Influence of the transformation of a non-proportional multiaxial loading to a proportional one on the high cycle fatigue life

The work here presented intends to study the influence of the shape of loading on the fatigue life in case of multiaxial loading. The practical undergoing problem is the fatigue life of high speed railways wheels. They are here considered as loaded in tension (or compression) and in torsion.Several multiaxial fatigue life criteria exist, but the most of them use in their formulation a proportional signal. However, actual loading are non-proportional, and the problem consists in transformation of a non-proportional signal to a proportional one. The Palin-Luc’s criterion will be the basis of this work and extension to variable amplitude multiaxial alternated loading will be proposed.After presenting some multiaxial criteria, we propose a method for transforming the signals. Then, experiments and results are presented and discussed in view of a fatigue life prediction of the wheel.