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Development of Magnetostrictive Sensor Technology for Plate Inspection, 15-9077

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Principal Investigators
Hegeon Kwun
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.

Nondestructive Evaluation of Materials and Structures Program
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