The Detection Of Impact And Crack Of The Aviation Aircraft Structure Based Optical Fiber Bragg Grating

With the new technology applied to the process of aircraft design and manufacture continuously,the performance of the aircraft becomes enhanced a lot,the service live becomes longer.At the same time,factors such as structural shocks and crack test the structural health of aircraft structure all the time,and aircraft structural health monitoring has been widely concerned by researchers.Based on its unique advantages,fiber Bragg grating(FBG)sensor has become a hotspot in the researcher's attention in the field of structural damage detection.When applied to the structural damage detection,it has many advantages over traditional sensors.So,it has a great research significance and application value to design a high precision sensing network based on FBG for the impact and crack detection of aircraft structural.For the problem of complicated structure,low real-time and establishing a training set of traditional positioning system,the FBG sensor combined with rectangular strain rosette structure is adopted to establish the model of detecting the main strain direction angle,the principal strain direction of the impact is respectively measured by two FBG rectangular strain rosette structures placed in different locations,and their intersection point determines the impact source coordinates.At the same time,for the structure of the four edges simply supported plate,a novel method based on immunity curve is proposed for determining the impact load.Under the plane strain,FBG sensor is affected by the transverse effect and transverse strain,transverse effect correction factor model and the strain of decoupling model are established,which proves that the rectangular strain rosette structure used for localization is not influenced by the transverse effect.At last,a method that detects impact position and impact load based on FBG rectangular strain rosette structures is proposed.For the problem of the traditional blind source separation method needs to know the numbers of cracks in advance,the method combined cross validation algorithm with blind source separation method is introduced.For the problem that the acoustic emission signals contain the impact and friction acoustic emission signals,the method based on weighted censored algorithm is adopted to eliminate fake crack signal.For the problem that the FBG wavelength is difficult to determine,a wavelength drift extraction strategy is designed based on threshold method.A last,a method that locate multi-crack is proposed.At the same time,from the aspects of low accuracy and low real-time of traditional parameter identification system,for the detection of detected point by FBG,establish transverse effect correction factor model to improve accuracy,for the problem of the dynamic particle swarm optimization algorithm fall into local optimal easily,the principal strain direction angle is adopted to coarsely locate the center of the crack,and then initialize the particle,to improve the performance of accuracy and real-time,the weighted factor is modified and the terminating condition is designed,and to test the performance of PSO,a well-known benchmarks of the mathematical test function are first solved.And then a method combined a FBG rectangular strain rosette structure,improved PSO and the BFM model is put forward.To verify the feasibility of the proposed method,the experiment simulation platform is set up,the experimental results show that the localization accuracy is within 2.9 cm,real-time localization around 1 ms,error of impact load prediction with 3 N.At the same time,the optimum algorithm simulation results show that the average number of iterations of the proposed algorithm is 17,the average error is 2.04,the average time is 1.95 s,and the learning factors should be greater than 0.4.The feasibility of the proposed method is verified.