Learning Forum

[fx213]

Hello,

I wanted to make a query on the damping factors α and β that we select, when we decide to add damping in a transient dynamic, harmonic or modal damped analysis. How do we calculate these factors, that related to the mass damping and stiffness damping respectively, based on tests data?

Do we use some values or equations existing in the literature,that includes a material-dependent damping ratio and element damping?

Damping factor alpha, α is the constant mass matrix multiplier and beta, β is the constant stiffness matrix multiplier in the damping matrix C in ANSYS for vibration damping.

How could I use ALPHAD and BETAD Commands in ANSYS, in case that I can calculate these factors in that way?

I am interested in applying damping in a transient dynamic FEA analysis and specifically for an elastomer material to study.

Thank you.

Kind regards,

FX

[peteroznewman]

What test data do you have?

[fx213]

Hi,

I have axial compression, radial compression and tensile uniaxial test data only for rubber specimens.

[peteroznewman]

Great!  What damping test data do you have?

[fx213]

I don`t have damping test data available for these tests.

[peteroznewman]

When you said, "How do we calculate these factors, that related to the mass damping and stiffness damping respectively, based on tests data?" I thought you had some damping data.

"Do we use some values or equations existing in the literature,that includes a material-dependent damping ratio and element damping?"  Yes, look up some values of damping ratio in the literature that relate to this material.

If you come up with a desired damping ratio, I can help convert that to Rayleigh damping coefficients α and β but you need to specify the frequency range over which you want the damping ratio to be correct. Damping is frequency dependent, so you should build a Modal analysis and understand what the natural frequencies are in your structure.