Title: Application of the Method of Caustics to the Stress-freezing Technique
Abstract: The caustic method is a very powerful technique for measuring the value of the stress-intensity factor. The caustic pattern, however, cannot be obtained in the frozen-stress models in the immersion fluid by the conventional caustics technique. The reason for this phenomenon is studied by using the individual values of the optical constants. It is shown that the optical constants of the frozen-stress model, which determine the shape of the caustic pattern, have very different aspects from those at room temperature. The caustic pattern in the frozen-stress model is theoretically calculated by using those optical constants and it is also confirmed experimentally. Some practical techniques to apply the caustic method to such a frozen-stress model are shown.