Efficient ground vibration testing of aircraft based on output-only modal analysis during taxi

2017 ◽  
Author(s):  
Yves Govers ◽  
Julian Sinske ◽  
Jan Schwochow ◽  
Goran Jelicic ◽  
Ralf Buchbach ◽  
...  
Keyword(s):  
Modal Analysis ◽  
Ground Vibration ◽  
Vibration Testing ◽  
Output Only

Output-only modal analysis for non-synchronous data using stochastic sub-space identification

2021 ◽  
Vol 230 ◽  
pp. 111702
Author(s):  
Lin-Jun Lu ◽  
Hua-Fei Zhou ◽  
Yi-Qing Ni ◽  
Fei Dai
Keyword(s):  
Modal Analysis ◽  
Output Only

Modal analysis of low-level-light aiming sight-glass based on vibration testing conditions

2009 ◽  
Author(s):  
Youtang Gao ◽  
Si Tian ◽  
Jianliang Qiao ◽  
Jun Niu ◽  
Benkang Chang
Keyword(s):  
Modal Analysis ◽  
Vibration Testing ◽  
Testing Conditions ◽  
Low Level

scholarly journals Output-Only Modal Analysis Based on Improved Empirical Mode Decomposition Method

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Shiqiang Qin ◽  
Qiuping Wang ◽  
Juntao Kang
Keyword(s):  
Modal Analysis ◽  
Empirical Mode Decomposition ◽  
Modal Parameters ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Random Decrement Technique ◽  
Mode Decomposition ◽  
Frequency Components ◽  
Output Only ◽  
Emd Method

The output-only modal analysis for bridge structures based on improved empirical mode decomposition (EMD) is investigated in this study. First, a bandwidth restricted EMD is proposed for decomposing nonstationary output measurements with close frequency components. The advantage of bandwidth restricted EMD to standard EMD is illustrated by a numerical simulation. Next, the modal parameters are extracted from intrinsic mode function obtained from the improved EMD by both random decrement technique and stochastic subspace identification. Finally, output-only modal analysis of a railway bridge is presented. The study demonstrates the mode mixing issues of standard EMD can be restrained by introducing bandwidth restricted signal. Further, with the improved EMD method, band-pass filter is no longer needed for separating the closely spaced frequency components. The modal parameters extracted based on the improved EMD method show good agreement with those extracted by conventional modal identification algorithms.

Operational Modal Analysis of Aluminum Beams

2007 ◽  
Vol 50 (1) ◽  
pp. 74-85 ◽  
Author(s):  
S. Rudroju ◽  
A. Gupta ◽  
S. Yandamuri
Keyword(s):  
Modal Analysis ◽  
Impact Test ◽  
Force Measurement ◽  
Operating Conditions ◽  
Impact Testing ◽  
Operational Modal Analysis ◽  
Normal Functioning ◽  
Large Structures ◽  
Output Only ◽  
Ambient Excitation

Natural frequencies obtained by modal analysis are important to engineers interested in predicting the dynamic behavior of structures. Traditional modal analysis involves impact testing or shaker testing, where response signal and input force are measured to obtain the transfer function. However, for large structures, input excitation force measurement may be difficult, if not impossible. Large structures may be subjected to ambient excitation; operational modal analysis (OMA), also known as output-only modal analysis, has been used for extracting modal parameters of these types of structures. The main advantage of operational modal analysis is that no artificial excitation is needed, and the analysis is based on measurements of only the output data of the system. Operational modal analysis tests are performed under the actual operating conditions of the system without any change of boundary conditions; the tests use the ambient loads as input and thus do not interfere with the normal functioning of the system. In this study, six aluminum beams of different configurations (beams with and without cuts of various lengths) were used for conducting experiments. Results based on impact test, shaker test, and operational modal analysis are presented.

Quadratic Mode Shape Components From Ground Vibration Testing

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
L. H. van Zyl ◽  
E. H. Mathews
Keyword(s):  
Mode Shape ◽  
Ground Vibration ◽  
Axial Displacement ◽  
Vibration Test ◽  
Transverse Displacement ◽  
Vibration Testing ◽  
Linear Mode ◽  
Quadratic Mode ◽  
Acceleration Signals ◽  
Shape Component

Points on a vibrating structure generally move along curved paths rather than straight lines. For example, the tip of a cantilever beam vibrating in a bending mode experiences axial displacement as well as transverse displacement. The axial displacement is governed by the inextensibility of the neutral axis of the beam and is proportional to the square of the transverse displacement; hence the name “quadratic mode shape component.” Quadratic mode shape components are largely ignored in modal analysis, but there are some applications in the field of modal-basis structural analysis where the curved path of motion cannot be ignored. Examples include vibrations of rotating structures and buckling. Methods employing finite element analysis have been developed to calculate quadratic mode shape components. Ground vibration testing typically only yields the linear mode shape components. This paper explores the possibility of measuring the quadratic mode shape components in a sine-dwell ground vibration test. This is purely an additional measurement and does not affect the measured linear mode shape components or the modal parameters, i.e., modal mass, frequency, and damping ratio. The accelerometer output was modeled in detail taking into account its linear acceleration, its rotation, and gravitational acceleration. The response was correlated with the Fourier series representation of the output signal. The result was a simple expression for the quadratic mode shape component. The method was tested on a simple test piece and satisfactory results were obtained. The method requires that the accelerometers measure down to steady state and that up to the second Fourier coefficients of the output signals are calculated. The proposed method for measuring quadratic mode shape components in a sine-dwell ground vibration test seems feasible. One drawback of the method is that it is based on the measurement and processing of second harmonics in the acceleration signals and is therefore sensitive to any form of structural nonlinearity that may also cause higher harmonics in the acceleration signals. Another drawback is that only the quadratic components of individual modes can be measured, whereas coupled quadratic terms are generally also required to fully describe the motion of a point on a vibrating structure.

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