A non-proportionality description was proposed based on the analysis of several commonly used non-proportionalities in multiaxial fatigue. Furthermore

a new multiaxial low cycle fatigue life prediction model was developed by combining the newly defined non-proportionality with the strain parameter of the design criterion for non-proportional fatigue in the American Society of Mechanical Engineers(ASME) code case

which was considered as the basic damage parameter. On the basis of analytical study

conclusions can be drawn as follow:(1) the defined non-proportionality can accommodate arbitrary paths with the given contour under variable amplitude and non-periodic loadings;(2) compared with two commonly used models

the predicted multiaxial fatigue lives of 304 stainless steel under 14 strain paths using the proposed model agree better with the experimental results

which are almost within two-time scatter band of the test results.