SBIR/STTR Phase I: Using Variable Polarization Ultrasonic Shear Waves to Isolate and Quantify the Competing Effects of Microstructure and Stress on the Acoustic Properties of Steel

This Small Business Innovation Research (SBIR) Phase I project will develop prototype equipment to achieve control of acoustic shearwaves in ferromagnetic materials, and introduce innovative technology to enable scientists and engineers to utilize variable shear wave polarization as a new tool for measuring and characterizing material properties. This will greatly enhance non-destructive testing of metals.To establish the feasibility of the proposed technique, a specially configured Electromagnetic Acoustic Transducer (EMAT) will be used to demonstrate electronic steering of shear wave polarization. Acoustoelastic relationships, relative to polarization angle, will then be analyzed for several steel samples of varying microstructure with the objective of establishing a measurement method capable of accurately determining longitudinal stress, independent of sample microstructure. Commercial applications exist for both rapid, in-situ, nondestructive assessment of microstructure, and for longitudinal stress measurement in steel members. Specific examples include monitoring and process control at critical stages of steel manufacture and thermomechanical processing; improving railroad safety through early detection and preemptive correction of extreme rail stress that can contribute to train derailments; and verification of correct load distribution in older or compromised steel structures such as bridges, stadiums, factories and multi-story steelframe buildings.