LAUSR

Abstract In this study, the relationship between surface topography and strain was established for annealed 0.2 mm thick AISI 304 stainless steel sheet that had been hydroformed. The effect of the die diameter on the surface topography was also examined. Sheets were bulged using stepwise application of hydraulic pressure; forcing the sheet metal through 5 mm and 11 mm diameter open dies. The strains at the pole of the bulge of the work pieces were determined analytically using the Jovane analytical method, this was achieved by measuring the height of the pole of the bulge for every applied hydraulic pressure for a particular die. The surface topography at the micro level was found by scanning the bulge of the sample using an atomic force microscope over an area of 60 μm × 60 μm. The results of this study indicate that the bearing ratio was unaffected by the change in strain for both the 5 mm die and the 11-mm diameter dies and that roughness decreases as the diameter decreases for similar strains. The average, root mean square, peak-to-peak roughness and the maximum depth of the surface profile show a linear relationship with the strain