Based on the critical plane method

a multiaxial damage parameter and a life prediction model were proposed.Differ from the traditional damage parameter whith takes the maximum shear strain range as the critical plane

this damage parameter

taking the maximum damage plane as the critical plane

integrates the maximum shear range with the normal strain range and the maximum normal stress on the maximum shear range plane and reflects the reduction fatigue life owing to the additional cyclic hardening with the non-proportional loading.It is convenient for engineering application because there is no material constants in this parameter and no need to consider the mean stress.Experimental verifications show that the proposed parameter gives better satisfactory results for three checked metals under proportional and non-proportional loading.The life prediction result of a turbine disk transmission arm pin hole using this parameter further proves the engineering applicability of taking the maximum damage plane as the critical plane.