While performing a modal analysis on a sheet metal assembly, the model was meshed with plate elements. A second analysis was performed with the same geometry,but with brick elements. The results between the plate elements and brick elements is quite different. Can someone give me an idea why this would be?
I am going to take a guess that the frequencies from the brick model were higher. That can be explained by the stiffness of brick elements in a bending mode. Brick models with bending usually need more than one element through the thickness to accurately capture the bending. (You may be able to compensate for that issue if you include the midside nodes for the brick parts. That setting is under the Element Definition.)
If the plate model has higher frequencies, then something is wrong in the setup. Either the weight of the models is different, or the boundary conditions are different.
John Holtz, P.E.
Senior User Experience Designer, Simulation
Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)