Basic Research And Application Of Magnetic Memory Testing Technology

This thesis discuss deeply metal magnetic memory testing on mechanism and application. To set out from magnetic memory testing foundation study, carried on magnetic memory testing under static loading condition about the specimens which are made from Q235A,2Cr13,X80, and the stress of every level selected was tested by EMS2003 metal magnetic memory testing system, we obtained the metal magnetic memory signal law of multi-sample under different states, further, the relationship between metal magnetic memory signal and the crack width,the magnetic memory signal varying characteristic of before and after heat-treatment also discussed., we carried on a field test of girth welds.Research shows the shapes characteristics of the curves under different states of elastic-plastic stage are similar, the shapes are similar straight lines and only exist one zero-crossing points, the zero-crossing points of smooth specimen changed during drawing process, there are some errors in zero-crossing points and the crack place; the zero-crossing points of defect specimen and the crack place are almost the same; the zero-crossing points after fracture of the two forms of specimens and the crack place are almost the same; magnetic memory characteristic value│k│and H_P(y) has definite features, so we could use them to forecast the state of the materials.The examination experiment on tube pieces'crack part show magnetic density and magnetic field gradient vary with the crack width; the metal magnetic memory signal before and after heat-treatment shows the metal magnetic memory testing not only can be used to test the stress concentration of weld, but also can evaluated the result of the heat treatments; field application add to evidence showing the practicability of the metal magnetic memory testing. This paper provides certain theoretical basis and checking basis for the practical use of this advanced technology.