Selecting Suitable Probes Distances for Sizing Deep Surface Cracks Using the DCPD Technique

[+] Author and Article Information
Fumio Takeo

Department of Mechanical Engineering, Hachinohe National College of Technology, Hachinohe 039-1192, Japan

Masumi Saka, S. Reaz Ahmed

Department of Nanomechanics, Tohoku University, Sendai 980-8579, Japan

Seiichi Hamada, Manabu Hayakawa

 Tokyo Electric Power Company, Tokyo 100-8560, Japan

J. Pressure Vessel Technol 129(1), 205-210 (May 28, 2006) (6 pages) doi:10.1115/1.2409319 History: Received February 14, 2006; Revised May 28, 2006

In this study, the way to enhance the sensitivity of evaluating deep surface cracks by DCPD technique using four probes is considered. The potential drops across two-dimensional cracks having different depths are analyzed by the three-dimensional finite-element method. The effect of the distance between current input and output probes and the distance between measuring probes on the change in potential drops are analyzed for a wide range of crack depths. By extending the distance between current input and output probes, the change in potential drop with the change in the depth of deeper crack becomes large. But the voltage of potential drop becomes small to measure. Finally, the way to select the appropriate distances between the probes for the measuring sensor is shown from the viewpoints of sensitivity and the required current.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Evaluation of a 2D surface crack using four probes DCPD technique

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Figure 2

Relationship between V1∕V0 and b∕s1(s2=s1∕2): (a) for the range of b∕s1≤10 and (b) for the range of b∕s1≤1

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Figure 3

Relationship between V1∕V0 and b(s2=s1∕2)

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Figure 4

Relationship between V1 and b(s2=s1∕2)

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Figure 5

Relationship between V1∕V0 and b(s2=s1∕4)

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Figure 6

Relationship between V1 and b(s2=s1∕4)

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Figure 7

Effect of s2 on the increment of V1 for the change in crack depth from bmm to (b+1)mm: (a) relationship between ΔV1 and b, and (b) relationship between ΔV1∕V1 and b

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Figure 8

Examples of the effect of material thickness on the change in potential drop (ρ=26.6×10−8Ωm): (a)s1=30mm, s2=3mm(I=10A) and (b)s1=3mm, s2=1.5mm(I=1A)

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Figure 9

Flow chart for evaluating deep surface cracks by selecting suitable probes distances shown in Table 1




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