A Finite Element and Experimental Study of Sheet Deformation as Influenced by Drawbead End Geometry

Drawbeads have been playing an important role in deep drawing processes. The restraining force exerted by the drawbeads is important in enhancing the part formability. It is found that improper drawbead design will result in defects such as wrinkles and splitting. Thus, the drawbead geometry, especially its end radius, is a critical aspect in the die design. The present investigation focuses on the influence of the drawbead end radius and blankholder force on the sheet deformation patterns. The experimental results reveal that a drawbead with end radius equal to its cross sectional radius will cause severe deformation and wrinkling downstream of its end. With drawbead end radius twice the size of its cross sectional radius, the deformation in the downstream side of the drawbead end becomes smoother, hence improving the severe deformation and wrinkling. A higher blankholding force also suppresses the wrinkling near the drawbead end. A corresponding finite element model successfully corroborates such trends.