Comparison between viscous and hysteretic damping models

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Comparison between viscous and hysteretic damping models

 

Author: Shen, Guodong
Title: Comparison between viscous and hysteretic damping models
Degree: M.Sc.
Year: 2011
Subject: Hong Kong Polytechnic University -- Dissertations
Damping (Mechanics)
Department: Dept. of Civil and Structural Engineering
Pages: xii, 91 p. : ill. ; 30 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2412766
URI: http://theses.lib.polyu.edu.hk/handle/200/5975
Abstract: Damping models are set up to perform the dynamic motion with energy dissipation. This study aims to investigate the relations between viscous and hysteretic damping models, and to emphasize the results by numerical cases and experimental study. The relations between two models with proportional damping have been found out based on normalization procedures. There exist two numerical normalization procedures to derive the mode shapes base on the two different damping models by solving the eigenproblem of a dynamic system. Although the two procedures are different, the derived mode shapes are almost the same except differing by a complex scaling factor. The relations between two models secondly have been found out based on modal identification procedure. We have two FRF models to extract the modal parameters and mode shapes base on two damping models. By performing curve-fitting or other methods on the two similar FRFs we can find the damping parameters and the corresponding mode shapes separately. The two FRF models should be the same because they are derived out based on the same system. So we found the relation between modal parameters based on two FRF models as nᵣ=2ξᵣ and for proportional case there also exists a scaling factor between the two mode shapes. Numerical case study was carried out to illustrate the relationship found in normalization procedures and experimental study was carried out to find out which model is more accuracy for a real system. Finally we confirm that the difference between structure vibration properties derived out from viscous damping model and hysteretic damping model is really small and this can be ignored safely. But the damping mechanism of hysteretic damping model that the damping is proportional to displacement and not to velocity conforms to the experimental result better.

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