The reflection of the fundamental torsional guided wave from multiple circular holes in pipes

Localised corrosion is a major concern in the petrochemical industry, and often occurs as clusters of pits. A study of the reflection from two and three small circular holes in pipes with the fundamental torsional guided wave incident is presented. FE analyses with both part and through thickness holes at different relative positions are presented, and are a step towards estimation of the scattering behaviour of multiple and random defects. The validity of employing the superposition technique in estimating reflection coefficients is assessed. Results show that the reflection coefficient for the T(0,1) mode is dependent on absolute frequency and axial separation, and independent of circumferential position. Employing superposition is found to be valid down to defect centre to centre separation distances of two diameters in the worst case, with improved validity with shallower defects. Results from the FE analyses are validated experimentally.

► Guided wave reflectionmultiple holes predicted and measured.
► Superposition shown to be valid at separations greater than two diameters.
► Validity of superposition improved with shallower defects.
► Reflection of T(0,1) mode independent of circumferential hole locations.
► Reflection of T(0,1) mode depends on absolute frequency and axial hole separation.