Discussion Forum

Hello,

I am trying to model the natural frequency of a MEMS resonator affected by thermal stresses. I've been having difficulty getting accurate results, so I've stripped down the problem as much as possible and something seems to be fundamentally wrong with my methodology.

I now have a square plate with a thermal expansion node and want to evaluate the natural frequency at various temperatures. I've added a fixed point constraint in the middle of my plate to give a reference point in order to perform a prestressed eigenfrequency study as well as an eigenfrequency study (unstressed). I've made sure to place the BC at a node in the eigenmode to not distort it in either study.

The BC that I've applied should not be appying any stress onto my plate (the solution store backs this up) yet both studies give conflicting results. The eigenfrequency study shows increasing frequency with decrease temperature (which seems physical as the dimensions of my plate are shrinking) while the prestressed study shows a decrease in frequency with a decreasing temperature.

Is it possible to capture the effects of thermal expansion (purely from a dimensional perspective) in the presstressed eigenfrequency study? Am I making a wrong assumptions somewhere?

Thanks,