Operational Modal Analysis Techniques used for Global Modes Identification of Vehicle Body Excited from a Vehicle in Idle Engine

2012 ◽  
Author(s):  
Robson Demetrius Araujo Abreu ◽  
Frederico Moura
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Vehicle Body ◽  
Analysis Techniques ◽  
Global Modes

Brake Moan Noise Study through Experimental and Operational Modal Analysis Techniques in a Passenger Car

2017 ◽  
Author(s):  
Alexis Klauber Chaia Kléperon ◽  
Robson Demétrius Araújo Abreu ◽  
Rômulo Morais Bitencourt ◽  
Francis José Marochi Almeida
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Passenger Car ◽  
Analysis Techniques

Operational Modal Analysis for Dynamic Characterization of a Ro-Lo Ship

2014 ◽  
Vol 58 (04) ◽  
pp. 216-224 ◽  
Author(s):  
Esben Orlowitz ◽  
Anders Brandt
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Operating Conditions ◽  
Operational Modal Analysis ◽  
Mode Shapes ◽  
Dynamic Characterization ◽  
Sea Trial ◽  
Global Modes ◽  
Bending Modes

The dynamic characteristics of ship structures are becoming more important as the flexibility of modern ships increases, for example, to predict reliable design life. This requires an accurate dynamic model of the structure, which, because of complex vibration environment and complex boundary conditions, can only be validated by measurements. In the present paper the use of operational modal analysis (OMA) for dynamic characterization of a ship structure based on experimental data, from a full-scale measurement of a 210-m long Ro-Lo ship during sea trial, is presented. The measurements contain three different data sets obtained under different operating conditions of the ship: 10 knots cruising speed, 18 knots cruising speed, and at anchor. Natural frequencies, modal damping ratios, and mode shapes have been successfully estimated for the first 10 global modes. Damping ratios for the current ship were found within the range 0.9%–1.9% and natural frequencies were found to range from 0.8 to 4.1 Hz for the first 10 global modes of the ship at design speed (18 knots). The three different operating conditions showed, in addition, a speed dependency of the natural frequencies and damping ratios. The natural frequencies were found to be lower for the 18-knots condition compared with the two other conditions, most significantly for the vertical bending modes. Also, for the vertical bending modes, the damping ratios increased by 28%–288% when the speed increased from 10 to 18 knots. Other modes were not found to have the same strong speed dependency.

Application of Operational Modal Analysis on Railway Vehicles Using on Track Measurements

2013 ◽  
Author(s):  
Lara Mª Erviti Calvo ◽  
Gorka Agirre Castellanos ◽  
Igor Alonso Portillo
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Modal Parameters ◽  
Railway Vehicle ◽  
Correct Identification ◽  
Static Test ◽  
Railway Vehicles ◽  
Analysis Techniques ◽  
Behavior Design ◽  
Nonlinear Components

Nowadays the application of experimental modal analysis techniques on railway vehicles is gaining importance. A correct identification of modal characteristics allows improving the dynamic behavior design of the vehicle and so reaching higher running speeds and accomplishing better comfort levels. So far, in the railway sector only conventional modal analysis techniques have been used. With these techniques, the modal parameters are determined during a static test by measuring the responses of the system to one or multiple known forces. This paper presents the application of the Operational Modal Analysis (OMA) technique on a railway vehicle. This technique determines the modal parameters employing only the responses of the system to an unknown excitation. In this way, the data to be used can be acquired during on track test which presents three main advantages. The first one is that the nonlinear components of the suspensions are working in their normal operating condition which is difficult to achieve during a static test. The second one is that the wheel spinning effect is taken into account. Finally, the test can be combined with other type of track tests, reducing the period of time before delivery of the vehicle to the client. In the case under study, the OMA technique is applied by means of commercial software to measurements performed on a passengers train. The modal parameters obtained for the carbody and one of the bogies are presented.

scholarly journals Transmissibility-Based Operational Modal Analysis: Enhanced Stabilisation Diagrams

2012 ◽  
Vol 19 (5) ◽  
pp. 1085-1097 ◽  
Author(s):  
Gert De Sitter ◽  
Christof Devriendt ◽  
Patrick Guillaume
Keyword(s):  
Modal Analysis ◽  
Power Spectra ◽  
Element Model ◽  
Operational Modal Analysis ◽  
Second Step ◽  
New Approach ◽  
Analysis Techniques ◽  
Estimated Parameters ◽  
Using Data ◽  
Acoustical Data

Recently it has been shown that also transmissibilities can be used to identify the modal parameters. This approach has several advantages: because of the deterministic character of the transmissibility functions, the estimated parameters are more accurate than the results obtained with the power spectra based operational modal analysis techniques. Another advantage is that the transmissibility functions do not depend on the colouring of the unknown forces. A disadvantage of the transmissibility based operational modal analysis techniques is that non-physical modes show up in the stabilisation diagrams. In this contribution it will first be shown that those non-physical modes will show up when traditional stabilisation diagrams are used. In a second step, a new approach of selecting the physical modes out of a set of estimated modes will be discussed and the new approach will be validated using data generated with an acoustical Finite Element Model. Finally, the approach will be validated using real acoustical data.

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