An assessment of damping identification methods (original) (raw)
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Identification of damping: part 1, viscous damping
2001
Characterization of damping forces in a vibrating structure has long been an active area of research in structural dynamics. The most common approach is to use “viscous damping” where the instantaneous generalized velocities are the only relevant state variables that affect damping forces. However, viscous damping is by no means the only damping model within the scope of linear analysis. Any model which makes the energy dissipation functional non-negative is a possible candidate for a valid damping model.
A procedure for the parametric identification of viscoelastic dampers accounting for preload
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2012
Passive vibration isolators are usually made of viscoelastic materials. These materials have non-linear characteristics that change their dynamical properties with temperature, frequency and strain level. The vibration isolator's mathematical modeling and optimal design requires the prior knowledge of the stiffness and damping of the applied viscoelastic material. This work presents a dynamical characterization methodology to identify the stiffness and damping of three samples of viscoelastic rubber with hardness of 25, 33 and 48 SHORE A. The experimental apparatus is a onedegree of freedom vibratory mechanical system coupled to the viscoelastic damper. Sweep sine excitations are applied to the system and the resulting forces and vibration levels are measured. The amplitude of the excitation is controlled to achieve a constant RMS level of strain in the viscoelastic samples. The experimental results are obtained for conditions of no pre-strain and with a 10% of pre-strain. The time domain data is post-processed to generate frequency response functions that are used to identify the damping and stiffness properties of the viscoelastic damper.
Damping modelling and identification using generalized proportional damping
2005
ABSTRACT In spite of a large amount of research, the understanding of damping forces in vibrating structures is not well developed. A major reason for this is that, by contrast with inertia and stiffness forces, the physics behind the damping forces is in general not clear. As a consequence, modelling of damping from the first principle is difficult, if not impossible, for real-life engineering structures.
Damping models for structural vibration
Cambridge University, 2000
This dissertation reports a systematic study on analysis and identification of multiple parameter damped mechanical systems. The attention is focused on viscously and non-viscously damped multiple degree-offreedom linear vibrating systems. The non-viscous damping model is such that the damping forces depend on the past history of motion via convolution integrals over some kernel functions. The familiar viscous damping model is a special case of this general linear damping model when the kernel functions have no memory.
Towards identification of a general model of damping
SPIE proceedings series, 2000
R��sum��/Abstract Characterization of damping forces in a vibrating structure has long been an active area of research in structural dynamics. In spite of a large amount of research, understanding of damping mechanisms is not well developed. A major reason for this is that unlike inertia and stiffness forces it is not in general clear what are the state variables that govern the damping forces. The most common approach is to use viscous damping where the instantaneous generalized velocities are the only relevant state variables. However, ...
Experimental Identification of Generalized Proportional Viscous Damping Matrix
2009
A simple and easy-to-implement algorithm to identify a generalized proportional viscous damping matrix is developed in this work. The chief advantage of the proposed technique is that only a single drive-point frequency response function (FRF) measurement is needed. Such FRFs are routinely measured using the standard techniques of an experimental modal analysis, such as impulse test.
Viscoelastic Damping Technologies–Part II: Experimental Identification Procedure and Validation
This is the second of two companion articles addressing an integrated study on the mathematical modeling and assessment of the efficiency of surface mounted or embedded viscoelastic damping treatments, typically used to reduce structural vibration and/or noise radiation from structures, incorporating the adequate use and development of viscoelastic (arbitrary frequency dependent) damping models, along with their finite element (FE) implementation, and the experimental identification of the constitutive behavior of viscoelastic materials. In the first article [Vasques, C.M.A. et al., Viscoelastic damping technologies-Part I: Modeling and finite element implementation, Journal of Advanced Research in Mechanical Engineering 1(2): 76-95 (2010)] viscoelastic damping has been tackled from a mathematical point of view and the implementation, at the global FE model level, of time and frequency domain methods, namely the internal variables models, Golla-Hughes-McTavish (GHM) and anelastic displacement fields (ADF)
Analytically driven experimental characterisation of damping in viscoelastic materials
Aerospace Science and Technology, 2015
The damping assessment of highly dissipative materials is a challenging task that has been addressed by several researchers; in particular Oberst defined a standard method to address the issue. Experimental tests are often hindered by the poor mechanical properties of most viscoelastic materials; these characteristics make experimental activities using pure viscoelastic specimens prone to nonlinear phenomena. In this paper, a mixed predictive/experimental methodology is developed to determine the frequency behaviour of the complex modulus of such materials. The loss factor of hybrid sandwich specimens, composed of two aluminium layers separated by the damping material, is determined by experimental modal identification. Finite element models and a reversed application of the modal strain energy technique are then used to recover the searched storage modulus and loss factor curves of rubber. In particular, the experimental setup was studied by comparing the solutions adopted with the guidelines given in ASTM-E756-05. An exhaustive validation of the values obtained is then reported.
Identification of damping: Part 3, symmetry-preserving methods
2002
In two recent papers (Adhikari and Woodhouse 2001 Journal of Sound and< ibration 243, 43} 61; 63} 88), methods were proposed to identify viscous and non-viscous damping models for vibrating systems using measured complex frequencies and mode shapes. In many cases, the identi" ed damping matrix becomes asymmetric, a non-physical result. Methods are presented here to identify damping models which preserve symmetry of the system. Both viscous and non-viscous models are considered.
Vibrations in Physical Systems, 2016
An approximate method for determination of dynamic characteristics of structures with viscoelastic dampers is proposed in this paper. A fractional derivative is used to describe the dynamic behaviour of viscoelastic dampers. The method is based on a continuous dependency of the sensitivity of eigenvalue on a certain artificially introduced parameter which scaled up the influence of the damping term in the eigenvalue problem. Some results of a representative calculation are also presented and briefly discussed.