SBIR Phase I: Using Ultrasonic Shear Polarization Contrast to Locate and Size Defects

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This Small Business Innovation Research (SBIR) Phase I project will determine the feasibility of a novel ultrasonic non-destructive method for detecting and characterizing defects such as fatigue cracks in metals. Existing ultrasonic methods have difficulty detecting cracks in the presence of the typical surface pitting found on pipes, pressure vessels, storage tanks and other steel plate and beam structures, particularly if access to the inner or outer surface is limited or costly. The proposed method, Shear Polarization Contrast (SPC), uses a proprietary transducer to generate and analyze shear waves with arbitrary polarization, generated on one surface and reflected from the far surface back to the transducer, to distinguish highly polarization-sensitive features such as cracks (highly anisotropic) from benign pitting and corrosion that are less polarization-sensitive (relatively isotropic). In Phase I, polarization sensitivity will be analyzed for various combinations of defect orientation and size in the presence of varying degrees of pitting to develop and validate a predictive model for crack detection threshold and sizing accuracy. After Phase II prototype development, the anticipated Phase III laboratory and field instruments will allow thorough non-destructive evaluation of components and structures, including the interior and both surfaces, while only requiring access to one surface.The broader impact/commercial potential of this project will be improved safety and protection of capital investment in critical civil, energy, petrochemical and industrial infrastructure. This project will incorporate novel techniques to electronically steer the polarization of acoustic shear waves to analyze and characterize their interaction with the physical, internal micro-structure of engineering materials, providing new analytical capabilities for Non-Destructive Testing, materials analysis and forensic engineering. For example, inaccessible inner surfaces of plate and beam components in aging critical infrastructure such as bridges could be inspected for cracks, the remaining useful life of these structures estimated, and a plan for reinforcement, replacement or demolition could be implemented. Until now, this capability did not exist. Resultant commercial equipment will be a field-deployable system integrating a proprietary Electromagnetic Acoustic Transducer (EMAT), specialized electronics and software. EMATs require minimal test surface preparation, allowing production to continue for even high temperature processes, reducing or possibly eliminating loss of production and the inconvenience of emptying vessels. The system?s competitive advantage is the unique ability to test and characterize cracks in the interior volume and on both surfaces, as well as classify cracks located under and within pitted and rough areas, only requiring access to one surface.