A reflex spectrographic technique for in-plane strain analysis
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A reflex camera that incorporates a light source and spectroscope for recording in-plane displacement fringes formed by reflective diffraction gratings is described and illustrated.
A technique for replicating reflective diffraction gratings on plane metallic surfaces is given in detail.
Typical fringe patterns of a mild-steel tension specimen containing a long shallow notch obtained using 6000-lines/inch gratings show the elastic deformation of the specimen.
The method should prove a useful supplement or alternative to reflective photoelasticity in elasto-plastic studies, particularly when strain distributions in the transition region are of interest.
KeywordsMechanical Engineer Light Source Fluid Dynamics Transition Region Elastic Deformation
angle of incidence
angle of emergence ofp-th order passing through grating G1 at point A
angle of reflection ofp, s-p order sequence at point B
angle of emergence ofp, s-p, r-s order sequence from grating G1 at point C
phase of emergent beam on leaving point C
fractional displacement of the rulings of the reference grating G1 at point C with respect to those on the model grating G2 at point N
wavelength of light
amplitude ofu component of emergent sequence
amplitude of emergent sequence
phase constant depending upon position of point C
fractional position of point A in ruling
phase constant depending upon order sequenceu
spectral order numbers
thickness of air gap
number defining order sequence
ordinate of point C
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