The Influence of the Blank Holder Force during Forming Process of a U-Shaped Part Made from AZ31 Magnesium Alloy

Abstract

In case of sheet metal forming the main dimensional errors are caused by the springback phenomena. The present work deals with numerical simulation related to draw bending and springback of U - shaped part made from magnesium alloy. The current paper is trying to prove out the important role of the blank holder force with respect to the forming process. Though novel approaches relating to the formality of magnesium alloy sheets, the change of springback due to the characteristic of each process should be verified by finite element method. Springback refers to the elastic recovery of deformed parts. Springback occurs because of the elastic relief from the bending moment imparted to the sheet metal during forming. Springback is mainly influenced by the sheet thickness, the punch and die profile radii, initial clearance between punch and die, friction conditions, rolling direction of the materials, blankholder force and by material properties. In this study, the magnesium alloy strips with two types of material having the thickness of 1mm, are used to investigate springback characteristics in U-shape bending. The Dynaform 5.6 software was used to simulate the forming process, in which the blank holder force takes values between 15 and 35 kN. In this study, the springback was analyzed by U-forming at room temperature conditions with different blank holder forces. Springback decreased with the increase of the blank holding force. Excessive holding force cause irregular thinning of the material, especially in the radius area.