Actuation principle and property of magnetically controlled shape memory alloy actuators

This paper introduces the operation principle of magnetically controlled shape memory alloy (MSMA) actuators based on the shape variation of the NiMnGa alloys under external magnetic field. The experimental results show that the relationship between strain of MSMA and magnetic field is a nonlinear characteristic with saturate nature. Under the condition of constant temperature and magnetic field, the strain of the MSMA reduces linearly with respect to the pre-pressure increment. The magnetic control property of MSMA is sensitive to the temperature variation, and can be held only in the martensite phase. The tested dynamic magnetically conductive characteristics of MSMA show that the magnetic permeability of the MSMA is not constant, and reduces with respect to the increment of magnetic field. The relative saturate magnetic permeability of MSMA is about 1.5. Therefore, the MSMA is almost a non-magnetically conductive material.