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Detection of corrosion fatigue in boiler tubes using a spike EMAT pulser

  • US 6,125,703 A
  • Filed: 06/26/1998
  • Issued: 10/03/2000
  • Est. Priority Date: 06/26/1998
  • Status: Expired due to Term
First Claim
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1. A method for detecting damage in a ferromagnetic workpiece, comprising the steps of:

  • positioning a pair of EMAT coils adjacent to an outer surface of the workpiece at a non-zero angle with respect to one another;

    applying a spike pulse to one of the EMAT coils for a period of time which is less than the time required to generate a toneburst signal in the one of the EMAT coils in order to magnetostrictively generate a shear horizontal polarized wave in the workpiece, wherein the shear wave is capable of being reflected by a flaw in the workpiece;

    receiving a reflected wave from a flaw in the workpiece at the other EMAT coil; and

    analyzing the received reflected wave and comparing an amplitude thereof to an amplitude of a reflected wave produced by a known calibration standard flaw and producing an indication that a flaw has been detected in the workpiece when the amplitude of the received reflected wave exceeds a predetermined percent of the amplitude of the reflected wave produced by the known calibration standard flaw.

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