Detection of Micron-Scale Flaws Through Nonlinear Wave-Mixing

Storage of hydrogen is challenging due to high storage pressures and potential for hydrogen embrittlement. Frequent inspections of storage vessels are required to ensure safety but available technologies are unable to detect features on the micrometer scale that can influence remaining useful life. There exists a need for a system that can resolve micrometer scale features and relate these to the remaining useful life of infrastructure. Luna proposes develop an inspection system that leverages nonlinear interactions between two mixed acoustic waves to identify the presence of micrometer flaws in steel. The development effort will focus on EMAT technology to allow non-contact inspections and rapid surface scanning. During Phase I the feasibility of identifying micrometer-scale flaws in steel alloys using non- collinear wave mixing will be demonstrated using a breadboard system. This demonstration will include measurement techniques, transducer assemblies, and analytical routines that will transition to the Phase II system. A library of samples of two different steel alloys with seeded flaws will be produced and inspected using both conventional techniques and novel wave- mixing techniques. As part of the development effort, we will investigate the potential of single transducer probes as well as phased array probes in order to guide the direction of the Phase II architecture. Plans for the Phase II architecture and for verification and validation activities will during Phase II will be addressed.