MEASURING FRACTURE TOUGHNESS WITH A CHEVRON-NOTCHED CRACK-ARREST SPECIMEN

Initiation toughness K sub Ic and arrest toughness K sub Ia are important properties because of their value for predicting structural performance in a fracture mechanics analysis. However, the current ASTM standard procedures for measuring K sub Ic (E399) and K sub Ia (E1221) specify tests that are difficult to conduct and prone to failure for mild steels employed in nuclear reactor applications. This research focused on the development of a modified specimen and test procedure intended to improve on the current standards. The chevron-notched crack-arrest (CNCA) specimen is a hybrid design that is 25 percent smaller than the specimen prescribed in E1221. Preliminary experiments employing the CNCA specimen were performed at room temperature (23 deg C) with A533-B reactor grade steel. The success rate was 100 percent for arrest tests and 75 percent for reinitiation experiments.