Microdeep drawability of very thin sheet steels

The purpose of the present study is to clarify the microdeep drawing characteristics of very thin sheet steels of below 0.2 mm thickness. An experimental study was conducted with specially developed experimental apparatus. In this study, a relative punch diameter D-p/t (D-p: punch diameter, t: thickness of sheet material) was chosen as an important experimental parameter and ranged from 10 to 100. Drawability was evaluated, and the similarity laws in deep drawing were examined with sheet steels of 0.05, 0.1, 0.2 and 1.0 mm thickness. For D-p/t from 10 to 100, ordinary drawability was obtained for very thin sheet steels without a large amount of blank holder pressure, and a decrease in value of limiting drawing ratio was observed with an increase in D-p/t. The similarity law of thin sheet metal drawing is adapted above D-p/t = 40 because the drawing mechanism below D-p/t = 20 should differ from the above D-p/t = 40. The differences are also revealed in the shape of drawn cups. For D-p/t = 10 and R-d/t = 5.0, bending is the dominant forming mechanism since blank holder pressure has little effect on drawability and no effect on the working material during the latter half of the drawing process. Therefore, the drawing behavior seems similar to that in drawing thick sheet metals and is characterized as microdeep drawing of very thin sheet metals. (C) 2001 Elsevier Science B.V. All rights reserved.