Project Title:

High-Frequency, Magneto-Optic Eddy-Current Imager for the Detection of Shallow Cracks

13.09-0056
911281
High-Frequency, Magneto-Optic Eddy-Current Imager for the Detection of Shallow Cracks
Physical Research, Inc.
25500 Hawthorne Blvd, Suite 2300
Torrance
CA
90505-6828
David
Thome
310-378-0056
KSC
NAS10-11864
272

13.09-0056
911281

Abstract:

High-Frequency, Magneto-Optic Eddy-Current Imager for the Detection of Shallow Cracks
The purpose of this project is to improve substantially the capabilities of magneto-optic
eddy-current imaging (MOI) technology. This technology has recently been developed
for rapid inspection of surface breaking cracks near rivets and second-layer cracking
and corrosion in aluminum aircraft alloys. Commercial MOI instruments, geared to
the evaluation of aging aircraft, are now available and are suitable for the rapid
inspection of large, relatively flat surfaces. They are also useful for directly
imaging residual or induced magnetic fields in ferromagnetic materials, but are presently
limited to excitation frequencies of 100 kHz or less. Recent testing of graphite
composite honeycomb material bonded to an aluminum core also showed very promising
results for imaging and detection of delaminations. The technology offers the advantages
of rapid inspection, direct imaging, improved data presentation, and greater sensitivity
to detection of small surface cracks, such as those emanating from rivets. There
is a need to extend the range of these instruments for inspection of more complex
shaped components, using higher frequencies to detect and image shallow, tight surface
cracks. This may allow eventual replacement of present dye penetrant inspection techniques.
Development of magneto-optic, eddy-current imaging technology at higher frequencies
and power levels will open the door for use on titanium alloys and the rapid detection
of small, shallow, surface-breaking fatigue cracks, allowing better discrimination
between actual cracks and surface scratches. Non-destructive inspection will thus
be improved in the aerospace industry for both production and in-service evaluation.
nondestructive testing, magneto-optics, crack detection