DETERMINATION OF J-Q LOCUS AND SHIFT OF T0 FOR FOUR RPV MATERIALS

摘要

The subject of this paper is evaluation of loss of constraint for three types of specimens: Pre-cracked Charpy V-notch specimens with deep crack, pre-cracked Charpy V-notch specimens with shallow crack and small cruciform specimens. This task was solved by UJV Rez a.s. within work package WP1.1 "Fracture properties" of PERFORM60 project in 2013. The approach used for solution of this task consisted in application of two-parametric fracture mechanics, in particular, J-Q locus. J-Q locus diagrams were constructed for four RPV materials/material conditions: (1) 20MnMoNi5 5 base metal in irradiated condition, (2) S3NiMol/OP41 TT weld metal in irradiated condition, (3) 22NiMoCr3 7 base metal in unirradiated condition, and (4) 22NiMoCr3 7 base metal in irradiated condition. For each material and each type of specimen, based on Q-parameter value at general yielding, the value of T-stress was estimated and based on this T-stress value, the relative shift of Master Curve reference temperature, AT_0, due to shallow crack effect and/or biaxial loading effect was predicted. The predicted relative shifts of T_0 (with respect to T_0 obtained for pre-cracked Charpy V-notch specimens with deep crack) were then compared with the corresponding relative T_0-shifts determined from experiments in a standard way (without using Q-parameter). In some cases, a very good accordance was found, and in other cases, where the difference was larger, the predicted relative shifts of T_0 were conservative.