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.
