Performance And Devices Of Magnetostrictive Multilayered Composites

The big eddy current loss in high frequency can be overcomed for magnetostrictive multilayered composites because Terfenol-D layers were separated by resin and they can't form a large scroll current loop in the vertical direction of the magnetic field. Meanwhile the brittleness of magnetostrictive material can be reduced by resin. This greatly expanded the application of giant magnetostrictive materials. Based on the broad application prospects of magnetostrictive composites in high-frequency devices, even in the field of ultrasound, the magnetostrictive multilayered composites and theirs application has been researched, as follows.1. The magnetostriction of Terfenol-D multilayered magnetostrictive composites have been calculated based on the mechanical theory. And the epoxy bonded Terfenol-D multilayered magnetostrictive composites have been prepared. The static magnetostriction of samples and the prepress effect of their magnetostriction have been researched. Then the samples were annealed in the vacuum at 423 K for 15 min at the magnetic field of 240 kA/m. Effects of the compressive stress and the magnetic field heat-treatment on the magnetostriction have been investigated. It is found that the magnetostriction of the samples can be improved, especially under the compressive stress.2. The magnetostriction of Terfenol-D / Fe-Ga multilayered magnetostrictive composites has been calculated based on elongate in-phase model and elongate freeness model. The calculating result can provide a guidance for manufacture of Terfenol-D / Fe-Ga multilayered composites and the application of its corresponding magnetostrictive devices.3. The output displacement of the transducer based on Terfenol-D multilayered magnetostrictive composite has been researched in the frequency ranges of 0.1Hz to 6000Hz. It is found the dynamic displacement is affected evidently by the frequency of AC magnetic field. Terfenol-D multilayered magnetostrictive composites have effectively enhanced the output displacement of the transducer at stair resonance frequency and the application frequency range. In addition, the bow wave wastage has been reduced for the transducer based on Terfenol-D multilayered composites.4. The magnetoelectric coefficient (ME coefficient)αof magnetoelectric laminated composite magnetic field sensor has been calculated by means of equivalent circuit method based on magnetostrictive constitutive equations and piezoelectric constitutive equations. The ME coefficient equation shows that ME coefficientαis decided by performance parameters and the volume ratio of Terfenol-D and PZT. The theoretical result of ME coefficient accords to the experimental result of ME coefficient at 70Hz.5. Epoxy bonded Terfenol-D/PZT/Terfenol-D laminated composite magnetic field sensors have been manufactured using the product effect of Terfenol-D and PZT. The magnetostriction of Terfenol-D and the output voltage of Terfenol-D/PZT/Terfenol-D laminated composite magnetic field sensors have been measured. It is found that the ME coefficient is greatly affected by the DC bias magnetic field, the frequency of AC magnetic field, the size of AC magnetic field and the direction of magnetic field. The results have provided a guidence for the application of Terfenol-D/PZT/Terfenol-D multilayered composite magnetic field sensors in the measurement of magnetic field.