Optimization of Blank Holder Force to Control Wrinkling and Fracture of Cylindrical Cups in Deep Drawing

摘要

The Predominant failure modes in sheet metal parts (deep drawing process ) a re wrinkling , fracture. In many cases these defects may be eliminated by appropriate control of the blank holding force (BHF). This paper summarizes the results of a resent study on the formability of rectangular or cylindrical par ts from Extra Deep Draw (EDD) steels . Wrinkling , fracture limits have been determined and BHF control methods have been developed to eliminate defects, improve part quality, and increase the draw depth. The prediction and prevention of wrink l ing and fracture a re extremely important in the design of tooling and process parameters in deep drawing process. Forming process of Extra Deep Draw ( EDD ) Steel alloy sheets can be investigated by using deep drawing process. When the BHF is 70 80 N / m m 2 the steel sheets with a thickness 5 mm can be produced in the cups without any defects such as wrinkling, tea r ing. A 3 D explicit finite element analysis is used to investigate the influence of various BHF schemes on sheet metal formability limits especially wrinkling, and fracture. The ro le of relevant parameters of each blank holding technique is also investigated . Experiments were conducted using a die block of 250 mm diameter and punch 240 mm on EDD steel alloys of blank size is 165mm and thickness 5 mm.