Cantilever MEMS, Eigenfrequency vs Temperature

Hello everybody,

I'm trying to simulate the change of the eigenfrequency when the cantilever temperature increases. In theory, when the temperature increases the eigenfrequency decreases.

I built a bilayer cantilever (Aluminium and Titanium), I included a solid mechanics module and a heat transfer in solid module. I defined a variable for the structure's temperature then I made a parametric sweep [range(273,10,313)] and 2 steps analysis: a stationary one and an eigenfrequency.

Finally, I simulated it and I noticed that the eigenfrequency of the sctructure increased with increasing the temperature, what is the problem? why is it not decreasing?


Thank you.

Regards.
-Fran