Research on structural health monitoring method for locating space debris impact on spacecraft seal structures

During long-term work,the spacecraft seal structure suffers impacts from the space debris.If the damage can not be detected immediately,disastrous consequences will happen. Therefore the detection of the impacts caused by space debris is essential and meaningful.This work focuses on an ultrasonic guided wave structural health monitoring (SHM)system developed for the spacecraft seal structure inspection.In part one of the study,the Finite Element Modeling of the reinforced panel is created using the finite element software ABAQUS.Then the simula-tion of the impact made by a small iron ball is presented,and the velocity of the ball increases from 500m/s to 10000m/s.Besides,the elastic wave propagation in the panel is also discussed, and the elastic wave propagation characteristics in the stiffened panel are analyzed.The wavelet transform method is used to find out the appropriate analysis frequency of the elastic waves.The conclusion is that the signal components in 50kHz is the optimal selection to detect and locate the iron ball impact.In part two,permanently mounted ultrasonic piezoelectric (PZT)disc sensors arranged as a spatially distributed array is considered for in situ impact monitoring.The impact location and imaging algorithm is based upon the cross correlation between waveforms received by two different transducers.The cross correlation waveforms,which capture the arrival time difference between two pairs,are similarly distributed and summed to form the final image via a hyperbolic relationship.In order to find out the optimal solution among the sensor number,the accuracy of the impact location and the time-consuming,several different arrangements of the sensors are presented.A comparison based on location accuracy in central region,border area and computing time-consuming is made to find out the optimal sensor arrangement in the reinforced panel.In part three,the effects of the algorithm and the sensor arrangement are tested in a labo-ratory environment.Hammer percussion is used as a substitute for the iron ball impact in these tests.As many as 20 repeated hammer shocks are made for each selected point in the stiffened panel.The results verify the accuracy and stability of the algorithm for impact detection and lo-calization in the complex spacecraft structure.