AN Identification Method of Damping Matrix for Frame Structures

2011 ◽  
Vol 243-249 ◽  
pp. 967-970
Author(s):  
Sha Sha Dong ◽  
Wei Ying Wang ◽  
Fu Shun Liu ◽  
Zhi Qiang Gao
Keyword(s):  
Modal Analysis ◽  
Dynamic Characteristic ◽  
Experimental Modal Analysis ◽  
Frame Structure ◽  
Frame Structures ◽  
Order Complex ◽  
Identification Method ◽  
Damping Matrix ◽  
Complex Modes ◽  
Different Parts

Nowadays, damping is still the important dynamic characteristic that is the least understood and the most difficult to quantify. The advantage of the proposed damping matrix identification method is that several low order complex modes achieved by Experimental Modal Analysis (EMA) are capable of calculation precision. In order to identify the damping matrix, this paper also proposes a general damping matrix decompositon technique, which can be used in the situation that different parts of the structure have different damping. Then a five-story frame structure is applied to demonstrate the proposed method ,and the results obtained show the suitability of this approach for damping matrix identification in frame structures.

The Dynamic Research of Industrial Sewing Machines Based on the Modal and Operational Deformation Analysis

2013 ◽  
Vol 432 ◽  
pp. 269-274
Author(s):  
Ya Jun Li ◽  
Li Zhang ◽  
Yan Miao Ma ◽  
Bin Liu
Keyword(s):  
Noise Reduction ◽  
Modal Analysis ◽  
Dynamic Characteristic ◽  
Fundamental Frequency ◽  
Experimental Modal Analysis ◽  
Harmonic Vibration ◽  
Modal Parameters ◽  
Deformation Analysis ◽  
Sewing Machine ◽  
Harmonic Frequencies

The vibration of the operational sewing machine is caused mostly by the fundamental frequency of the motor and its harmonic frequencies. The experimental modal analysis was conducted on a certain industrial sewing machine to identify its modal parameters. The operational deformation analysis was carried out and the actual deformation in the first six harmonic frequencies of the main speed frequency was obtained. Finally, the dynamic characteristic was identified by analyzing how each mode influences the harmonic vibration. This paper provides a valuable reference for noise reduction of the sewing machine.

scholarly journals Vibration Analysis of the Drivetrain in Dependence on the Type of Gearbox Suspension Bushing

2021 ◽  
Vol 71 (1) ◽  
pp. 121-130
Author(s):  
Struz Jiri ◽  
Hruzik Lukas ◽  
Havlik Jiri
Keyword(s):  
Modal Analysis ◽  
Analytical Method ◽  
Vibration Analysis ◽  
Great Distance ◽  
Experimental Modal Analysis ◽  
Main Subject ◽  
Shaft Length ◽  
Heavy Truck ◽  
Different Parts ◽  
Fft Analysis

Abstract In the vast majority of technical applications, there is a necessity to transmit the torque from drive to driven machine together with the demand to overcome great distance between given devices. One of the solutions of this problem is the use of a cardan shaft. Operations of connecting shaft and drivetrain are accompanied by oscillations negatively influencing the driver comfort. Main subject of this article is the measurement of vibrations on different parts of a heavy truck and its evaluation by FFT analysis. Measurements are performed with two kinds of suspension bushing which are compared with to each other. Based on the previous measuring, influence of cardan shaft length was also investigated. First of all, dependency on the length of the cardan shaft on deflection angles for V arrangement was evaluated by analytical method. The theoretical introduction is followed by research of eigen frequency depending on the length of the cardan shaft. The results obtained by modal analysis in FEM are verified by experimental modal analysis [1].

Experimental Modal Analysis of CNC High Precision Surface Grinder with Horizontal Spindle and Rotary Table MGK7350

2010 ◽  
Vol 97-101 ◽  
pp. 3637-3641
Author(s):  
Yong Cai ◽  
Ze Yu Weng ◽  
Nan Nan Zhang ◽  
Jin Hua Yang ◽  
Wei Hua Yuan
Keyword(s):  
Modal Analysis ◽  
Dynamic Characteristic ◽  
High Precision ◽  
Experimental Modal Analysis ◽  
Weak Links ◽  
Modal Parameters ◽  
Rotary Table ◽  
Modal Test

The dynamic characteristic of CNC high precision surface grinder with horizontal spindle and rotary table MGK7350 was studied by using modal test. Through the analysis of modal parameters, the weak links were pointed out.

The Directly Damaged Identification Method of Frame Structures Based on Residual Force Vector

2008 ◽  
Vol 385-387 ◽  
pp. 313-316
Author(s):  
Wan Jie Zou ◽  
Wei Lian Qu
Keyword(s):  
Damage Identification ◽  
Frame Structure ◽  
Frame Structures ◽  
Connectivity Matrix ◽  
Matrix Perturbation ◽  
Vector Equation ◽  
Force Vector ◽  
Structure Damage ◽  
Identification Method ◽  
Residual Force

By using the intrinsic character of the frame structures, a new direct damage identification method of the frame structures based on residual force vector is presented. The stiffness connectivity matrix is obtained by sensitivity analysis. The stiffness matrix perturbation of the damaged structure can be expanded by the stiffness connectivity matrix, then substituting it into residual force vector equation, the new residual force vector equation expressed by the stiffness connectivity matrix is obtained. This equation can be solved directly, so the stiffness perturbation of layers is got, by it, the damaged locations and the extents of the frame structures are identified. At last, a numerical example of a seven-layer frame structure is given, the identification result shows that, only with the first-order mode of the damaged structure, the damage can be identified accurately. Even in considering of some degreed noise of the mode parameters, the structure damage can be identified well, demonstrating the effectiveness of presented method.

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-).

The Use of Modan 3D in Experimental Modal Analysis

2013 ◽  
Vol 486 ◽  
pp. 36-41 ◽  
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.

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