Calculation of Springback and Its Variation in Channel Forming Operations

An approximate plane strain analysis of the springback of sheet metal which has been bent under tension around a small radius is presented. The tensile load can be applied either before the bending takes place (called a “preload”) or after bending (“postload”). Some of the material and process parameters which govern springback are identified, and it is shown that postloads are always more effective than preloads in reducing spring-back. In principle, if all parameters are fixed, the springback would be constant from part to part and the required overbend could be determined. In practice, the material and process parameters have unavoidable variations. Using the springback model developed here, a Monte Carlo simulation is carried out to estimate the effects of these variations. It is found that the metal thickness has the greatest impact on springback variation.