Development And Experimental Research Of Metal Magnetic Memory Testing System Based On Giant Magneto-Resistance Effect

Metal magnetic memory testing method, a kind of ferromagnetic workpiece inspectionmethod of detection, is the latest discovery in the field of non-destructive testing. Thedistribution of stress concentration area of a ferromagnetic work piece was detected andreflected by this method, so it can early diagnosis the fatigue damage of a ferromagneticwork piece. This study focus on the magnetic memory signals, the principle of magneticmemory signal and the principle of magnetic memory testing which was based on the GiantMagneto-Resistance(GMR) effect was analyzed, a metal magnetic memory signal dataacquisition system based on the GMR effect was made up and applied to510L stretchingpiece for metal magnetic memory signal detection and analysis. The main work contentsand achievements are as the following three main areas:(1) A magnetic memory testing system which is based on the GMR effect wasdesigned.The sensitivity of the data collection system was improved by The detection probewhich was composed by GMR effect sensor;the accuracy of analog to digital conversionwas increased by ADS836416-bit A/D conversion chip;the data processing ability of thesystem was improved by the high-performance DSP chip of TMS320LF2407A whichworks as its control the core.(2) Has developed the software of system, including lower computer data acquisitionand transmission procedures; Digital filtering algorithm was simulated andanalyzed by the MATLAB7.1software, and the software was also used forMagnetic memory signal digital filter calculation, and gradient value calculationand waveform display.(3) Has completed the effectiveness experiment and performance experiment ofthe system. the effective of the system was verified by the experiment of detectionthe prefabricated specimens of crack; the signal amplitudes were quantified byanalysis the magnetic memory signal of510L steel specimen under differentstress-strain phase, and the detection accuracy of the system is0.0176A/m.Experimental results show that the system which was based on the GMR effect of magneticmemory testing can effective, sensitive detection the magnetic memory signal offerromagnetic specimen, by metal magnetic memory signal of the stress concentration zoneof specimen was located by testing the zero-crossing point of its magnetic memory signal, and to determine sample parts judging the intensity of stress concentration area was judgedby by gradient value of the magnetic memory signal.