Optimal design of transducers based on the Halbach arrays permanent magnet structure

For enhancing the static magnetic field and reducing the size of torsional guided wave magnetostrictive patch transducer (MPT) with permanent magnets, a MPT with Halbach arrays is proposed. The structural parameters design of the MPT can be guided by finite element simulation. It is found that increasing the central angle of the radially magnetised magnets can increase the strength of the static magnetic field, and it can be adjusted through designing the radial size and lift-off distance of the magnets. The Halbach magnet arrays composed of circumferentially magnetised magnets with a circumferential size of 6 mm and radially magnetised magnets with a circumferential size of 4 mm are selected to experimentally compare with the alternating magnetised magnet arrays composed of magnets with a circumferential size of 10 mm. The results show that the static magnetic field strength can be increased by 54.7% using Halbach magnet arrays. The proposed MPT composed of the Halbach magnet arrays and a linear solenoid array can excite and receive T(0,1) guided wave. Compared with the alternating magnetised magnet array MPT, the guided wave signal amplitude is increased by about 70% generated and received by the MPT with the Halbach magnet arrays.