Self-sensing Properties Of Magnetic Shape Memory Alloy Actuator

As further studies of active materials, possibilities of developing the self-sensing actuator using the active material are enhanced increasingly. Magnetic shape memory alloy is a new smart material, which has large shape variation, fast dynamic response and easy to control. It also has power density and electromechanical energy conversion efficiency, making it key material using in the new kinds of smart drives and sensors.In this thesis,the crystal structure and shape variation mechanism of MSMA are introduced in the microscopic. In the macro side, the control characteristics of magnetic shape memory alloy have been analyzed, and the applications and perspective have been given. The relationship between the strain of MSMA and the temperatures, external magnetic field and pre-stresses provides a theoretical basis for the study on self-sensing properties of magnetic shape memory alloy actuator.For developing self-sensing actuators based on magnetic shape memory alloy (MSMA), the sensing properties of MSMA actuator are studied. An testing set is developed to measure and analyze relationships among the strain, stress, temperature and magnetization of the MSMA actuator. The testing set is compose of magnetic induction unit, pre-stressing unit, mechanical shock, and measuring unit, etc., in which the pendulum is used to produce controllable and reproduceable mechanical shock that is perpendicular to the direction of magnetic field and acted on the pre-stressed MSMA actuator being in stationary magnetic field. This field is produced by a permanent magnet embedded in its magnetic circuit.As the MSMA actuator is impacted, the corresponding responses of strain, magnetization, and temperature are measured, and relationships between impacting force and them are analyzed. It is a voltage inducing from deformation of the actuator caused by mechanical shock, which influences magnetization of the actuator. The result of experiment shows that in stationary magnetic field, mechanical shock can produce deformation of the MSMA actuator in a certain range, thereby influence its magnetization, and obtain induced voltage in the coil consequently. There are coincidence relations between impacting force or acceleration and parameters mentioned above in a certain range. It is an aid to research and develop MSMA Actuators with self-sensing.