An Analysis of Drawbeads in Sheet Metal Forming: Part II—Experimental Verification

This paper presents experimental results obtained for a variety of drawbeads typical of automotive applications, and compares the results with those obtained from the numerical model presented in the first part of this work (Triantafyllidis et al., 1986). The deformation process is divided into two phases: the “locking/clamping” phase as the binder closes to form the sheet around the drawbead, and the “pulling” phase as the panel is formed, causing the material to be drawn through the bead. Metals considered are SKDQ steel, aluminum, and brass. Dry and lubricated conditions are investigated. Good correlations between model and experiment are obtained for strain distributions over the sheet and excellent agreement is observed in the binder clamping forces. Using a Coulomb friction law in the model, horizontal restraining forces are compared to experimental results. The model is shown to accurately predict the influence of variations in material, geometry, and friction conditions. However, the correlation between the model and experiment is not as good in two cases: as the punch (male bead) reaches the “locked” condition, and in the initial stages of “pulling” deformation. Reasons for the discrepancies are discussed.