A new method based on damage equivalent principle was developed for multi-axial fatigue test loading spectrum formation.It could be applied to uniaxial stress destroying mode with several dangerous positions under multi-axial loading.Firstly

the stain histories of the initial crack position were decomposed into a series of simple individual cycles by the rain-flow counting algorithm.And these cycles were divided into several groups by the stain amplitude

then all the combinations of multi-axial loading cycles were searched according to the damage equivalent principle

and several constant multi-axial loading cycles were found.After these constant cycles were linked

the fatigue test loading spectrum was presented

with the damage equivalent to the origin loading spectrum.According to the test of simple structure

the method can assure the equivalent damage of the test spectrum and the origin spectrum

and the operation is simple and feasible.