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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Structure Damage Identification Technique,Based on OPCM Sensors and Gabor wavelet,Y.,Luo,R.R.Gong J.Z.Gu G.Q.Zhao,Faculty of Science,Jiangsu University,Zhenjiang,，Jiangsu,212013,P.R.China,AET(Acoustic Emission Technique),Prominent advantage,real time monitoring,dynamic monitoring,convenience,covering large areas,acquiring original damage information by AE sensors,Introduction,SHM(Structure Health Monitoring),Significance,Crack-growth detection and monitoring,PZT sensors,Advantage,high sensitivity,wide bandwidth,high measure precision,stabilization,acquiring original damage information by AE sensors,Disadvantage,have uniform sensitivity to orthotropic stress waves,sensing signal easily influenced by transverse stress wave,influence the damage identification,Fig.1 The model of OPCM sensor,Model and characteristics of OPCM sensors,The coupling relation equation between induced strain and the deformation of piezoelectric phase is,From above equation,the obvious orthogonality can be seen because longitudinal and traverse piezoelectric strain constants,is commonly,.,Characteristics,OPCM sensor,good flexibility,high intensity,large strain,light weight,its orthotropic characteristics to stress wave,distinguish stress wave of different components on the same surface,Research,prove orthotropic characteristics by computation with FEM and experiment,Comparing between PZT and OPCM,Fig.2 The numerical simulation result of FEM,Comparing between PZT and OPCM,Fig.3 FFT of experiment result,OPCM sensor is only sensitive to the longitudinal wave for its orthotropic sensing characteristics.,PZT sensor is more complex in resonance characteristics and havent the different direction sensitivities for its isotropy.,Under pulse load,Structure damage identification,Location method,Fig.4 One dimensional AE source location,The distance between sensor A and AE source is,Structure damage identification,Discussion,as ,AE source location is at the middle of two sensors;,as ,AE source location is at the position of sensor A;,as ,AE source location is at the position of sensor B.,when the AE source locates outside of the two sensors,time difference will be and induce to false location result that AE source will be located at sensor A or sensor B.,signal processing technique,Gabor wavelet,presenting a signal in the time-frequency domain,better resolution in the time-frequency domains compared with other wavelets,Research,Based on OPCM single sensitivity and Gabor wavelet time-frequency analysis,damage identification technique is also discussed in this paper.,Gabor wavelet time-frequency analysis,Consider two harmonic waves of equal unit amplitude propagating in the x-direction,Gabor function,is,Its Fourier transform is,Gabor wavelet time-frequency analysis,Gabor,wavelet transform result is,It indicates that the magnitude of the WT takes its maximum value,frequency,and time,Structure damage identification,Improved location method,-transmission method,The distance between sensor A and AE source is,Where is time difference between the first two-peak values of received signal.,(1),Experiment research,Experiment setup,Fig.5 Integrated steel rod,Fig.6 Steel rod with defect,a OPCM sensor,infiniium54820A oscillograph,two steel rods show as follows,Experiment research,Experiment result and signal processing,Fig.7 Signal processing of integrated steel rod,According to the time difference t&the group velocity 4579m/s gained from experiments.,The distance the AE source and OPCM sensor can be worked out by,Eq,.1.,The result Is respectively 449.9mm and 464.1mm and the relative error is 2.3%and 5.5%,Experiment research,Experiment result and signal processing,Fig.8 Signal processing of steel rod with defect,Experiment research,Experiment result and signal processing,Dynamic damage identification,The AE source location result is respectively 449.9mm and 464.1mm and the relative error is 2.3%and 5.5%.,Static defect identification,The change section location(thought as static defect in this work)result is 240.6mm and the relative error is 10%.,Conclusions,(1)The orthotropic characteristics of OPCM sensor are demonstrated by FEM and experiment.,(2)Compared with locating source using traditional one-dimension location method of acoustic emission,transmission wave method only uses one sensor and can avoid the influence of threshold setup and different sensitivities of sensors on damage location.,(3)Transmission wave method can give qualitative analysis for the isotropic elastic rod with change section(it is thought as static defects in this paper,in practical engineering such as change section by erosion or other factors).,Other research in our workshop,In locating defect of two-dimension structure using traditional acoustic emission(AE)technique,its accuracy mainly depends on the following factors:threshold setup of sensor passages,different sensitivities among various sensors,and static defects.,In order to solve thes。