Research On Concrete Internal Damage Location Algorithm Based On Acoustic Emission

Acoustic emission technology plays an irreplaceable role as a means of structural health monitoring in practical engineering applications.Acoustic emission source localization is an important aspect of acoustic emission technology.Accurately obtaining the location of the sound source will help to evaluate the damage degree of engineering structures.Reasonable processing and analysis of acoustic emission signals and accurate positioning of sound source location are the key scientific and technical problems to reveal the internal damage area and development trend of engineering structures.In practical engineering applications,the ultimate goal of acoustic emission detection is to accurately locate and monitor the location and development of structural defects,so as to take corresponding remedial measures.This paper briefly introduces the basic concepts of acoustic emission and acoustic emission source localization methods,and focuses on how to reduce the measurement error of sound velocity in civil engineering positioning and detection and optimize the efficiency of positioning algorithms to improve the positioning accuracy of acoustic emission sources.A sound source localization algorithm without speed measurement is established.At the same time,based on this method,an improved constrained total least squares localization algorithm based on alternating direction multiplier method is proposed,and an example verification and experimental research are carried out.The main research contents and conclusions of this paper are as follows :1)The traditional positioning method needs to measure the wave velocity in advance,and the deviation between the predetermined wave velocity and the real-time value will lead to a large positioning error.Therefore,this paper proposes a new closed-form solution for acoustic emission source positioning without velocity measurement to reduce the error caused by wave velocity measurement.Firstly,the nonlinear control equation of the unknown sound velocity of each sensor is established.At the same time,in order to reduce the selection of reference sensors,three sensors are selected to transform the nonlinear control equation into a linear equation of unknown wave velocity,and the residuals of the linear equations are calculated.Then,in order to reduce the ill-posedness of the linear equations,an orthogonal projection operator is introduced to calculate the acoustic emission source coordinates.The lead breaking test results show that the positioning accuracy of the new method is better than other traditional methods and the feasibility of the algorithm is verified by numerical cases.2)In order to solve the problem that the traditional analytical algorithm has poor target positioning performance under large time difference measurement error,based on the given closed solution as the initial solution,an improved constrained total least squares method based on alternating direction multiplier method is proposed for target positioning.Firstly,the hyperbolic positioning equation is transformed into a set of pseudo-linear matrix equations.Based on the constrained total least squares method,a variable is introduced to improve the objective function in the algorithm,and the optimization problem of one variable is transformed into the optimization problem of two variables.The closed-form solution proposed in the third chapter of this paper is used as the initial solution,and then the alternating direction multiplier method is used for iterative solution to obtain the rough estimation of the target position.The coefficient matrix is updated by the coordinate calculation of the rough estimation,and the accurate estimation of the coordinate position of the sound source is obtained by the second iteration.Finally,the influence of the number of acoustic emission sensors and the time difference measurement error on the positioning accuracy of the algorithm is given by numerical examples.It is verified that the algorithm can still maintain good positioning accuracy when the time difference measurement error is large.3)In order to verify the feasibility of the improved positioning algorithm in Chapter 4,the anode is energized at the steel bar to accelerate the corrosion process to simulate the corrosion cracking of concrete.The whole process is monitored by acoustic emission.Based on the improved positioning algorithm in Chapter 4,the location of the crack source is located and analyzed,and the whole development process of rust expansion cracking of reinforced concrete specimens is studied.The experimental results show that the positioning algorithm can accurately locate the location of crack cracking and corrosion damage,and has high positioning accuracy.