On the creep rupture life prediction

Combined effects of stress, sigma(A), and fracture cavitation on the creep ru ptu re life, t(R), have been studied in conventionally cast MAR-M 002 al loy tested at 1173 K (900 degrees C) over a limited range of stress (sigma( A) = 200-400 MPa). It is predicted that the creep fracture cavity growth is controlled by the coupled power-law creep with the grain-boundary diffusio n mechanism. On the basis of this prediction the Edward-Ashby model overest imates the creep rupture life although this model correctly describes the t rend in the data. The observation of a linearity between the cavity density , N-A and the epsilon(R)t(R)sigma(A)(4) indicates that this relationship ca n be used to predict the creep time, t(R), where epsilon(R) is the rupture strain. Furthermore, another empirical method is the creep-fracture paramet er, K-f = sigma(f)(pi a(c))(1/2), approach, developed using the modified Gr iffith-lrwin type of relationship, which can also be used to predict the cr eep rupture life in the present alloy, where of is the creep fracture stres s (or the applied stress, sigma(A)) and a(c) the crack (or cavity) size. (C ) 1998 Kluwer Academic Publishers.