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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
Article

Abstract

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.

Keywords

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.

Nomenclature

α

angle of incidence

βp

angle of emergence ofp-th order passing through grating G1 at point A

βp,s−

angle of reflection ofp, s-p order sequence at point B

βT

angle of emergence ofp, s-p, r-s order sequence from grating G1 at point C

φC

phase of emergent beam on leaving point C

ρC

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

λ

wavelength of light

au

amplitude ofu component of emergent sequence

A

amplitude of emergent sequence

Cc

phase constant depending upon position of point C

fA

fractional position of point A in ruling

ku

phase constant depending upon order sequenceu

r,s,p

spectral order numbers

t

thickness of air gap

u

number defining order sequence

xC

ordinate of point C

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References

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    Middleton, E., “A Reflection Technique for the Survey of the Deflection of Flat Plates,” to be published in Experimental Mechanics.Google Scholar
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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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