2005 Fiscal Year Final Research Report Summary
Research on Highly Sensitive Quantitative Nondestructive Evaluation Techniques of Closed Cracks and Branched Cracks
| Project/Area Number |
16360048
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Tohoku University |
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Principal Investigator |
SAKA Masumi Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (20158918)
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| Co-Investigator(Kenkyū-buntansha) |
MIHARA Tsuyoshi Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (20174112)
JU Yang Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (60312609)
TOHMYOH Hironori Tohoku University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (50374955)
HAYASHI Takahiro Nagoya Institute of Technology, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (30324479)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Nuclear Power Plant / Non-Destructive Testing / Closed Cracks / Branched Cracks / Welded Part / Ultrasonic Testing / Nonlinear Ultrasonics / Direct Current Potential Drop Technique |
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| Research Abstract |
1. Enhancement of signal-to-noise ratio by optimizing the averaging conditions for reducing the ultrasonic scattering noise
Austenitic stainless steel, AISI316L, was treated in this study. For reducing the ultrasonic scattering noise from the grain boundary, the optimum sampling conditions and the optimum scanning conditions were obtained.
2. Ultrasonic inspection of closed back-wall cracks in welded part
Specimens containing the unknown fatigue cracks were prepared, and the crack closure stress and the depth of cracks have been successfully determined by solving the ultrasonic inverse problem. Furthermore, it was shown that the ultrasonic responses for stress corrosion cracking at the back-wall of the thick-walled welded specimen were enhanced remarkably by cooling the surface of the specimen with Dry Ice and ethanol.
3. Evaluation of closed cracks by nonlinear ultrasonics
The nonlinear ultrasonic technique was adopted to inspect the closed cracks, and the relationships between the behavio
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r of nonlinear ultrasonic waves and the crack closure stress were obtained. Furthermore, by using the second harmonic waves, weak bonding, stress corrosion cracking, and so on were visualized.
4. Enhancement of sensitivity of DCPD technique
The sensitive direct current potential drop technique, which controls the current flow in the tested pipe by locally heating the outer surface of the pipe, has been proposed, and the ability of the present technique has been provided. Furthermore, a new DCPD sensor with repeatable contact unit for the probes has been developed, and the precise and repeatable measurements of potential drop have been achieved.
5. Combination of various techniques for reliable QNDE
Abilities of ultrasonic inspection including that of nonlinear ultrasound and sensitive DCPD techniques were compared for inspecting the various types of specimens having flaws. It was verified that the combination of these techniques were effective for realizing the reliable QNDE of closed cracks and branched cracks. Less
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