Search

With the advancement of manufacturing, the precision requirements for various high-precision processing equipment and instruments have further increased. Due to its noncontact nature, simple structure, and controllable performance, electromagnetic levitation has broad application prospects in ultra-precision instruments and ground testing of aerospace equipment. Research on vibration isolation technology using electromagnetic levitation is imperative. This paper reviews the latest research achievements of three types of passive isolators and five active isolation actuators. It also summarizes the current research status of analytical methods for passive isolators and the impact of isolator layout. This study explores current isolators' achievements, such as the development of passive isolators that generate negative stiffness and require mechanical springs for uniaxial translational vibrations, single-function actuators, and control systems focused on position and motion vibration control. Based on the current isolators' characteristics, this review highlights future developments, including focusing on passive isolators for heavy loads and multi-axis isolation, addressing complex vibrations, including rotational ones, and developing methods to calculate forces and torques for arbitrary six-DOF movements while improving speed. Additionally, it emphasizes the importance of multifunctional actuators to simplify system structures and comprehensive control systems that consider more environmental factors. This provides significant reference value for vibration isolation technology using electromagnetic levitation. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation (EML) is a promising technique allowing to melt various materials, including refractive metals, while avoiding physical contact between the molten material and components of the melting system, thus avoiding contamination of the molten material. EML coils act both as a container and a heating source for a conductive sample placed within it. EML systems are difficult to optimize for specific tasks and computational simulations are often used to aid the process. Development of simulations of EML processes is an ongoing field of research. Obtaining precise experimental measurement data of EML processes is important for development and verification of computational simulations. This study aims to provide experimental data of simultaneous measurements for magnetic field, Joule heating and lift force in different conical EML coils with a counterturn. [ABSTRACT FROM AUTHOR]

This study investigated the migration patterns of oxygen in the deoxidation process of Ti-48Al alloy scrap using electromagnetic levitation (EML) technology. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to analyze the oxygen distribution patterns and migration path during EML. The refining process resulted in three types of oxygen migration: (1) escape from the lattice and evaporation in the form of AlO, Al2O; (2) formation of metal oxides and remaining in the alloy melt; (3) attachment to the quartz tube wall in the form of metal oxides such as Al2O3 and Cr2O3. The oxygen content of the scrap was dropped with a deoxidation ratio of 62%. It indicated that EML can greatly promote the migration and removal of oxygen elements in Ti-Al alloy scrap. [ABSTRACT FROM AUTHOR]

The piston in the Labyrinth piston compressor (LPC) usually runs eccentrically in the cylinder, which results in large internal leakage and low volumetric efficiency. An active electromagnetic control method based on the electromagnetic levitation theory was proposed in this paper to control the piston eccentricity, and a triple close-loop multi-factor coupled feedback control strategy composed of a current loop, a velocity loop, and a displacement loop was designed to realize the levitation control of the piston. The experimental research shows that there is serious piston eccentricity in the LPC, and the piston eccentricity is positively correlated with the increase of compressor pressure ratio and speed. By adopting the active electromagnetic control system proposed in this paper, the piston eccentricity is significantly reduced, and the maximum reduction is over 88%. Further research shows that the volume flow rate and volumetric efficiency of the LPC with control are maximum improved by about 45.6% and 44%, respectively. In conclusion, the piston eccentricity in the LPC could be effectively reduced by adopting the active electromagnetic control method proposed in this paper, thus improving its performance. [ABSTRACT FROM AUTHOR]

