Characterization of anisotropy in sheet metals using digital image correlation

Abstract

This study develops and applies an in house two-dimensional digital image correlation (2D-DIC) system to investigate the anisotropic behavior of sheet metals under uniaxial tensile loading. Two materials, SUS304 stainless steel and DP1200 dual-phase steel, were examined. Tensile specimens were prepared along three orientations with respect to the rolling direction: rolling direction (RD), diagonal direction (DD), and transverse direction (TD), and the tests were performed in accordance with ISO 6892-1. The DIC method provided full-field displacement and strain measurements on the specimen surface, enabling the determination of stress-strain curves, Lankford coefficients, normalized yield stresses, and yield surface characteristics. The results show that SUS304 exhibits high ductility, strong strain hardening capacity, and more pronounced planar anisotropy than DP1200. In contrast, DP1200 shows higher tensile strength but lower elongation, and its Lankford coefficients and normalized yield stresses are closer to isotropic behavior. Comparison of the yield criteria indicates that Hill48 represents the anisotropic response more accurately than the von Mises criterion. Hill48-R agrees better with the experimental Lankford coefficients, whereas Hill48-S more accurately describes the normalized yield stresses.