Hi,
I have mass and stiffness matrices from ansys in HB form and I converted them in Matlab sparse matrix form.
But mass matrix is in terms of Degrees of freedom (DOF) and the total deformation information from transient structural analysis is at each node.
Since my model has 3 dof per node, if total no of nodes is n, my mass matrix in (3*n x 3*n) and deformation vector at specific time is (nx1). I want to get the product of the two. How can I read information in terms of nodes from mass matrix?
Is there any way I can rewrite mass matrix in nodes dimension?
Any help is highly appreciated.
Thanks,
Prachi
I was wondering, if you have 3 DOF then you might also have 3 components of the displacements. Then you have a mass value in the mass matrix (it can be a lumped or consistent mass matrix) corresponding to each DOF.
If you are considering a resultant displacement only, then probably you can form a lumped mass matrix, assuming only 1 DOF per node and use that. For doing that you assume that mass in the element is equally distributed at all the nodes of that element and then using standard globalization procedure you can get the mass matrix, which will be of dimension (nx1), where n is node number. More information regarding lumped mass matrix can be found in any FEM book. Some of the links are mentioned. (Ch.10 from the google book link)
https://books.google.co.il/books?id=SnHRBQAAQBAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
http://www.colorado.edu/engineering/CAS/courses.d/MFEMD.d/MFEMD.Ch16.d/MFEMD.Ch16.pdf
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