Adaptive Strain Measurement for Sheet Metal Stampings

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.