The solidification of Inconel 718 alloy (IN718) from undercooled liquid is studied. The solidification kinetics is evaluated in melted and undercooled droplets processed using the electromagnetic levitation (EML) technique by the temperature–time profiles and solid/liquid (S/L) interface movement during recalescence. The kinetics is monitored in real time by special pyrometrical measurements and high-speed digital camera. It is shown that the growth velocity of γ -phase (the primary phase in IN718), the final crystalline microstructure (dendritic and grained), and the mechanical properties (microhardness) are strongly dependent on the initial undercooling Δ T at which the samples started to solidify with the originating γ -phase. Particularly, with the increase in undercooling, the secondary dendrite arm spacing decreases from 28 μm to 5 μm. At small and intermediate ranges of undercooling, the solidified droplets have a dendritic crystalline microstructure. At higher undercooling values reached in the experiment, Δ T > 160 K (namely, for samples solidified with Δ T = 170 K and Δ T = 263 K), fine crystalline grains are observed instead of the dendritic structure of solidified drops. Such change in the crystalline morphology is qualitatively consistent with the behavior of crystal growth kinetics which exhibits the change from the power law to linear law at Δ T ≈ 160 K in the velocity–undercooling relationship (measured by the advancement of the recalescence front in solidifying droplets). Study of the local mechanical properties shows that the microhardness increases with the increase in the γ ″ -phase within interdendritic spacing. The obtained data are the basis for testing the theoretical and computational of multicomponent alloy samples. [ABSTRACT FROM AUTHOR]

With the advancement of manufacturing, the precision requirements for various high-precision processing equipment and instruments have further increased. Due to its noncontact nature, simple structure, and controllable performance, electromagnetic levitation has broad application prospects in ultra-precision instruments and ground testing of aerospace equipment. Research on vibration isolation technology using electromagnetic levitation is imperative. This paper reviews the latest research achievements of three types of passive isolators and five active isolation actuators. It also summarizes the current research status of analytical methods for passive isolators and the impact of isolator layout. This study explores current isolators’ achievements, such as the development of passive isolators that generate negative stiffness and require mechanical springs for uniaxial translational vibrations, single-function actuators, and control systems focused on position and motion vibration control. Based on the current isolators’ characteristics, this review highlights future developments, including focusing on passive isolators for heavy loads and multi-axis isolation, addressing complex vibrations, including rotational ones, and developing methods to calculate forces and torques for arbitrary six-DOF movements while improving speed. Additionally, it emphasizes the importance of multifunctional actuators to simplify system structures and comprehensive control systems that consider more environmental factors. This provides significant reference value for vibration isolation technology using electromagnetic levitation.

The aim of this review is to succinctly review recent progress in experimental and theoretical investigation of the viscosity of binary and multicomponent Ni–Al-based industrial alloys, summarising the current state of knowledge of the topic. Viscosity data are important for simulation of microstructural evolution during solidification-related processes such as casting. Therefore, to obtain accurate predictions of defect-free microstructure, only reliable input data are required. Based on the synergy between experiment and theory, a review of the literature provides a critical evaluation of temperature- and composition-dependent viscosity data available from existing studies carried out over the last 60 years. The purpose of this review is threefold: to discuss container-based viscometer methods and alternative containerless processing via electromagnetic levitation during parabolic flights and on board the International Space Station; to analyse the viscosity models including their validation; and to refer to the first two points, to interpret the viscosity data. [ABSTRACT FROM AUTHOR]

Containerless measurements of the thermophysical properties density, viscosity, and self-diffusion by electromagnetic- (EML) and electrostatic levitation (ESL) are compared. The development history of the two techniques is briefly traced. The levitation principles and the measurement techniques for the properties considered are discussed. In the case of the density, data measured by both techniques are available for a liquid NiTi alloy. The results agree within a systematic error of ± 1 %. The data measured in EML exhibit a significant larger scatter. Viscosity data cannot be measured in ground-based electromagnetic levitation, so the comparison is carried out for a NiB alloy investigated in ESL and a classical viscometer. Good agreement was found as well. No significant difference is observed in self-diffusion data of various systems between different levitation techniques. [ABSTRACT FROM AUTHOR]

