Determination of the minimum quantity of irradiated ferritic steel specimens for small punch DBTT testing

Abstract

The small punch (SP) test technique using TEM disk miniaturized specimens has been developed to evaluate the ductile-brittle transition temperature (DBTT) for irradiated ferritic structural steels. The SP tests were performed for F-82 (8Cr-2W-V), F-82H with Ta and HT-9 (12Cr-lMo-V-W) ferritic steels under consideration for demonstrating a determination procedure of specimen numbers required to evaluate the reliable DBTT shift of irradiated materials. It was shown that the temperature dependence of SP fracture energies with scatter in miniaturized testing can give reliable information on the DBTT by use of the statistical analysis based on the Weibull distribution. It has become possible to estimate the reliable DBTT and lower-bound SP fracture energy curve using the statistical analysis of the data partitioning method. The determining procedure of the minimum quantity of irradiated specimens prior to irradiated material testing has been summarized in a flow diagram.