Research On GMR Effect Based Crack ECT Tech And System For Nonferromagnetic Metal Material

Modern key equipment broadly worked under high-temperature, high-speed, high-pressure, or high-loading conditions while their key components were made of new alloy materials, mainly nonferromagnetic metals. The cracks in these important components would then threaten the security of the whole system, and even cause serious accidents. Therefore, researches on crack detection of nonferromagnetic metal are very important. Supported by a National Natural Science Foundation and a project in National High Technology Research and Development Program 863, this paper researched the Giant Magneto Resistance (GMR) effect based crack ECT technology and system for nonferromagnetic metal. It discussed how to appreciate the GMR sensor for the usage of ECT and how to demarcate the detect ability of the probe for eddy current magnetic field, designed a detect system and carried out experiments to show the feasibility of this tech for crack detection. The detailed content and chapter arrangement of this paper were given as follow:Chapter 1 explained the importance of crack detection on materials. The outstanding performance of ECT was then discussed by comparing with the other frequently-used crack detecting methods. Then continually, this chapter talked about the situation of ECT and its development trend while the application of the GMR effect exhibited a possible development for ECT. According the research subject, chapter one offered the frame of this paper, and brought forward the researched content.Chapter 2 introduced the principle of GMR effect and the application of GMR recently. It also introduced the way GMR sensor worked, analyzed its character, and discussed the key character for GMR sensor for the ECT, then carried out an optimal selection for the research in this paper as an example for GMR selection.Chapter 3 discussed how the electronic ECT work and the insufficiency of electronic ECT, analyzed the eddy current distribution around the crack, and summarized the influence factors for GMR based ECT tech. The method and signal function for GMR based crack ECT was then carried out. Through the function, this chapter discussed the probe demarcation method.Chapter 4 researched the detecting system, designed the probe and signal processing circuit, carried out the hardware prototype of the system.Chapter 5 carried out experiments. It firstly debug the system to check whether the system work, secondly demarcated the detect ability of the system to guide the crack detection experiment, thirdly carried out crack detection experiments. The experiments showed the detect ability of GMR based crack ECT that it got a good SNR (Signal to Noise Ratio).Chapter 6 summarized the research and development work in this paper. Taking the National Natural Science Foundation project and other connected project into consideration, it also gave proposal and useful advices for the further research.