There seems to be an issue with constrained modal.
Model a simple cantilever beam, 100 x 200 x 1000mm and assign 304 stainless steel as the material.
The first two free modes calculate to 490.4Hz 2 node, short-way and 899.4Hz, 2 node tall way. Accurate. Excellent. Note: 20mm global mesh.
Restrain one small surface and the modes are 79.78Hz short-way oscillation and 155.6Hz tall-way oscillation with 20mm global mesh.
Refining the mesh to 5mm at the restrained end, the modes are 79.75Hz and 155.5Hz.
Classical calculation of the first mode of a rectangular section cantilever beam is
I = b*d^3/12
Short-way: I = 0.2m*0.1m^3/12 = 0.00001667m^4
Tall-way: I = 0.1m*0.2m^3/12 = 0.00006667m^4
Mode 1, Short-way = 501.1Hz
Mode 1, Tall-way = 1002Hz
Compare the free mode 'Inspire' results 490.4Hz and 899.4Hz to the restrained hand calculation 501.1Hz and 1002Hz and it is believable.
Why do the resonant frequencies drop so severely for the restrained cantilever beam model? 79.75 and 155.5Hz for the first two modes is not right.