Abstract
The multimode and dispersion characteristics of Lamb waves make them difficult to apply to nondestructive evaluation. This paper presents a paired configuration of a meander-line coil electromagnetic acoustic transducer (EMAT) to generate a single-mode symmetric and antisymmetric Lamb wave in aluminum plates. In the paired structure, the bias magnetic field of the EMAT that generates symmetric mode Lamb waves is perpendicular to the plate surface, while the bias magnetic field of the EMAT that generates antisymmetric Lamb waves is parallel to the plate surface. The symmetric and antisymmetric exciting forces generated by these two EMATs are consistent with the dispersion equations of single symmetric and antisymmetric Lamb wave modes, respectively. The numerical simulations and experiments verified that the presented paired configurations of meander-line coil EMATs can effectively control the generation of single-mode Lamb waves at low frequencies.
Highlights
Metallic plates are widely used in aircraft, rockets, and petrochemical industries as well as in pressure vessels [1,2]
Single-mode Lamb waves generated by piezoelectric lead zirconate titanate (PZT) transducers or polyvinylidene fluoride (PVDF) have been demonstrated [7,8,9,10]
We investigate the electromagnetic acoustic transducer (EMAT) based on the Lorentz force mechanism to generate single-mode Lamb waves
Summary
Metallic plates are widely used in aircraft, rockets, and petrochemical industries as well as in pressure vessels [1,2]. Single-mode Lamb waves generated by piezoelectric lead zirconate titanate (PZT) transducers or polyvinylidene fluoride (PVDF) have been demonstrated [7,8,9,10] These methods require the transducer to be bonded to the structure and are suitable for structural health monitoring but are difficult to apply when detecting moving objects or scanning. The Lamb wave mode control methods proposed in [11,12,13,14] can generate a single omnidirectional Lamb wave mode, these methods are difficult to apply to the meander-line coil EMAT. After that, based on the exciting force conditions of symmetric and antisymmetric Lamb wave modes, two novel paired EMAT configurations were proposed to control the Lamb wave modes. We summarize the performance of the proposed paired EMAT configuration for controlling the excitation of Lamb wave modes
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