Experimental and numerical investigation on galling behavior in sheet metal forming process

During the sheet metal forming, one of the major causes for die failure is transfer and accumulation of adhered material to the die surface, generally referred to as galling behavior. In the present work, the galling mechanism in sheet metal forming is investigated by a multi-scale approach. Firstly, the macro-galling behavior in square cup drawing of high-strength steel is examined by laboratory experiment and numerical simulation. Then, the first-principle calculations are used to present an insight to the atomic level galling at TiC/bcc-Fe interface. As a result, the macro-galling behavior in sheet metal forming is dominated by the critical contact pressure and the effective sliding distance. At atomic scale, the theoretical modeling using perfect crystals suggests that the separation most likely occurs at TiC/bcc-Fe interface or within the sub Fe slab, where the initiation galling would be arose and then formed as micro-adhesion.