Rail inspection has seen steady, incremental advances for decades. From early Sperry ultrasonic inspection cars to EMATS, rail NDE has followed a tried and true path ñ launch carefully selected critical angle waves to inspect a region of the rail under or near the sensors. In this proposal, we take a fundamental departure from that tradition to better differentiate critical defects. Our approach uses multimode guided waves as probing energy to detect nonlinear differential signals. Unlike earlier acoustoelastic techniques, this approach uses the nonlinear properties of crack closure to clearly differentiate real defects. This approach should enhance defect detection probability at a cost comparable to current systems. The Differential Guided Wave Nonlinear Spectroscopy (DGWNS) system has two detection windows, each able to sense rail defects. First, direct scattering of the lower frequency guided waves is produced by the defect. Second, recently available computational nonlinear technology can sort through multimode complex effects that occur at the defect site. DGWNS may provide a unique new tool finally able to radically advance rail inspection. Nascent has assembled an exceptional team for this research including Norfolk Southern railroad, The College of William & Mary, and Allied Aerospace Industries, Inc.
