Multi-Layer Deep Structure NDI

ABSTRACT: An innovative NDI method, General Remote Field Eddy Current (GRFEC) method, is proposed for aircraft multi-layer deep structure NDI. GRFEC method is characterized by its deep penetration and high sensitivity features in multi-layer and complex deep structure NDI. The outstanding features have been proved by the AFRL validation/evaluation programs and published at 2014 AA&S Conference and 2014 ASIP Conference. Due to the deep penetration ability flaw can be detected directly from surface of a structure. This improves flaw detection beyond the first layer in multi-layered, complex, and difficult to access structures. Two approaches are proposed to upgrade GRFEC method. 1). to validate GRFEC systems ability in determining hidden flaw parameters and conditions directly from the structure surface, such as flaw location, length and orientation of a crack, single or multiple cracks, etc. Influence to flaw signal from structure geometry, such as edge condition and distance between fasteners, will also be addressed. The goal is enable straightforward NDI inverse problem solutions to avoid complicated inverse-problem algorithms and numerical modeling. 2). to provide easy airplane data capture and periodical NDI data storage approaches. Instant display of long-term periodical NDI data will be enabled in GRFEC system for a large number of inspected locations/fasteners. Any sudden change in inspected signal of a location/fastener should be a strong indication of possible defect or structure variation at the location before the last inspection time. Since no structure disassembly is involved in implementation of the NDI, all the work can be done quickly. Furthermore, the 2nd approach may possibly become a new way of Structure Health Monitoring (SHM) using a GRFEC system. ; BENEFIT: Anticipated Benefits/Potential Commercial Applications of the Research or Development. Significant improvement of overall NDI capabilities is promised by using the proposed GRFEC method, not only in reduction of the burden of time and cost intensive inspection, but also in insurance of the reliability of the inspection results, as well as in increase of the safety of continuous operation for the aging Air Force aircraft fleets.