Determination of Structural Damping Using the Impulse Response Function

This paper shows how the impulse response of each individual resonance in a frequency response function is calculated via a series of weighting functions and then used for damping calculations.

The technique is not new (1)* but previously it has been indicated (2, 3) that when using pseudo-random excitation, T > 2.5τ must be fulfilled in order to make accurate damping measurements, where T is the Fast Fourier Transform record length and τ is the decay constant of the damping.

It is shown that tolerable damping estimates can be made even if the record length T is as small as 0.05τ. This is because the short record length produces an aliasing phenomena on the amplitude of the impulse response function only - not on the slope of the decay.