Magneto-mechanical Behavior of Magnetic Shape Memory Alloy and Its Application in Hydraulic Valve Actuator

Abstract

Magnetic shape memory alloy(MSMA) has recently emerged as a new type of multifunctional material exhibiting excellent performance as fast response and large strain. With a combination of the characteristics of ordinary smart materials and conventional shape memory alloy, it is qualified for high performance actuator. Constitution equations are derived based on the magnet-strain effect of MSMA, and temperature is introduced as an influential factor to modify the model. The present equations are improved to cover the shortage of inaccuracy in calculating the strain when the material is preloaded. Experiments are conducted to explore the magnetic field induced strain, and data are applied to establish nero-network based models to build the nonlinear relations between strain, stress and other related parameters. It is shown in the results that the energy density of MSMA is 70 kJ/m3 and energy conversion efficiency is 80%. Taking high speed on/off valve as an example, the characteristics of MSMA hydraulic valve actuator are considered. Valve design, magnetic field and fluid flow simulations are carried out. On analysis of dynamics of valve actuation system, the results show that the response frequency of the poppet valve system driven directly by MSMA can reach as high as 200 Hz, and the dynamic response time is nearly 5 ms.