NDE OF A CRACK BY USING CLOSELY COUPLED PROBES FOR DCPD TECHNIQUE

In order to enhance the sensitivity of the d-c potential drop techniqu e, the principle of a technique using the closely coupled probes is pr oposed. A calibration equation for this technique is derived, where th e path-independent integral j(e) for electric crack problems is utiliz ed. Experiments on laboratory specimens are discussed which validate t he use of the calibration equation for the nondestructive evaluation o f cracks. It is shown that the sensitivity of the present method using closely coupled probes is higher than that of the usual method using a uniform current flow in the region far from the crack.