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BELL SYSTEM TECHNICAL JOURNAL 



Similarly 



c = r 



(8.12) 



This reduces the constants and modulii to 21 of each. 



If a transformation is performed that is permitted by the symmetry of 

 the medium the elastic modulus matrix is unaltered. The monoclinic 

 system has a binary axis. If we choose this as xz and rotate the axes 180° 



about this by means of the matrix a = I — 1 I we have S' = 



V 1/ 



Equating terms, those whose signs differ in 5 and 5' must vanish. 



Proceeding in this way through the 32 crystal classes we arrive at the 

 ten following matrices that cover the elastic behaviour of all 32 classes. 



The C matrix is 

 entirely analogous 



(8.13) 



The C matrix is 

 entirely analogous 



(8.14) 



