Re: How to assembly a stiffness matrix ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg60071] Re: How to assembly a stiffness matrix ?*From*: Oliver Ruebenkoenig <ruebenko at imtek.uni-freiburg.de>*Date*: Thu, 1 Sep 2005 02:13:07 -0400 (EDT)*References*: <df3ito$mmo$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Ciao Francesco, we have a lot of open source tools to do that in mathematica. You can download the software from: http://www.imtek.de/simulation/mathematica/IMSweb/index.html If you have questions you might want to join the mailing list under: http://elmo.imtek.uni-freiburg.de/mailman/listinfo/ims To you question: I have a data structure imsMakeElementMatrix and imsAssemble. You fill all the element matrices with imsMakeElementMatrix and put them into the imsAssemble command and done you are. The online documentation can be seen here: http://www.imtek.de/simulation/mathematica/IMSweb/imsTOC/Numerics%20and%20Algor$ If you are into finite elements you might enjoy some of our application examples at: http://www.imtek.de/simulation/mathematica/IMSweb/imsTOC/Application%20Examples$ For transient problems I can recommend model order reduction. Assume you have a high dimensional system of equations (say 30000 DOFs) you may be able to find an approximate system of ( say 20 DOFs !!! ) that has very much the same behaviour and then time integrate that ( which is of course _very_ fast ) in the last step you do a re-projection to the original system. For online documentation have a look at: http://www.imtek.de/simulation/mathematica/IMSweb/imsTOC/Application%20Examples$ Please note: The online documentation is slightly dated - some 4 weeks or so and not all documentation has all the nice pictures inside... We also have some tools to input for example ANSYS generated stuff (mesh, element files and so on ) into mathematica. Nice export to povray and VTK script are possible. Does this help? Oliver On Wed, 31 Aug 2005, Francesco wrote: > I have a structure ( i.e. a crane ). I split the structure in a certain > number of simple elements ( shaft or beam ). > For each element i can build a local stiffness matrix of 12x12 element. > Then i need to assembly this little matrixes in the big structure > matrix. Dimension of the structure matrix is equale to: ( number of > nodes x 6 ). nodes are cross point between elements. > > Each element matrix has a specifical location in the big matrix. > > How i can assembly the big structure matrix, starting by the single > element matrix ? > What i want to input is only the dimension of the structure matrix and > the data of each single element matrix. The big structure matrix should > be calculated by Mathematica. > > Thanks in adavance for help and sorry for my very bad english > > Regards, > > Francesco > > Oliver Ruebenkoenig, <ruebenko at imtek.de> Phone: ++49 +761 203 7385