Method and Apparatus Generating and Detecting Torsional Waves for Long Range Inspection of Pipes and Tubes: 6,624,628

A method and apparatus is shown for implementing magnetostrictive sensor techniques for the nondestructive evaluation of ferromagnetic pipes or tubes. A magnetostrictive sensor generates shear waves and/or torsional waves in ferromagnetic pipes or tubes, which waves travel therethrough in a direction parallel to the longitudinal axis of the pipe. A circumferential magnetization is generated in the ferromagnetic pipe or tube by a DC or low frequency voltage establishing a current along the longitudinal axis and past the magnetostrictive sensor. Reflected shear or torsional waves may represent defects in the pipe or tube.