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Electric Field Analysis of Simultaneous Evaluation of Crack on an Inner Pipe Surface and Pipe Wall Thickness Using Direct-Current Potential Difference Method of Multiple-Probe Type

[+] Author and Article Information
Naoya Tada

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

Makoto Uchida

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

J. Pressure Vessel Technol 134(4), 041501 (Jul 27, 2012) (10 pages) doi:10.1115/1.4005862 History: Received July 10, 2010; Revised November 06, 2011; Published July 26, 2012; Online July 27, 2012

The direct-current potential difference method (DC-PDM) is a promising nondestructive technique for evaluating cracks in the conductors on the basis of change in current paths or the potential difference due to cracks. In a previous study, the authors proposed a method for the simultaneous evaluation of the location and size of a semi-elliptical crack on the back surface of a plate and the plate thickness. Its theoretical validity and practical utility were shown by numerical analyses and experiments. This study extends the method to the simultaneous evaluation of a crack on the inner surface of a pipe and the pipe wall thickness. The related electric field analyses are performed using the finite element method. The results show that the location, length, and depth of a semi-elliptical crack on the inner surface of the pipe and the pipe wall thickness can be evaluated based on the distribution of the potential difference measured on the outer surface of the pipe. This extension will prove useful for various practical cases, which are often seen in the piping of power-generating and petrochemical plants.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Analysis model for identifying semi-elliptical crack on the inner pipe surface with a multiple-probe sensor

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Figure 2

Geometric conversion from pipe model to the equivalent plate model

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Figure 3

Flowchart of the entire evaluation process of the crack geometry and pipe wall thickness

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Figure 4

Flowchart of the evaluation process of equivalent plate model

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Figure 5

Finite element mesh for condition C-2

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Figure 6

Distribution of normalized potential difference on the outer pipe surface

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Figure 8

Evaluation results from 50 sets of potential differences with ±1% scatter

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Figure 9

Evaluation results from 50 sets of potential differences with ±3% scatter

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Figure 10

Evaluation results from 50 sets of the average of six potential differences with ±1% scatter

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Figure 11

Evaluation results from 50 sets of the average of six potential differences with ±3% scatter

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