Research On Metal Magnetic Memory Testing For Remanufacturing Components Based On Stress-magnetic Coupling Mechanism

It has become an urgent problem for manufacturing industry to repair the typicalstructural components. The nondestructive testing (NDT) of ferromagnetic componentsin service is an essential step in remanufacturing. It will decide whether a component canbe remanufactured or not. Traditional NDT methods can’t realize the early warning andthey are helpless for micro defects and unformed defects. Magnetic memory technologycan accomplish the early detection of artifacts and prevent from the accidents. Magneticmemory testing will provide powerful methods and tools for remanufacturing.The paper studied the magnetic memory signals on the surface of remanufacturingcomponents under force-magnetic coupling mechanism. The main research contentsstudied in this paper is as follows.(1) We studied the surface leakage magnetic field of ferromagnetic material, weanalysis the influence of the size of the defect and applied magnetic field on the leakagemagnetic field. The study shows that all the size of the defect and applied magnetic fieldwould affect the distribution characteristics of leakage magnetic field.(2) The Q345steel was chosen as the object to study the influence of applied magneticfield on the normal component of magnetic memory signal during the fatigue loads. Weexplored the mechanism of metal magnetic memory, and provide data for quantitativeresearch of metal magnetic memory technology. The study shows that the normalcomponent of magnetic memory signal and its gradient value increased with the increaseof cycles under the same applied magnetic field; When applied magnetic field increases,the peak of normal component and gradient of metal magnetic memory signals increase,the peak of gradient value of the normal component of metal magnetic memory signalsincreases with the increase of cycles.(3) Q275steel was chosen as the object to study the relation between normalcomponent of magnetic memory signal and applied magnetic field during the tensile loads.The study shows that the magnetic memory signal is not only related to stress under thetensile force, but also related to saturation magnetization, the earth’s magnetic field,applied magnetic field, effective domain density and initial magnetic state of thespecimens.(4) To choosing the retired drive axle housing as the object, we studied the magneticmemory testing method for remanufacturing structural components. Fatigue experimentwas firstly carried out for standard parts of the axle housing material, and then we studied the relation between deformation and surface magnetic signal on a series of retired driveaxle housing. Establishing criterion of magnetic memory testing method for the retiredaxle. The study shows that the initial surface magnetic memory signal of the axle housingare different before loading but it shows regular changes after loading; the peak ofgradient value of normal component of magnetic memory signal are corresponding withdeformation of axle housing.