Analogic Engineering, Inc.
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TECHNICAL SUMMARY

 

The aim of this NSF Phase I proposal was to prove the feasibility of employing variable polarization ultrasonic shear waves generated by a proprietary Electromagnetic Acoustic Transducer (EMAT) and custom instrumentation for detecting and sizing defects in engineering structures and components. The research sought to establish a thorough understanding of how the novel ultrasonic sensor functions, the potential advantages and limitations, and to form a solid basis for ongoing product development. The successful Phase I research has resulted in a new Non-Destructive Evaluation (NDE) test method that has been named Shear Polarization Contrast (SPC). The SPC method exploits the EMAT and instrumentation capabilities by subjecting the test material to two shear waves having a common propagation path but orthogonal polarizations, and comparing (contrasting) these two responses. Since cracks modify the local elastic tensor in a highly directional way, the interaction between the crack and the two shear waves propagating along the crack plane depends on whether the polarization (particle motion) is perpendicular (most affected) or parallel (least affected) to the crack surface. With the underlying acoustic phenomena now understood, and repeatable accurate procedures developed to locate and size defects, the PI is confident that a test instrument can be developed and employed in a broad range of industrial applications. In Phase II, field and laboratory instrumentation incorporating SPC will be developed and then marketed in Phase III to researchers, NDE service providers and equipment suppliers that service the various industries reliant upon storage vessels, structural components, piping, etc. that are made of metals and require structural integrity testing.

 

Typically, before testing can commence, tanks and large pressure vessels must be  prepared for testing, which can involve being taken out of service, emptied of their contents, and surface preparation. The SPC method has great potential to reduce inspection time and costs during manufacturing and field testing, by testing the volume, outer and inner surfaces of large engineering structures without requiring access to both surfaces. In particular, inaccessible inner surfaces of pipes, storage vessels (oil, chemical, etc.), plate and beam components in aging infrastructure such as bridges, steel-frame buildings, and ships could be inspected. Due to the nature of EMATs, minimal outer surface preparation would be required since the ultrasonic sound waves are created and detected directly in the material surface electromagnetically, and the usual fluid or gel couplants are not required. Also for this reason, higher temperatures can be tolerated than many other NDEmethods, further reducing interference in applications such as

manufacturing and industrial processing. In many applications, this new technology will allow testing to be done while production continues, which will save labor cost and eliminate lost revenues from production down-time.

 

 

ACKNOWLEDGEMENTS

 

This research supported by NSF SBIR Phase I Award No. IIP-1014355 “Using Ultrasonic Shear Polarization Contrast to Locate and Size Defects"

 

Analogic Engineering, Inc. wishes to thank Professor Krishnan Balasubramaniam, Dr. R. Dhayalan, Professor C. V. Krishnamurthy and others at the Indian Institute of Technology Madras, Centre for Nondestructive Evaluation (IITM/CNDE) for their collaboration with Dr. Bruce Maxfield on this project and other work on polarized shear wave scattering which includes more complex geometries such as defects in lap joints. Dr. Dhayalan, working with Dr. Maxfield, has developed a periodic permanent magnet SH wave EMAT to study adhesive bonding with the first application in the area of aluminum lap joints.

 

Analogic Engineering, Inc. wishes to acknowledge Dr. Jonathon L. Benson, CEO, Wyoming Technology Business Center, the University of Wyoming and Wyoming Business Council for making this research possible thanks to the superior facilities, administrative support and communications capabilities provided.

          EMAT RESEARCH PROJECT 2010


Project Title:                    Using Ultrasonic Shear Polarization Contrast to

                                      Locate and Size Defects

Grant Support:                  National Science Foundation SBIR Phase I

Award Number:                 IIP-1014355

Commencement Date:        6/1/10

Completion Date:              12/31/10

Principal Investigator (PI):  Steven J. Turner

Senior Scientist:                Dr. Bruce W. Maxfield