Evaluation of Current Procedures for Dynamic Fracture-Toughness Testing

Instrumented impact test requirements for impact velocity, inertial loading, time to fracture, and frequency response were developed as a part of a large testing program sponsored by the Electric Power Research Institute (EPRI). These test procedures relied heavily on current ASTM standards plus the composite experience of investigators throughout the world. This paper provides experimental verification of the EPRI developed procedures and clarifies some of the empirical relationships used in the procedures. The material investigated was a 4340 steel (R c 52) which was relatively insensitive to loading rate. Load-time information obtained simultaneously from an instrumented tup and strain-gaged specimen was analyzed for tests performed at various impact velocities. The results indicate that the EPRI developed procedures are conservative and allow reliable fracture-toughness measurements to be made.