A simplified approach for evaluating bendability and springback in plastic bending of anisotropic sheet metals

Precise predictions of springback after bending and bendability (the minimum bending radius) are the key to the design of the bending tool, to control of the bending process and to the assessing of the accuracy of part geometry. The effects of the normal anisotropic value R and the strain hardening exponent n on the pure bending of sheet metal have been studied. The highlight of this paper is that a simple approach, incorporating the normal anisotropic value R and the strain hardening exponent n, is developed to estimate springback, bendability and the maximum bending moment in pure bending. Comparison between predicted values and published experimental results has been made, a consistent agreement being achieved, reflecting the reliability of the present model. It is concluded that (i) the springback is almost proportional to the normal anisotropic value R, (ii) it decreases sharply with respect to smaller strain-hardening n-values or smaller thickness ratio t/2p-values, and (iii) at large strain-hardening n-values or large thickness ratio t/2p-values, the springback will concentrate to a small range. The minimum bending radius is proportional to the sheet thickness t, decreases with the normal anisotropic value R, and decreases sharply with the strain hardening exponent n to a small range. The maximum bending moment increases with the normal anisotropic value R; increases sharply with the sheet thickness t but decreases with the strain hardening exponent n. (C) 1997 Elsevier Science S.A.