Constitutive description of creep curves based on internal stress evolution

A constitutive description of creep curves is derived from the time evolution of the internal stress in creep determined by means of strain transient dip test technique and from the kinetic equation between this stress and the instantaneous creep rate. Several constitutive equations have been tested on creep curves of aluminium. It is shown that fitting of the curves and its statistical judgement cannot be used as the only criterion for an investigation of the evolution and role of the internal stress in creep. Such procedure must be completed by another independent procedure. As an appropriate procedure, the measurement of the internal stress in the steady state creep has been successfully applied.