BOISE, ID-In a project commissioned by Lockheed Martin Aeronautics, Positron Systems demonstrated that its Photon Induced Positron Annihilation (PIPA) and related technologies can reliably and accurately measure the effectiveness of cold expansion techniques in metal alloys. The company says that this capability will lead to improved inspection intervals and lower maintenance costs in the aerospace sector. Further, with PIPA's multi-layer damage assessment capability, early damage in subsurface layers can be detected, thereby providing a method for quantifying damage without component disassembly.
Many fastener holes in aerospace components are "cold worked" to produce a compressive residual stress field around the hole to improve resistance to fatigue cracking. Other nondestructive testing methods cannot accurately assess the effectiveness of cold working on fastener holes in aluminum alloys because of their material characteristics. Further, current techniques are not easily deployed in the field to inspect in-use components.