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A double-action hydraulic forming simulator (“Simulator”) has been designed to investigate sheet forming processes accurately and systematically. The new machine allows precise control of several process variables. In this study, the Simulator and new scale-model fender dies have been employed for experiments to evaluate the effects of the Blank Holding Force (BHF) control in sheet forming. By the experimental approach, it has been made clear that quality defects of panels formed by stamping processes, such as wrinkles, surface distortion, and fracture, can be suppressed by increasing or decreasing the BHF during the operation. The two simple BHF control patterns, the increasing method and the decreasing method, are effective enough to improve the quality of products and are practical for industrial application.

A new technique for measuring the friction coefficient between the punch and workpiece during sheet forming operations has been developed at the Ohio State University. Various materials, such as interstitial-free (IF) steel, high strength (HS) steel, an aluminum alloy (2008T4) and 70/30 brass, were tested under dry and oil lubrication conditions at different punch rates and process conditions. The results show that punch friction depends on the angle of wrap, which varies with punch stroke, and on the strain rate, which depends on punch velocity. The O.S.U. Friction Test is described and typical results are presented which verify the usefulness of the new procedure.

Finite element modeling (FEM) can be a valuable addition to computer—integrated manufacturing(CIM) along with other kinds of analysis and representational tools such as computer—aided design(CAD), manufacturing(CAM) and engineering(CAE). A FEM program for analyzing sheet stamping operations has been developed using an explicit elastic—plastic formulation based on nonlinear membrane theory and Coulombic friction. Simulations of typical automotive stamping operations (Honda City front fender, Toyota oil pan, and Mazda RX—7 front and rear fenders) have been carried out and results presented. Single—action press operation is simulated in three stages and a linear shell program is used during the initial stage. The ability to obtain results for complex parts encourages the future use of FEM in conjunction with CAE, CAD, CAM in an interrelated CIM system.