Test Researcxh On Signal Amplifier And Filtering Effexct Of Acoustic Emission Used Ultrasonic Transformers

Acoustic emission testing technique is one of dynamic non-destructive testing diagnostic technology,has been widely used in Real-time monitoring of equipment.Acoustic emission signal of metal materials is very weak,and the signal decays in the process of propagation,so we may not achieve the useful and real acoustic emission signal when it is monitored.Taking these aspects,how to amplify acoustic emission signal is becoming the key to get effective signal.In this paper firstly the production of acoustic emission waves,the propagation characteristics and species,the testing principle of acoustic emission and the analysis method of the signal were introduced.Then the problem that the relay signals may face to again decay with the use of the waveguide pole when the sensor can’t install directly to the tested surface in process of detection were described,and the theory that designing an amplitude transformer with resonance theory to guided wave can amplify the signal amplitude and has the effect of band-pass filter,based on the theory of amplitude transformers in power ultrasonic;have been put forward,through the analysis,the step-like amplitude transformers which have the largest amplification have been recommended,many the step-like amplitude transformers were manufactured in the practical testing.Chengdu DongKe signal collection card and its analysis system are chosen to complete the experiment of acoustic emission test.Through lots of experiment,whether the acoustic emission signal have the amplification and filtering effect have been demonstrated.The experimental research about the enlarge size,different materials,different resonant lengths,different cross-sectional area ratio,different length of the large end and little end etc.have been done.With MATLAB spectrum analysis,the test data processing,the comparing and analyzing amplification and filter effect of each test,and using a polynomial fitting spectrum graph to solve the signal bandwidth,have been fulfilled.The results that amplitude transformers can possess the signal amplifier and band pass filters were indicated,and may be used in the practical application of acoustic emission testing.