1 December 1991 Measurement of the dynamic crack-tip displacement field using high-resolution moiré photography
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An electromagnetic device has been used to produce a planar tensile stress pulse in a plate of poly methyl methacrylate (PMMA). The pulse has a profile which is approximately square in time. It is incident on a through crack, resulting in the sudden application of a constant mode I load. This causes the stress intensity factor to increase proportionally to (loading time)½. High resolution moiré photography is used to produce fringe patterns in real time, which are recorded with a high speed image converter camera at an inter-frame time of 2μs. The moiré technique uses a specimen grating of 75 lines mm−1 which is imaged onto a reference grating of the same pitch, using optical filtering in the transform plane to double the effective frequency to 150 lines mm−1. The photographs are digitized and analyzed with an automatic system based on the 2-D Fourier transform to extract one component of the displacement field to a sensitivity of approximately 1μm. This has been compared with an analytical solution for the problem.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Martin B. Whitworth, Jonathan Mark Huntley, John E. Field, "Measurement of the dynamic crack-tip displacement field using high-resolution moiré photography", Proc. SPIE 1554, Second International Conference on Photomechanics and Speckle Metrology, (1 December 1991); doi: 10.1117/12.57499; https://doi.org/10.1117/12.57499

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