2001 Fiscal Year Final Research Report Summary
Detection of Flaws and Evaluation of Deterioration by Use of Multi-Frequency Ultrasonic
| Project/Area Number |
12650463
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
土木材料・力学一般
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| Research Institution | Fukui University of Technology |
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Principal Investigator |
KOBAYASHI Shoichi Fukui Univ. of Tech., Construction Eng., Professor, 工学部, 教授 (90025908)
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| Co-Investigator(Kenkyū-buntansha) |
SAWASAKI Masayuki Fukui Univ. of Tech., Construction Eng., Assoc. Professor, 工学部, 助教授 (80148189)
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| Project Period (FY) |
2000 – 2001
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| Keywords | TOFD method / Detection by sound / Detection using a microphone / Shape of flaw / Scanning / Change of phase velocity / Reduction of amplitude / Frequency spectrum |
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| Research Abstract |
The followings are obtained :
1) UItrasonic System : An ultrasonic measuring system was constructed by use of a square-wave pulser, receivers, a gate, an oscilloscope together a sing-around unit and filters. In addition an acoustic system using a microphone and amplifier was set up for impact tests.
2) Detection of Surface cracks : Depth of a surface crack was measured by TOFD method. The shape was estimated by scanning over the surface.
3) Detection of interior Flaws : Interior flaws were detected by the impact method. Inspection by human ears was useful for the detection. Using the scanning technique, the size can be estimated. Using a microphone and amplifier together with a recorder, size and depth of flaws can be estimated by comparing the amplitudes and spectra with the standard ones.
4) Evaluation of deterioration : As a model, the deterioration due to the uniaxial compression (homogeneous deterioration) was studied. a)Phase velocities of longitudinal and shear waves, respectively, propagating in the perpendicular direction to the compression axis decrease according to the increase of stress (progress of deterioration) and abruptly change at the ever-experienced stresses when re-loaded. b)The amplitude of the received waves accordingly decreases, and the reduction is more dominant in high-frequency waves. c)The spectra did not change so much.
5) How to evaluate deterioration : a)Detection and estimate the size and the depth of flaws can be simply done by hearing the impact sound by human ears. Using a microphone system they can be done more accurately provided that standard data are at hand. b)The homogeneous deterioration can be evaluated using the data of phase-velocity change or data of amplitude reduction of received waves.
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