Sergey Vinogradov

DETECTION OF AXIAL CRACKS IN TUBE AND PIPE USING TORSIONAL GUIDED WAVES

Guided‐waves are now widely used for long‐range inspection of piping and tubing for detection of corrosion metal loss areas and circumferential cracks. The reflection coefficient of guided‐waves from a defect is proportional to the circumferential cross‐sectional area of the defect. Since axial cracks have negligibly small circumferential cross‐sectional area, they are usually undetectable. However, when the depth of axial crack reaches about 70‐percent of wall thickness, the interaction mechanism between the torsional wave and the axial crack changes and the crack begins to produce detectable signals accompanied with characteristic tailing signals. Experimental data from various sized pipes including a seam‐welded pipe with lack of fusion are presented and potential interaction mechanisms are discussed.

Review of magnetostrictive transducers (MsT) utilizing reversed Wiedemann effect

Magnetostrictive transduction has been widely utilized in NDE applications, specifically for generation and reception of guided waves for long-range inspection of components such as pipes, vessels, and small tubes. Transverse-motion guided wave modes (e.g., torsional vibrations in pipes) are the most typical choice for long-range inspection applications because the wave motion is in the plane of the structure. Magnetostrictive-based sensors have been available for several years for these wave modes based on the Wiedemann effect. For these sensors, a permanent magnetic bias is applied that is perpendicular to the direction of the propagated guided wave. This bias field strains the material that the guided wave is generated in preferentially in the desired particle motion direction. A time-varying magnetic field oriented parallel to the direction of guided wave propagation is also induced in the material. This time-varying field is induced using an electric coil located near the material surface. The intera...