Three Dimensional Magnetic Imaging of Damage in Multiple Layer Aircraft Structures

"JENTEK's Meandering Winding Magnetometer Arrays (MWM-Arrays) have recently demonstrated the capability to detect and image corner cracks, less than 0.1 in. long, in the third layer of 727 lap joints. JENTEK's efforts to date have focused on relativelythin structures, e.g., up to 0.1 in. thick. This proposed effort will focus on detection of 0.050-in. long corner flaws at fasteners in the first through fourth layers of relatively thick structures - 0.1 to 0.5 in. thick. What is proposed here is theapplication of enhanced MWM-Arrays with inductive sensing elements and/or giant magnetoresistive (GMR) sensing elements, used in combination with a three-dimensional image reconstruction algorithm, along with methods to remove interferences from thefasteners to reveal the presence of cracks. This will include enhanced detection as well as determination of the location and size of cracks. We will use model-based inversion methods of multiple layered structures and multiple frequency data to removethe interferences from the fasteners and the contributions of successive layers to "peel the onion" and reveal cracks in lower layers. Phase I will demonstrate the required capability on actual components, while Phase II will further enhance thecapability and deliver a fieldable system that meets Air Force requirements. The enhanced MWM-Array technology developed in this SBIR would provide the Air Force with a fieldable tool that not only solve