| The acoustic emission technology is a dynamic nondestructive testing techniqe with little restricted conditions,and has very important position in fault diagnosis and structural health monitoring,so it will has wide prospect of application in the near future.The reason of causing the acoustic emission phenomenon is that the stress in mteral or structure exceeds the yield limit stress of the material or causes defect in material leading to the emission of strain energy in the form of stress waveform.So we can confirm the position of the plastic deformation and fracture by the acoustic emission source location,and this can provide early warning for the safety utility of material and structure.The location method based on time difference of arrival is the common source location method.But the acoustic emission signal obtained from rock is non-stationary and transient signal;these features will cause serious disturbances of obtaining the first arrival time of the acoustic emission signal.At the same time,the different algorithms affect the accuracy of source location.Aiming at these problems,the acoustic emission experiments of uniaxial compression based on sandstone are carried out,then the theoretical analysis is going on based on the data of acoustic emission.Firstly,the power exponent thread function is applied on the wavelet packet coefficient,solving the problem that the signal usually loses some useful information when being denoised,and the comparisons between the new method and the traditional soft and hard denoising methods verify the effectivity of the method.Secondly,the least square method and partical swarm algorithm are combined to improve the least square-partical swarm location method,solving the problem of low efficiency in source location.Thirdly,to solve the changing velocity of wave propagating through the defective and anisotropic areas,the source location method that the velocity is confined in the disturbed range is used,which improved the accury of location in the condition that the velocity is disturbed.Then,the interval analysis is used to obtain the source position represented by interval value,which can be nearer to true acoustic emission source,solving the low accuracy of traditional source position represented by a point.In the last,the maximum likelihood method and the AIC method are combined to pick the first arrival time,and the method obtains a more accurate result,and all the proposed methods is verified by the acoustic emission signal collected throughout the uniaxial compression test of rock.The research of this paper has important theoretical significance on the offline analytical of acoustic emission signal and important practical significance on improving the application of acoustic emission testing technology. |
