Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

mass and stiffness matrix

Please login with a confirmed email address before reporting spam

Hello,

I am trying to work with the mass and stiffness matrices exported from a COMSOL model to MATLAB. I have done the Frequency domain analysis (sol1) and Eigenfrequency analysis (sol2). In order to analyse the matrices I have calculated the eigenvalues and compare with those obtained in the eigenfrequency study, but I have found two problems:

- The mass matrix exported from the Frequency Domain study (sol1) is null. Is ther any parameter to set in the study to obtain this matrix?.

- The eigenfrequencies calculated in MATLAB do not match with those obtained in the Eigenfrequency analysis (sol2). I have used the following script:


model=mphload('bars.mph');

MA = mphmatrix(model,'sol2','out',{'K','E'});


K = MA.K;
M = MA.E;
K1 = MA1.K;
M1 = MA1.E;
Kf = full(K);
Mf = full(M);
lambda = real(eig(Kf,Mf));
omega = sqrt(lambda);
f = omega/(2*pi);
f_sorted = sort(real(f));

I will appreciate your assistance,

Kind regards,

Diego


0 Replies Last Post Sep 26, 2016, 6:55 p.m. EDT
COMSOL Moderator

Hello Diego Calero

Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.

If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.