PREDICTION OF IN-FLIGHT FUNDAMENTAL MODE OF LAUNCH VEHICLE STRUCTURE FROM TWO POINT GROUND VIBRATION TESTS

1997 ◽  
Vol 204 (4) ◽  
pp. 681-689
Author(s):  
A. Joshi
Keyword(s):  
Fundamental Mode ◽  
Ground Vibration ◽  
Launch Vehicle ◽  
Vehicle Structure ◽  
Vibration Tests

FEATURES OF SIMULATING THE FORCE ACTIONS FROM A DAMAGED ENGINE AT GROUND VIBRATION TESTS OF AN AIRPLANE

2016 ◽  
Vol 47 (6) ◽  
pp. 649-663
Author(s):  
Regina Vladimirovna Leonteva ◽  
Vsevolod Igorevich Smyslov
Keyword(s):  
Ground Vibration ◽  
Vibration Tests

Experimental Study on Ground Vibration Caused by the Blast Loading of an Explosion Vessel

2021 ◽  
pp. 2250003
Author(s):  
Jie Gong ◽  
Quan Wang ◽  
Baisheng Nie ◽  
Ze Ge
Keyword(s):  
Explosive Charge ◽  
Blast Loading ◽  
Ground Vibration ◽  
Propagation Distance ◽  
Vibration Velocity ◽  
Frequency Distributions ◽  
Hilbert Huang Transform ◽  
Propagation Law ◽  
Vibration Tests ◽  
Vibration Parameters

To investigate the ground vibration caused by the internal blast loading of an explosion vessel while evaluating the damage caused by vibration propagation to surrounding buildings, a series of explosion vibration tests were carried out using an explosion vessel. The blasting vibration monitors recorded the vibration parameters, and the vibration velocity frequency distributions were analyzed by the Hilbert–Huang transform (HHT) method. The results show that the explosion vibration velocity is closely related to the explosive charge and propagation distance. The effect of an explosive charge and propagation distance on the vibration amplitude at frequencies of 20–60[Formula: see text]Hz is not apparent, but at frequencies of 5–10[Formula: see text]Hz, low-order frequencies are noticeable. Furthermore, the energy amplitude and vibration action duration increase with increasing explosive charge and decrease with increasing propagation distance. The results provide an essential reference for studying the propagation law and effects on ground vibration waves produced by blast loading in an explosion vessel.

In-situ ground vibration tests in Southern Taiwan Science Park

2010 ◽  
Vol 17 (8) ◽  
pp. 1211-1234 ◽  
Author(s):  
Cheng-Hsing Chen ◽  
Tsung-Chen Huang ◽  
Yung-Yen Ko
Keyword(s):  
Ground Vibration ◽  
Science Park ◽  
Southern Taiwan ◽  
Vibration Tests

FLUTTER CALCULATION BASED ON GVT-RESULTS AND THEORETICAL MASS MODEL

Aviation ◽  
2009 ◽  
Vol 13 (4) ◽  
pp. 122-129 ◽  
Author(s):  
Wojciech Chajec
Keyword(s):  
Mass Distribution ◽  
Normal Modes ◽  
Ground Vibration ◽  
Small Mass ◽  
Mode Shapes ◽  
Mass Model ◽  
Stiffness Properties ◽  
Theoretical Mass ◽  
Vibration Tests ◽  
Calculation Software

Ground vibration tests (GVT) are a typical source of data for flutter prediction. In this paper, a simple, lowcost method to calculate flutter is presented. In this method, measured frequencies, mode shapes of an airplane are used and, additionally, the theoretical mass model of it. If the theoretical mass model is used, it is possible to calculate generalized masses of modes and cross mass couplings between them. The mass couplings of normal modes should be zero. Orthogonalization is correction of the mode shapes to lead the couplings to zero. The possible orthogonalization methods are presented in chapter 2. Based on eigenmodes of airplane configuration during GVT, it is possible to determine the eigenmodes of the same free airplane after a relatively small mass change, i.e. for another mass distribution that was not investigated by GVT. In the procedure presented in chapter 3, it is assumed that geometric and stiffness properties do not change. The methodology was used in the own flutter calculation software that is useful for flutter prediction of light airplanes and sailplanes. Santrauka Dažnuminiai bandymai žemėje yra tipinis informacijos šaltinis flaterio skaičiavimui. Šiame straipsnyje pateikiamas paprastas ir pigus flaterio skaičiavimo metodas. Šiame metode naudojamos lėktuvo išmatuotų dažnuminių modų formos ir teorinis lėktuvo masių modelis. Naudojant teorinį masių modelį galima apskaičiuoti apibendrintas modų mases ir masių ryšius tarp jų. Normalinių modų masių ryšys turi būti lygus nuliui. Ortogonalizavimu koreguojamos modų formos, siekiant ryšius sumažinti iki nulio. Galimi ortogonalizavimo metodai pateikti antrame skyriuje. Remiantis lėktuvo laisvųjų svyravimo modomis, gautomis dažnuminių bandymų žemėje metu, galima nustatyti kitokio masių pasiskirstymo įtaką laisvųjų svyravimų modoms. Procedūroje, pateiktoje trečiame skyriuje, manoma, kad geometrinės ir standumo savybės nesikeičia. Ši metodologija buvo panaudota savoje programinėje įrangoje flateriui skaičiuoti, kurią galima naudoti lengvų lėktuvų ir sklandytuvų flaterio skaičiavimui.

