Investigation of dependences of metal sheet variable blank holding force

The present paper is a continuation of the authors' works. The paper examines a variable blank holding force of sheet metal on overall forming details. We present a new analytical expression which characterizes a variable holding force. This expression covers all the main components affecting forming components, such as: strain rate, the actual material stress state, static and dynamic friction coefficients, the specific details of the thickness as a function of punch displacement, and two very important empirical factors. These empirical coefficients directly charactere variable blank holding force by changing its shape and size. Comparison of constant and variable blank holding force strain rate state after the full forming operation of an investigated metal sheet part is presented in the forming limit diagram (FLD) diagram, where clearly can be seen that a variable blank holding force significantly reduces final plastic strain value.