DE3044841

A method of determining the impact fracture toughness Kid of construction materials, for example structural steels or plastic materials, without the need of performing a load measurement at the striking hammer is provided. The elastic response of the specimen to the impact process, i.e. the dynamic stress intensity factor versus time curve, KIdyn(t), is determined in pre-experiments. The shadow optical method of caustics in reflection with an appropriate high strength steel is utilized for establishing this impact response curve. The dynamic fracture toughness for a given constructional material is then determined by performing an impact experiment and measuring the time to fracture tf. KId is obtained from the measured tf-value and the pre-established impact response curve which corresponds to the experimental test conditions. The presented measuring procedure is used for determining the dynamic fracture toughness of two different steels at different test temperatures.