I find myself in a bit of a predicament; I’m hoping someone can assist. I am conducting a frequency analysis of an assembly that is comprised of shells and I am getting conflicting results depending on which side of the shell is flipped (bottom/top). The shells are generated from a mid surface that is in the model so you would think that it would not matter which face is oriented towards the other face; however, this is not the case. If I bond a green (top) to orange (bottom)it results in a lower natural frequency. Inversely, if I bond a orange (bottom) to orange (bottom) it results in a higher natural frequency. I am in SolidWorks Simulation 2011 by the way. Through Simulation Help is suggest that the mid plane orientation color does not matter, but as I have described my results show that it does. Can anyone help or explain to me what is occurring?
I'm not familiar with the SolidWorks Simulation interface, but are you sure that the shells are centered on the original midplane surface? If the shells are offset to one side or the other, then it would make sense that you would get different natural frequencies, since the distance between the centers of the two sets of shells would be different.