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?