An evaluation technique for forming limit strains of zircaloy-4 and zirlo sheets based on FEA solutions

Abstract

In this study, we determine the forming limit strains (FLS) for zircaloy-4 and zirlo. First, we obtain true stress-strain curves for the two materials by the weighted-average method. Then we experimentally evaluate FLSs by limit dome height (LDH) tests. Theoretical forming limit curves (FLC) are obtained using regressed stress-strain relations, and it is shown that they are in a good agreement with experimental data. Further, we establish an FE model for determining FLSs. The LDHT model is used for the region between uniaxial and plane strain (ε2<0); for the section ε2≥0, we use a biaxial tensile model and apply various displacement ratios. As experimental FLSs the presumed strain obtained by Gaussian regression is taken, while as analytical FLS we take the real strain at the point of local thinning. The analytical FLSs are shown to be in a good agreement with experimental and theoretical values.