Abstract
Caustic method is an optical method to measure the stress intensity factor of cracks. The method is widely used by the researchers of fracture mechanics, since it has three advantages. The first advantage is the simple optical system. Usually one doesn't need to use a laser as a light source. The second is that the higher-order terms of the stress field near crack tips don't much affect the stress intensity factors measured by caustic method. The last is that the caustic method can be applied easily to measure the dynamic stress intensity factor of fast propagating cracks, because it is an optical method. However, one often needs to develop new techniques when he or she applies the caustic method to dynamic fracture phenomena. The present article describes the holographic caustic method that can record and reconstruct caustic beams of fast propagating cracks at the instant of dynamic fracture. The holographic caustic method makes it possible to figure out the stress field near the tips of fast propagating cracks.
