Magnetic and resonance properties of the Y0.5Sr0.5Cr0.5Mn0.5O3 polycrystal

The magnetostatic and magnetic resonance properties of the Y0.5Sr0.5Cr0.5Mn0.5O3 polycrystalline system have been experimentally studied. The intracrystalline ferromagnetic interaction turned out to be prevalent while the intercrystalline interaction appears to have antiferromagnetic character. We found that two absorption lines are observed in the spectrum in the magnetic ordering region at T < 80 K. The high-field line corresponds to the interacting parts of polycrystal related to the disordered shells and the low-field peak is system of ferromagnetic particles.

Haptic Interface with Twin-Driven MR Fluid Actuator for Teleoperation Endoscopic Surgery System

Magnetorheological fluids (MRFs) are composite materials made of ferromagnetic particles, medium oils, and several types of additives. We have developed an actuation system for the fine haptic control of leader-follower robots. In this study, we developed a haptic interface with two link-type twin-driven MR fluid actuators and two MR fluid brakes for a teleoperation endoscopic surgery system and conducted evaluation tests for a remote operational task with a leader-follower robot system. For evaluations, we adopted the NASA-TLX questionnaire as a subjective assessment method. According to the experimental results, the total success rates were 0.462, 0.333, and 0.591, for the first haptic, middle no-haptic, and second haptic phases, respectively. The force information of the haptic forceps helped users to perceive grasping sensation on their fingers. Statistical analyses on the answers to the questionnaire indicate no significant differences. However, a decreasing tendency in the mental stress in the complicated manipulation tasks for fragile objects is observed.

Single-double chains micromechanical model and experimental verification of MR fluids with MWCNTs/GO composites coated ferromagnetic particles

Magnetorheological (MR) fluid is a typical intelligent material which is widely adopted in the mitigation of civil engineering structures, and it is normally composed of nano-sized or micro-sized iron particles, carrier fluids and additives. Because of the complexity of its composition, it is one of the research hotspot to propose a micromechanical model which can effectively describe the micromorphological transformation as well as characteristics of MR fluids. In this study, a single-double chains micromechanical model of MR fluids is proposed by taking into consideration of the influence of volume fraction and magnetic induction on the microstructure evolution of MR fluids based on the coupled field as well as magnetic dipole theory. Additionally, the shear yield stress test of the self-prepared MR fluids with multi-wall carbon nanotubes(MWCNTs) and graphene oxide (GO) composites coated ferromagnetic particles is carried out by MCR302 rotational rheometer and the results have been compared with the theoretical values of the single-double chains micromechanical model to verify the effectiveness and accuracy of the proposed model.

Characteristics of a Magnetic Bulk Thermostat for Granular Gas Investigations in Microgravity

A magnetic thermostat employing soft-ferromagnetic particles and a varying magnetic field has been developed to investigate a homogeneous granular gas system in microgravity. While the thermostat’s mechanism of creating homogeneous distribution of the particles was shown earlier, its characteristics have not been understood well due to limited access to a microgravity environment. Therefore, a parametric study by numerical simulation based on the discrete element method is carried out in this paper to evaluate effects of tunable parameters in the thermostat. The result shows the capability of the system and provides a wide range of options and improvements for future experiments. Moreover, it predicts that the thermostat allows variation of homogeneity and excitation level of the granular gas just by changing the magnetic parameters without using any mechanical means. In addition, the suggested improvement is experimentally implemented and evaluated in a drop tower test.

Determining Impact Forces on a Ferromagnetic Particle in the Process of Magnetothermal Surface Reinforcement of Products from Thermoplastic Polymers

The author considers the forces acting on a ferromagnetic particle from the side of the magnetic and thermal fields, as well as the forces opposing its penetration from the side of the surface layer of the polymer. The calculation of the forces acting on a ferromagnetic particle in the process of its introduction into the surface layer of the polymer is carried out using the example of nickel and polypropylene. The balance of forces required for the introduction of a ferromagnetic particle into the molten surface of a thermoplastic polymer and stable fixation in it is calculated. The universality of the approach used is shown for calculating the parameters of surface modification of thermoplastic products with different properties by ferromagnetic particles of different dispersion and characteristics.

Magneto-orientation response of ferronematic with a tilted orientation of the director and magnetization

The article considers orientational transitions induced by a magnetic field in a highly dispersed suspension of ferromagnetic particles in a nematic liquid crystal – ferronematic. We research the case when, in the absence of an external magnetic field between the directions of the liquid crystal director and magnetization of the impurity particles, a constant pretilt angle is maintained, and the coupling of the liquid crystal molecules to the surface of the ferroparticles is assumed to be soft and planar. An example of such an impurity is ferromagnetic carbon nanotubes magnetized at a certain angle to their long axes. On the basis of the continuum theory, the equilibrium values of the orientation angles of the liquid crystal director and magnetization are calculated for different values of the pretilt angle. The results of calculations are compared with the previously considered case of planar coupling between the director and magnetization. Analytical expressions are obtained for determining the orientational and magnetic structure of the ferronematic in the case of weak magnetic fields. The magnetization of the ferronematic is studied for different values of the pretilt angle.