Laser-Generated Acoustic Signal Interaction with Surface Flaws on Rail Wheels |
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| Authors: | Shant Kenderian Donatella Cerniglia B Boro Djordjevic Robert E Green Jr |
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| Affiliation: | 1. Center for Nondestructive Evaluation , Johns Hopkins University , Baltimore, Maryland, USA;2. Center for Nondestructive Evaluation , Johns Hopkins University , Baltimore, Maryland, USA;3. Materials Science and Engineering Department , Johns Hopkins University , Baltimore, Maryland, USA |
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| Abstract: | Long- and short-range acoustic-signal interaction with surface-breaking cracks and geometric boundaries of the rail-wheel tread area are presented in this article. Ultrasonic signals are generated using a laser-line source of varying length and distance from a crack and are detected with a 1-MHz contact transducer to map the sound field behind the crack in the near, intermediate, and far fields of the insonified region. The factors that affect the behavior of a laser-generated surface acoustic wave propagating along the tread area of a rail wheel are discussed. A signal normalization method is proposed to help in sensing the presence of a crack from the transmitted signal unaffected by the boundary effect of the complicated wheel geometry, diffraction of the acoustic wave around the crack tip, and source-to-crack length ratio and separation distance. |
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| Keywords: | Cracks laser ultrasound line source rail wheel shadow zone sound field |
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