Hi,

You can compute the damping ratio from the frequency response function (FRF) using the amplification factor (Q), which is a measure of how undamped a system is. When analyzing a frequency response plot with multiple peaks at natural frequencies, you can determine the damping ratio at each peak:

1. Extract the natural frequency (f_n) where the curve has the maximum amplitude (A_max).

2. Compute the value of A_max divided by the square root of 2.

3. At this amplitude value, you will find two intersections with the curve, and extract the respective frequencies (f_1 and f_2).

4. Compute the amplification factor (Q) using the equation: Q = (f_n) / (f_2-f_1).

5. Calculate the damping ratio using the formula: damping ratio = 1 / (2*Q).

Are you using this approach?

Regards,

Ashish Khemka