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In this article, the enforcement of a user defined blank shape and size is formulated into an inverse finite element program, FAST_FORM3D. In this type of analysis, the geometric input to the program is a designed part mesh with extended edge and the boundaries of a user defined blank. An iterative procedure is developed to construct a new part mesh, which, upon unfolding, produces a blank that matches closely the user defined blank. The new technique is tested using the NUMISHEET'93 deep drawn square box benchmark. A convergence study is presented to show the performance of the developed iterative scheme. A practical example is included to demonstrate the usability of the new technique in design cases when simple straight-sided blank is needed for ease of blanking operation. The predicted thickness strain displays a good agreement with the experimentally measured results.

A fast Springback capability was developed for up-front design of sheet metal stampings and related operations such as trimming. The intent, by analyzing formability and springback results, is to design a part and a robust process that will produce a World Class Quality. The FAST_SPRINGBACK program is based on a linear elastic Finite Element formulation with a degenerate 3-D shell element having 6/9 nodes. The starting point for the program is the forming strains that are available from FAST_FORM3D (a One Step FEM code) or alternatively other incremental forming software. A summary of validation results is outlined, ranging from analytical solutions for four basic membrane modes of deformation (balanced biaxial, plane strain, uniaxial tension and pure shear). Validation for pure bending mode is performed against experimental data obtained from a specially designed test rig. Validation based on standard benchmarks such as Numisheet 93 is also presented.

This article describes a fast design oriented tool to provide predictions of springback in automotive stampings. The new program, FAST_SPRINGBACK, utilizes the results of another membrane finite element code, FAST_3D, which performs a one step simulation of the forming process. The significant feature of the new springback tool is its ability to quickly predict the different modes of springback deformations as well as residual stresses that will affect the final shape and performance of the formed part. An important aspect of the program is its capability to integrate with existing CAD tools, thus enabling the designer to perform checks on the candidate part geometry in the early design stages.