FINITE ELEMENT MODELING AND DEFECT CHARACTERIZATION FOR GAS TRANSMISSION PIPELINES INSPECTION
Udpa, L., Katragadda, G., and Lord, w Department of Electrical and Computer Engineering Materials Characterization Research Group, Iowa State University, Ames, IA 50011 USA
Keywords; Finite element modeling, Magnetic flux leakage, defect, pipelines, inverse problem
ABSTRACT
Magnetic Flux Leakage (MFL) methods are widely used for the inspection of gas transmission pipelines for detecting both internal and external corrosion in pipes. The MFL inspection tool magnetizes the ferromagnetic pipewall and the leakage flux caused by the presence of a defect is detected using Hall element sensors. Defects in the pipewall are characterized on the basis of the information in the Hall probe signals. However, a major problem in the development of defect characterization procedures is related to the fact that the MFL measurements are influenced by a number of parametric variables including tool velocity, pipewall permeability, sensor type and location, pipe thickness, stress, etc. An understanding of how these test conditions and operational variables affect the MFL signals is, therefore, crucial for the design of robust signal interpretation schemes. The ability to develop theoretical models has proven invaluable in understanding the field/flaw interaction in parametrically controlled environment. This paper describes the issues and challenges involved in the modeling of an MFL tool in motion inside a gas transmission pipeline and the use of numerical models in the solution of inverse problems.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 1, pages 269 - 274 Publisher:Ashgate Publishing Company
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