186 



BELL SYSTEM TECHNICAL JOURNAL 









 

 

 

 

 ntn — niii 



The TT ten- 

 sor is anal- 

 ogous ex- 

 cept that 

 Tree = 



TTll — 7ri2 



Cubic Sys- 

 tem 23,432 



2 4 2 

 — 3,43w,— 3 — 



m mm 



3 Constants 















mu 



























mu 









 

 

 

 

 mu 



The TT ten- 

 sor is en- 

 tirely anal- 

 ogous 

 (95) 



Isotropic 

 Systems 2 

 Constants 



mn mi2 miz 

 mi2 mil Wi2 

 Wi2 mi2 mil 





















 

 



WU — Wi2 





 











mn — mn 



2 









 

 











mn — mn 



The IT ten- 

 sor is anal- 

 ogous ex- 

 cept that 



T66 = 

 TTu — 7ri2 



From measurement^ on the photoelastic effects at high pressure for cubic 

 crystals, it has become apparent that the second derivatives of equation 

 (44) are not sufficient to represent the experimental results and derivatives 

 up to the fourth power should be included. This extension, however, is not 

 considered in the present paper. 



VII. Photoelasticity in Isotropic Media 



The photoelastic effect in isotropic solids has been used extensively in 

 studying the stresses existing in machine parts and other pieces. For this 

 purpose a plastic model cut in the shape of the original is used and is loaded 

 in a similar manner to that of the machine part to be studied. Since stresses 

 are aj)plied, the tf, photoelastic constants are most useful. If we look along 



"> H. B. Maris, Jour. Optical Society of Amer., Vol. 15, pp. 194-200, 1927. 



