Determination of Stress Intensity Factors of a Three-Dimensional Surface Crack by the Caustics and Photoelastic Methods

In fracture problems, stress intensity factors obtained theoretically or by experimental analysis have been effectively utilized in analytical evaluation of the effect of cracks. Use of the caustics method to determine the stress intensity factors of two-dimensional cracks has been established theoretically and experimentally. However, relatively few experimental analysis concerning the three-dimensional crack by using caustics method have so far been conducted. In this paper, the distributions of stress intensity factors along the crack front of a three-dimensional elastic solid have been determined by using the method of reflected caustics in combination with the photoelastic stress freezing method. In order to make a comparison between two experimental results for stress intensity factors determined by the caustics and photoelasticity, two kinds of experimental models with three -dimensional surface cracks were used. There was satisfactory agreement between the results of two methods.