Prokofiev A., Lenchine V., Shakhmatov E.

Estimation of damping properties is one of most important tasks in structural dynamics. Despite noticeable development of finite element methods (FEM) results of the modeling can be inaccurate especially for complex structures at comparatively high frequencies. Therefore experimental techniques are widely employed for estimation of energy dissipation in a structure. Impact hammer method with analysis of the decay curve in time domain or accelerance function (frequency domain) is commonly used in engineering practice. Unfortunately accuracy of calculations is impaired by noise components of the recorded time signal. It is proposed method to calculate logarithmic decrement corresponding to natural frequencies of a structure with linear viscous friction that does not depend on amplitude of excitation. The method is based on Morlet wavelet transform of a measured decay curve. The derived formula enables to extract logarithmic decrement without complex signal processing and computational procedures. The technique can be employed for decay curve containing several natural frequencies. The proposed procedure should be applied to every frequency apart. Details of the signal processing are described. The technique is not sensitive to noise component presented in a measured signal. It provides high accuracy in detection of damping properties of a structure even at not satisfactory signal-to-noise ratio. This fact is demonstrated by calculation results when noise is added to the original signal. Logarithmic decrement of the pipe’s natural mode is calculated as a demonstration of the method. Examples also show robustness of the technique to noise components. These peculiarities of the proposed method make it attractive for practical implementation.