Abstract

Small Punch (SP) test is one of the miniature test methods, which is a quasi-destructive testing method that evaluates the mechanical properties from limited volumes of materials. Structural materials in nuclear power plants experience degradation in the neutron irradiation environment during the operation, and this aging is assessed by measuring the Charpy index temperature shift of materials at 41J (T41J). However, there are many difficulties in deriving T41J or the fracture toughness from the SP test due to the difference in the failure mode between the SP tests and the conventional Charpy impact and fracture toughness tests. In this study, a method to predict the index temperature at 41J by using the key parameters obtained from SP load-displacement curve was proposed. T41J prediction methods using the fracture energy and displacement after the maximum load in SP test were proposed, and an analysis of the correlation between the key parameters of SP test and the fracture toughness values was performed. As a result of applying displacement after the maximum load parameter of SP curve, it showed better prediction than the fracture energy parameter, and the fracture mode in transition curve of SP was consistent with that of Charpy impact test.

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