Size effects on the upper shelf energy of a neutron irradiated pressure vessel weld metal

Abstract

The methodologies published earlier for predicting the upper shelf energy (USE) of full size Charpy specimens based on subsize test data appear to work satisfactorily for either highly materials (USE > 200 J) or relatively brittle materials (USE ≪ 100 J). A methodology is proposed here that works well for pressure vessel weld materials in both unirradiated and irradiated conditions having USE in the intermediate region (100 J < USE < 200 J). The methodology uses partitioning of the USE into two components, USE p and δUSE ( = USE - USE p). USE p is the absorbed energy for a specimen fatigue-precracked to half the width. The predicted value of the USE of full-size specimens is a sum of two terms. The first term is equal to product of the normalized δUSE of the subsize specimen and the full-size normalization factor for δUSE. The second term is equal to the product of the normalized USE p of the subsize specimen and the fracture volume of the full-size precracked specimen. The predicted values were within about 10% of the measured values for both unirradiated and irradiated materials.