Circular Grid System — A Valuable Aid for Evaluating Sheet Metal Formability

The circular grid system, in which a pattern of 0.05-0.25 in. diameter circles electrochemically marked on sheet specimens is used, permits a visual display of the magnitude and direction of the strain from point-to-point of a stamping. Strain values obtained from the grid are plotted relative to an empirical failure curve to indicate proximity of a stamping to failure. Analysis of the strain distribution allows one to reduce the die tryout period, assist in establishing material specifications, evaluate die modifications, and monitor die variables throughout production runs.