Modal analysis of a typical fighter aircraft using transient testing technique

Balasubramaniam, R and Ramakrishna, DS and Vijayakumar, PS (1985) Modal analysis of a typical fighter aircraft using transient testing technique. Technical Report. National Aeronautical Laboratory, Bangalore, India.

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Estimation of dynamic performance of individual structural13; ,components of an aircraft and the aircraft as a whole is very valuable for designers. Measurements of dynamic properties of the aircraft and its components therefore foqm a vital input to analysis. One of the earlier methods in the measurement was to,apply a controlled sinusoidal force input to the component and the ratio of output response to input force i.e. compliance versus excitation frequency is plotted. This frequency response data can then be used to estimate damping properties at each13; natural frequency. However, this approach is time consuming and I tedious. Transient testing technique generally overcomes these short comings.In this paper transient test technique is applied to carryout13; modal analysis on a full scale typical fighter aircraft. The aircraft is tested on ground with partially inflated tyres. One hundred and thrity nine locations are chosen for transient inputs using a n instrumented hammer and on-line data reduction for modar propsrties is carriedout using a minicomputer. The paper presents results upto first six modes the natural frequency,modal mass modal stiffness and damping. Mode shape plots for all the six modes are also presented. A critical discussion of the experience gained while carryingout these tests on (a)13; test set-up, (b) choice of locations for excitation, (clactual test procedure is presented. Comparison of results of overall system natural frequencies and damping is made with available component natural frequencies and damping ratios.The paper also discusses various advantages and disadvantages of sweep-sine, step relaxtion, random and transient test methods as applied to the modal analysis of aerospace structures

Item Type: Monograph (Technical Report)
Uncontrolled Keywords: Vibration;Modal analysis;Transient testing
Subjects: ENGINEERING > Structural Mechanics
Depositing User: M/S ICAST NAL
Date Deposited: 03 Oct 2006
Last Modified: 24 May 2010 04:21

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