Austenitic stainless steels (SSs) are widely used structural materials in fast reactors. Owing to the high toughness of austenitic SSs, measurement of their fracture toughness requires the use of elastic-plastic methods [1,2]. Though, for very accurate evaluation of toughness, precracked and large size specimens are necessary, there is continuing interest and effort in obtaining conservative estimates of Jid (dynamic fracture (initiation) toughness) or JR (J fracture resistance) curves using small and blunt notched specimens, particularly Charpy V-notch (CVN) specimens [2-4]. These methods, when validated, will be useful not only for quality control purposes, but even for conservative engineering design. In this paper, instrumented impact test results obtained at room temperature from CVN and precracked CVN (PCVN) specimens of AISI 316 SS in various aging and cold-work (CW) conditions are reported. JR curves obtained for CVN and PCVN specimens by keycurve procedure [2] are compared with each other and with those obtained using the procedure proposed by Schindler [4]. A new (shift) procedure is suggested for obtaining JR curves from unprecracked CVN specimens. This seems to be promising, but its range of validity and applicability needs further validation and verification by tests on materials with different toughness levels. 2. MATERIAL AND EXPERIMENTAL DETAILS Material tested was AISI 316 SS in the solution-treated (ST), ST + 1073 K/50 h aged (H5), ST + 1073 K/1008 h aged (H8), ST + 20% cold-work (CW) and CW + double age (GT) conditions (see [3] for full details). Initial crack aspect ratio (a/W, where a is the crack length and W is the specimen width) varied from 0.2 (CVN) to 0.8. The CVN and PCVN specimens were tested at room temperature on a 358 J capacity Tinius Olsen Model 74 instrumented impact machine. Full details of the material, precracking, test and data reduction procedure are reported elsewhere [2,3]. All tests reported here were done at the maximum impact machine velocity, V0 = 5.12 m.s -1. 3. JR CURVE REDUCTION PROCEDURES 3.1. Key-curve and Shift Methods The JR curves are obtained from the test records of both CVN and PCVN specimens using the power-law key-curve procedure described by Sreenivasan et al. [2] . The JR curve obtained from CVN specimen is much higher than the PCVN-JR curve (which is mostly conservative and most likely to approximate the true material property). Hence, in this, the JR curves obtained using (unprecracked) CVN specimens are referred to as pseudo-JR curves. However, the key-curve JR curves from CVN and PCVN specimens seemed to show similar slopes [2]. This suggests the possibility that the PCVN-JR curves can be obtained by applying a suitable scaling or translation to the pseudo-JR curves (shift method). This aspect is explored in this paper.
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