Nondestructive Inspection (NDI) of Small-Diameter Titanium Tubing

New technology is needed for the nondestructive inspection (NDI) of microscopic defects in the thin-wall, titanium alloy hydraulic lines used on aircraft. Once mounted on an aircraft, these tubes are difficult to access externally, making inspection of the tube from the inside the most practical method for NDI. The Navy has identified a specific need for the NDI of titanium tubing with diameters ranging from 0.25 to 0.75 inches. The defects are micro-cracks with depth dimensions of 0.5 to 1.0 mils in tubing with wall thickness that is typically 22.5 mils. These defects are exceedingly small and will require new technology for dependable detection. RMD proposes a new inspection technology based on high resolution, 3-D imaging of magnetic fields induced in titanium tubing to locate and characterize microscopic defects. The proposed NDI system will use a new sensor technology to produce an advanced sensor array with minute elements measuring only 3 microns (0.1 mils). An array of microscopically small "zig-zag", magnetoresistive (MR) sensor elements will detect and map variations in induced magnetic fields caused by micro-cracks in titanium tubes measuring 0.5 mils. The proposed sensors have high bandwidth, >1 GHz, for exceptionally high speed scanning and inspection. The sensors are fabricated on silicon that is compatible with high volume, low cost production with integrated amplifiers and signal processing circuitry on the same chip. The technology can analyze and image defects in true 3-D. RMD has assembled a strong research team with substantial experience in sensor and instrumentation design and fabrication. Previous research by the PI and his collaborators has established a foundation for the development of the proposed new technology for NDI of microscopic defects.