On the Bifurcation of the Remaining life under Multi-level Fatigue

It is very important to predict service life wit h interaction effect under fatigue loading. For example, when the loading order is from low to high, the damage evolution for two or multi-level fatigue may de celerate the damage rate. The remaining life under two or multi-level fatigue i s more than that expected by the damage theory, sometimes it is even much more t han the whole life in the original material. In this paper, with the advanced no nlinear dynamics, according to the two or multi-level formula in the fatigue da mage theory, an experiment is performed by computer simulation, and the bifurcat ion phenomena is discovered in the results. Furthermore, with the coaxing effect s, this phenomenon can be explained as a nonlinear property in the procedure of fatigue damage evolution. In fact, those formulas in the fatigue damage theories were formulized on the basis of many experiments, so they can be applied to eng ineering problem accurately. To study them, the bifurcation phenomenon and chaot ic motion may also be found in the procedure of fatigue damage.