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Experiment Study on Basic Problem of Magnetic Memory Testing

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Tutor: RenJiLin
School: Nanchang University of Aeronautics and
Course: Measuring Technology and Instruments
Keywords: magnetic memory testing,magnetic suspending liquid,magnetic domain,two-dimension
CLC: TG115.28
Type: Master's thesis
Year:  2013
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Due to the great potential of the Metal Magnetic Memory (MMM) testingtechnology in the field of pre-diagnosis of ferromagnetic materials early injury in recentyears, the technology is becoming a very hot research topic in a non-destructive testingof new technology. In this paper, the basic test£¬the basic theory£¬software simulationand other research methods are used; The widespread concerned basic problem ofmagnetic memory testing at this stage is researched in multi-level and constructiveadvices are provided for our modern industrial inspection.Firstly, the chemical precipitation and orthogonal experiment methods are used.Magnetic suspension configuration is suitable for surface morphology of magneticdomain observation of silicon steel sheet and Q235steel samples. Design static loadtensile test to let the flat tensile specimen have different residual stress, whilemeasuring the changes of specimen surface magnetic flux leakage signal under variousdraw stage, followed by the sample for metallurgical processing, then observe themagnetic domain morphology by the microscope under different stress conditions, andthe results are analyzed. The results show that: with the static load increases, themagnetic flux leakage of the sample signal increases, and the change of the normalcomponent is more pronounced than the tangential component; when themagnetostriction coefficient is positive, as the load increases, the magnetic domainsrotate towards the direction of stress and orientation; the variation of the magnetic fluxleakage signal change and the organizational change of the magnetic domains canreflect the stress change of the specimen.Then20steel and Q235tablet tensile specimens are applied, combining ANSYSfinite element software simulation and actual testing, the impact of stress on the two-dimensional magnetic flux leakage signal on the surface of the specimen is studied inthe geomagnetic field. The results show that: as the load increases, the specimen surfacemagnetic flux leakage signal increases then decreases and then increases; near the roundhole the normal signal appears to zero value phenomenon, and the tangential signal hasa great value; In addition, it explore a more effective way for criteria after the testresults are analysis by the amount of multi-feature. Finally, the metal magnetic memory diagnostic, the precision Gauss Meter and themagnetic particle inspection machine are used to test the aviation parts, a comparativeanalysis of the test results of the three methods are carried out. The results show that theuse of magnetic memory techniques can detect the stress concentration areas of thespecimen characterized by crack.In short, the magnetic memory testing technology as a non-destructive testing ofnew technologies, the development time is not long, in the theoretical system test andapplied research that there is still a further improve the process. The future developmentof the magnetic memory testing related recommendations and prospects are given.
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