Research On The Influence Of Magnetic Field And Temperature Field On Magnetic Barkhausen Noises

Magnetic Barkhausen Noise nondestructive testing comes into our sight because it is fast and accurate,and the multi-parameter measurements can be done in the same time,which makes it get a lot of attentions.However,at present,there are not many researches on the mechanism of MBN.Therefore,this paper,first at all,starts with the knowledge of the magnetism and briefly explains how the MBN signals produce,which lays a theoretical foundation for the subsequent research.Afterwards,this paper introduces the three kinds of stresses that affect the safety of the ferromagnetic materials,which they are the tensile and compressing stress,the temperature stress and the residual stress.It compares several testing methods and show the testing of MBN is much better than others because of its superiority.After that,this paper describes how the Barkhuasen jump works.The formula of the average volume of the magnetic Barkhausen jump is deduced step by step.First of all,the general formula is deduced from the experiment how to detect the Barkhausen jump.After that,it gets the irreversible magnetic permeability in the irreversible displacement of the 180° domain wall when the Barkhausen jump occurs;then it gets the reversible magnetic permeability during the reversible displacement of the 180° domain wall;and then with the theory of "molecular field" of the ferromagnetism,the relational expression formula of saturation magnetization is deduced.Then the three parameters are substituted into the average volume formula to obtain a complete theoretical model.In the end,the average volume formula reflects the influence of the magnetic field and the material temperature on the MBN signal.The formula shows that when the magnetic intensity is constant,the maximum value of the average volume of MBN decreases with increasing temperature,and the trend becomes more and more gentle;when the material temperature is constant,the maximum value of average volume of MBN increases with the increase of magnetic intensity,but the change of the maximum value is still small compared with the change under temperature changes.Then this paper conducts the experiment in the different magnetic intensity values at a fixed temperature value and in different temperature values at a fixed magnetic intensity value.Then it compares the experimental curve with the theoretical curve.Two curves have a very good relationship,which means the formula can provide the theory basis for practical using of MBN testing.