A method is developed for the simplified evaluation of multiple cracks, based on the d.c. potential drop technique. A subregion containing cracks is considered. The distribution of the potential drop for the cracks except for end cracks in the subregion is measured and calculated numerically by assuming a value for the depths of the end cracks and by assuming any value for the depths of other cracks. Modifying the depths of the other cracks is repeated until the difference between measured and calculated potential drops is minimized, where the depths of the end cracks are fixed. Evaluation of the centre crack in the subregion is made for different assumed depths of the end cracks. To make the evaluation independent of the depths of the end cracks, a subregion is extended to increase successively the number of cracks considered. Multiple cracks are sized well enough by this method.
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