Integrating a Stress Corrosion Crack Model into Finite Element Electromagnetic NDT Code

Abstract

The maintenance of infrastructure subject to aging in harsh environments demands the highest level of confidence in nondestructive evaluation. One of the most critical issues in the inspection of gas transmission pipelines remains the detection of stress corrosion cracking (SCC). The magnetic flux leakage (MFL) method [1] is widely used to detect cracks in steel. Numerical simulation using the finite element method (FEM) has been proven to be an efficient and inexpensive means of studying the interaction and redistribution of electromagnetic fields [2]. This article describes a stress corrosion crack model and its implementation in a finite element code for simulation of magnetic flux leakage inspection. For a complicated, minimal density of the mesh is desired to implement a code with reasonable requirements of computer memory and computation time. On the other hand, simulations need to be accurate enough to be experimentally validated. Traditional FEM assumes, that all the properties of materials are constants within each element. An approach with conductivity and permeability, varying within elements around a crack, is developed in this paper.