A method is developed to evaluate nondestructively multiple cracks on the surface of materials. The method is based on the d.c. potential drop technique. Multiple two-dimensional cracks of unknown depth are inspected, where the distance between the cracks is known. First the distribution of the potential drop between both sides of each crack is measured on the cracked surface. Next the distribution of the potential drop is calculated numerically by assuming the depth of every crack. Then by comparing the measured and calculated potential drop, a correction factor is obtained for the assumed depth of the respective cracks. Modifying the crack depth by the correction factor is repeated until the difference between the measured and calculated distributions of the potential drop is minimized. It is shown that multiple cracks are sized accurately by the present method.
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