Effect of blank-holder force on springback of ultra-thin copper sheets

Abstract

After forming by plastic deformation, it’s rare that the part produced retains its shape perfectly after removing the tools, the shape and dimensions that the tools imposed on it. This change in shape is mainly due to springback. This study focuses on the springback of U-shaped channels made of thin sheets of beryllium copper alloy 0.1 mm thick. The intensity of springback depends on several factors of part geometry and process parameters. Among the parameters of the process, we investigated the clamping force, which is an essential factor influencing the final shape of the part. It is shown that the springback is inversly proportional to the clamping force. As a consequence, there is no significant change of the geometry of the final part. Indeed, uneder high clamping force, the internal stresses (already existing in the material) become very important, which makes it possible to attenuate significantly the local moment effect in bending. The result is an uniform distribution of residual stresses in the thickness of the sheet which is studied in this paper.