Effect Of Different Crack Morphologies On Acoustic Emission Propagation Characteristics In Concrete

In recent years,acoustic emission detection technology has been widely used in the field of concrete materials and has obtained good application results.It is found that although acoustic emission detection technology is effective for concrete materials,there are still problems,the main problem is that the presence of crack defects in concrete will lead to inaccurate positioning of acoustic emissions.Therefore,it is particularly important to study the influence of crack defects on the propagation characteristics of acoustic emission signals,and then solve the problem of correcting the location of acoustic emission damage considering the existence of crack defects.In the crack damage detection of concrete components,different forms of crack defects have an important impact on the detection signal.Therefore,it is very important to establish the relationship between crack parameters and detection signals in different morphological forms to evaluate the crack damage of concrete structures.In this paper,the experimental and simulation study of acoustic portability in concrete with different forms of crack(crack depth,crack angle,crack distance sound source position,number of cracks,crack straightness)defects are carried out.Here’s what was done:(1)The influence of different forms of crack defects on the propagation characteristics of acoustic emission signals was studied by acoustic emission detection experiment.The relationship between different forms of crack defects and wave velocity is obtained,and the relationship between different forms of crack defects and sound wave propagation speed is established,and the damage localization of acoustic emission technology in concrete materials is corrected based on different crack morphological factors to improve its positioning accuracy.Secondly,the material properties(density,elastic modulus,Poisson’s ratio)of concrete are tested,which provides a theoretical basis for numerical simulation of the propagation characteristics of acoustic emission by different crack morphologies.(2)The influence of different crack morphologies on the propagation characteristics of acoustic emission signals was numerically simulated.Through experiments,the parameters were set and the Hanning window function was used for signal excitation.The relationship between different crack morphologies and wave velocities,as well as the relationship between cracks and defect echoes in different morphologies,were obtained.The analysis shows that the influence of crack defects of different morphologies on the propagation speed of sound waves shows a linear trend.When the crack angle is from 0 to 90 degrees,with the increase of crack angle,the wave velocity gradually decreases,the defect echo peak gradually increases,and when the crack angle is 90 to 180 degrees,the wave velocity gradually increases with the increase of the crack angle,and the defect echo peak gradually decreases.The effect of crack depth on wave velocity is relatively small;The wave velocity increases with the increase of crack moment sound source distance.With the increase of the number of cracks,the wave velocity gradually decreases,and the peak of defect echo gradually increases.The law is the same as the results of the acoustic emission test.(3)Finally,the acoustic emission propagation characteristics of different crack morphologies are verified by numerical simulation,and the concrete specimens are tested by spontaneous acoustic emission method through the acoustic emission system instrument and set the same parameters(center frequency,excitation mode)as the numerical simulation,and the numerical simulation results are verified.