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In this study, a method is proposed to evaluate the stress intensity factor using isochromatics multiplied and extracted from original isochromatic images 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 intensities so that each point of the resultant image has a positive, zero or negative value. The isochromatics are then obtained as a series of points whose value is zero, which are extracted using 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 R, G and B isochromatics near the crack tip. |
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