VARIABLE CONTACT CONDITIONS INFLUENCE ON FORMABILITY OF THIN SHEET METALS BY DEEP DRAWING

Abstract

Presented in the article is comparative view of experimental results of pure deep drawing (deep drawing of cylindrical cup with flat bottom) in conditions of constant blank holding force with different contact conditions (dry, oil, polyethylene foil) on one side and the results of deep drawing with variable blank-holding force and different contact conditions on the other side. Variable blank-holding force implies the possibility of programme control of any kind of force dependence on travel. Classical autobody steel sheet metal is used, and strain distributions fi1, fi2 and fi3; (in dependence on location on work piece and in forming limit diagram —FLD), drawing force, work piece depth and the appearance of defects (wrinkles and fracture) are being observed. Three program controlled variable blank-holding force models are used: decreasing, increasing and combined. First results, presented here, show that variable blank-holding force has significant influence on conditions of friction on work piece flange, and thus on deep drawing process and work piece characteristics. That influence may result in significant improvement in technology of deep drawing of thin sheet metals.