On the material's sensitivity to non-proportionality of fatigue loading

Many researches have shown that fatigue behaviour of a number of materials is significantly different in non-proportional loading conditions when compared to proportional ones. These differences concern stress-strain characteristics, fracture, the phenomena taking place in the material, and finally fatigue life. The aim of this study is to provide a survey on basic experimental results and methods of taking into account a material's sensitivity to non-proportionality of loading in multiaxial fatigue life estimation models for metals.