An Experimental and Analytical Study on the Limit Drawing Ratio of Stainless Steel 304 Foils for Microsheet Forming

A series of micro-deep drawing experiments were conducted on stainless steel 304 foils with four thicknesses that were heat treated at four different temperatures. Due to heat treatments, a variety of different grain sizes and T/D ratios (the number of grains throughout thickness) were obtained. In this study, the limit drawing rations (LDR) of these foils were obtained; it has also been found that the factors that influence LRD of the foils include, but are not limited to, thickness, grain size, and T/D ratios. Tensile tests were conducted to obtain their mechanical properties that were used for two macroempirical equations to predict the maximum drawing load and LDR. It has been verified that the two equations can be applied to foils that are not thinner than 150 mu m for reasonable predictions. However, the size effects are more noticeable and significant for the foils that are less than or equal to 100 mu m so that the macroscale empirical equations cannot be applied to them.