Research On Time-domain Clustering Characteristics And The Characterization Method Of Cluster Characteristics Of Acoustic Emission Sources In Concrete Components

It is very popular for the acoustic emission non-destructive testing technology in the concrete field.However,the theoretical research of acoustic emission non-destructive testing needs to be strengthened due to the Various factors in the concrete field,especially the analysis of the relationship between acoustic emission signal parameters and mechanical parameters such as stress.The clustering characteristics of acoustic emission sources means the uneven distribution characteristics of acoustic emission sources in the time domain and the spatial domain.The physical mechanism of clustering characteristics of acoustic emission sources is the change of stress.In earthquake engineering,the clustering characteristics of earthquake have been studied earlier and more frequently;however,it is urgent to study the clustering characteristics of acoustic emission sources inside concrete structures and the relationship with stress changes.From the theory analyze and experimental Research,the paper studies the cluster characteristics of acoustic emission source,and analyzes the relationship between acoustic emission signal parameters and stress.In this paper,three groups of plain concrete short columns are subjected to axial and eccentric uniaxial compression tests of 8mm and 16 mm respectively.This paper analyzes the cluster characteristics of acoustic emission sources based on experiments and study the relationship between acoustic emission parameters and stress parameters based on the cluster characteristics of acoustic emission source.The main work and conclusions of the paper are as follows:(1)Analyze from two aspects: the comparative study of acoustic emission events and seismic events and the meaning of cluster characteristics,and draw the distribution map of acoustic emission events in time and space at the same time.The results show that acoustic emission events have cluster characteristics in the time and space domains;the manifestation of the cluster characteristics of acoustic emission events is the uneven distribution in the time domain and space;(2)Use mathematical statistical models and relevant knowledge of probability statistics to study clustering characteristics of acoustic emission events from the qualitative and quantitative.The results show that for the qualitative study,the cluster characteristics of acoustic emission events are reflected in the large difference in the frequency of acoustic emission events in different time periods.For the quantitative characterization,the cluster characteristic parameter-time variation coefficient is greater than 1 for acoustic emission events.In the first half of the time period,the time-domain clustering characteristics of acoustic emission event in the eccentric compression short column are more significant than that of the axial compression short column;in the whole time period,the result is the opposite.(3)Analyze the distribution law of acoustic emission signals within the cluster segment by the optimal segmentation method.The distribution of acoustic emission signals in the cluster section also has dense and sparse unevenness,this law is similar to the overall force process of the specimen;and its clustering law is similar to the acoustic emission event clustering law during the overall force of the component.The clustering phenomenon of acoustic emission source has self-similarity.(4)Firstly,derive the existing relationship between acoustic emission events and stress.Secondly,compare the time distribution of acoustic emission events and the changes in stress with time,and finally analyze the relationship between acoustic emission event ratio and stress ratio.It is obtained that the clustering characteristics of acoustic emission events stems from the changes in the internal stress of the specimen,and the clustering of acoustic emission events is where the stress rises and greater,the clustering characteristics of acoustic emission events become more significant with the increase of stress.(5)Analyze the changes of the energy sum and the average stress in the total active screen,and analyze the relationship of both.The research shows that energy and average stress have the same law of change,and the both change have turning points at similar positions,and the slope on both sides of the inflection point increases;the energy sum increases with the increase of average stress.