2004 Fiscal Year Final Research Report Summary
Micro crack detection based on the spatio-temporal gradient method
| Project/Area Number |
15560360
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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 |
Measurement engineering
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| Research Institution | Saga University |
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Principal Investigator |
TERAMOTO Kenbu Saga University, Department of Mechanical Engineering, Associate Professor, 理工学部, 助教授 (70207489)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Lamb wave / Non-destructive testing / Spatio-temporal gradient analysis / Array signal processing |
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| Research Abstract |
1:The first results presents a defect characterization method by spatio-temporal gradient analysis over the Lamb wave field. The surface ultrasound waves that propagate in the direction of the layer are potential candidates of non-destructive evaluation(NDE) methodology. The proposed method has an ability to classify the surface acoustic wave field through the rank of the covariance matrix defined over the four-dimensional vector space which is spanned by following components : a vertical displacement, its vertical velocity, and a pair of shear strains of the surface. The covariance matrix provides the information about defects. The determinant of the covariance matrix, therefore, is proposed as the index of homogeneity of the object surface. In this study, the computational process in wave field near the defects is discussed and their physical meanings are investigated through FDTD-simulations and acoustic experiments.
2.The second results are shown as follows.
In this study, the local phase velocimetry based on the spatio-temporal gradient analysis is derived theoretically. The proposed method has an ability to characterize the phase velocity of the Lamb-wave propagation through the linearity among the 4-dimensional vector which is composed by following components : (1)a vertical (z-directional) displacement, (2)its vertical particle velocity, (3)x-directional and (4)y-directional out-of-plane strains. In this study, the computational process of the local velocimetry is discussed and their physical meanings are investigated through numerical and acoustical experiments.
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