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Defect Shape Recovering by Parameter Estimation Arising in Eddy Current Testing  

Kojima, Fumio (Graduate School of Science and Technology, Kobe University)
Publication Information
Journal of the Korean Society for Nondestructive Testing / v.23, no.6, 2003 , pp. 622-634 More about this Journal
Abstract
This paper is concerned with a computational method for recovering a crack shape of steam generator tubes of nuclear plants. Problems on the shape identification are discussed arising in the characterization of a structural defect in a conductor using data of eddy current inspection. A surface defect on the generator tube ran be detected as a probe impedance trajectory by scanning a pancake type coil. First, a mathematical model of the inspection process is derived from the Maxwell's equation. Second, the input and output relation is given by the approximate model by virtue of the hybrid use of the finite element and boundary element method. In that model, the crack shape is characterized by the unknown coefficients of the B-spline function which approximates the crack shape geometry. Finally, a parameter estimation technique is proposed for recovering the crack shape using data from the probe coil. The computational experiments were successfully tested with the laboratory data.
Keywords
Identification; inverse problems; parameter estimation; finite element method; boundary element method;
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