Study On The Coupling Method Of Impact Echo Method And Infrared Thermal Imaging Method For The Detection Of Internal Defects In Concrete

Concrete is made of aggregate,cement,sand,water and other materials mixed in a certain ratio,and is easily affected by the construction process during pouring.At the same time,due to design defects,poor construction quality control,natural disasters or structural aging,concrete structures inevitably suffer from damage such as cracks,honeycombs,holes,wear and erosion during use,thus endangering the safety of the entire structure.These defects affect the working performance of the concrete structure from different degrees,and may cause major safety accidents in serious cases.How to detect internal defects in concrete scientifically,efficiently and on a large scale is a popular topic in engineering and academia,and no effective research has been conducted in academia on the combination of non-destructive testing techniques.Infrared inspection techniques as well as echo inspection techniques have the advantage of convenience and speed,and are widely used in non-destructive testing.Since the infrared thermal imaging method does not detect deeper defects with high accuracy,the impact echo method is used to detect deep defects,and then their detection information is fused to study.In this paper,on the basis of infrared thermal imaging nondestructive testing technology and impact echo nondestructive testing technology,a combination of theoretical research,experimental analysis,and probabilistic modeling research and analysis is conducted in accordance with the technology road-map for concrete infrared detection technology and concrete echo detection technology,and the main research content is as follows:(1)Through the current review of concrete internal defect detection methods,the research results achieved by infrared thermal imaging technology as well as impact echo technology are sorted out and summarized,and the combination of infrared thermal imaging method and impact echo method is proposed to be jointly applied to concrete internal defect detection methods,and the relevant theories as well as technical principles are elaborated.(2)A test on the detection of internal concrete defects based on an external auxiliary radiation heat source was carried out.The test was conducted to study the changes of surface temperature and the reflection of internal defects in concrete specimens during daylight heating by thermally stimulating the surface of concrete containing various types of internal defects by daylight heating.The test verified the effectiveness and feasibility of infrared thermography for detecting internal defects in concrete under daylight heating conditions,and compared the effect of different types of defects identification to obtain the law of internal imaging of concrete and the degree of influence of defect type on the detection effect,and initially determined the applicable detection range of infrared thermography.At the same time,the problems found in the test process are sorted out and summarized to provide a basis for the establishment of the probability model and data analysis for the subsequent detection and identification.(3)A test on the detection of internal defects in concrete based on impact echo detection technology was carried out.The test was conducted to study the reflection of internal defects in concrete specimens by means of the propagation of elastic waves inside the concrete material and the principle of test surface excitation of concrete specimens containing no type of defects inside.The test through the different types of defect identification effect comparison,the concrete internal defect output cloud pattern and the type of defects on the degree of influence on the detection effect,the initial determination of the impact echo method of the applicable detection range.At the same time,the problems found in the test process are sorted out and summarized to provide a basis for the establishment of the probability model and data analysis for the subsequent detection and identification.(4)for the infrared detection test process and echo detection test process in the applicable range of detection results to identify defects probability model establishment,the image transformation,temperature difference curve law,normal distribution,off-air index parameters and other related mathematical calculation methods,the results of each group of tests to sort out and summarize the establishment of probability models.Then the probability model of infrared detection technology and the parameters related to the probability model of echo detection technology are coupled with the information fusion study by comsol software,and the coupled probability model is established.Through the coupled probability model and test results and pre-buried defects comparison analysis,the optimization effect of the probability model,clear its application scope and limitations.