Development of Magnetostrictive
Sensor Technology for Plate Inspection, 15-9077
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Sang Young Kim
Inclusive Dates: 04/01/98 - Current
Background - An increasingly competitive
business environment has forced industries to reduce operating costs. Some industries such
as gas, oil, petrochemical, chemical, and electric power, operate and use large equipment
or structures that require a high capital investment. The maintenance costs for these
structures constitute a large fraction of the overall operating cost. To reduce
maintenance costs without compromising operational safety, industries are searching for
better and more efficient ways to inspect their equipment and structures.
The Institute has developed and patented a nondestructive
evaluation (NDE) technology called the magnetostrictive sensor (MsS). The MsS is a device
that electromagnetically generates and detects elastic guided waves in a ferromagnetic
material such as carbon steel. With MsS® technology, elastic guided waves in sonic or
ultrasonic frequencies are generated and propagated in a structure under inspection, and
waves reflected from structure defects are detected, typically, by the pulse-echo method.
The occurrence time of a defect signal (from the time of initial pulse) and the signal
amplitude is then used to determine the location of the defect (from the sensor position)
and its severity. The elastic guided waves can propagate a long distance (more than 100
feet in typical plant piping) and thus can be used to probe a long section of a structure
quickly. In addition, the MsS, being an electromagnetic sensor, can be applied without
direct physical contact to the surface of the part under inspection (for example, over
coating or painting on the pipe) and, therefore, can be applied with minimum supporting
activities. With the guided wave's long-range probing capability and the MsS's
noncontact-sensing capability, MsS technology provides a cost-effective method of
inspecting large structures globally.
MsS technology has been successfully applied to piping and
tubing inspection, and the commercialization of the technology for this application
has begun. In addition to tubular structures, industry also needs cost-effective NDE
methods for plate-like structures such as aboveground storage tanks and steel liners in
nuclear power plant containments. This project is aimed at extending the MsS applicability
to inspection of plate-like structures. It was motivated to meet the industrial needs and
to secure and maintain the Institute's technical initiative and leadership in the
development of this new and exciting technology.
Approach - The MsS used for piping or tubing
inspection employs coils that encircle the structure. For plates, the accessibility is
limited to one side of the structure, preventing the encircling coil-type MsS from being
used. Instead, a MsS probe that uses a coil wound around a U-shaped core and is
electromagnetically coupled to the plate under inspection will be developed. The MsS probe
for plate inspection will be developed through a systematic approach, which includes the
design and evaluation of preliminary MsS probe designs, prototyping, and capability
demonstration on laboratory plate samples.
Accomplishments - Preliminary and prototype
MsS probes were designed and fabricated. Using these probes, guided plate waves of
symmetric and antisymmetric longitudinal (S0 and A0) Lamb wave modes and shear horizontal
(SH) wave mode were successfully generated and detected in a 0.5-inch x 4-foot x 20-foot
carbon steel plate. Preliminary results using an artificial defect in the plate confirmed
the capability of the MsS technology to globally inspect plates over long distances.
For more information, please contact
Glenn M. Light, Ph.D.
of Materials and Structures Program
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