Dynamic Characteristic Of Array Transducer Of Rare Earth Giant Magnetostrictive

With the development of society, acoustic nondestructive testing is applied in engineering more and more widely. It has become an important means to ensure the quality, such as bridges, ams and tunnels and so on. Rare earth giant magnetostrictive transducer is an acoustic wave transmitter. Because of its high transmit power, high energy, wide frequency band, small aftershocks and repeatability characteristics, it was selected as the ideal source of large-scale projects detection.In this article, the wave nondestructive testing techniques, magnetostrictive materials and rare earth giant magnetostrictive transducer were firstly introduced. Then the electromagnetic method and piezoelectric-Piezomagnetic method which are used for rare earth giant magnetostrictive transducer design were introduced. Finally, a single rod of Terfenol-D, double rods of Terfenol-D and three rods of Terfenol-D rare earth giant magnetostrictive transducer internal magnetic field and output displacement were studied. Main contents and findings are as follows:(1) A single rod of Terfenol-D rare earth giant magnetostrictive transducer dynamic output displacement and the internal magnetic field were studied The results showed that, when the coil around the Terfenol-D rod higher than the Terfenol-D rod, the magnetic field on the Terfenol-D rod larger than when the coil around the Terfenol-D rod is equal to the Terfenol-D rod, but the axial magnetic field uniformity worse, closing magnetic circuit of the magnetic induction intensity on the Terfenol-D rod was lager than opening magnetic circuit, and the axial magnetic field uniformity better. The dynamic output displacement was depended on the current pulse width, and the transducer output displacement decay rate associated with excitation current pulse width was at first increased and then decreased again increased.(2) Double rods of Terfenol-D and three rods of Terfenol-D rare earth giant magnetostrictive transducer dynamic output displacement and the internal magnetic field were studied. The results showed that, the internal magnetic field changes with time trend of double rods of Terfenol-D rare earth giant magnetostrictive transducer is the same with applied excitation current. The transducer output displacement decay rate associated with excitation current pulse width is at first increased and then decreased again increased. Three rods of Terfenol-D rare earth giant magnetostrictive transducer output displacement is larger than a single rod of Terfenol-D rare earth giant magnetostrictive transducer. (3) A single rod of Terfenol-D and three rods of Terfenol-D rare earth giant magnetostrictive transducer frequency, delay time and transmit acoustic energy were studied by experiment. The results showed that, a single rod of Terfenol-D rare earth giant magnetostrictive transducer frequency and delay time are both larger than three rods of Terfenol-D rare earth giant magnetostrictive transducer. With the same excitation current pulse width, three rods of Terfenol-D rare earth giant magnetostrictive transducer transmitting acoustic energy was significantly higher than a single rod of Terfenol-D rare earth giant magnetostrictive transducer.The results of this study will pave the way to further design and optimize of the rare earth giant magnetostrictive transducer. It is an important guidance for the use of rare earth giant magnetostrictive transducer in the acoustic detection of large-scale projects.