IDENTIFICATION OF DAMPING CHARACTERISTICS OF VISCOELASTICALLY DAMPED STRUCTURES USING VIBRATION TEST-RESULTS

Damping plays an important role in structural stability and vibration control and so frequently special efforts are taken to increase struct ural damping, of which the most effective measure to date is the visco elastic damping treatment. However, damping properties, especially tho se of viscoelastic damping, are the most difficult to model analytical ly but can only be revealed by vibration test. This paper examines the feasibility of identifying damping characteristics of viscoelasticall y damped structures whose damping and stiffness characteristics are fr equency dependent by correlating finite element modelling with vibrati on test results and presents an effective method for achieving such an objective. Measured frequency response function data are used instead of conventional modal data, since in the case of viscoelastically dam ped structures that are frequency dependent modal data me not defined while frequency response functions can be easily measured. The method is developed based on the practical assumption that the measured coord inates are incomplete and the identified damping matrix is physically meaningful and possesses the same physical connectivity as that of the stiffness matrix. Computational aspects regarding the practical appli cation of the proposed method are discussed. Several numerical case st udies are given to demonstrate the practical applicability of the prop osed method.