Research On The Response Factors Of Magnetic Barkhausen Noise

With the extensive application of ferromagnetic materials in machinery and equipment,aerospace,natural gas transportation and national defense industries,the detection of internal stress,fatigue damage and crack is particularly important for ensuring the normal operation and safety performance of the equipments.The traditional detection methods are likely to cause irreversible damage to the subject,and the magnetic Barkhausen noise(MBN)can meet the rapid and non-destructive on-site inspection requirements.At present,the research of MBN nondestructive testing(NDT)technology is mainly focused on stress detection,but MBN is affected by many factors,which is easy to cause measurement error.Therefore,the influence of the response factors on the MBN signal is analyzed in this paper,which lays a foundation for the wide use of MBN and the elimination of interference.Based on the magnetic domain theory,this paper describes the mechanism of MBN signal.According to the characteristics of MBN signal,the hardware system of MBN signal detector is designed and built,including detection sensor,signal generator,signal conditioning circuit.Then,the response mechanisms of MBN signal to magnetic field,stress and temperature are deeply analyzed.Based on previous research results,the formula is improved by combining the external magnetic field effect and improved model of "molecular field" theory.And the effect of the stress and temperature on MBN signal is further explained by the experiment.Finally,the relationships between MBN signal and hardness,carbon content,elastic modulus and surface roughness are studied through experiments.The experimental results show that:(1)MBN signal decreases linearly with hardness,and it can be applied to nondestructive testing of hardness;(2)With the increase of carbon content,MBN signal increases first and then decreases.When carbon content is 0.55 wt%,MBN signal has the maximum value.This paper proposes a combination method of MBN-hardness tester for nondestructive evaluation of carbon content;(3)Within a certain range,MBN signal first increases and then decreases with the increase of elastic modulus;(4)MBN signal decreases with the increase of roughness,and the attenuation speed decreases.In the range of Ra less than 2.536μm,roughness has great influence on MBN detection,and it is easy to cause detection error.According to the response characteristics of MBN signals to the material properties,we find that the relationship between MBN signal and response factors can be used for the detection of these factors.But some response factors will bring errors to MBN detection.Therefore,in order to ensure the reliability of the measurement results we need sample consistent with the workpiece to calibrate before measurement.