I've modelled a 1/2 inch long steel filament, with a diameter of .0004 inch. With simple fixed ends (rotation allowed) and using beam elements, Solidworks Simulation (SS) predicts a first natural frequency of about 1000 Hz. The closed form solution from Roarke's structural book predicts about 60 Hz. Using solid elements, and just 3 or 4 of them, SS predicts a first frequency of around 100 Hz. Why does Simulation give such a wrong answer? Or did I make a mistake?