Research On Time Difference Tomography Algorithm And Structural Damage Detection Method

With the development of science and technology,the damage detection technology of structural parts is more and more mature.At present,the damage detection technologies for structural parts mainly include electromagnetic detection,infrared thermal wave technology,etc.,but these detection technologies still have some shortcomings for the overall detection of structural parts.The tomographic imaging method can realize the overall detection of the structural parts,form the overall damage image of the structural parts,and accurately locate the location,size and shape of the damage.In long-term practical use,it is found that it is difficult to place sensors for some complex structural parts,and more sensors are needed.Because the sensor itself has a certain size,there is a certain interference to the damage results.So the method of jet lag tomography is studied in this paper.The method requires less sensors and has high detection accuracy.This paper study on structure damage theory,the research and for multiple boundary detection model,make the sensor placement can be arbitrary arrangement within the test area,further improve the detection accuracy,next to the time difference algorithm and image reconstruction algorithm research,and analysis of various algorithms,jet lag tomographic imaging detection system to get the final design structure damage state as a whole.The main research contents of this paper are as follows:(1)Study on fatigue damage characteristics of elastic waveAccording to the relevant knowledge of elasticity,the relationship between wave velocity and elastic modulus is obtained by dynamic analysis of elastic body.The formula of damage and elastic modulus is derived from continuum damage mechanics,and the relation between wave velocity and damage is established.(2)Research on time difference algorithm of structural partsThe advantages and disadvantages of different time difference algorithms are compared and the appropriate time difference algorithm is selected.The factors affecting the accuracy of the time difference algorithm were analyzed,and the acoustic emission experiment platform was built to extract the actual lead breaking waveform,and the actual lead breaking waveform was used to compare various algorithms.(3)Research on multi-boundary discrete model and image reconstruction algorithmIn this paper,the construction of discrete model of time difference tomography is studied,and the construction method of multi-boundary model is designed.The image reconstruction algorithm based on total variational constraint is studied,and the simulation model is established to analyze and compare each image reconstruction algorithm.Finally,the image reconstruction algorithm with good stability and convergence is selected.(4)Design and research of damage detection system for jet lag tomographyThe detection scheme of the hardware system for damage detection of time difference tomography was designed and the hardware selection was carried out to obtain broken lead waveform through the hardware system.The software system of damage detection by time difference tomography is designed to calculate the wave velocity field image and the damage state of the whole structure.Finally,the system is tested through experiments.