Modeling the Magnetic Field Distribution for Pipe Corrosion Pit with ANSYS Software

The Metal Magnetic Memory (MMM) Method, as an advanced pipeline non-contact and trenchless online inspection technology, is being used increasingly. But how to determine the characteristics of pipe defects from a detected magnetic field signal is still an unsolved problem. Here, the authors propose a new analysis method for this problem by calculating the magnetic field distribution signal of a corrosion pit in buried metal pipe with ANSYS® software. The main steps of this method can be summarized as: solving the stress concentration for corrosion pit with ANSYS® Mechanical module firstly, then coupling the contribution of stress with magnetic permeability by a user ANSYS® APDL subroutine, and finally, calculating the magnetic field signal of the pit in earth magnetic field with ANSYS® Emag module. Five different corrosion pit positions are calculated and discussed. The results show that this method can model a corrosion pit magnetic field signal successfully. This method can be potentially used to analyze magnetic field signals of other more complex cases, such as influences of pit size and depth and combination effects of pits.