Influence and optimization design of structure parameters on a giant magnetostrictive transducer

Abstract

To design and obtain a giant magnetostrictive ultrasonic transducer (GMUT) composed of double Terfenol-D rods with the best vibration performance near the operating frequency 20 kHz, the influence of structure parameters on the vibration performance of the window-type of GMUT is simulated and analyzed. The calculation shows that as the length of the rod, the thickness of the permanent magnet, and the thickness of the magnetizer increase, the GMUT output amplitude firstly increases and then decreases; the GMUT amplitude increases as the increase of the window width (distance between two Terfenol-D rod axes). The window width has the greatest influence on the uniformity of the axial magnetic field inside the rod, while the influence of rod length, permanent magnet thickness, and magnetizer thickness decrease in sequence. The relationship between magnetic field uniformity, shear stress, and GMUT output amplitude is complicated, however, the shear stress and amplitude have certain optimal values. To achieve the best vibration performance of the transducer, it is appropriate to take the magnetizer thickness of 3–5 mm, the permanent magnet of 3–5 mm, the Terfenol-D rod length of 19–24 mm, and the window width of 65–67 mm. A prototype GMUT was fabricated for experimental testing. The maximum output was 6.1 μm at the excitation current of 1A.