1 April 2015 Separation of Lamb waves modes using polarization filter of 3D laser measured signals
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Abstract
Interpretation of Lamb waves signals can rise serious difficulties due to their multi-modal nature. Different modes propagating with different velocities can be misleading with damage reflected components. As a solution to this problem we propose a technique capable of modes separation based on a polarization filter. Both S0 and A0 Lamb modes exhibit elliptical polarization, however, their polarization parameters, i.e. the ratios of in-plane and out-of-plane displacements and phase-shifts between these components are different. Furthermore, these parameters can be considered constant in a narrow frequency band. Therefore, if the vertical and horizontal components of the wave motion are available, it is possible to apply signal processing technique referred to as oblique polarization filter. This operation is based on phase-shifts and amplifications of the in- and out-of-plane components, which results in orthogonal, linearly polarized A0 and S0 waves signals. In this paper the proposed technique will be illustrated using both numerical simulations and experimental data. The simulations of wave propagation were performed using local interaction simulation approach (LISA) assuming isotropic material. The experiments were performed using 3D laser scanning Doppler vibrometer that allowed to capture the in-plane and out-of-plane wave components.
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Lukasz Ambrozinski, Tadeusz Stepinski, Tadeusz Uhl, "Separation of Lamb waves modes using polarization filter of 3D laser measured signals", Proc. SPIE 9437, Structural Health Monitoring and Inspection of Advanced Materials, Aerospace, and Civil Infrastructure 2015, 94371E (1 April 2015); doi: 10.1117/12.2084047; https://doi.org/10.1117/12.2084047
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