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APPENDIX A 

 EPISTEMOLOGY OF BIREFRINGENT COATING TECHNIQUE 



1. History of the Birefringent Coating Technique 



The birefringent coating technique of experimental stress analysis 



(7) 

 was originated by Mesnager in France, 1930. He was the first to suggest 



bonding a photoelastic material to a polished surface and then relate the 



strains in the coating to the surface strains of the structure. 



Mabboux* ' in France, 1932, suggested using heterogeneous inclu- 

 sions of photoelastic material in concrete structures, and using a Norren- 

 berg doubler to nneasure the stress. This arrangement has few applications,, 

 since the inclusion merely acts as a single strain gage. 



Oppel*^' in Germany, 1937, deternained notch stresses with a 

 birefringent coating. The plastic which he used, however, was not suffi- 

 ciently sensitive optically for general applications. 



D'Agostino and colleagues of the United States reported a bire- 



fringent coating technique in 1954. Their results, however, were applicable 

 only for flat parts. 



Zandman, while in France, discovered an epoxy formula and 

 reported in 1953 that the plastic could be used satisfactorily on a practical 

 basis for elastic or plastic ranges and for any size or shape. The Zandman 



f 1 1 \ 



method* 'has been used widely in Europe and was introduced in the United 



