Differential Permeability Testing Technology Of Stress Concentration And Fatigue Damage For Ferromagnetic Specimen

With the rapid development of science technology and the greatly improved ofpeople’s living level, the requirement of people for safely is rapidly increase. The newmethod and new technologies of non-destructive testing continue to emerge, such anmagnetic memory test technology, barkhausen effect test technology and so on.Differential permeability testing technology, also known as sensitive differentialpermeability detection technique, or extreme of differential permeability testingtechnology, can not only detect stress concentration and fatigue damage conditions ofthe specimens, but also detect austentic-martensitic transformation of components to beproduced by the strain or temperature. Extreme differential permeability detectiontechnology is a new detection methods, which provides a new idea for measuring themagnetic permeability.Combined with differential permeability detection technology correlative theories,have analyzed relationship of extreme differential permeability,detection signal and thefatigue damage degree and stress concentration status。 Have established theexperimental platform of differential permeability detection technology, which includesa sensor component, excitation signals and detect signals component. Have optimizedthe correlative system parameters. When using the current source，the best frequencyis1300Hz, the best currents of0.1A; when using the voltage source, the best frequencyis400Hz, the constant voltage is less than4V. Set the correlative parameter, constantvoltage of4V, frequency of300Hz. Through detection air, the25#steel, and the45#steelto set mark. The stretch experiment, fatigue experiment, heat treatment experiment,defects fabrication experiment have been performed for25#steel and45#steelrespectively, have researched the relation of differential permeability of specimen andthe detection signal, and have researched the relationship of differential permeability ofspecimen and the stress concentrate parameter, fatigue damn damnification parameter,heat treatment parameter, defects property parameter.Through experiments and data analysis, it shows that the differential parameterand the detection signals for25#and45#steel, all rapidly decrease with the increasing ofstress concentration. Fatigue test indicate, for45#steel, differential permeability anddetection signal increases with the increase of fatigue degree and the number of thefatigue damage. For25#steel, in opposition to45#, differential permeability and detection signal decrease with the increasing of fatigue degree and number of thefatigue damage.Through the above the experiment and correlative data analysis, it shows thatdifferential permeability detection technology can accurately detect stress concentrationdegree and fatigue damage status for ferromagnetic material, and has broad applicationprospects.