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Research Papers: NDE

# Three-Dimensional Identification of Semi-Elliptical Crack on the Back Surface by Means of Direct-Current Electrical Potential Difference Method With Multiple-Probe Sensor (PVP2006-ICPVT-11-93359)

[+] Author and Article Information

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

Akira Funakoshi

Kobe Shipyard and Machinery Works, Mitsubishi Heavy Industries, Ltd., 1-1, Wadasaki-cho 1-chome, Hyogo-ku, Kobe, 652-8585, Japanakira̱funakoshi@mhi.co.jp

J. Pressure Vessel Technol 131(2), 021501 (Dec 09, 2008) (9 pages) doi:10.1115/1.3006952 History: Received March 14, 2007; Revised August 26, 2008; Published December 09, 2008

## Abstract

Cracks are popular defects initiated in structural components and their accurate evaluation is very important to assure the reliability of various plants. The direct-current electrical potential difference method is known as one of the most effective methods for the evaluation of the cracks. In this paper, a method of three-dimensional identification of a semi-elliptical crack existing on the back surface of a conductive plate by the direct-current electrical potential difference method with a multiple-probe sensor is proposed. The geometrical condition of the crack was specified by six parameters, the surface and inward angles of the crack plane, $θsur$ and $θin$, the length and depth of the crack, $c$ and $a$, and the two-dimensional location of the crack center, $(yc,zc)$, on the back surface. The identification was carried out based on the distribution of electrical potential difference on the surface of the plate measured with a sensor composed of grid-arranged multiple probes called the “multiple-probe sensor.” As an approximate cracked body and a quick analysis method were used, a number of repeated electrical potential field analyses necessary for the identification of the crack became possible within a practical time. The validity of the method was numerically confirmed by carrying out the identification based on the result of the finite element analysis. The proposed method could be extended to the online monitoring of a semi-elliptical crack initiated on the inner surface of tubular components by means of the multiple-probe sensor placed on the outer surface.

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## Figures

Figure 2

Surface and inward angles, length and depth, and two-dimensional location of a semi-elliptical crack on the back surface

Figure 3

Flowchart of crack identification

Figure 4

Step-by-step explanation of approximate cracked body used in the present electrical potential field analysis

Figure 5

Distribution of the normalized potential difference of probe pairs for conditions 1,2,3,4,5,6,7,8,9; c=15mm, a=15mm

Figure 6

Distribution of the normalized potential difference of probe pairs for conditions (10)–(18); c=10mm, a=15mm

Figure 7

Distribution of the normalized potential difference of probe pairs for conditions (19)–(27); c=15mm, a=10mm

Figure 1

Direct-current electrical potential difference method with the multiple-probe sensor

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