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Non-Destructive
Evaluation
Superconducting QUantum Interference Devices (SQUIDs) are
ideally suited for the Non-Destructive Evaluation (NDE) of
materials owing to their extraordinary sensitivity and enormous
bandwidth, extending from true dc to several megahertz.
Typical NDE applications involve high spatial resolution measurements
of the magnetic fields emanating from a sample in order to
generate an image of the local magnetic fields near the sample
surface, or to quantify the temporal development of these
fields, or both. Using these magnetic field images, valuable
information about deep-lying features in the sample can be
obtained.
Typical NDE applications fall into three
different categories:
·
The
imaging of surface and sub-surface features, flaws, defects
and voids in materials (solid or liquid, metallic or insulating)
by the application of ac induction fields;
·
The imaging of materials
that have been pre-magnetized by a pulsed or static background
magnetic field;
·
The imaging of intrinsic
or applied electric currents in electronic circuits or materials.
In the aerospace industry, SQUIDs are being
used to obtain magnetic images of cracks in aircraft wheel
rims and to inspect jet engine turbine blades for inclusions,
as well as to image defects in models of typical aircraft
lap joints. Other applications include the evaluation of steel
plates used to build ship hulls and the inspection of concrete
infrastructure such as bridgework. Recent R&D applications
include the imaging of diamagnetic and paramagnetic tracers
in non-metallic composites, magnetic flux trapped in superconducting
thin films, the development of corrosion pits in metals and
the response of ferromagnetic materials to stress.
High-Tc
SQUID magnetometers
and STARCryo's advanced PC-based SQUID control electronics
products marketed under the trade name pcSQUID™ are being
used by a number of researchers at leading research
institutions around the world for a variety of NDE applications.
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