Measurement of Fracture Toughness for Brittle Materials under Mixed-Mode Impact Loading Using Center-Notched Disk Specimen
Yoshiaki YAMAUCHI, Motohiro NAKANO, Keizo KISHIDA and Tatsuya OKABE
Abstract:An impact fracture test method has been developed to measure fracture toughness under mixed mode I/II loading using a center-notched disk specimen. The test is executed in such a way that diametrical impact load are applied to the specimen, which is set with the crack inclining toward the direction of loading at a definite angle. Time variation of the energy release rate is accurately evaluated by the convolution integral of the dynamic response function for the cracked disk. Dynamic and quasi-static tests were performed and fracture toughness for brittle materials was measured. The results indicated that the dynamic fracture toughness for the present brittle materials was not lower than the static one under pure mode I/II and mixed-mode loading. Comparing the results with some representative criteria, it was found that these criteria were not suited to interpret the fracture under mixed-mode loading in the present brittle materials. Key Words:Fracture toughness, Impact fracture, Mixed-mode loading, Brittle materials, Alumina ceramics, Graphite, Glass, Finite element method