Damping Ratio Evaluation of the Conventional-model Estimated Formulas by the Half Power Method and Proposal of the Practical Exact Formulas

Abstract

At present, attenuation elements such as the rubber vibration isolator are utilized in order to reduce the resonance of machine structure and building. Especially, "the halfpower method" has been recognized for the identification of damping ratio ζ which shows the damping performance of vibration system for the steady-state response in forced vibration. However, according to the conventional approximate analysis, the error increases over ζ= 0.1, and it is not correspondent to the actual circumstances. On the other hand, the development of the high damping material recently advances, and the case in which it is over the ζ=0.1 damping ratio is increasing very much. Derivation of the exact formula which can correspond for these is urgently necessary. In this report, 1 degree of freedom equivalent model that spring and dashpot were parallelly connected at the mass was set, and it considered response magnification of the force excitation and transmissibility of vibration of the displacement excitation. Especially, half power method using the peak angular frequency was proposed, and then, practical range of damping ratio ζ spread by this method was shown.