X-ray microtomography has been utilized for the observation of crack initiation and growth in a high-strength aluminum alloy. Procedures for evaluating local crack-driving forces such as J and CTOD, which were developed by the present authors, have been applied to analyze localized crack initiation and growth behaviors. The former is realized by tracking microstructural features that are located in tomographic imaged in high density. The latter is directly measured in 3D images. In order to raise the accuracy of the microstructural tracking technique, a trajectory prediction technique has been introduced, thereby substantial improvement in the ratio of tracked markers has been realized. Extensive formation of micro cracks ahead of a crack tip has been observed, being followed by premature crack initiation and growth. It has been clarified that the micro cracking occurs far beyond (more than 10 times) a large strain region that has been predicted in the conventional fracture mechanics. The current methods could offer a highly effective way of assessing such 3D local fracture behavior quantitatively.
All Science Journal Classification (ASJC) codes