Estimation of frequency-averaged loss factors by the power injection and the impulse response decay methods

Abstract

This paper describes a comparison, both analytically and experimentally, between two widely used loss factor estimation techniques frequently used in statistical energy analysis. Analytical models of simple spring/mass/damper systems were created to compare frequency-averaged loss factor values from the single subsystem power injection method and the impulse response decay method. The parameters of the analytical models were varied to study the effects of the total number of modes, amount of damping, location of modes within frequency bands, and the width of the frequency bands on loss factor estimation. The analytical study shows that both methods give accurate loss factor values as long as the damping values remain realistic for linear systems and at least one modal resonance is present in each frequency band. These analytical results were verified experimentally by measuring the loss factors of simple steel plates, with and without damping treatments applied.

Panel Damping Loss Factor Estimation Using the Random Decrement Technique

“…If the excitation point is located on a node line, the loss factors will be over estimated. [8,9] With some engineering judgment and precaution taken during experimentation, these errors can be overcome. Loss factor estimation from the Reverberation Decay Method (RDM) is based on the calculation of the decay rate of free vibrations after the steady state excitation is suddenly interrupted.…”

“…From the Hilbert transformation of decaying response, the exponential decay or envelope can be computed. The loss factor can be then calculated by measuring the decay rate of this envelope and using the following relation [1,8]: …”

“…This may be due to the possibility of the excitation point being positioned on multiple node lines. [8,9] The averaging of autocorrelation function converges quickly with fewer triggers to the simulated loss factor, hence it is recommended for experimental analysis. Also in these simulations, modal damping was constant for all the modes.…”

Study on the Dynamic Mechanical Properties of Viscoelastic Materials Based on Asymmetrical Sandwich Beams

“…The sandwich beams are all of 250 mm length and has one identical 0.1-mm-thick damping layer. Firstly, the geometrical parameter Y can be obtained according to its definition formulas Equation (4). When the effective bending stiffness, uncoupled bending stiffness and system loss factor are achieved by the Kerwin-Ungar theory [10,11], the modal characteristics (modal frequencies, bending stiffness ratios and structure loss factors) can be achieved.…”

“…Specifically, to measure the damping properties of materials, the system damping of structures are usually tested firstly. Methods for the determination and identification of the damping parameter include the decay rate method [3,4], the half-power bandwidth method [5], the power input method [6,7], the circle-fit method [8] and the integral method [9], etc.…”