Abstract
Pulse holographic microscopy is applied to take photographs of a rapidly bifurcating crack in PMMA plate specimen. Two photographs are taken simultaneously on both surfaces of the specimen. Crack opening displacement, COD, is measured along the two branch cracks as well as the mother crack. The two branch cracks are through cracks and have the same CODs on the both surfaces of the specimen. One of the two branch cracks has COD that is proportional to square root of the distance r from the crack tip, consequently, the COD gives the energy release rate of the branch crack. The total energy release rate of the bifurcating crack can be given by COD of the mother crack. It is found that the two branch cracks have energy release rate of 56% and 44% of the total energy release rate, respectively.
