Effect of specimen geometry on Charpy impact test results for ferritic steel irradiated in JMTR

In order to develop the small-scale specimen technology in Charpy impact testing for ferritic steels, the effects of specimen size and notch geometry on the upper shelf energy (USE) and ductile-to-brittle transition temperature (DBTT) were investigated for Japanese Ferrite/Martensite Dual Phase Steel (JFMS). Miniaturized specimens with different sizes and notch geometry, together with full size specimens, were irradiated to 3x1022 n/m2 in the Japan Materials Testing Reactor (JMTR) and were Charpy impact tested. The USE for miniaturized specimens, normalized by Bb2 or (Bb)3/2 (B is the specimen thickness, b the ligament size), was essentially independent of specimen size and notch geometry and decreased by the irradiation, but the decrease was larger in full size specimens than in miniaturized specimens; the normalized USE for miniaturized specimens was distinctly higher than that for full size specimens. The DBTT of miniaturized specimens was strongly dependent on notch geometry, but its dependence decreased as compared with that for unirradiated JFMS. It is shown that these results may be useful in determining the USE and DBTT for full size specimens from those for miniaturized specimens. (author)