| Landing gear is an important component of the main load-carrying structures of plane, and hasdirectly relationship with the plane landing and take-off security. Structural health monitoring is thebase of monitoring equipment status and fault diagnosis, with current concerns of aviation and largeinfrastructure safety, the technology has been paid of increasing attention. In this paper, the typicalstructure of the landing gear materials-steel, steel pipe, which was made with300M steel, had ahealth monitoring study respectively. In these researches, propagation characteristics of steel plateLamb wave and steel tube guided wave were simulated and analyzed, and electromechanical couplingof damaged structures which were based on piezoelectric monitoring was analyzed.According to the monitoring requirements, a set of active health monitoring system with thepiezoelectric incentive/sensing diagnosis technology and monitoring equipment was developed for theexperimental research of the on-line monitoring, orientation, image recognition and prediction ofplate、tube structure damage of landing gear300M steel material.The developed fiber Bragg grating vibration sensor used the form of a double grating to overcome thetemperature-strain cross-sensitivity, and achieved monitoring of the physical quantities such asvibration and shock during health monitoring of aircraft landing gear structural vibration fatigue.This paper includes the following aspects:First, draw Lamb wave frequency dispersion curve of steel plate and steel tube in the method offinite element numerical analysis software, in view of the complexity of Lamb wave propagationcharacteristics, which contain characteristics such as frequency dispersion、multimould and soon,simulat the process of Lamb wave propagation. Later played the electromechanical couplinganalysis, do research on the modal of steel plate which have paste the piezoelectric on it in two status:health and damage. Then analyze the influence of different operating conditions to waveformcommunication in steel tube.Second, according to the research content and laboratory condition, designed scheme and buildthe experimental system. Use of piezoelectric ceramic (PZT) as incentive and response respectively tothe test, find out the corresponding change rule of the response waveform process before and afterdamage. Based on the signal wavelet packet energy spectrum decomposition, we extract characteristicvector to construct the damage index. Third, use the damage image reconstruction algorithm, through the influence of linearsummation of each group incentive/sensing signal’s change to express the probability distribution ofdefects in the image, not only detect the damage occurs, position, scope and extent informations, alsoexpected to monitoring more than two damages. Using threshold processing, we can quantitativeestimate the scope of the damage, reflect the extent of the damage clearly. Experiment results andactual conditions according well.Fourth, use the LS_SVM regression method to detection the damage position in steel. Do loadingtest in different positions of steel tube specimen surface, and extraction the feature of wavelet packetspectrum decomposition energy of sensor’s response signal, provide the training sample and testsample, finally using LS_SVM regression to predict damage position.Fifth, according to the requirements of vibration test，develope a kind of optical fiber gratingvibration sensor based on bow beam sensitive characteristic. This system realized the temperaturecompensation by use of double gratings, it shows good sensitivity and repeatability, small frequencyresponse error, applicable to physical quantities monitoring such as vibration and impact of planelanding gear structure vibration fatigue health monitoring. |
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