1997 Fiscal Year Final Research Report Summary
Measurement of interior displacement field by an embedded laser speckle photography.
| Project/Area Number |
08650056
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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 |
Applied optics/Quantum optical engineering
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| Research Institution | Science University of Tokyo |
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Principal Investigator |
MACHIDA Kenji Science University of Tokyo, Mechanical Engineering, Assistant professor, 理工学部, 講師 (50089380)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Speckle Photography / Young's fringe / 2-D Fourier Transform / Interior Displacement / Image Processing / Mixed Mode / Stress Intensity Factor / Interface Crack |
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| Research Abstract |
The image-processing system based on a 2-D Fourier transform and iteration using the bounded Newton- Raphson algorithm is presented for the analysis of Young's fringes patterns created from double-exposure speckle photography. The fringe spacing and orientation are determined using only one Young's fringes pattern without any other diffraction halo patterns. This image-processing system enables us to analyze the fringe spacing and orientation or Young's fringes pattern with high accuracy and speed. Displacement in the near-crack-tip fields was measured on transparent compact normal and shear specimens made of Plexiglas under mixed-mode loading by speckle photography. The stress-intensity factors (SIF) along the crack front were cvaluated by the displacement extrapolation. A finite element analysis was carried out on the same specimens. The accuracy of SIF was discussed by comparison between the virtual crack extension method and the displacement method for mixed-mode problems. The variation of SIF with load application angle was discussed on different planes from the free surface to the center of the specimen. SIF are nearly uniform from the midsection to a depth of 3mm of the specimen. Therefore, it is sufficient to measure SIF at a depth of 3mm of the specimen. SIF at the central part of specimen largely differ from SIF obtained by 2-D plane strain analysis. SIF of homogeneous material under mixed-mode loading can be measured with high accuracy by embedded speckle photography. This method was lied to measure SIF of interface crack problems. Steel and an epoxy resin were used as dissimilar materials. The displacement along the crack lines at the free surface was measured by speckle photography. At the free surface of the specimen, SIF obtained by speckle photography agree with SIF obtained by finite element analysis. SIF of the interface crack can also be evaluated by speckle photography.
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