Study On The Magnetostriction Of Tb-Dy-Fe Single Crystal And Its Application In Micro-displacement Actuator

The Tb-Dy-Fe giant magnetostrictive material, a new type of magneto (electro)-mechanical energy conversion material with large magnetostriction and rapid response, is a perfect element for micro-displacement actuator. In general, polycrystal or twin magnetostrictive materials are used as the drive unit in micro-displacement actuator. However, the displacement output of the actuator under low magnetic field is small and its precision is limited, as a result of motion restriction of magnetic domain walls by grain boundaries in polycrystal or twin magnetostrictve materials. Complicated water-cooling structure must be considered in this kind of actuator in order to improve its precision.Recently bulk Tb-Dy-Fe single crystals have been obtained by magnetic levitation cold crucible without contamination in Wuhan University of Technology. These excellent single crystals, possessing a large displacement output under low magnetic field, build a foundation for the fabrication of the high precision micro-displacement actuators. The purpose of this research is to manufacture an advanced micro-displacement actuator with this high performance single crystal as the driving unit. The magnetic circuit of the actuator is designed, which involves the bias field and the exciting field, and their influences on the working characteristic of the actuator are studied in the experiment. In order to reduce the dead-section and enlarge the optimal workaround, the magnetic parameters are optimized. An efficient heat insulation layer is adopted to prevent the drive coil from heat effect. The influences of the pre-stress on the working characteristic of the actuator are analyzed by the measurement of displacement. A numerical current source with alternative working mode and current range is manufactured to provide program-set steady current for the drive coil. The impulse mode can efficiently reduce the coil heat and measurement error. Two measuring methods for the micro-displacement are explored in this paper, and the conclusion is drew that the lever measurement can remarkably improve the result precision.The maximal displacement output of the fabricated actuator is 30-40 ju m, the displacement resolution is better than 30nm and the repeatability is nm,...