In-Plane Displacement Measurement Using Moire Fringes And Pattern Matching
| dc.contributor.author | Yen, Kin Sam | |
| dc.date.accessioned | 2016-11-24T01:30:10Z | |
| dc.date.available | 2016-11-24T01:30:10Z | |
| dc.date.issued | 2009-05 | |
| dc.description.abstract | A system for crack displacement sensing and measurement in concrete structures using circular grating moire fringes and pattern matching was reported in a recent research. However, the imperfection of the moire fringe extraction operation and the angular displacement detection caused error in pattern matching for displacement prediction. In this study, an improved in-plane (2D) displacement measurement system using the moire method integrated with image processing techniques has been developed. A set of simulated moire patterns was generated using two circular gratings of different pitch for the development of the moire fringes extraction algorithm. Circular gratings were first transformed into horizontal line gratings using Cartesian-to-Polar spatial transformation technique. The transformed line gratings were removed using a I-D vertical average filter and the unfiltered fringe pattern was inversely transformed to recover the complete circular moire fringes without the residual gratings. The proposed moire extraction method proved to have the highest gratings removal rate (41.4%) as compared to the iterative 2-D average filtering operation proposed in the past. The extracted moire fringes were compared to the stored fringe patterns in the database using the area-based pattern matching approach to estimate the displacement represented by the moire fringes. A total of 151 fringes patterns were captured for every 0.02 mm displacement increment from 0 to 3.00 mm in the x-direction and stored in the database for the pattern matching purpose. The matching of the moire fringes in y- and the x- and directions was done after angular compensation using a rotational angle detection algorithm. The average difference and its standard deviation of the pattern matching approach compared to the actual displacement were found to be 0.00 I mm and 0.022 mm respectively. The small difference between the actual displacement and the estimated displacement shows the high accuracy of the proposed pattern matching approach. To assess the applicability and practicality, the in-plane displacement measuring system was applied to measure the crack growth in a wall crack model and to measure the beam deflection in a three-point bending test to determine the elastic moduli of foam material. In crack growth measurement, the proposed measuring system produced output displacements with the average error of 0.003 mm. In determination of the elastic moduli of foam material, the proposed measuring system produces an elastic modulus of 27.27 MPa compared to the elastic modulus of 17.65MPa determined using conventional three-point bending test. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/3175 | |
| dc.subject | An improved in-plane (2D) displacement measurement system using the moire method | en_US |
| dc.subject | integrated with image processing techniques has been developed. | en_US |
| dc.title | In-Plane Displacement Measurement Using Moire Fringes And Pattern Matching | en_US |
| dc.type | Thesis | en_US |
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