Sensitivity of Forming Process to Variation of Material and Process Parameters

The robust operating window is a major problem during sheet stamping, but existing practical experience concerning process sensitivity is approximate and qualitative only. In this study, sensitivities of strain, punch force, and draw-in to the process and material parameters were calculated for a given part geometry. To ilustrate the influence and relative importance of n-value, anisotropy, friction, and restraining force selected results are presented, compared, and discussed. It was found that strain is the most sensitive, while punch force is least responsive. The restraining force has the strongest influence, and friction is relatively less important. Sensitivity responses are highly nonlinear, thus not allowing for extrapolation or generalization. The sensitivity calculations were performed following a proposed methodology, based on virtual experiments (numerical simulation). It allows variation of one selected parameter only, and keeps project time and cost lower. The methodology provided and the quantitative insight into complex stamping sensitivities can be useful while designing for new geometries, processes, and materials.