Abstract
To improve the output performance of embedded giant magnetostrictive actuators (GMAs) for non-circular hole precision machining and to describe the transient nonlinear hysteresis behavior of giant magnetostrictive material (GMM), the magnetostrictive process of GMM is analyzed in detail in this paper. Based on the J–A model and the Gibbs free energy model, a transient multi-field coupling model of GMM is developed by considering the eddy current effect, compression stress variation, and ΔE effect. The simulation results show that the hysteresis loop area increases with increasing driving frequency. The strain of GMM increases first and then decreases with increasing preloading stress. If the stiffness of the deformable bar is too large, the stress of GMM will increase rapidly, thus hindering the elongation of GMM. The simulation process combines the magneto-mechanical coupling model and the dynamic model of embedded GMAs. The simulation results at different excitation frequencies are basically consistent with the experimental data, indicating that the proposed model can predict the output displacement well and provide a theoretical basis for the optimized design of magneto-mechanical coupling for high-performance embedded GMAs.
Highlights
Driven by alternating magnetic field, giant magnetostrictive materials (GMMs) are subject to nonlinear coupling effects of various physical fields such as force, magnetism, and heat.1,2 Moffett et al.3 examined the magneto-mechanical characteristic of a Terfenol-D rod and found that the magnetostriction and magnetization curves greatly depended on the mechanical pre-stress and magnetic fields
The results show that the greater the stiffness of the deformable bar, the greater the reaction force of the deformable bar to GMM under the same driving magnetic field, which makes the actual elongation strain of GMM decrease
It is difficult to measure the stress of GMM, but we can measure the strain of the deformable bar instead
Summary
Driven by alternating magnetic field, giant magnetostrictive materials (GMMs) are subject to nonlinear coupling effects of various physical fields such as force, magnetism, and heat. Moffett et al. examined the magneto-mechanical characteristic of a Terfenol-D rod and found that the magnetostriction and magnetization curves greatly depended on the mechanical pre-stress and magnetic fields. The magnetostrictive strain curves in medium and high magnetic fields can describe the ΔE effect (Young’s modulus of a magnetostrictive material varies with the stress and magnetic field) and magnetic saturation well, which are more applicable than the linear constitutive model Both of them can only describe the rising section of GMM magnetostriction and cannot describe the hysteresis characteristics of GMA output displacement. In common magneto-mechanical coupling analysis theory, the linear piezomagnetic equation cannot describe the saturation phenomenon and the hysteresis nonlinearity; the free energy model can only describe the rise in the GMM magnetostrictive curve; the J-A model can describe the hysteretic characteristics, but it does not reflect the changes in Young’s modulus of GMM. The influence of the eddy current effect, compression stress variation, and ΔE effect are considered in the model, and simulation and experimental verification are carried out
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