scholarly journals Measurement of FRFs and Modal Identification in Case of Correlated Multi-Point Excitation

2008 ◽  
Vol 15 (3-4) ◽  
pp. 435-445 ◽  
Author(s):  
U. Fuellekrug ◽  
M. Boeswald ◽  
D. Goege ◽  
Y. Govers
Keyword(s):  
Modal Analysis ◽  
Conventional Method ◽  
Standard Procedure ◽  
Single Point ◽  
Ground Vibration ◽  
Modal Identification ◽  
Alternative Methods ◽  
Vibration Tests ◽  
Structural Point ◽  
Sine Sweep

The modal identification of large and dynamically complex structures often requires a multi-point excitation. Sine sweep excitation runs are applied when it is necessary to concentrate more energy on each line of the frequency spectrum. The conventional estimation of FRFs from multi-point excitation requires uncorrelated excitation signals. In case of multi-point (correlated) sine sweep excitation, several sweep runs with altered excitation force patterns have to be performed to estimate the FRFs. An alternative way, which offers several advantages, is to process each sine sweep run separately. The paper first describes the conventional method for FRF estimation in case of multi-point excitation, followed by two alternative methods applicable in case of correlated excitation signals. Both methods generate a virtual single-point excitation from a single run with multi-point excitation. In the first method, an arbitrary structural point is defined as a virtual driving point. This approach requires a correction of the modal masses obtained from modal analysis. The second method utilizes the equality of complex power to generate virtual FRFs along with a single virtual driving point. The computation of FRFs and the modal identification using virtual single-point excitation are explained. It is shown that the correct set of modal parameters can be identified. The application of the methods is elucidated by an illustrative analytical example. It could be shown that the separate evaluation of symmetric and anti-symmetric multi-point excitation runs yield obviously better and more reliable results compared to the conventional method. In addition, the modal analysis of the separate symmetric and anti-symmetric excitation runs is easier, since the stabilization diagrams are easier to interpret. The described methods were successfully applied during the Ground Vibration Tests on Airbus A380 and delivered excellent results. The methods are highly advantageous and may thus be established as a new standard procedure for testing aerospace structures.

The Displacement Measurement of Ground Wind Loads for Launch Vehicle

2014 ◽  
Vol 568-570 ◽  
pp. 100-105
Author(s):  
Tao Wang ◽  
Ze Huan Huang ◽  
Hui Zhang ◽  
Bin Zheng
Keyword(s):  
Image Processing ◽  
Digital Image Processing ◽  
Pressure Measurement ◽  
Measurement Model ◽  
Launch Vehicle ◽  
Displacement Measurement ◽  
Wind Pressure ◽  
Wind Loads ◽  
Structure Model ◽  
Vehicle Structure

This paper presented a method of the displacement measurement of ground wind loads for launch vehicle based on laser and Digital Image Processing Technology. The launch vehicle structure model was built by calculating the wind pressure. Measurement model and algorithm for single laser were given. In view of nonrigid component, a method for computing the centroid displacement was presented. Error analysis and error reducing measures were preliminarily discussed.

Ground Vibration Tests on a Flexible Flying Wing Aircraft - Invited

2016 ◽  
Author(s):  
Abhineet Gupta ◽  
Peter J. Seiler ◽  
Brian P. Danowsky
Keyword(s):  
Ground Vibration ◽  
Vibration Tests
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