Evaluation of stress intensity factor using white light photoelastic experiment

In this study, a method was proposed for evaluating the stress intensity factor using the isochromatics multiplied and extracted from original isochromatic images which obtained from a white light photoelastic experiment. This method utilizes R, G and B isochromatics, which are captured using a color CCD camera and an;image processor in dark- and light-field circular polariscopes. First, for each color, the dark-field intensities are subtracted from the light-field ones so that each point of the resultant image has a positive, zero or negative value. Then, the isochromatics are obtained as a series of points at which the value is zero, which are extracted using an image processing. The fringe orders are assigned to the extracted isochromatics using calibration curves. The stress intensity factor is determined using the Irwin method. This method is applied to an epoxy resin plate with a crack formed at one side under 3-point bending. The result shows that the stress intensity factor is accurately evaluated using the R, G and B isochromatics near the crack tip.