Testing Technology Of Ferromagnetic Material Based On Link Impedance Detection Technology

In this paper, we study a link impedance detection technology, this study is based on permeability test technology, combining with the characteristics of permeability testing technology, has higher detection sensitivity. Stress concentration and fatigue damage, the evaluation method of detection is put forward for the degree of stress focusing on the specimen and the degree of fatigue damage parts adopt the method of testing associated with impedance changes, found in advance degree of stress concentration and fatigue damage of ferromagnetic specimen. This method not only can detect the stress concentration and fatigue damage of the specimens, can also detect mechanical toughness and mechanics of brittle transition of ferromagnetic material, martensite austenite in disguised forms, dislocation defect density change, the change of the grain boundary, the ferrite pearlite carbon body shift, etc.This paper introduces the correlation impedance testing technology research status at home and abroad. Elaborated the associated impedance detection mechanism. Has set up a test platform for the associated impedance detection technology, and has carried on the ferromagnetic stress concentration and fatigue damage test specimens. The test system is mainly including sensor part, excitation signal and the detection signal. And the related parameters of the system are optimized by the test, find the best frequency is 400 Hz, the best voltage amplitude is 7 VPP ~ 15 VPP. About 20 # steel, 45 # steel and 40 Cr in tensile test, fatigue test. Test found that connection impedance particularly sensitive to the yield stress, when the stress exceeds the yield strength, associated impedance will be sharply reduced. According to the characteristics of the impedance, can effectively detect specimen one regional stress state. Experiment also found the link impedance parameters is closely related to the tensile stress and residual stress, decrease with the increase of tensile stress and residual stress. Can detect cause permeability variation of relative parameters of distribution with high precision. Experiment also found that the associated impedance particularly sensitive to late specimen fatigue. Experimental results verify the associated impedance detection technology can be sensitive to detect the inner stress concentration and fatigue damage of ferromagnetic materials, impedance detection technology has broad application prospects.