Helical comb magnetostrictive patch transducers for inspecting spiral welded pipes using flexural guided waves

Area of Science:

• Mechanical Engineering
• Materials Science
• Non-Destructive Testing

Background:

• Flexural waves in pipes propagate at a helix angle.
• Understanding flexural wave propagation is crucial for pipe inspection.
• Existing methods lack selectivity in exciting specific wave modes.

Purpose of the Study:

• To propose a novel Helical Comb Magnetostrictive Patch Transducer (HCMPT).
• To selectively excite a single predominant flexural torsional guided wave.
• To inspect seamless and spiral welded pipes using flexural waves.

Main Methods:

• Wavefront analysis to determine helix angle for flexural modes.
• Design and fabrication of a HCMPT with helical coupling and compound comb coil.
• Experimental verification of HCMPT performance for wave actuation and defect detection.

Main Results:

• The HCMPT effectively actuates flexural torsional mode T(3,1) at 64kHz with a 13-degree helix angle.
• Flexural torsional modes T(N,1) (N=1-5) were used to detect artificial defects in a seamless steel pipe.
• A 20-degree HCMPT successfully detected a 2.7% cross-section loss notch in a spiral welded pipe.

Conclusions:

• The proposed HCMPT offers selective excitation and direction control of flexural guided waves.
• HCMPT is a viable tool for non-destructive testing of pipes, including spiral welded variants.
• This technology advances the capability for inspecting pipes with complex weld geometries.