The Inversion Method Of Magnetic Flux Leakage Detection Of Ferromagnetic Materials And Analysis Of Its Influencing Factors

Ferromagnetic materials are widely used in many fields of national economy,and they will produce defects under the effect of pressure or environment.However,material defects can cause significant losses to national economy.Therefore,nondestructive testing is full of practical significance.Among the multiple methods of nondestructive testing,magnetic flux leakage detection is widely adopted because of its advantages of sensitivity,reliability,rapidity and low cost.Magnetic flux leakage testing problem can be divided into forward problem and inverse problem.Among them,the forward problem is the basis of the inversion problem.Therefore,the fast and accurate forward model can lay a good foundation for magnetic flux leakage inversion.First of all,this paper introduces the basic principle of interpolation calculation,and then divides the source area into several integral units,and each unit is thunk as a magnetic dipole model.This paper calculates the leakage magnetic field at any field point generated by each unit and then summarize them.So far,the magnetic dipole forward model has been derived.With the help of COMSOL finite element simulation software,the validity of this forward model for single defect and multiple defects is verified.Secondly,the singular value decomposition method is used to decompose the coefficient matrix of the magnetic dipole forward model.This method is used to acquire the least norm solution for the least squares problem of inversion question,which meets the minimum error requirement.Therefore,the singular value decomposition inversion model is derived.This paper verifies the correctness of the inversion algorithm by using single and multiple defects of different shapes and sizes.Finally,based on the composition of the inversion equation,this paper acquires the control variable method to explore the influence of factors such as subdivision size,number of measurements,data position and lift height on the accuracy of inversion,so that the best inversion result is achieved.Taking the arbitrariness of the source division shape into account,the source area is also divided into triangles,and the effects of triangular linear interpolation on forward problem and inversion problem are analyzed.