Effect of Tensile Force in Stretch-Forming Process on the Springback

Abstract

In the case of forming a sheet into cylindrical surface by stretching the sheet in circumferential direction under various conditions, the effects of time and magnitude of stretching are studied experimentally and theoretically. The experimental results are well explained by the results of theoretical calculations. The obtained results reveal that the springback decreases with an increase of the tensile force, and the amount of it is minimized when the sheet is only stretched after bending. It is also found that the difference in the springback between stretching after bending and stretching with bending is small for materials having a remarkable Bauschinger effect and large for materials having little such effect. Furthermore, it is found that if it is necessary to stretch the sheet during bending, in order to decrease the springback it is desirable that the tensile force be maintained as small as possible during bending and finally a large tensile force is worked after release of the first force.