Research On The Relationship Between Concrete Stress And Accumulated Acoustic Emission Based On Time Series

Concrete is the most widely used material in civil engineering,and safety monitoring and evaluation of concrete building structures is becoming increasingly important.As one of the non-destructive testing technologies,acoustic emission has its unique advantages in the research and application of concrete materials.How to use acoustic emission signal parameters to establish the relationship between acoustic emission parameters and mechanical parameters is crucial for analyzing and studying the process from mechanical damage to failure of concrete materials.This article is based on the experiment of concrete axial compression acoustic emission characteristics,and quantitatively describes the relationship between the cumulative amount of acoustic emission events and stress levels through time series analysis method.The cumulative amount of acoustic emission events is an important parameter to describe the degree of concrete damage,and there is a strong correlation between the process of concrete damage change and the observed value of the cumulative amount of acoustic emission events changing with stress levels.Time series analysis is the establishment of a time series model to predict the future or describe the changing patterns of a system based on the correlation between dynamic data presented during the evolution of phenomena or systems over time.As the stress level increases and damage accumulates,there must be a certain correlation between the cumulative sequence of acoustic emission events,which is consistent with time series analysis.Therefore,establishing the relationship between the two using time series analysis method is in line with objective logic.The main research work of the thesis is:(1)Based on the physical significance of acoustic emission phenomena and signal parameters,as well as the theory of acoustic emission rate process,this study explores the nonlinear and non deterministic quantitative relationship between acoustic emission parameters and mechanical parameters from a probability perspective,laying a theoretical foundation for the use of a new tool-time series analysis method to construct a quantitative model between the two.(2)Based on the time series analysis method and model,this paper studies the method and process of establishing a quantitative relationship between the measured acoustic emission characteristic parameters and mechanical response,including the stationarity test of the series,white noise test,model selection,parameter estimation and model validity test.(3)Using the data obtained from concrete specimen loading tests and based on a modeling method based on time series analysis model,a quantitative relationship between the cumulative amount of acoustic emission events and the stress level was established by replacing the time index with stress level.This describes the deterministic relationship and residual autocorrelation relationship of the cumulative amount sequence of acoustic emission events with the evolution of stress level.Establishing a quantitative relationship between the cumulative amount of acoustic emission events and stress levels through a time series model,the model reflects the variation pattern of the curve well.It can not only predict the cumulative amount of acoustic emission events at corresponding stress levels,but also provide a basis for predicting the instability and failure of concrete materials in advance.