Three-Dimensional Identification of Semi-Elliptical Surface Crack by Means of Direct-Current Electrical Potential Difference Method With Multiple-Probe Sensor

[+] Author and Article Information
Naoya Tada

Graduate School of Natural Science and Technology,  Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japantada@mech.okayama-u.ac.jp

Masayoshi Okada

Paper Converting Machinery Production Shop,  Mitsubishi Heavy Industries, Ltd., 5007 Itozaki-cho, Mihara 729-0393, Japanmasayoshi̱okada@mhi.co.jp

Jun Iwamoto

Chuo Research Center,  Noritz Corporation, 5 Minamifutami, Futami-cho, Akashi 674-0093, Japanj-iwamoto@noritz.co.jp

J. Pressure Vessel Technol 129(3), 441-448 (Nov 24, 2006) (8 pages) doi:10.1115/1.2748824 History: Received August 17, 2004; Revised November 24, 2006

A method of three-dimensional identification of a semi-elliptical surface crack by direct-current electrical potential difference method with a multiple-probe sensor was proposed and its validity was numerically examined. The condition of the surface crack embedded in a conductive plate was specified by the two-dimensional location of the crack center, length, and depth of the crack, and the surface and inward angles of the crack plane. Identification was carried out based on the distribution of the electrical potential difference around the crack measured on the surface of the plate with the “multiple-probe sensor” which is composed of many probes aligned in two orthogonal directions. The location and surface angle were evaluated using the point symmetry of the potential difference distribution. The inward angle was determined by the magnitude of symmetry of potential difference distribution with reference to the evaluated crack line. Finally, length and depth of the crack were determined using the exact solution of potential difference for an inclined inner elliptical crack which yields similar potential difference to that of the inclined semi-elliptical surface crack. The validity of the method was numerically confirmed by carrying out the evaluation based on the result obtained by finite element analysis.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Direct current electrical potential difference method with multiple-probe sensor

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Figure 2

Two-dimensional location, surface, and inward angles, length, and depth of semi-elliptical surface crack

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Figure 3

Summation of positive part of normalized increase in potential difference Σ[ΔV∕V0]+ of probe pairs and evaluation of two-dimensional location of the crack center: (a) z coordinate of the crack center, zc; and (b) y coordinate of the crack center, yc

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Figure 4

Evaluation of surface angle of crack

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Figure 5

Adjacent probe pairs

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Figure 6

Approximation for evaluation of length and depth of crack: (a) semi-elliptical crack on the surface; (b) V-shaped crack whose electric potential distribution is identical to the crack shown in Fig. 6; and (c) entire elliptical crack

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Figure 7

Distribution of normalized potential difference of probe pairs in multiple-probe sensor

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Figure 8

Relationship between symmetry parameter F and inward angle of crack θin



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