A generalised solution for the prediction of springback in laminated strip

Abstract With innovations in pressing and assembly processes, coupled with emphasis on minium weight designs, there is an increasing demand for high-strength thin-gauge metal or composite strip with more consistent material properties. With such materials, springback guidelines, which have been developed for softer, thicker and homogeneous strip, become increasingly inadequate. Springback is a phenomenon in which the strip unbends itself after forming. Insufficient allowance for springback often results in the formed component being out of tolerance, introducing problems during assembling or installation. Springback is induced by the elastic redistribution of the internal stresses during the release of the external load after the material has been subject to plastic deformation during forming. Numerous fundamental analyses have been made to quantigy springback behaviour. These studies have contributed greatly to a basic understanding of the springback phenomenon, although their applications to sheet metal forming processes require care, since the precise forming conditions must be known in order to apply the theories. Most fundamental analyses conducted into springback so far have been limited to homogeneous material. With increasing use of laminated and composite materials in modern engineering, it is important to characterise the springback behaviour of laminated strip. This paper presents details of a generalised solution for such a study. By introducing appropriate mathematical approximations to the general solution, closed-form expressions applicable to metallic coated strip are also derived.