Research On Barkhausen Noise Of Ferromagnetic Material In The Process Of Fatigue

Fatigue will come into being due to the repeated load when the ferromagnetic equipment in the process of serving for a long time,and catastrophe will happen because of it.Fatigue damage mode is common in construction material.However,conventional NDT technology cannot detect fatigue crack formation and formation of the early material properties change,but the Magnetic Barkhausen Noise(MBN)technique can detect the changes of magnetic parameters casused by microstructure change during the fatigue process of ferromagnetic materials,because of that,it is significant for estimating the fatigue life.The work in this article can be listed as follows(1)MBN mechanism researchBased on the theory of electromagnetics and ferromagnetism,the theory of metal fatigue and the characteristics of fatigue failure of metal were briefly introduced.The detection principle of MBN was described as well.The magnetic domain theory and magnetization theory of ferromagnetic material were emphasized,and the impact factors of MBN signal were studied.The researches of MBN in the stress measurement,microstructure change,hardness test and surface treatment process were illustrated in the paper.(2)Develop a MBN fatigue detection systemDevelop a reliable MBN fatigue detection system,including signal generation system,signal acquisition system and signal processing system,and the stability of detection system was tested.The high-performance MBN sensor was developed.Moreover excitation signal intensity and frequency were researched,as the results showed,the best incentives is 5 v,30 Hz.(3)Research of the MBN signal regularity in the fatigue process of Q235 steel and Q345 steel.Combining the theory of metal fatigue theory,the MBN signal characteristics in low cycle fatigue and high cycle fatigue of Q235 steel and Q345 steel were studied in this paper.As the result showed,the MBN fatigue system was reliable in detecting the MBN changes in the low cycle fatigue process.MBN signal declined with the increase of fatigue degree in the low cycle fatigue.However the relationship of MBN and fatigue degree was not obvious in the high cycle fatigue,the reason could be listed as follows: the randomness of the crack in high cycle fatigue will effect the test result,and also stress concentration had greater influence than fatigue.