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Recent advances in press and die building have provided the capability of restraining force (RF) variation during a sheet stamping stroke. Even though the commercial presses with VRF capabilities are now available, the full benefits cannot be attained because, for complex industrial stampings, it is difficult to select the VRF trajectory which will improve the stamping quality or achieve even more complex task of arriving at the desired design target. In this paper we demonstrate how numerical modeling can be used to select a proper VRF trajectory to achieve a postulated design target. The working numerical model using explicit LS-Dyna 3D code was successfully developed for time effective simulation of complex parts with variable binder force. Three case studies with the specific design targets of 1) springback, 2) punch force, and 3) maximum strain are presented and discussed. The results show strong nonlinear influence.

Robust operating window and subsequent quality of part are major concerns during sheet metal stamping. For a given part geometry, material, and lubrication conditions, the sheet restraining force is the key parameter controlling metal flow, thus influencing formability and quality of the resulting part. Recent advances in press and die building provide capability of the restraining force (RF) variation during a stamping stroke. In this study, a laboratory and numerical experiments were performed in an effort to better understand the effect of various VRF trajectories on stamping performance. The working numerical model using explicit LS-Dyna 3D code was successfully developed for time effective simulation of complex parts with variable binder force. Several trajectories are proposed and tested, showing strong nonlinear influence. This indicates the need for predictive approaches capable of establishing robust and optimal trajectories for individual complex industrial stamping designs.