TENSOR CONSTITUTIVE-EQUATIONS FOR DESCRIP TION OF ANISOTROPIC CREEP-BEHAVIOR OF ISOTROPIC MATERIALS FOLLOWING PLASTIC PRESTRAIN

Plastic prestrain can produce anisotropy in materials which are initia lly isotropic. This anisotropy strongly influences the creep behaviour of such materials. Non-linear constitutive equations with two argumen t tensors for the secondary creep behaviour are proposed, based on the representation theory of tensor functions. For practical applications , a simplified theory is presented in which a second order tensor as a n additional argument tensor describing plastic predeformation as a fu nction of different plastic prestrain paths. A few experimental tests have been carried out on the material INCONEL 617 (cf. Section 6) to v erify the theoretical approach.