Surface tension and viscosity of complex Ti-based industrial alloys are important for simulation of liquid assisted industrial processes such as casting, joining, crystal growth and infiltration. Modelling of the interface and mass transport during liquid-solid phase transition requires reliable surface tension and viscosity data. Therefore, to obtain accurate predictions of microstructural evolution during solidification related processes, only reliable input data are necessary. In the case of liquid Ti-Al alloys, the experimental difficulties related to high temperature measurements and reactivity of these alloys with supporting materials or containers as well as inevitable presence of oxygen may lead to data gaps including a complete lack of property data. An alternative for container-based methods are containerless processing techniques that offer a significant accuracy improvement and / or make possible to measure temperature and composition dependent thermophysical properties of metallic melts, as in the case of the Ti-Al-Cr-Nb system. Advanced mathematical models and computer simulations, developed in several theoretical frameworks, can be used to compensate the missing data; on the other side, for the validation of theoretical models, the experimental data are used. In the present work, an evaluation of the surface tension and viscosity of liquid Ti-Al-Cr-Nb alloys by means of the predictive models and a comparison to the available experimental data were done. The proposed methodology is a tool to assess the reliability of thermophysical properties data of multicomponent alloy systems. [ABSTRACT FROM AUTHOR]

This study investigated the migration patterns of oxygen in the deoxidation process of Ti-48Al alloy scrap using electromagnetic levitation (EML) technology. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to analyze the oxygen distribution patterns and migration path during EML. The refining process resulted in three types of oxygen migration: (1) escape from the lattice and evaporation in the form of AlO, Al2O; (2) formation of metal oxides and remaining in the alloy melt; (3) attachment to the quartz tube wall in the form of metal oxides such as Al2O3 and Cr2O3. The oxygen content of the scrap was dropped with a deoxidation ratio of 62%. It indicated that EML can greatly promote the migration and removal of oxygen elements in Ti-Al alloy scrap.

Round-robin measurement of surface tension of high-temperature liquid platinum was conducted free of any contamination from the supporting materials and oxygen adsorption, using an electrostatic levitator (ESL), two electromagnetic levitator (EML), and an aerodynamic levitator (ADL). The measured temperature dependences of the surface tension using ESL and two EMLs were in good agreement and were expressed as σ=1,798±74.3−(0.12±0.0445)×(T−2,041)\sigma =\mathrm{1,798}\pm 74.3-(0.12\pm 0.0445)\times (T-\mathrm{2,041}) [10–3 N·m–1] (1,900–2,600 K). However, the surface tension values measured with ADL were slightly lower than those exceeding the uncertainty of the measurement plots at high temperatures.

There are numerous methods used for measuring the coefficient of thermal expansion of alloys and density change at low temperatures, but it is difficult to accurately measure the volume and density of high-temperature melts, particularly during the process of rapid volume change during material phase transformation. This article proposes a method for measuring and analysing the volume and density changes in high-temperature alloy melts using high-speed photography and computer MATLAB program image analysis technology, which includes the ordinary image threshold segmentation method, the elliptical fitting method, and the local dynamic threshold segmentation method. The ordinary image threshold segmentation method is best suited to samples with clear boundaries; the elliptical fitting method is the simplest and can be used to analyse samples with unclear boundaries; and the local dynamic threshold segmentation method is the most accurate and best suited to samples with unclear boundaries. These techniques will aid in understanding the variations in the volume and density of high-temperature melt samples during the phase transition process. [ABSTRACT FROM AUTHOR]

In this study, to improve pulverization of Fe–Si alloy, the evolution of its microstructure under container and containerless solidification conditions were investigated using electromagnetic levitation melting technology. The results indicated that the microstructure changed from dendritic crystals during container solidification to equiaxed crystals with containerless solidification. With an undercooling of 280K obtained by containerless solidification, the pulverizing sensitive elements (Al, P) disperse better in FeSi2 phase. The equiaxed Si grains with relatively uniform grain size obtained under ΔT=280K are distributed in random orientation. High angle grain boundaries are significantly more present with the increase of misorientation within FeSi2 grains. This texture is closely related to recrystallization in favor of grain refinement, which is attributed to the melt oscillation and dendrites remelting-recrystallization effects occurring in containerless solidification.

