Springback prediction and elasticity modulus variation

Angular precision of air bending is directly related to the precision of the calculated punch stroke, which is computed in order to achieve the required sheet profile before the springback. The calculated springback accuracy depends on the elasticity modulus which, as it is well-known, decreases with increase of plastic prestrain. During the bending process, the strain varies along the plate profile from the punch tip to the contact point of the plate with the die, but also in each cross-section along the thickness. In this contribution a formula is established allowing to calculate the springback taking into account the variation of the elasticity modulus. Experimental results have shown that for many materials reliable results are obtained by applying the developed formula and that for some materials, the latter has to be corrected by a single coefficient regardless of the thickness-tooling-angle combination.status: publishe