Anisotropic creep modeling based on elastic projection operators

Abstract

The paper presents a unified approach for creep modeling of anisotropic materials, and is specified in more detail to the cases of isotropy, cubic symmetry and transversal isotropy. Thereby an additive decomposition of the elastic and inelastic strain tensors into dilational and isochoric Kelvin modes is assumed. Each of these modes is obtained from fourth order projection operators, resulting from solution of the eigenvalue problem for the fourth order anisotropic elasticity tensor. For simplicity the amount of strain rate for each mode is determined with a Norton type ansatz in terms of an equivalent stress, and the experimental phenomenon of primary creep is taken into account by a back stress tensor of Armstrong-Frederick type, which is also decompose into Kelvin modes. Two numerical creep simulations investigate the crystal orientation for a compact tension specimen made out of CMSX-4 superalloy.