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In this paper, an adaptive strain methodology is developed for experimental strain measurement in sheet metal panels. The principle involves etching uniform small square grids on the panel, and measuring strains adaptively from deformations of large squares comprising of many smaller grids. The methodology uses FEA predicted strains as input and accounts for the experimental noise. The methodology overcomes the inability of the existing practice to simultaneously measure both low and high strain features, and in addition, saves considerable measurement time. The methodology is simple and can be easily integrated with automated strain measurement systems. The algorithm is distinguished for plane strain or radial symmetric panels whose strains vary along 1D (one dimension) and for other panel types whose strains vary along 2D (x and y). Correspondingly, the adaptive methodology is demonstrated for a hemispherical punch stretched and a box drawn panel.

In recent years the use of tailor-welded blanks (TWB) has grown significantly, but there still exists serious concern on the poor formability in the stamping of TWB, which is commonly considered to relate to the uncertainty in the weld line movement. This paper proposes a drawbead design methodology to achieve weld line movement control. Based on the properties, geometries and frictions of base-metals constituting the TWB, the magnitudes and ratio of drawbead restraining force (DBRF) between the two sides of the base metal sheets across the weld line, which is the function of drawbead depth, can be determined for minimizing the weld-line movement and enhancing TWB formability. In the case of 2D strip drawing with TWB, lower restraining force should be used in the side of thicker base metal to reduce weld line movement.