21/4Cr-1 Mo鋼のクリープき裂成長挙動の評価

抄録

Creep crack growth behavior of 21/4 Cr-1 Mo steel at 550°C was investigated by energy rate line integral, C^* under conventional constant load control and deflection rate control. The same relationship of da/dt versus C^*-integral was obtained by both of the control methods. The increasing deflection rate control test proposed in this paper was found to be a very efficient method because a wide range of creep crack growth data can be obtained stably on a single specimen. Various formulae to experimentally determine C^*-integral of CT specimens were compared. Equation (3) considering the axial force as well as the bending effect agreed with the analytical results by the finite element method in the range of a/W≥0.5.
The result of C^*-integral estimation using the fully plastic solution, agreed with the experimental results in steady state creep conditions, when the plane strain solution was applied. Although the C^*-integral approach with the fully plastic solution seems prospective for practical creep crack growth prediction, more investigations are needed under various conditions.