Reply To: Stiffness Calculation: Modal vs. Static Structural Analyses

[Erik Kostson]

 

 

 

 

 

 

 

Hi

The resonance for the first long. mode is not like ~K/M so not as a mass spring system.

It is more like this.In a rod or bar (fixed at one end) the freq. of the first long. mode is given by: freq. = c_speed_longwave/(4*L) – input the values (E=1050E6,rho=7850, and L=0.01 m) and one gets about 9000 Hz which is not far from the Ansys results.
c_speed_longwave ~ sqrt(E_modulus/rho_density)

For more info on elastic waves and structural vibrations see perhaps some text books (e.g.: Wave Motion in Elastic Solids)

Hope this helps.

Erik