Numerical simulation on alternating current field measurement and sensitivity analysis of detected signal

In order to develop the visualization technique for alternating current field measurement (ACFM), the application basis of ACFM was investigated with a numerical simulation method. A general digital model of ACFM was established, by means of the ANSYS CAE system. In the model, the physical parameters and gap thickness of a crack were well modeled, and the singularity resulted from crack was well treated. This model can be used to determine the magnetic distribution in the vicinity of any crack with irregular shape. The effects of lift-off and material properties on the magnetic distribution were evaluated and discussed by using the model. The numerical simulation results show that ACFM is not sensitive to the changes of magnetic conductivity, electric conductivity and lift-off. It is more feasible to detect the crack on the mild steel, compared with the eddy current testing. The researched conclusions may provide a theoretical basis for the development of virtual prototype of ACFM visualization products.