Efficient analytical modelling for Pulsed Remote Field Eddy Current evaluation of stratified tubular structures

Stratified Tubular Structures (STSs), such as pipeline, are extensively adopted in such engineering fields as nuclear, petroleum, chemical and aerospace, etc. Wall-thinning Defects (WTDs) are usually found within in-service STSs, and taken as critical flaws which demand to be detected and assessed during STS inspection. It is crucial to non-destructively evaluate the integrity of STSs, particularly WTDs before catastrophic accidents occur. Pulsed Remote Field Eddy Current technique (PRFEC) has been found applicable for evaluation of WTDs in ferromagnetic STSs. In this paper, an efficient analytical model for PRFEC of STSs subject to WTDs is established based on the Extended Truncated Region Eigenfunction Expansion (ETREE). The closed-form expressions of PRFEC responses to WTDs in STSs are formulated. The model is verified by Finite Element Modelling (FEM), and found promising in fast computation of PRFEC signals with high accuracy. The research benefits the inverse problems regarding PRFEC of WTDs in STSs.