Evaluation of dynamic crack initiation and growth toughness by computer aided Charpy impact testing system

The validity of the newly developed CAI system (Computer Aided Instrumented Charpy Impact Testing System) for the evaluation of the dynamic elastic-fracture toughness parameters, i.e. the dynamic crack initiation toughness (KId, JId) and growth toughness (JR curve, tearing modulus: Tmat) was investigated in various materials (SS41 steel, HT80 steel and ASTM A533 Grade B Class 2 steel for the reactor pressure vessel. Ductile cast iron (DCI), 7075 aluminum alloy and Ti-6Al-2Sn-4Zr-6Mo alloy were also partially used). The dynamic elastic-plastic fracture toughness parameters (JId and Tmat) values in various materials could be easily obtained from the single load-deflection curve of the precracked specimen using the CAI system. The introduction of the side grooves was found to be effective to obtain the valid JId value using the standard size Charpy specimen. In addition, the strain rate dependency of the specimen compliance (Cs), and the effect of the specimen size on Jd value and impact velocity on the geometry of the load-deflection curve were studied. (orig./HP)