THE EFFECT OF RESTRAINING FORCE ON SHAPE DEVIATIONS IN FLANGED CHANNELS

Quantitative relationships have been obtained between restraining force and shape deviations, such as springback and side wall curl, in flanged channels made of SKDQ and high strength steels. It is observed that shape deviation is greatly reduced if the applied restraining force is beyond the yield strength of the material. However, due to the restriction of die entrance and punch corners, this condition cannot be readily achieved in the conventional bead system as side wall fracture intervenes. To circumvent this constraint, a so-named 'intermediate restraining' process has been developed to form high quality flanged channels in one single operation. The suggested process is displacement control and, in practice, should be applicable to any material once its physical properties are known.