Non-proportional loading-induced damage: A review of experimental methodology, damage evolution and modelling

The loading paths experienced by components during multi-pass forming processes often exhibit significant non-proportionality. However, traditional damage models are predominantly developed and validated under proportional loading conditions, which introduces limitations in their application, as they fail to characterise damage evolution accurately under non-proportional paths. Consequently, developing damage models capable of effectively accounting for non-proportional loading history is paramount. This paper systematically reviews recent advances in damage research under non-proportional loading paths. It encompasses the design of experimental methodologies for non-proportional loading, quantitative characterisation methods for damage, microscopic damage mechanisms and methods for damage modelling. Finally, building upon a summary of existing achievements, future research directions in this field are outlined.