An average inverse power ratio method for the damping estimation from a frequency response function

The well-known bandwidth method, especially the half-power bandwidth method [1], [3] and [4] (Bishop and Gladwell, 1963; Nashif et al., 1985; Yin, 2008) is probably the simplest method for the damping estimation from a frequency response function (FRF). This method is quite efficient for simple model test cases when modes are well separated. However, the determination of the two frequencies corresponding to a given power ratio value requires numerical interpolations of experimental discrete data of frequency response functions. In this paper, an average inverse power ratio method is proposed. The average value is computed at two frequencies symmetrically located from a peak amplitude frequency. Then the damping ratio can be estimated by using a formula similar to that of the bandwidth method. In this way, the damping estimation becomes straightforward from the FRF data. This new method could be useful for engineers in practice due to its extreme simplicity.