Abstract
One method of determining the strains on the surface of a metal part is by the use of a birefringent coating. Because of the thickness of the coating, however, the observed fringe order depends not only on the surface strains but also on two other factors, namely, the curvature that the surface undergoes and the variation of strain acrose the thickness of the coating. These thickness effects have already been studied in a paper dealing with one dimensional variations in strain. In the present paper, the solution is extended to a two-dimensional deformation with radial symmetry. An experiment is described in which the surface strains produced by the impact of a bullet on a flat plate are determined from the birefringence of a surface coating taking into account the effects of strain gradients and curvature. The values of surface strain are compared with measurements made by means of a square grid inscribed on the metal surface. A procedure is suggested for determining an unknown surface strain having radial symmetry from the total birefringence of the surface coating when the change in curvature of the metal surface under load is known or can be determined separately.
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Bibliography
Mesnager, M., “Sur la Determination Optique des Tensions Intérieures dans les Solides à Trois Dimensions,”Compt. rend., Paris, 190, 1249 (1930).
Oppel, G., “Das polarisationsoptische Schichtverfahren zur Messung der Oberflächenspannung am beanspruchten Bauteil ohne Modell,”Ver. duet. Ing., Z., 81, 803–804 (1937).
D'Agostino, J., Drucker, D. C., Liu, C. K., andMylonas, C., “Epoxy Adhesives and Casting Resins as Photo-Elastic Plastics,”Proc. Soc. Exp. Stress Anal., XII (2),123–128 (1955).
D'Agostino, J., Drucker, D. C., Liu, C. K., andMylonas, C., “An Analysis of Plastic Behavior of Metals with Bonded Birefringent Plastic,”-om|Ibid. Proc. Soc. Exp. Stress Anal., XII (2),115–122 (1955).
Duffy, J., “Effects of the Thickness of Birefringent Coatings,” Technical Report No. 34, Contract DA-19-020-ORD-798, Division of Applied Mathematics, Brown University (April 1958). Experimental Mechanics, 74–82 (March 1961).
Lee, T. C., Mylonas, C., and Duffy, J., “Thickness Effects in Birefringent Coatings with Radial Symmetry,” Technical Report No. 1, Contract DA-19-020-509-ORD-4674, Division of Appl. Mathematics, Brown University (April 1959).
Mindlin, R. D., A Discussion on the paper byGoodier, J. N., andLee, G. E., “An Extension of the Photo-elastic Method of Stress Measurement to Plates in Transverse Bending,”Jnl. Appl. Mechanics, Trans. ASME 8 (4),A187-A189 (December 1941).
Duffy, J., and Mylonas, C., “Preliminary Tests on Aluminum Specimens with Birefringent Coating Permanently Deformed by Impact,” Technical Report No. 22, Contract DA-19-020-ORD-798, Division of Appl. Mathematics, Brown University (July 1955).
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The results presented in this paper were obtained in the course of research sponsored by the Ballistic Research Laboratories of Aberdeen Proving Ground under Contract DA-19-020-ORD-4674.
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Lee, T.C., Mylonas, C. & Duffy, J. Thickness effects in birefringent coatings with radial symmetry. Experimental Mechanics 1, 134–141 (1961). https://doi.org/10.1007/BF02322903
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DOI: https://doi.org/10.1007/BF02322903