FRICTION EFFECTS DURING DEEP DRAWING OF CYLINDRICAL COPPER PIECE

The coefficient of friction in deep drawing processes of copper blanks is experimentally investigated under conditions of dry friction and lubrication using mineral oil. The variations of the coefficient of friction are calculated through differences in the diagrams "Drawing force - Punch travel" measured under three different blank-holder forces. At both cases of dry friction and lubrication the values of the coefficient of friction are shown depending on the development of plastic deformation. During the first geometrical stage of deep drawing a larger drawing force is observed at dry friction. During the second geometrical stage a larger drawing force is observed at lubrication friction. The observed results could be explained by the different influence of the friction conditions during the blank flange deforming and may be useful in drawing out friction laws, investigation of the wear and mechanisms of plastic deformation.