boundary conditions in cosmosworks.

[spmech]

Hi Everybody,
i have a down-to-earth problem but could not find the solution.
i am doing the frequency analysis of an optics table, basically made of two granite legs and a granite top. in use, the legs will be resting on the ground without any fixing but restrained in position. the table top will also rest on the legs by gravity without any fixing.
the problem is, in cosmosworks, i am not able to provide 'simply supported' boundary condition. the model is meshed with solid elements and whenever 'no ranslation' is provided it is basically conveted to fixed BC. can this problem be solved in cosmosworks or i am doing some gross mistake?

thanks in advance for any help.

 

[jmagri]

A couple of thoughts come to mind with this one. If you are doing frequency analysis the default condition globally bonded. This will prevent the model from coming apart. You can however do a couple of things with the restraints. Where the floor meets the legs try restraining the edge. Or if that doesn't quite cut it put a split line on the bottom surface of the leg in the middle and restrain that. This will allow rotation of the legs in a radial manner.

Another approach is to put a small cylindrical form on the bottom of the leg.

The intersection of the legs and the table are another problem. Here the model will need a contact set or a very soft spring between the legs and the table. If this isn't done the model will bond them. If this weren't the case the deformation would occur without bounds and the calculation of the natural frequency cannot be done.

Hope this helps

 

[zx82]

How about using a roller?