Application of ball punch tests to evaluating fracture mode transition in ferritic steels

This paper describes an investigation of the applicability of a ball punch test to evaluating the fracture mode transition in ferritic steel specimens equivalent to transmission electron microscopy (TEM) discs. Both static and dynamic test conditions and specimens with and without several intentional defects were examined. High displacement rates (> 4 mm/s) resulted in adiabatic heating of the specimen during testing. Smooth specimens were found to provide more reproducible and useful data than specimens containing holes and gooves. A good correlation was found between the absorbed energy beyond maximum load and fracture mode transition, with the later characterized by either fracture appearance or Charpy impact energy. (orig.)