Material Induced Anisotropic Damage

The anisotropy in damage can be driven by two different phenomena; anisotropic defor-mation state named Load Induced Anisotropic Damage (LIAD) and anisotropic (shape and/or distribution) second phase particles named Material Induced Anisotropic Damage (MIAD). Most anisotropic damage models are based on LIAD. This work puts emphasis on the presence of MIAD in DP600 steel. Scanning Electron Microscopic (SEM) analysis was carried out on undeformed and deformed tensile specimens. The martensite morphology showed anisotropy in size and orientation. Consequently, significant MIAD was observed in the deformed tensile specimens. A through thickness shear failure is observed in the tensile specimen, which is pulled along the rolling direction (RD), whereas a dominant ductile fracture is observed when pulled perpendicular to RD. The Modified Lemaitre’s (ML) anisotropic damage model is improved to account for MIAD in a phenomenological manner. The MIAD parameters are determined from tensile tests carried out in 0o, 45o and 90o to the RD. The formability of DP600 is lower in the RD compared to that in 90o to the RD, due to the phenomenon of MIAD.