Combined electromagnetic acoustic transducer (EMAT) and electro permanent magnets (EPMS) for bias field control
Systems and methods for non-destructive testing of specimens are disclosed herein. In one embodiment, an electromagnetic acoustic transducer (EMAT) includes an electro-permanent magnet (EPM) configured to controllably apply a biasing magnetic flux to a target location. The EPM includes a hard magnet, and a soft magnet at least partially enclosing the hard magnet. The EPM also includes a magnetizing coil having a plurality of turns at least partially encircling the soft magnet. The magnetizing coil is configured to controllably magnetically bias the soft magnet when a current is applied to the magnetizing coil.
1. An electromagnetic acoustic transducer (EMAT), comprising:
an electro-permanent magnet (EPM) configured to controllably apply a biasing magnetic flux to a target location, comprising:
a hard magnet,
a soft magnet at least partially enclosing the hard magnet, and
a magnetizing coil having a plurality of turns at least partially encircling the soft magnet and the hard magnet, wherein the magnetizing coil is configured to controllably magnetically bias the soft magnet when a current is applied to the magnetizing coil; and
a sensor coil configured to provide an alternating magnetic field to the target location,
wherein the EMAT is configured to controllably coordinate the EPM and the sensor coil to perform non-destructive testing of the target location.
2. The EMAT of claim 1 , wherein the hard magnet, the soft magnet, and the magnetizing coil are coaxially aligned perpendicular to the target location.
3. The EMAT of claim 1 , wherein the hard magnet, the soft magnet, and the magnetizing coil are coaxially aligned parallel to the target location.
4. The EMAT of claim 1 , further comprising a yoke providing magnetic communication between a first end and a second end of the EPM.
5. The EMAT of claim 1 , wherein the yoke is made of a ferromagnetic material.
6. The EMAT of claim 5 , wherein the ferromagnetic material comprises steel.
7. The EMAT of claim 4 , wherein the yoke partially encloses the EPM.
8. The EMAT of claim 1 , further comprising a chassis configured to at least partially house the EPM.
9. The EMAT of claim 8 , wherein the chassis comprises wheels configured to move the EMAT along the target surface.
10. The EMAT of claim 8 , wherein the chassis comprises skid pads configured to move the EMAT along the target surface.
11. The EMAT of claim 1 , further comprising control electronics configured to control the EPM and the sensor coil in order to perform ultrasonic non-destructive testing at the target location.
12. The EMAT of claim 1 , further comprising an electrical connector configured to provide electrical connection between the EMAT and a power source and/or controller housed separately from the EMAT.
13. A method of operating an electromagnetic acoustic transducer (EMAT), comprising:
passing a first pulse of electrical current through a magnetizing coil adjacent to a soft magnet of an electro-permanent magnet (EPM);
in response to passing the first pulse of electrical current, polarizing the soft magnet to a first polarization, wherein the soft magnet at least partially encloses a hard magnet of the EPM, and wherein the hard magnet is in the first polarization;
passing a second pulse of electrical current through the magnetizing coil adjacent to the soft magnet;
in response to passing the second pulse of electrical current, polarizing the soft magnet to a second polarization, wherein the second polarization is opposite from the first polarization.
14. The method of claim 13 , further comprising directing a magnetic flux to a sensor coil of the EMAT.
15. The method of claim 14 , further comprising generating acoustic waves to perform a non-destructive testing of a specimen at a target location.
16. The method of claim 15 , further comprising detecting a flaw in the specimen based on reflected acoustic waves.
17. The method of claim 15 , wherein passing the first pulse of electrical current is done in preparation for the non-destructive testing of the specimen.
18. The method of claim 13 , wherein passing the second pulse of electrical current is done in preparation for repositioning or shipping of the EMAT.
19. The method of claim 13 , further driving an alternating current through a sensor coil of the EMAT to provide an alternating magnetic field at a target location.
20. The method of claim 13 , wherein the magnetizing coil at least partially encircles the soft magnet.
21. The method of claim 13 , wherein the hard magnet and the soft magnet are co-axial.
22. The method of claim 13 , wherein the hard magnet and the soft magnet are concentric.
23. The method of claim 13 , wherein the hard magnet and the soft magnet are bi-axial.
24. The method of claim 13 , wherein the hard magnet and the soft magnet are cylindrical.