Two Dimensional Quantification Testing Of Metal Magnetic Memory

Metal magnetic memory (MMM) technology is a new non-destructive testing(NDT) technique that detects the stress concentration positions and stress concentra-tion degrees of ferromagnetic component by metal magnetic memory effect. It can b-eforehand diagnose the stress concentration positions, micro-defects, early failureand damage contrast with the normal non-destructive testing,so it can prevent suddenfatigue damage. it is the only effective new method of non-destructive testing whichcan early diagnosis of metal component so far. But many factors can affect thesignals by using the magnetic memory technology. in the current state of study, thesingle normal characteristic parameters of magnetic memory is used to evaluate, thereliability is not high. And metal magnetic memory testing has not break through inthe quantitative analysis, also fail to achieve the purpose that accurately reflect thestate of stress.Work was deploied by numerical simulation and experiments based on themagneto-physics and magnetic technology in this paper.The method of vectorialresultant was adopted to extract tangential component signals of metal magneticmemory due to the problem that the tangential component signals of metal magneticmemory is very hard to be extracted, and its effectiveness has been verified. Therelationship between tangential component signals of magnetic memory with stressconcentration positions and stress concentration degrees has been researched understatic tension conditions testing of the ferromagnetic metal30CrMnSiNi2A and20#steel, and the K curve of tangential component signals of magnetic memory hasbeen analysised. The result shows that the tangential component signals of metalmagnetic memory can be effectively extracted by the method of vectorial resultant;The stress concentration positions and stress concentration degrees can be reflectedintuitively and accurately by tangential component signals of metal magneticmemory. It is proved that the stress concentration positions and stress concentrationdegrees can be effectively determined by tangential component signals of metalmagnetic memory. The normal characteristic component of magnetic memory andthe tangential characteristic component of magnetic memory are mutual authentica- tion of each other and also make up for each other.the shortcomings of previousmethod which use a single normal component signals as characteristic parametershas been changed.The normal component signals and the tangential component signals of metalmagnetic memory are extracted by two-dimensional magnetic field scanning sysem,the two-dimensional curve of metal magnetic memory is obtained by the analysis oflissajous figure,The relationship between normal characteristic component of magne-tic memory, tangential characteristic component of magnetic memory and areas oflissajous figure with stress concentration degrees under different ferromagnetic mat-erials and different loads has been researched. The results show that the areas oflissajous figure increase with the augment of stress when the load of ferromagneticmetal exceed the yield point.40Cr steel specimen is as an object for high-cycle fatigue experiments, Therelationship between stress concentration, fatigue damage with tangential componentsignals and normal component signals of magnetic memory during high-cycle fatig-ue has been researched. The results shows that, k curve of the normal componentsignals of magnetic memory appears the peak mutation(kmax), k curve of thetangential component signals of magnetic memory appears the phenomenon ofzero-crossing during high-cycle fatigue in the position of Fatigue damage, the kmaxvalue of normal component and tangential component of magnetic memory increasesgradually with the augment of the degree of fatigue damage, the degree of fatiguedamage can be assessed effectively by the the kmax value.