2023 Volume 62 Issue 1 Pages 169-174
The use of copper alloys with high mass density will increase with the popularization of electric vehicles. To reduce vehicle weight, high–strength alloys are developed, and the shapes of parts become more complex. As a result, sheet forming of copper alloys becomes more difficult. In the future, sheet forming analysis will be required for copper alloys as it is for general structural materials. To achieve high accuracy in sheet forming analysis, it is necessary to measure the yield surfaces under biaxial stress states. There are few studies on the measurement of yield surfaces and modeling with anisotropic yield functions for copper alloys. The authors proposed a simplified identification method for yield surfaces that does not require the use of specialized material testing equipment. The method uses uniaxial tensile, plane strain tensile, and hydraulic bulge (equibiaxial tensile) tests. The equivalence of plastic work and the associated flow rule are assumed for the yield surface identification. The yield surface can be obtained from the circumscribing polygon of the contour of equal plastic work. In this study, the yield surfaces of tough pitch copper (C1100) and 7/3 brass (C2600) sheets in different work hardening states were measured. The yield surfaces of copper and brass can be approximated by yield functions for aluminum alloys proposed by F. Barlat (Yld2000–2d and Yld2004–18p).
