Accurate prediction of large radius air bending using regression

Abstract

Abstract The industrial importance of air bending applications with high strength steels has increased in recent years. However, the limited bendability of high strength steels leads to the necessity of using large radius punches. The usage of such tooling causes a change of the loading scheme from traditional 3-point bending to 4-point bending. Therefore, the traditional formulas used for the prediction of bending parameters, such as springback and bend allowance, lack accuracy. In the current contribution, a regression model is proposed in order to achieve an accurate prediction of bending characteristics. The model is based on phenomenological observations of bending parameters, and fitting of well-established formulas. Large radius bending is used mostly for high-strength steels, thus the investigation is performed for Domex 700 MC and Weldox 1300 with thicknesses of 4 and 6 mm. The following bending parameters have been investigated: contact points position, bend allowance, bending force, and springback. The predicted values are compared with a wide range of experimental tests and the coefficient of determination (R2) is calculated in order to assess the prediction accuracy.