Rupture life of materials obeying exponential and power law creep.

Based on the void growth and damage mechanics, the rupture time tr is derived as a function of the creep exponent n and the reference stress σo and the corresponding time to, for materials obeying exponential and power law creep. The analysis is extended to obtain parameters for prediction of long time behaviour. For materials which obey a simple power law creep, the parameter is shown as P=log tr+(n- nr)log(1-Dc) and for materials which obey an exponential function the parameter is given as P=log tr+(nr-n) Dc where nr is the reference creep exponent and Dc is the critical size of the void at fracture, which is related to the applied stress σ as Dc=1-σ/σo