Metal-wire-based twin one-dimensional orthogonal array configuration of PZT patches for damage assessment of two-dimensional structures

This article presents a new field-deployable algorithm harnessing the metal-wire-based variant of the electromechanical impedance technique, warranting drastically lesser number of piezo sensors, for damage detection and localization on large two-dimensional structures such as plates. The metal-wire-based approach is a new variant of the electro-mechanical impedance technique. Although less sensitive than the conventional electro-mechanical impedance technique, it is a panacea in situations where direct bonding of lead zirconate titanate (PZT) patches on the host structure is not possible, such as inaccessible structural locations, parts under continuous impact from external loads, brittle materials (triggering signatures without any peaks) or high-temperature locations. This article first reports detailed experimental investigations into the practical aspects of the metal-wire-based electro-mechanical
impedance technique. These cover the effect of various associated parameters, such as the wire cross-section, shape, discontinuity and other related issues. Repeatability of signature is also investigated along with the effect of possible breakage in the wire and inadvertent bending. The technique is further adapted by replacing the wire by a thin foil, which is found to improve the damage sensitivity substantially. The proposed algorithm for damage localization on two-dimensional structures uses the PZT patches in the metal-wire-based orthogonal twin-array configuration. The metal-wire-based electro-mechanical impedance technique is first simulated through finite element method, coupled with the basic impedance model, to test the algorithm on the numerical model of a mild steel plate, 1200 mm x 970 mm x 8 mm in size. The algorithm is then validated through full-scale test on the actual plate, covering damage at various locations. The developments of this article shall pave way for practical application of the metal-wire-based electro-mechanical impedance technique on large two-dimensional structures with minimum number of sensors, especially in situations where the direct electro-mechanical impedance technique is not feasible to be used.