CONSTITUTIVE DESCRIPTION OF CREEP CURVES BASED ON INTERNAL-STRESS EVOLUTION

A constitutive description of creep curves is derived from the time ev olution of the internal stress in creep determined by means of strain transient dip test technique and from the kinetic equation between thi s stress and the instantaneous creep rate. Several constitutive equati ons have been tested on creep curves of aluminium. It is shown that fi tting of the curves and its statistical judgement cannot be used as th e 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 o f the internal stress in the steady state creep has been successfully applied.