Effect of Axial Normal Stress and Bending Moment between Contact and Non-Contact Zone on Forming Accuracy for Flexible Stretch Bending Formation

Abstract

Flexible 3D stretch bending (FSB) is a technology that uses multi-point molds instead of traditional integral molds to bend and deform profiles. Since the position of a multi-point mold can be adjusted in the horizontal and vertical directions, a set of molds can be used to form profile products with different contour structures. Due to the contact area and non-contact area between the multi-point mold and the surface of the profile, the forming accuracy of different areas is different. Thus, the axial normal stress and bending moment of the contact zone and non-contact zone between the profile and roller dies are studied in this article. By simulating the change in axial normal stress at the same position in the middle of a web along the axial direction, it is found that the axial normal stress shows little difference in the contact zone and non-contact zone. The value of axial normal stress in the non-contact zone is relatively stable, and there is a small increase on the side near the clamp. By simulating the axial normal stress of different cross-sections in the middle areas of three groups of webs, it is found that there is a linear relationship between the axial normal stress and the distance from inner curved surface. The bending moment of the profile in the contact zone is obviously greater than that in the non-contact zone, and the bending moment gradually decreases to near zero from the contact zone to the non-contact zone. The bending deformation of the profile in the contact zone is obviously greater than that in the non-contact zone, which results in the deviation between simulated bending displacement and theoretical bending displacement in the contact zone and non-contact zone.