Research On Structural Defect Detection Technology Based On Infrared Thermal Technology

Infrared radiation imaging has become a noticeable non-destructive testing method because of its non-contact,fast and large area of primary detection.In this paper,the key technologies and their quantification in infrared radiation imaging detection are studied.The main key technologies involved are as follows: Infrared Radiation Imaging Detection Experiment and Processing Technology of Sequence Thermal Images;Heat Conduction Model and Finite Element Analysis and Calculation of Infrared Radiation Imaging Detection;Infrared thermography algorithm processing technology;Pulse Phase Radiation Imaging Detection Technology.The problems are analyzed from multiple aspects of qualitative and quantitative analysis.In recent years,FRP reinforcement of concrete beams and columns has become a popular method in the field of building reinforcement,and the interfacial peeling failure behavior between FRP and concrete has been one of the hotspots of research.Infrared thermal imaging technology is still in the primary stage in the field of building detection,but it has been applied to the detection of interface defects of FRP reinforced concrete structures,including CFRP and BFRP.There are few research results,but it has shown considerable potential.Therefore,the interface defects of concrete structures strengthened with FRP sheets will be studied by means of experiment and Simulation in this paper.To explore the relationship between environmental factors and provide theoretical basis and experimental data for subsequent research.The details are as follows:Firstly,on the basis of infrared heat conduction analysis,CFRP sheet reinforced concrete specimens were made,and interlayer defects were reserved.Defect depth and area were qualitatively tested.The relationship between temperature change and contrast change of each defect and its influencing factors were analyzed.Subsequently,a reasonable finite element model was established to simulate the experiment and verify the previous conclusions.Although infrared thermal imaging technology has large imaging area and noncontact,it is vulnerable to environmental impact and has low resolution of thermal image.We use common image processing algorithms to analyze the interlayer defects of FRP reinforced concrete structures,which significantly improves the imaging effect,and analyze the characteristics of various algorithms.At the same time,the original algorithm is improved and a gradient algorithm based on center rotation is proposed.In the quantitative analysis of defect area,according to the rule of defect area detection in time series images,the optimal time period of defect area detection is determined,and the factors affecting the quantitative detection are analyzed.Through the experimental results,the previous detection algorithms are compared,and the detection accuracy is significantly improved by the gradient algorithm of center rotation.Pulse Phase Thermal Imaging Testing(PPT)is a new infrared nondestructive testing technology,which has the characteristics of anti-interference and deeper detection depth.In view of the blank of this algorithm in the detection of interlayer defects of concrete structures strengthened with BFRP sheets,PPT method is used to detect and locate the internal defects.Through some experiential calculation,the blind frequency of defect signal is accurately obtained,and a new result correction method is proposed.Finally,through C# programming,the infrared thermal imaging processing software is designed and implemented,and some more difficult functions are realized,such as fast and accurate processing of the original infrared thermal image and importing it into the database.It facilitates the real-time detection and data processing of scientific research and engineering personnel.