Biaxial Fatigue Life Prediction Approach Research

Fatigue phenomenon is very popular in real engineering problems which arealways submitted to multiaxial fatigue loading. Although some important progress formultiaxial fatigue has been made in recently years, the corresponding theories andexperimental research for multiaxial fatigue are still not mature enough. Therefore,the corresponding systematic research for multiaixal fatigue life prediction will stillbe full of important significance and application prospect. Additionally, it isreasonable to apply uncertainty theory into multiaxial fatigue life model due to someuncertainties in materials and fuzziness in life model. Based on these points, thispaper tries to propose several different fatigue life models including uncertainty lifemodel and the corresponding works are as followed:1. By combining the fuzzy set theory with the existing multiaxial high-cyclefatigue criteria, a method is proposed to establish the multiaxial fatigue fuzzycriterion which can take into account the scattering and uncertainty of the fatiguefailure. A fuzzy reliability method is then formulated to obtain the multiaxial fuzzyP-S-N curve based on this fatigue criterion, which can be helpful for engineeringdesign.2. A new path-dependent factor, which can describe well the loading path effectfor non-proportional fatigue life, is proposed. Based on this factor, two kinds oflow-cycle multiaxial fatigue models are presented. The effectiveness of the first one isdemonstrated by11kinds of materials under20paths. The second one is evaluated by4kinds of materials’ fatigue data.3. Based on fatigue equilife curve, a new approach for high-cycle multiaxialfatigue, which can consider the effect from material properties on proportionalloading fatigue life, is proposed. Moreover, this method also uses one groupnon-proportional loading data under circular path to determine the material sensitivityfor multiaxial fatigue life reduction under non-proportional loading. At last,experimental data from4kinds of materials are used to demonstrate the effectivenessand accuracy of this new approach.