August 22, 2023 at 5:58 am
I need to extract the mode shape vectors of some cantilever plate to make a correlation between some of them analytically.
I used the workbench to simulate the problem and added the next APDL command to extract both mass and stiffness matrices in MMF:
*SMAT, MatKS, D, IMPORT, FULL, file.full, STIFF
*SMAT, MatMS, D, IMPORT, FULL, file.full, MASS
*Export, MatKS, MMF, matK_MMF.txt
*Export, MatMS, MMF, matM_MMF.txt
Then I did modal analysis , and I got the two files of mass and stiffness matrices in MMF.
I used the next Matlab code to solve the eigen problem in order to extract mode shapes.
K = zeros(462,462);
for r = 2:5515
K(matK_MMF(r,1), matK_MMF(r,2)) = matK_MMF(r,3);
M = zeros(462,462);
for r = 2:1999
M(matM_MMF(r,1), matM_MMF(r,2)) = matM_MMF(r,3);
lamda=diag(sort(diag(Lamda),'ascend')); % make diagonal matrix out of sorted diagonal values of input 'Lamda'
[c, ind]=sort(diag(Lamda),'ascend'); % store the indices of which columns the sorted eigenvalues come from 'lamda'
This code ran syntactically without any errors .
I checked for the first natural frequency, omegaHz(1,1), which is supposed to be 208.53 Hz as shown in the workbench analysis , but unfortunately it was 64023 Hz .
Would you please show me what is wrong with that problem?
Or is there any possible way to extract mode shapes vectors or modal matrix directly from ANSYS ?