Method and System for Generating and Receiving Torsional Guided Waves in a Structure Using Wiedemann and Inverse Wiedmann Effect

• US 20090174399A1
• Filed: 01/07/2008
• Published: 07/09/2009
• Est. Priority Date: 01/07/2008
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Ihi Southwest Technologies Inc. (IHI Corporation)
• Inventors: Vinogrador, Sergey A.
• Granted Patent: US 7,821,258 B2
• Time in Patent Office: Days
• US Class Current: 324/238
• CPC Class Codes: G01N 2291/0425 Parallel to the surface, e.g. creep waves
• CPC Class Codes: G01N 27/82 for investigating the presence of flaws
• CPC Class Codes: G01N 29/2412 using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18
• CPC Class Codes: G01N 29/32 Arrangements for suppressing undesired influences, e.g. temperature or pressure variations , compensating for signal noise

Abstract

A method is shown for magnetostrictive testing of structures using magnetostrictive techniques. A torsional guided wave is generated in the structure either directly, or through a magnetostrictive strip dry coupled or bonded to the structure. A permanent magnetic field is created by either permanent magnets or DC current for a permanent bias in a bias direction in the magnetostrictive strip and/or structure. By pulsing the magnetic field with an AC current pulse, a torsional guided wave will flow through the structure in the same direction as the permanent bias. By saturating the permanent magnetic field, a maximum torsional guided wave is reflected from defects in the structure to given an improved signal to noise ratio.

Claims

1. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure, said method comprising the following steps:

first creating a permanent magnetic field at a location in said structure, said permanent magnetic field having a bias direction;

applying a pulse of alternating current to a AC coil adjacent to said location, but perpendicular to said bias direction;

second creating an alternating magnetic field pulse at said location from said pulse of said alternating current;

generating a torsional guided wave from said alternating magnetic field pulse, direction of propagation of said torsional guided wave being in the same direction as said bias direction;

reflecting said torsional guided wave off said defects in said structure;

detecting said reflected torsional guided wave; and

processing said detected reflected torsional guided wave to determine size and/or location of said defects.

2. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 1 including a magnetostrictive strip dry coupled or bonded to said structure at said location.

3. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 2 wherein said first creating step is caused by DC current flow adjacent said magnetostrictive strip.

4. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 3 wherein said DC current flow is through a DC coil wound lengthwise around said magnetostrictive strip and said alternating current is through said AC coil wound perpendicular to said DC coil around said magnetostrictive strip.

5. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 4 wherein said applying step including generating said pulse in a pulse generator and transmitting said pulse via a transmitter to said AC coil.

6. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 5 wherein said detected reflected torsional guided wave is conditional in a signal conditioner, processed in a signal processor and analyzed in a signal analysis for said determination of said size and/or location of said defects.

7. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 2 wherein said magnetostrictive strip is in a circular configuration with a gap between ends thereof and said structure is tubular.

8. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 7 wherein said AC coil is wound around a short axis of said magnetostrictive strip.

9. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 1 wherein said structure is tubular, said first creating step is with a large permanent magnet inside a circular shielding strip within a tubular structure, said large permanent magnet creating a magnetic bias lengthwise along said tubular structure, said second creating step being caused by said alternating current in said AC coil wound around a short axis of said shielding strip.

10. The method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure, said method comprising the following steps:

securing a magnetostrictive strip to said structure;

first creating a permanent magnetic field in said magnetostrictive strip, said permanent magnetic field having a bias direction perpendicular to a longitudal axis of said magnetostrictive strip;

applying a pulse of alternating current to an AC coil adjacent to said magnetostrictive strip, but perpendicular to said bias direction;

second creating an alternating magnetic field pulse in said magnetostrictive strip from said pulse of said alternating current;

generating a torsional guided wave in said magnetostrictive strip from said alternating magnetic field pulse, direction of propagation of said torsional guided wave being in the same direction as said bias direction;

transferring said torsional guided wave from said magnetostrictive strip to said structure;

reflecting said torsional guided waves off said defects;

receiving said reflected torsional guided wave; and

processing said received reflected torsional guided wave to determine size and/or location of said defects.

11. The method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 10 wherein said securing step is by dry coupling or bonding.

12. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 10 wherein said AC coil is wound around a short axis of said magnetostrictive strip prior to said securing step.

16. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 11 wherein said first creating step being with a series of permanent magnets for said permanent magnet field.

17. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 12 wherein said magnetostrictive strip is circular with a gap between the ends thereof and said structure is tubular.

18. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 17 wherein said first creating step is by DC current flowing through a DC coil wound around a longitudinal axis of said magnetostrictive strip and perpendicular to said AC coil.

13. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 13 wherein said first creating step is by a DC current flowing through a DC coil wound longitudinally around said magnetostrictive strip, but perpendicular to said AC coil, said winding occurring before said securing step.

14. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 13 wherein said pulse of said alternating current is generated in a pulse generator and transmitted by a transmitter to said AC coil.

15. A method of nondestructive testing of a structure using magnetostrictive techniques to determine defects in the structure as recited in claim 14 wherein said reflected torsional guided wave is conditioned in a signal condition, processed in signal processor and analyzed in a signal analysis for said determination of said size and/or location of said defects.