordance with the logistic curve in a satu-ration zone. This proposal is used to formulate the fatigue strength criterion. The functions and parameters of received criterion are concretized and comparisons with experimental results for axial cyclic tension for sheet aluminum alloy specimens are given