Yield loci of anisotropic sheet metals

Abstract

Four sheet metals, having quite different combinations of R-values and strain-hardening behavior were tested in uniaxial tension, uniaxial (through thickness) compression, balanced biaxial tension (bulge test), and plane-strain compression. The results were compared with predictions based upon three different anisotropic yield criteria. Although no single yield criterion proved to describe adequately all of the test results, different criteria provided the best agreement with particular metals. Results from through-thickness compression and bulge tests were nearly identical.In bulge testing, strains were determined from photographs of printed grids while the radius of curvature at the top of the dome was obtained using a projected fringe technique that involved a holographic grating. Radii measured by this technique were smaller for all materials than those measured by the conventional spherometer.