modal analysis

[marouaha]

hello,
Can i determine the effect of friction on the modal damping values? using a finite element method

 

[marouaha]

or i must applay a sunusoidal force and then determin the modal damping

 

[Rhei]

Hi,

the normal modes analysis available in Nastran does not take into account the damping, in fact the equation of motion is

[M]{a} + [K]{u} = 0

which is the equation of motion for undamped free vibration (where: [M] is the mass matrix, [K] the stiffness matrix, {a} the acceleration and {u} the displacement vectors).

To take into account modal damping you need to run a frequency analysis with a force applied to the structure.

Regards

 

[marouaha]

hi,
can you dtermine the strain energy to calculate the damping??
thx regard