Experimental modal analysis of a multi-degree-of-freedom system with random parametric excitation and non-linear damping

1990 ◽  
Vol 4 (3) ◽  
pp. 257-268
Author(s):  
Takeshi Kawashima ◽  
Taro Shimogo
Keyword(s):  
Modal Analysis ◽  
Parametric Excitation ◽  
Experimental Modal Analysis ◽  
Degree Of Freedom ◽  
Non Linear ◽  
Linear Damping

scholarly journals A Decrement Method for Quantifying Nonlinear and Linear Damping in Multi-Degree of Freedom Systems

2006 ◽  
Author(s):  
Craig Meskell
Keyword(s):  
Natural Frequencies ◽  
Degree Of Freedom ◽  
Pass Band ◽  
Response Measurement ◽  
Free Decay ◽  
Decay Test ◽  
Non Linear ◽  
Linear Damping ◽  
The Time Domain ◽  
Single Response

A method is presented which can estimate the linear and non-linear damping parameters in a lightly damped multi-degree of freedom system. This in effect allows the system to be decomposed into a set of single degree of freedom nonlinear systems. Only a single response measurement from a free decay test is required as input. This ensures that the magnitude of the damping parameters is not compromised by phase distortion between measurements. The response is band-pass filtered in the time domain, with the pass band centered on each of the natural frequencies. This provides a set of free response measurements, one for each mode. However, it does introduce a restriction in that the natural frequencies must be distinct and separated somewhat. The instantaneous energy of each trace is used to describe the long-term evolution of the mode. Practically this is achieved by using only the peak amplitudes in each period. In this way the stiffness and inertial forces are effectively ignored, and only the damping forces are considered. For this reason, the method is not unlike the familiar decrement method, which can be used to estimate the viscous damping in linear systems. The method is developed in the context of a weakly non-linear, lightly damping two degree-of-freedom system, with both linear and Coulomb damping. Simulated response data is used to demonstrate the accuracy of the technique.

Detection and description of non-linear phenomena in experimental modal analysis via linearity plots

2005 ◽  
Vol 40 (1) ◽  
pp. 27-48 ◽  
Author(s):  
Dennis Göge ◽  
Michael Sinapius ◽  
Ulrich Füllekrug ◽  
Michael Link
Keyword(s):  
Modal Analysis ◽  
Experimental Modal Analysis ◽  
Non Linear

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

2015 ◽  
Vol 39 (1) ◽  
pp. 145-149 ◽  
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-).

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