Determination of the dynamic fracture toughness using a new stress pulse loading method

Abstract This paper presents a method for the determination of the dynamic fracture toughness K Id of metallic materials at loading rates K I of about 2×10 6 MPa m 1 2 /s . The method is derived from the known split Hopkinson pressure bar technique and uses a well-defined stress pulse for the loading of a fatigue precracked specimen. The interpretation of the experimental data is strictly based on a numerical analysis of the specimen under the given dynamic loading conditions. It is shown, that a conventional quasi-static approach would yield incorrect fracture toughness values. The results for some steels confirm, that the fracture toughness decreases with increasing loading rate. Therefore, in some sense the fracture toughness versus temperature curve determined with the presented stress pulse method can be regarded as lower bound curve.