Galfenol-Based Directional Magnetostrictive Patch Transducer for Guided Lamb Wave Techniques

摘要

This paper presents the development of a Galfenol-based directional magnetostrictive patch transducer (MPT) and the results of experimental investigations with the developed MPT for guided Lamb wave (GLW) applications. We used three magnetostrictive materials such as nickel, polycrystalline Galfenol, and single-crystal-like Galfenol (i.e. a highly textured Galfenol) with a 1-inch-diameter thin disc form to design the proposed MPT used to evaluate the directionality for sensing the GLW propagation in thin aluminum plates. Prior to the GLW inspection using the MPTs, the magnetostriction of the magnetostrictive patches was experimentally measured by a strain gauge, and electron backscatter diffraction (EBSD) patterns were captured and analyzed to explore grain configurations and crystal orientations of the patches. The material level analysis validated that the highly textured Galfenol behaves like a single crystal with large magnetostriction along a <100> orientation. Therefore, the developed MPT using the single-crystal-like Galfenol was expected to exhibit high directional sensitivity of the GLWs traveling in the metallic plate, corresponding to the preferred orientation of the Galfenol patch. The experimental study of the MPT-based GLW approach demonstrated that the MPT using the single-crystal-like Galfenol exhibits excellent sensitivity to the incoming GLWs along the <100> preferred direction, while the nickel-based MPT has omnidirectional GLW sensitivity in the plate specimen. In addition, the MPT using the polycrystalline Galfenol showed two preferred directions for sensing the GLWs, corresponding to <110> orientations.