Figures

 Fig.1 Scheme for image processing analysis in the crack growth experiment.

Fig.2 (A) An example for a typical caustic set-up (B) The geometric relation of the incident light between the crack tip and screen. (C) Set-up for two set of data acquisition method.

Fig.3 image # 1 and the distribution of gray level of pixel

Fig.4 (A) Original image # 2 (B) Image # 2 after low pass filtering (C) Image # 2 after Sobel operation

Fig.5 The distribution of thickness variations obtained by image #1 processing

Fig.6 The values of stress intensity factor ( frac kg mm^3/2) vs. time (sec) obtained by image #2 processing

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