Shear-lag modelling of surface-bonded magnetostrictive transducers for shear horizontal wave generation in a non-ferromagnetic plate

The fundamental shear horizontal (SH) wave in thin-walled structures shows appealing features for structural health monitoring (SHM) applications. Its efficient generation and reception however remain a critical and challenging issue. Magnetostrictive transducers (MsTs) show proven ability in exciting strong SH waves due to the high piezomagnetic coefficient of the ferromagnetic foil. In this study, to investigate the fundamental SH wave generation using MsTs and their design, a theoretical model is established based on the shear-lag model and the normal mode expansion method. The coupling of an MsT with a host plate is achieved by a bonding layer, whose mechanical property is modelled through the continuous shear stress across the thickness. The theoretical model is validated using finite element simulations in terms of generation mechanism and some typical features associated with the fundamental SH wave component. Meanwhile, wave field is visualized using a 3D Laser scanning vibrometer system. Experimental results within a wide frequency range show a good agreement with the theoretically predicted results. Influences of the coil configuration and bonding conditions are further investigated using the proposed model. The study offers guidelines to system design and optimization for fundamental SH wave generation in views of guided-wave-based SHM applications.