The Relative Importance of Creep Hardening, Softening, and Damage in the Determination of Creep Failure Using a Monkman–Grant-Type Relation Derived Within the 4-θ Methodology
摘要
An analysis of minimum creep rates vs. time to failure is a suggested approach to the evaluation of long-term creep rupture. But this requires constancy of this relation over all test conditions. This paper therefore used the 4-θ methodology to study in more detail the role of creep mechanisms in determining the nature of this relationship and from this, the stability of the relationship. It was found that the Monkman–Grant constant depended negatively on the rate of damage accumulation, the initial strain rate, and the rate of hardening, but positively on the strain at failure. It was also found that at 833 K and a high stress, θ4 was the major determinant of failure times. But as the stress level fell, the parameters θ3 and θ1 become more important. The growing importance of θ3 with decreasing stress implies a bigger role for damage accumulation with decreasing stress (as