Constraint Effects of Clad on Underclad Crack

Abstract

The finite element method is applied to two-dimensional elastic-plastic analyses for underclad crack problems. The analyses are performed for rectangular specimens with an underclad crack, which are composed of A533B class 1 steel and a clad material, to obtain the fracture mechanics parameter J-integral and the stress distribution ahead of a crack tip. The Q-factor proposed by O’Dowd and Shih is calculated from the stress distribution ahead of a crack tip, and the constraint effect of a crack tip due to a clad material or the effect of a clad material on the fracture toughness of a base material is discussed in terms of the Q-factor. Clad thickness, crack length, and the material property of a clad material are varied to examine their effects.

In-plane and out-of-plane constraint effects under pressurized thermal shocks

“…If the SIF of an assumed crack is too large this may lead to the crack initiation and in the worst case even to the failure of the RPV. The integrity of RPV has been widely studied by using one or twoparameter methods (Shum et al, 1994;Miyazaki et al, 1996;Kim et al, 2002;Qian et al, 2008;Qian and Niffenegger, 2013a,b). In order to get a more precise result, the fracture toughness from the test standards should be adjusted to different points of the crack front by considering both the in-plane and out-of-plane constraint.…”

Constraint Effect on Fracture Behavior of Underclad Crack in Reactor Pressure Vessel

“…The testing temperature for the type-A specimens was À120 C. For the type-B specimens, which had UCCs, according to Ref. [12], the expected K Jc would be higher than that for the type-A specimens because of the lower constraint effect. Therefore, the tests for the type-B specimens were performed at À130 C to obtain valid K Jc values, that is, values satisfying the ASTM standard [8].…”

“…Such a shallow crack decreases the plastic constraint at the crack tip, and the apparent K Jc for the postulated crack would be higher than that for a specimen with a deep crack. Furthermore, in terms of the effect of cladding, the plastic constraint for UCCs is lower than that for surface cracks [12]. The apparent K Jc for UCCs would be higher than that for surface cracks due to this low plastic constraint.…”