Research On Automatic Ultrasonic TOFD Detection Technology Based On Crawling Robot

Large welded structures,including tanks and pipes,are indispensable and important infrastructures in modern society and have a huge impact on the national economy and human life.As the weld is the weakest part of the welded structure,easy to produce defects,so the quality of the weld control has always been one of the important NDT.Ultrasonic TOFD(Time Of Flight Diffraction)imaging detection technology has been developed specifically for weld inspection,showing clear technical advantages.However,due to the wide distribution of defects in large-scale welded structures and the difficulty of manual access,the application of traditional artificial TOFD imaging technique has been greatly restricted and must be followed in the direction of automated imaging inspection.In addition,the existing technologies can not meet the needs of Application requirements for thin layers material weld or near surface defect inspection.Based on the above background,under the support of the National Natural Science Foundation of China,"Research on the Theory and Technology of High Performance Automated Phased Array Ultrasonic Imaging of Cylindrical Components"(No.51675480),this paper proposes the study of automated ultrasound TOFD Detection Technology based on the crawling of robotic vehicles.On the basis of systematic understanding of the current research status and development trend of ultrasonic TOFD imaging detection technology,the overall technical program of automatic ultrasonic TOFD imaging detection for large welded structures is made.Complete the design and development of crawler robotic vehicle and key technologies research on ultrasonic TOFD detection signal pretreatment and near-surface defect ultrasonic TOFD imaging detection,and a set of automated ultrasonic TOFD imaging detection system was developed based on the crawling robot.The main research contents and innovation of this paper are as follows:In Chapter one,discuss the function of large welding structure and the importance of developing nondestructive testing of the weld.The research status and development trend of ultrasonic TOFD imaging technology are systematically summarized.The challenges of ultrasonic TOFD imaging technology are analyzed,and the research direction of this paper is clarified.The content of each chapter is arranged.In Chapter two,the principle of automatic TOFD imaging was analyzed and the theoretical basis of quantitative ultrasonic testing of weld defects was established.Based on the clear function and performance targets,the design of the overall scheme of automated ultrasonic TOFD inspection system based on robot crawling was completed.In Chapter Three,complete the design and development of the mechanical body of the four-wheeled magnetic adsorption crawler robot and the compacting mechanism of ultrasonic TOFD probe,and carry out the statics and dynamics analysis of the related mechanical structure.In Chapter four,the research of ultrasonic TOFD imaging technology for near-surface defects is carried out.The EMD(Empirical Mode Decomposition)technique is used to decompose the TOFD detection signal,and the decomposition signal is reconstructed according to the modal selection criteria,so that the de-noising of the original TOFD signal can be achieved.At the same time,combined with the Embedded Signal Identification Technique(ESIT),the time-domain parameters of defect wave were extracted to detect near-surface defects by TOFD imaging.In Chapter five,based on the distributed architecture and modular design strategy,a multi-mode communication bus is used as the information transmission bridge.Based on the research and development of hardware modules such as field measurement and control,ultrasonic testing and high-speed communication,and software modules such as client and server,Developed a set of automatic ultrasonic TOFD detection system based on robot crawling scan At the same time,using the developed system to carry out experiments on artificial test blocks to confirm the feasibility and effectiveness of the paper research and development techniques.In Chapter six,Summarize the research work of the full text,and prospect the further research in the future.