Study On The Characteristics Of Acoustic Emission Signal In Typical Mechanical Response

This paper is supported by the National Natural Science Foundation(No.51675258)and the National key Research and Development Program(No.2016YFF0203000).the National Natural Science Foundation(No.51675258,No.51261024)and the Science and Technology Research Project(No.GJJ150699)of Jiangxi Education Department.Energy is an important support for social development,and people have a long history of using petrochemical energy and wind energy.In the petrochemical industry,leakage of pipeline systems occurs frequently.The leakage of fluid in the pipeline will not only cause serious waste of resources,but also affect the quality of products in production,and even lead to explosion,fire,gas leakage and other safety accidents.In the production process of wind power energy,the environment where the wind turbine is located is relatively harsh,and the load on the tower is very complex when it is working.The collapse of the tower occurs from time to time,causing great economic losses to the enterprise.Acoustic emission(AE)technology is a real-time dynamic non-destructive testing technology,which has the advantages of high detection efficiency,large effective detection range,low requirements for the detection environment,and finding early damage status.Therefore,AE technology has great potential in engineering applications,and has been widely used in many industrial detection fields.The thesis conducts experimental research on the gas leakage of the pipeline system and fan tower operation status.Through the analysis of AE technology,we can obtain whether the leakage occurs in the pipeline system and the location,as well as the stress concentration of the tower status information.In the experimental study of gas leakage in the pipeline system,the influence of the pressure in the pipeline,the size of the leakage hole and the signal propagation distance on the AE signal was analyzed.(1)The increase of leakage size will increase the amplitude,average signal level and root mean square voltage of the AE signal to a certain extent;when it is below 0.2MPa,the ringing count can reflect the pressure at the time of leakage;The increase of signal propagation distance will make each AE parameter decrease.(2)Using BP neural network and Support vector machine to judge whether the leakage occurred in the pipeline system and the location where the leakage occurred.In the experimental study of the operating state of the fan tower in working,the relationship between the stress concentration state of the tower and the AE signal under different wind conditions was analyzed,and the method of monitoring using by AE technology was studied.The results show that:(1)The AE method is used to determine the location of stress concentration,and the effect is good.The re-inspection using the magnetic memory method can greatly improve the judgment accuracy of the stress concentration location.(2)the ring count,amplitude and energy of the AE signal are continuously decreasing with the stress concentration increasing.As the stress concentration increases,the ring count,amplitude and energy of the AE signal continue to decrease;in the frequency range above 100 k Hz,the amplitude of the AE signal continues to increase,and the main frequency band changes from about 180 k Hz To about 250 k Hz;the peak-to-peak value of the magnetic memory signal is also helpful to determine the degree of stress concentration.