Experimental Mechanics

, Volume 8, Issue 1, pp 19–24 | Cite as

A reflex spectrographic technique for in-plane strain analysis

This paper describes a technique whereby the optical advantages of grooved diffraction gratings are utilized to permit displacement patterns to be obtained from opaque models
  • E. Middleton
  • L. P. Stephenson


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.


Mechanical Engineer Light Source Fluid Dynamics Transition Region Elastic Deformation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



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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Copyright information

© Society for Experimental Mechanics, Inc. 1968

Authors and Affiliations

  • E. Middleton
    • 1
  • L. P. Stephenson
    • 1
  1. 1.Department of Civil EngineeringUniversity of TasmaniaHobartAustralia

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