The Acoustic Emission Source Localization And Damage Identification In Pipeline Considering Elastic Wave Propagation Path

With the aging of pipeline systems in recent years,pipeline disasters have occurred frequently.Therefore health monitoring of pipeline systems is critical.At present,there are numerous technologies for pipeline system detection and monitoring.Among them,acoustic emission technology,as a passive monitoring technology,is widely used in the online monitoring of pipelines.Acoustic emission technology detection content mainly contains the identification and evaluation of the occurrence of leaks and the location of the leak source.Traditional pipeline leak source positioning mainly considers the axial distance of the pipeline,ignoring the true propagation path of elastic waves,and does not consider the influence of the pipe diameter and the circumferential position of the leak source.Especially in the short distance detection of large diameter pipelines,these can have a non-negligible impact on the positioning accuracy.In this paper,the spatial localization of acoustic emission sources is investigated by considering the real propagation path of elastic waves in the pipeline to address the above problems.The law of acoustic emission signal change caused by pipeline leakage is also explored to complete the identification and localization of pipeline damage.The current status and trends of pipeline acoustic emission detection development are described by combing Chinese and foreign literature.Several acoustic emission localization methods based on time delay estimation and related acoustic emission signal processing methods are summarized.An experimental study of the variation of the leakage signal due to different pressures on the pipeline was conducted for the most common damage condition of pipeline leakage.The effects of pressure variations on the signal RMS voltage and power spectrum were investigated.It was found that in the time domain,the RMS voltage of the signal increases with increasing pressure.The increasing trend of RMS voltage tends to moderate as the pressure increases.In the frequency domain,the power spectrum maintains a low gain level when the signal is not leaking.When the leakage occurs,the power spectrum has a clear gain peak.As the pressure increases,each peak gain increases,especially in the high frequency part.The propagation characteristics of the signal over the pipe structure were investigated.The following two conclusions were found.The first is that the signal attenuation is not monotonically decreasing when propagating on the pipe wall,and the signal amplitude at the far end is higher than that at the near end in the local pipe section;the second is that the signal amplitude in the circumferential distribution of the pipe and the location of the leak source are regular.The signal amplitude at the position of 0° and 180° relative to the source is larger than the amplitude at other positions.Therefore,the angular positioning of the leak source can be completed by the characteristics of the circumferential distribution of the amplitude and the signal time delay between sensors.The effects of different pipe diameters and differences in the circumferential position of the leak source on the pipe on the linear localization of conventional pipe acoustic emission were investigated by simulation summary and experimental verification.It was found that the error increased with the increase of the circumferential relative angle between the leak source and the sensor for the same pipe diameter.The maximum error arises at a relative angle of 180°.The error increases with increasing pipe diameter at the same relative angle.Therefore,for leak location in large diameter pipes,the circumferential angle of the pipe diameter and the leak source should be taken into account,otherwise it will cause the error of location.Finally,a spatial localization algorithm of pipeline acoustic emission considering elastic wave propagation path is proposed to address the shortcomings of traditional linear localization of pipeline leakage.Its feasibility is verified by means of finite element simulation and experimental validation.The algorithm achieves circumferential angle and axial distance localization of the leak source.It also avoids the disadvantage that traditional linear localization requires the sensor arrangement to be distributed at both ends of the source,otherwise the localization fails.The spatial localization of the leak source can be accomplished by arranging the sensor array at one end only.