Photoelastic Method for Determination of Mixed-mode Stress-intensity Factors
用光弹性法测定复合应力强度因子

In engineering structures, it is difficult to determine stress-intensity factor at crack tip with analytic method and sometime also difficult with numerical method because of complexity of shape and load as well as no determinability of boundary condition. However photoelastic method remedies these deficiencies. In this paper, a cylindrical bar was made with epoxy resin, a crack in the cylindrical bar model was prepared with mechanic process, and the stress was frozen after loading the model. Photoelastic method was used to analyze stress distribution around the crack tip of the cylindrical bar. When a cylindrical bar with cyclical crack is subjected to bending and torsion, the crack top far away from the median axis of the cross section is in a situation of mixed-crack. The three-dimensional photoelastic stress-frozen method is an effective method for determination of complex threedimensional question. In this paper, the two-parameter method was used for determination of I mode stress-intensity factor and a slice cutting step-by-step method was used for determination of HI mode stress-intensity factor. The error of results is small.