PIPELINE INSPECTION USING A TORSIONAL GUIDED-WAVES INSPECTION SYSTEM. PART 2: DEFECT SIZING BY THE WAVE FINITE ELEMENT METHOD
Abstract
This paper represents the second part of the work that considers the identification and sizing of machined defects in a pipeline. This study deals with the torsional-mode reflection from defects and structural singularities in an industrial pipeline in order to perform the defect sizing. The wave finite element method (WFEM) is used to construct a numerical database of reflection coefficients from rectangular defects by varying thickness, axial and circumferential extents. Calculation is made depending on the frequency. The approximation of defects' sizes is carried out by sweeping the numerical database to find the suitable combination of dimensions for a given defect. The axial and circumferential extents are evaluated by fixed intervals for each possible thickness. Reflections from structural singularities (elbows, concrete blocks, clamps and welds) are also treated by comparing reflection coefficients obtained by the WFEM to those evaluated experimentally. Results show a good agreement for most of the structural singularities but not for the others.
