When a hypersonic vehicle travels in the Earth and Mars atmosphere, the surface of the vehicle is surrounded by a plasma layer, which is an envelope of ionized air, created from the compression and heat of the atmosphere by the shock wave. The vehicles will lose contact with ground stations known as the reentry communication blackout. Based on the magnetohydrodynamic framework and electromagnetic wave propagation theory, an analytical model is proposed to describe the effect of the effectiveness of electromagnetic mitigation scheme on removing the reentry communication blackout. C and Global Positioning System (GPS) bands, two commonly used radio bands for communication, are taken as the cases to discuss the effectiveness of the electromagnetic field mitigation scheme. The results show that the electron density near the antenna of vehicles can be reduced by the electromagnetic field, and the required external magnetic field strength is far below the one in the magnetic window method. The directions of the external electric field and magnetic field have a significant impact on the effectiveness of the mitigation scheme. Furthermore, the effect of electron collisions on the required applied electromagnetic field is discussed, and the result indicates that electron collisions are a key factor to analyze the electromagnetic mitigation scheme. Finally, the feasible regions of the applied electromagnetic field for eliminating blackout are given. These investigations could have a significant benefit on the design and optimization of electromagnetic mitigation scheme for the blackout problem.

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This paper focuses on the resonance frequency shift characteristic of Terfenol-D rods for magnetostrictive actuators. A 3D nonlinear dynamic model to describe the magneto-thermo-elastic coupling behavior of actuators is proposed based on a nonlinear constitutive model. The coupled interactions among stress- and magnetic-field-dependent variables for actuators are solved iteratively using the finite element method. The model simulations show a good correlation with the experimental data, which demonstrates that this model can capture the coupled resonance frequency shift features for magnetostrictive actuators well. Moreover, a comprehensive description for temperature, pre-stress and bias field dependences of resonance frequency is discussed in detail. These essential and important investigations will be of significant benefit to both theoretical research and the applications of magnetostrictive materials in smart or intelligent structures and systems.

This paper focuses on the behavior of field-dependent viscoelasticity for magnetorheological elastomers (MREs). A novel nonlinear constitutive model for magneto-viscoelastic behavior of MREs is proposed. The model considered here is thermodynamically motivated and based on the second law. An extended three-parameter standard linear solid model is proposed to describe the viscoelastic behavior of MREs, where the effect of particles on the elastomers at zero field is taken into account. Furthermore, the nonlinear magnetization and the local magnetic field within the ferromagnetic particle are incorporated to describe field-dependent constitutive behavior based on the dipole model. Then a set of analytical expressions of the constitutive law for MREs are obtained, and the parameters appearing in the model can be determined by those measurable experiments in mechanics and physics. The quantitative results demonstrate that this model can well capture the constitutive relation under both quasi-static and dynamic shear loading.

Vibrations that occur in various engineering structures have potential damage to the structural system. An important structural system is the intelligent structure containing magnetostrictive materials. To suppress the vibration of the intelligent structure, an active vibration control model is established for the structural system based on giant magnetostrictive material. The active control law of disturbance feedforward and state feedback is applied to the control model combined with the giant magnetostrictive actuator. Numerical examples of active control systems are performed under the operating conditions of sinusoidal and initial excitation. The vibration isolation effect of different excitation gives a detailed discussion. The results show that our active vibration control has good vibration isolation effect for all cases of different frequencies, even for the resonant case. The effect of feedback gains on vibration control is good in low excitation amplitude, thus it must combine the feedforward gain with feedback gains to achieve good control effect in high excitation amplitude. These conclusions will be of significant benefit to both theoretical research and the applications of magnetostrictive materials in active vibration control.