Construction of J-Q Locus for Material of Reactor Pressure Vessel WWER 440 in the Ductile-Brittle Transition Region

In the paper effect of shallow crack (in-plane constraint) on fracture toughness of reactor pressure vessel WWER 440 is examined, using two-parameter fracture mechanics approach. For this purpose, experimental tests were performed on 18 specimens of SEN(B) type and 18 specimens of SEN(T) type, for three relative crack depths a/W = 0.09, 0.16 (0.17), 0.5, for each type of loading. The tests were performed at the temperature near reference temperature To determined according to Master Curve concept, in the ductile- brittle transition region. Based on 2D and 3D FE calculations, values of two fracture parameters J and Q were determined. Due to different forms of stress fields found for the two types of loading, the Q-parameter was examined for different values of normalized distance from crack front, i.e. r.σo J= 2,4, 6, 8 and 10. Based on a reasonable criterion, the J-Q locus for the examined steel was suggested. Besides of this, also the shift of Master Curve reference temperature due to shallow crack effect was examined and compared with similar results valid for steel A533B