Inverse analyses for natural and multicracks using signals from a differential transmit-receive ECT probe

This paper describes the inverse analysis in the frame works of a round-robin test for the testing of steam generator tubes by eddy-current testing (ECT). An ECT probe with high space resolution was newly proposed, for the purpose of better and easier crack shape evaluations. This new probe is applied to the roundrobin testpieces including natural crack samples and a multicrack sample. Inverse problems of the crack shape reconstructions are solved by a fast forward simulator and the conjugated gradient method. Experimental ECT signals as well as results of reconstructions are shown. Treatments of a natural crack and multicracks are discussed.