1994 Volume 80 Issue 4 Pages 336-341
Long term creep rupture life has been estimated from short term data by the extrapolation based of the timetemperature parameter (TTP) methods. This work aims at discussing causes of the extrapolation error. Temperature dependence of rupture life can change at longer lives due to the change in fracture mechanism. The present forms of TTP, however, do not take the change into account, and this disregard is responsible for the extrapolation error. When the change occurs, one cannot correctly extrapolate rupture life even less than three times the longest test duration.On the other hand, rupture life can be extrapolated more than ten times without introducing a serious error when thechange is absent. The change in temperature dependence also influences the direction of deviation from true values.The extrapolation provides a conservative estimate when the temperature dependence of rupture life increases at longer lives, whereas it gives a nonconservative estimate when the dependence decreases.
