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In this paper, finite element prediction of sheet metal forming process is investigated using solid elements. A three-dimensional rigidviscoplastic finite element method with linear tetrahedral MINI-elements is employed. This technique has traditionally been used for bulk metal forming simulations. The solid element approach with remeshing capability is applied to simulating a plate metal forming process to reveal its possible problems. The similar approach is also applied to a typical sheet forming process. Both single- and double-layer finite element mesh systems are studied, with particular attention to their effect on the deformed shape of the workpiece and thickness variation of a cold sheet forming process. The procedure is applied to the well-known problem of the NUMISHEET93 international benchmark. The resulting predictions are compared with experimental observations found in the literature, and good agreement is noted. [ABSTRACT FROM AUTHOR]

Blank holder force (BHF) is one of the key parameters affecting the process of sheet metal stamping. Numerous researchers have demonstrated two primary failures (wrinkling and tearing) could be avoided if appropriate variable BHF profile was implemented during punch stroke. Several approaches are proposed to determinate optimal BHF by experiment or FEM simulation. In this study, new control objective was adopted based on the definition and analysis of BHF formability window. The PID controller was integrated into FEM code to conduct closed-loop forming simulation of step rectangle box, through which the optimal BHF trajectories were determined for each separated binder. The trajectories were verified on a multipoint variable BHF hydraulic press and showed good effect to avoid wrinkling and tearing. The proposed BHF determination approach in this paper can be applied to stamping parts of different geometry due to the application of new objective, which makes it a robust strategy. [ABSTRACT FROM AUTHOR]