A Constitutive Model of Creep Describing Creep Recovery and Material Softening Caused by Stress Reversals

The constitutive model of creep proposed by the present authors on the basis of a creep-hardening surface in creep strain space (CHS model) is first modified to incorporate creep recovery. It is assumed that total creep strain can be divided into two parts; i.e., a part which recovers anelastically after stress removal and an irrecoverable part. These two parts are described by McVetty’s equation and the CHS model, respectively. Then, the validities of the modified and the original CHS model are discussed by performing creep tests of type 304 stainless steel under cyclic reversed torsion combined with constant tension at 600°C.