Investigation of durability analysis method based on performance degradation analysis

One of the main concerns of mechanical structures is structural damage due to fatigue. This phenomenon is accentuated in initial flaw of structure, areas of stress concentration, and the connection of components, etc. Initial fatigue quality and configuration of structure have the most important effect on durability. However, obtaining equivalent initial flaw size (EIFS) of structure with durability tests is very costly and time-consuming. A new method of determining initial fatigue quality and crack growth rate is presented with performance degradation curves of specimens in this paper. Specimens with one rivet hole are used in the tests. According to test results and theoretic derivation, the relationship of crack length with loading cycle is established. Then, EIFS values are calculated and fatigue crack growth rates are estimated using exponential fitness technique. The applicability and validity of the method are verified with theoretic computation of fracture limit finally.