Abstract: The most components of engineering structures are usually subjected to a complex loading．It is unable to meet the requirements of engineering precision if a uniaxial fatigue model is used under multi-axial loading．The calculation of fatigue life prediction under multiaxial loading causes people’s attention more and more. A new multiaxial fatigue life prediction model is proposed based on the critical plane criteria. The model integrates the respective advantages of Fatemi-Socie(FS) model and Smith-Watson-Topper(SWT) parameter. The damage parameter in this model takes the sum of the maximum shear strain amplitude and the modified SWT parameter on the maximum shear strain amplitude plain. It can consider the effects of additional cyclic hardening due to non-proportional loading and mean stress on the multi-axial fatigue life of material. The proposed model can be applied to proportional and non-proportional loading. The model is evaluated by the multiaxial fatigue test data of pure titanium, BT9 titanium alloy, 304 stainless steel, S45C steel and 1045HR steel. The multi-axial fatigue life prediction results of these materials under proportional and non-proportional loading are almost within a factor of two scatter band of the test result. The result shows that the new multi-axial fatigue life model has high prediction accuracy.

Key words: Critical plane, Life prediction, Multi-axial fatigue, Proportional and non-proportional loading