Microstructural strain analysis by high-magnification moire interferometry

Jonathan Mark Huntley; S. J. P. Palmer; Howell Timothy Goldrein; L. Gunnar Melin

doi:10.1117/12.212633

23 June 1995 Microstructural strain analysis by high-magnification moire interferometry

Jonathan Mark Huntley, S. J. P. Palmer, Howell Timothy Goldrein, L. Gunnar Melin

Proceedings Volume 2545, Interferometry VII: Applications; (1995) https://doi.org/10.1117/12.212633
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

A high magnification phase-stepping interferometer has been constructed which has a spatial resolution of the order of one micrometers and a sub-mm field of view. Laser illumination is delivered to the microscope head by polarization-preserving single-mode optical fibers. The head itself is a compact unit consisting of collimating optics, objective lens, CCD camera, and a separate white light source. Phase gratings are cast on the polished specimen surface by replication from a master grating, in either silicone rubber or epoxy resin. Subsequent evaporation of a thin layer of gold onto the grating increases the reflectivity and reduces the speckle noise in the images. By switching between the laser illumination and the white light unit, it is possible to view the underlying microstructure in exact registration with the measured displacement fields. The instrument is illustrated with several applications including the visualization of delamination cracks in graphite-epoxy composites and measurement of the strain-to-failure of polymer-bonded-explosives.

Citation Download Citation

Jonathan Mark Huntley, S. J. P. Palmer, Howell Timothy Goldrein, and L. Gunnar Melin "Microstructural strain analysis by high-magnification moire interferometry", Proc. SPIE 2545, Interferometry VII: Applications, (23 June 1995); https://doi.org/10.1117/12.212633

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