Vibrations of doubly-rotated-cut quartz plates with monoclinic symmetry (Q1061544)

For certain doubly rotated cuts of quartz, the elastic stiffness constants have the same symmetry and absolute values as those for certain rotated Y-cuts; but 4 of the 13 constants have signs reversed. Mathematical solutions of corresponding problems for the two types of cut have the same form but the numerical results may be the same or different according as the constants with changed signs enter the solution as even or odd powers or products. Examples of both are exhibited.