Experimental determination of the dynamic fracture-initiation toughness of high-strength metals

摘要

In the case of materials that may be subjected to dynamic loads or extreme conditions, it is crucial to be aware of the evolution of their fracture behaviour with the strain rate. This study describes the detailed design and careful development of a novel experimental technique that allowed measuring the dynamic fracture-initiation toughness for a wide range of loading rates based on a strong theoretical background. For such a purpose, two high-strength metallic alloys were studied: (i) a very mild strain rate dependent alloy, the AA7017-T73, and (ii) an armour steel with well-established rate effects the Mars 240. The former was selected in order to validate the newly established experimental technique. The measured dynamic fracture-initiation toughness, as expected, gave almost identical results, therefore validating the technique. Once the technique was established, the dynamic fracture-initiation toughness of the Mars 240 steel at different loading rates was obtained. The results showed an increase on the dynamic fracture-initiation toughness with increasing loading rates.