Some Remarks on the Identification of Damping Parameters at the Boundary of Vibrating Systems

Peter Hagedorn; Ulrich Pabst

doi:10.1115/1.3005057

Some Remarks on the Identification of Damping Parameters at the Boundary of Vibrating Systems

Applied Mechanics Reviews ◽

10.1115/1.3005057 ◽

1995 ◽

Vol 48 (11S) ◽

pp. S107-S110

Author(s):

Peter Hagedorn ◽

Ulrich Pabst

Keyword(s):

Mathematical Modeling ◽

Modal Analysis ◽

Mechanical Systems ◽

Experimental Modal Analysis ◽

Steel Beam ◽

Modal Data ◽

Stiffness And Damping ◽

Parameter Values ◽

Vibrating Systems

In many cases, vibrating mechanical systems permit a reliable mathematical modeling with parameter values which are reasonably well known beforehand, except for the joints between different subsystems and at the boundaries. The boundary stiffness, which is often assumed as infinite, and the damping at the boundary, which is frequently ignored, are typically not well known. In this note, we discuss the identification of the boundary stiffness and damping parameters from modal data. As an example, we treat an elastic steel beam, for which an experimental modal analysis had been carried out in our laboratory.

Download Full-text

Online Estimation Techniques for Natural and Excitation Frequencies on MDOF Vibrating Mechanical Systems

Actuators ◽

10.3390/act10030041 ◽

2021 ◽

Vol 10 (3) ◽

pp. 41

Author(s):

Gerardo Silva-Navarro ◽

Francisco Beltran-Carbajal ◽

Luis Gerardo Trujillo-Franco ◽

Juan Fernando Peza-Solis ◽

Oscar A. Garcia-Perez

Keyword(s):

Degrees Of Freedom ◽

Frequency Estimation ◽

Mechanical Systems ◽

Algebraic Approach ◽

Estimation Algorithms ◽

Lumped Parameter ◽

Harmonic Components ◽

Stiffness And Damping ◽

Euler Bernoulli Beam ◽

Vibrating Systems

An online algebraic estimation technique for natural and forcing frequencies for a class of uncertain and lumped-parameter vibrating mechanical systems with n degrees of freedom is described. In general, realistic vibrating systems can be affected by unknown exogenous excitation forces with multiple and independent frequency harmonic components. Hence, natural frequencies as well as excitation force frequencies can be simultaneously computed from an algebraic approach into a small interval of time during online operation of the mechanical system. Measurements of an available output signal, associated with some specific degree of freedom, are only required for frequency estimation in time-domain. Information on mass, stiffness and damping matrices are not necessary for multifrequency estimation algorithms. Some analytical, numerical and experimental results on a cantilever Euler–Bernoulli beam are described to show and validate the acceptable estimation of multiple frequencies in forced multiple degrees of freedom vibrating systems.

Download Full-text

Experimental Modal Characterization of MEMS Switches

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.403-408.4598 ◽

2011 ◽

Vol 403-408 ◽

pp. 4598-4605

Author(s):

Joel M. Book ◽

Samuel F. Asokanthan ◽

Tian Fu Wang

Keyword(s):

Modal Analysis ◽

Mechanical Systems ◽

Noise Signal ◽

Experimental Modal Analysis ◽

Modal Parameters ◽

Mems Devices ◽

Micro Electro Mechanical Systems ◽

Mems Switches ◽

Stochastic Subspace Identification

MEMS devices, Micro Electro-Mechanical Systems, are electrical and mechanical systems with characteristic dimensions on the order of microns. Since these systems have moving mechanical parts, characterization of their dynamics, including their modal parameters, is highly desirable. This paper describes the validation of an existing implementation of the Stochastic Subspace Identification (SSI) algorithm, called MACEC, for experimental modal analysis of a micro-cantilever switch. A white noise signal applied to the built-in electrostatic actuator in the switches excited a response measured using microscanning Laser Doppler Vibrometry (LDV). The modal parameters found using MACEC matched well those predicted by theory, thus validating this combination for experimental modal analysis of MEMS structures.

Download Full-text

Effect of Bass Bar Tension on Modal Parameters of a Violin's Top Plate

Archives of Acoustics ◽

10.2478/aoa-2014-0015 ◽

2015 ◽

Vol 39 (1) ◽

pp. 145-149 ◽

Cited By ~ 3

Author(s):

Ewa B. Skrodzka ◽

Bogumił B.J. Linde ◽

Antoni Krupa

Keyword(s):

Modal Analysis ◽

Experimental Modal Analysis ◽

Mode Shapes ◽

Modal Parameters ◽

Normal Value ◽

Modal Damping

Abstract Experimental modal analysis of a violin with three different tensions of a bass bar has been performed. The bass bar tension is the only intentionally introduced modification of the instrument. The aim of the study was to find differences and similarities between top plate modal parameters determined by a bass bar perfectly fitting the shape of the top plate, the bass bar with a tension usually applied by luthiers (normal), and the tension higher than the normal value. In the modal analysis four signature modes are taken into account. Bass bar tension does not change the sequence of mode shapes. Changes in modal damping are insignificant. An increase in bass bar tension causes an increase in modal frequencies A0 and B(1+) and does not change the frequencies of modes CBR and B(1-).

Download Full-text

Damage evaluation of sandwich material on side plate hull using experimental modal analysis

Materials Today Proceedings ◽

10.1016/j.matpr.2021.04.293 ◽

2021 ◽

Author(s):

R.C. Ariesta ◽

A. Zubaydi ◽

A. Ismail ◽

T. Tuswan

Keyword(s):

Modal Analysis ◽

Experimental Modal Analysis ◽

Damage Evaluation ◽

Side Plate

Download Full-text

On the use of experimental modal analysis for system identification of a railway pantograph

International Journal of Rail Transportation ◽

10.1080/23248378.2020.1786743 ◽

2020 ◽

pp. 1-12

Author(s):

Petter Nåvik ◽

Stefano Derosa ◽

Anders Rønnquist

Keyword(s):

System Identification ◽

Modal Analysis ◽

Experimental Modal Analysis

Download Full-text

The Use of Modan 3D in Experimental Modal Analysis

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.486.36 ◽

2013 ◽

Vol 486 ◽

pp. 36-41 ◽

Cited By ~ 3

Author(s):

Róbert Huňady ◽

František Trebuňa ◽

Martin Hagara ◽

Martin Schrötter

Keyword(s):

Modal Analysis ◽

Vibration Analysis ◽

High Speed ◽

Mechanical Vibration ◽

Steel Sample ◽

Experimental Modal Analysis ◽

Image Correlation ◽

Optical Methods ◽

Mode Shapes ◽

Vibration Modes

Experimental modal analysis is a relatively young part of dynamics, which deals with the vibration modes identification of machines or their parts. Its development has started since the beginning of the eighties, when the computers hardware equipment has improved and the fast Fourier transform (FFT) could be used for the results determination. Nowadays it provides an uncountable set of vibration analysis possibilities starting with conventional contact transducers of acceleration and ending with modern noncontact optical methods. In this contribution we mention the use of high-speed digital image correlation by experimental determination of mode shapes and modal frequencies. The aim of our work is to create a program application called Modan 3D enabling the performing of experimental modal analysis and operational modal analysis. In this paper the experimental modal analysis of a thin steel sample performed with Q-450 Dantec Dynamics is described. In Modan 3D the experiment data were processed and the vibration modes were determined. The reached results were verified by PULSE modulus specialized for mechanical vibration analysis.

Download Full-text