Abstract
If photoelastic-coating materials exhibited thermal conductivity and thermal expansion equal to that of structural materials, and if strain-optical sensitivity did not vary with temperature, photoelasticcoating analyses could be conducted in thermal fields exactly as in room-temperature test. Methods for circumventing problems associated with these material properties are presented.
Corrections are introduced as analytically and empirically derived factors to account for birefringence resulting from differential thermal expansion of coating and workpiece. Surface strains induced by external loading and by thermal stresses can be performed in the temperature range of −60° F to +350° F for tests of extended duration and to +500° F for brief periods.
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Abbreviations
- T :
-
temperature
- σ:
-
stress
- τ:
-
shear stress
- ε:
-
strain
- Φ:
-
isoclinic parameter
- E :
-
modulus of elasticity
- ν:
-
Poisson’s ratio
- N :
-
photoelastic fringe order or birefringence
- t :
-
coating thickness
- K :
-
strain-optical coefficient
- 0 :
-
angle of incidence from normal to surface
- β:
-
pertaining to geometry of coating
- x, y, z :
-
acting along rectangular coordinate axes
- 1, 2, 3:
-
acting along principal directions
- u :
-
pertaining to the region of uniform stress distribution
- i, f :
-
initial and final conditions
- s, c :
-
pertaining to workpiece and coating
- α:
-
associated with differential thermal expansion
- 0:
-
pertaining to a straight boundary
References
Gray, R. M., “Initial Fringes in Photoelastic Models and Their Effects,” (Purdue University),Proc. Soc. Exp. Stress Anal. 11 (1),115–118 (1953).
Zandman, F., and Maier, H. N., “Six New Techniques for Photoelastic Coatings, Prod. Eng. 42 (July 24, 1961).
Maier, H. N., “Stress Analysis as a Guide to Structural Design, Doehler Jarvis Research Bulletin #3, April 1961.
Zandman, F., and Redner, S., “Study of the Feasibility of Stress Analysis of Propellant Grains Using the PhotoStress Technique,” Budd Instruments Div. Test Report, April 1960. Test performed under Air Force Contract AF33(616)6530 for Thiokol Chemical Corp., Elkton, Md.
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was formerly with Budd Instruments Div., Phoenixville, Pa., where this paper was prepared.
was formerly with Budd Instruments Div., Phoenixville, Pa.
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Zandman, F., Redner, S.S. & Post, D. Photoelastic-coating analysis in thermal fields. Experimental Mechanics 3, 215–221 (1963). https://doi.org/10.1007/BF02325765
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DOI: https://doi.org/10.1007/BF02325765