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Proceedings Paper

Measurement of the dynamic crack-tip displacement field using high-resolution moire photography
Author(s): Martin B. Whitworth; Jonathan Mark Huntley; John E. Field
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Paper Abstract

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.

Paper Details

Date Published: 1 December 1991
Proc. SPIE 1554, Second International Conference on Photomechanics and Speckle Metrology, (1 December 1991);
Show Author Affiliations
Martin B. Whitworth, Univ. of Cambridge (United Kingdom)
Jonathan Mark Huntley, Univ. of Cambridge (United Kingdom)
John E. Field, Univ. of Cambridge (United Kingdom)

Published in SPIE Proceedings Vol. 1554:
Second International Conference on Photomechanics and Speckle Metrology
Fu-Pen Chiang; Fu-Pen Chiang, Editor(s)

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