The link between creep rupture and creep crack growth for a power-law creeping material: A monkman-grant analogue

Abstract

Engineering materials under small loads at ambient temperatures creep and ultimately rapture by the nucleation growth and inter-linkage of creep cavities along grain boundaries. Cavities are generally observed on grain boundaries normal to the stress axis, and mechanisms of cavity nucleation and growth have direct consequences on creep rupture (CR) properties. Often, by studying the rupture time (t[sub j]), and its stress and temperature (T) dependencies, information on the cavitation mechanisms can be deduced. Within the similar temperature and stress ranges, a crack usually propagates by the nucleation and growth of creep cavities ahead of the crack tip, and the creep crack growth (CCG) rates are directly related to the mechanisms of cavity nucleation and growth under crack tip stresses. Therefore, attempts were made to correlate the crack velocity (v) with the load parameters, such as the stress intensity factor (K[sub I]) or C integral, which characterize the crack tip stress and strain fields in elastic and power-law creeping materials, respectively. If CR and CCG proceed ;by the same mechanisms of cavity nucleation and growth for a given material, a link between the two phenomena is expected because CCG is equivalent to the successive CR of crack tip ligaments. Inmore » the present paper, within the framework of quasi-equilibrium cavity growth and crack growth under extensive creep conditions, a link between the two phenomena is sought for a power-law creeping material, then its meaning and potential applications are discussed.« less