SPRINGBACK AND RESIDUAL-STRESSES AFTER STRETCH BENDING OF WORKHARDENING SHEET-METAL

Stretch-bending operations are widely used for the fabrication of airframe and automative structural components. The fabrication process involves bending of individual member to prescribed contour while applying of an initial stretch tension. Forming tools must be designed and built in a form which that produce the required contour within sufficient accuracy and tolerances satisfactory to the user applications. After plastic stretch bending, the bent section contains residual stresses as a result of the forming process. The magnitude of these stresses significantly affect the load carrying capacity and the fatique strength of the formed member. In this work, the primary emphasis is to evaluate the elastic springback and the residual stress after stretch bending of a rectangular section of 7075 Aluminum sheet. The variation of the amount of springback and the unfavorable residual stresses for elastic-plastic and fully plastic cases are given both in analytical and graphical form.