A frequency domain interpolation method for damping ratio estimation

Damping ratio is usually needed for structure dynamics analysis. To improve the accuracy of damping ratio estimation and make it benefit for engineering application has been a difficult problem. A new method for the estimation of damping ratio which is necessary for structure dynamics analysis is presented. Under-damped free vibration response and damped exponential signals have the same expression. At first, the frequency spectrum of a damped exponential signal is obtained by Fast Fourier Transformation (FFT); then the damping factor and frequency deviation are calculated by frequency domain interpolation, which employ the ratio of two neighboring spectral samples. The damping ratio is easily determined from the definite relationship between the damping ratio and damping factor. Experiment shows the good accuracy, compared with traditional methods, proving the reliability of the proposed method in engineering application. Thus, this frequency domain interpolation method provides an alternative way for damping ratio estimation.