SIZE EFFECTS ON THE UPPER SHELF ENERGY OF A NEUTRON-IRRADIATED PRESSURE-VESSEL WELD METAL

The methodologies published earlier for predicting the upper shelf ene rgy (USE) of full size Charpy specimens based on subsize test data app ear to work satisfactorily for either highly ductile materials (USE > 200 J) or relatively brittle materials (USE << 100 J). A methodology i s proposed here that works well for pressure vessel weld materials in both unirradiated and irradiated conditions having USE in the intermed iate region (100 J < USE < 200 J). The methodology uses partitioning o f the USE into two components, USE(p) and Delta USE (= USE - USE(p)). USE(p) is the absorbed energy for a specimen fatigue-precracked to hal f the width. The predicted value of the USE of full-size specimens is a sum of two terms. The first term is equal to the product of the norm alized Delta USE of the subsize specimen and the full-size normalizati on factor for Delta USE. The second term is equal to the product of th e normalized USE(p) of the subsize specimen and the fracture volume of the full-size precracked specimen. The predicted values were within a bout 10% of the measured values for both unirradiated and irradiated m aterials.