How to solve symbolic problem for two equal matrices?
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There's a rank-4 tensor C written in Mandel-Kelvin notation as 6by6 matrix. Assume it's orthotropic. After I rotate it, C2 = R*C*R', where R is provided in this form: https://scicomp.stackexchange.com/questions/35600/4th-order-tensor-rotation-sources-to-refer#:~:text=In%20this%20case%2C%20you%20can%20rotate%20stiffness%20and%20compliance%20tensors%20with . I want to equate C2 and C using symbolic variables as C11, C22,... But when I use: S = solve(C2 == C), matlab return all Cij = 0. That's not right. Any one can help me with that? I'm quite confused. Thanks in advance.
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Accepted Answer
Torsten
on 29 Apr 2022
Edited: Torsten
on 29 Apr 2022
If you add the two lines
[A,b] = equationsToMatrix(C_rot - C==0);
rank(A)
you'll see that
rank(A) = 9.
Thus your system only permits the trivial solution that all C's are zero.
Since MK is regular, everything else would have been surprising.
3 Comments
Walter Roberson
on 29 Apr 2022
rank() of a symbolic matrix that involves variables often does not recognize identities though.
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