This study is part of a series of studies aimed at measuring the thermophysical properties of molten phase change material-type metallic thermal energy storage materials near 873 K (600°C). The target material is Al–Si based alloys. First, as a feasibility study, density measurements of the molten state of three Al–Si binary alloys (Al–12.2Si, Al–50Si and Al–90Si in atomic%) were performed. A highly accurate non-contact density measurement method based on the static magnetic field superposition electromagnetic levitation (EML) method was employed as the density measurement method. The validity of this experimental method was confirmed, and density of molten Al–Si base alloys (ADC12 and Al–5.9mass%Si–1.6mass%Fe) were measured as a function of temperature with an expanded uncertainty of 1.2%. In addition, the surface tension of the alloys was measured by the droplet oscillation method using the EML technique. The surface tension was successfully obtained as a function of temperature with expanded uncertainty of 2.3%.

The basic parameters of an electromagnetic levitation systems are resistance of the coil, inductance of the coil, air-gap between magnet and the object, coil current, mass of the object, controller parameters and so on. The levitation systems are highly unstable and strongly non-linear. In real-life applications, these parameters are supposed to vary. A proportional–integral controller for the inner current control loop and a lead compensator for the position control loop have been designed and tested. The performance study under various parametric effects has been investigated broadly. Finally, both the stability for the proposed levitation system has been achieved with a better operating zone using linear state variable feedback controllers. The system dynamic performances have been recorded for variations of physical system parameters. The sensitivity/robustness of the set-up has been studied. This study will give an insight for designing any corrective measures and an overall idea to develop a levitation system. [ABSTRACT FROM AUTHOR]

Recently, research on non-contact conveyance systems using electromagnetic levitation technology has accelerated. We have constructed an electromagnetic levitation control system that keeps the relative distance between the electromagnet and steel plate constant. To investigate the levitation stability of thin steel plates, we performed magnetic levitation experiments on a thin steel plate with curvature. A physical disturbance was applied to the electromagnet units by vibrators. The electromagnet units were vibrated up and down by a vibrator. We investigated whether the bending magnetic levitation improved the levitation performance even if the magnetic levitation system was in a vibrating environment. We determined that it was possible to realize stable levitation for a steel plate under external disturbances during levitation at the optimal bending angle.

A new adaptive-like neural control strategy for motion reference trajectory tracking for a nonlinear electromagnetic suspension dynamic system is introduced. Artificial neural networks, differential flatness and sliding modes are strategically integrated in the presented adaptive neural network control design approach. The robustness and efficiency of the magnetic suspension control system on desired smooth position reference profile tracking can be improved in this fashion. A single levitation control parameter is tuned on-line from a neural adaptive perspective by using information of the reference trajectory tracking error signal only. The sliding mode discontinuous control action is approximated by a neural network-based adaptive continuous control function. Control design is firstly developed from theoretical modelling of the nonlinear physical system. Next, dependency on theoretical modelling of the nonlinear dynamic system is substantially reduced by integrating B-spline neural networks and sliding modes in the electromagnetic levitation control technique. On-line accurate estimation of uncertainty, unmeasured external disturbances and uncertain nonlinearities are conveniently evaded. The effective performance of the robust trajectory tracking levitation control approach is depicted for multiple simulation operating scenarios. The capability of active disturbance suppression is furthermore evidenced. The presented B-spline neural network trajectory tracking control design approach based on sliding modes and differential flatness can be extended to other controllable complex uncertain nonlinear dynamic systems where internal and external disturbances represent a relevant issue. Computer simulations and analytical results demonstrate the effective performance of the new adaptive neural control method. [ABSTRACT FROM AUTHOR]

We proposed the determination method of the normal spectral emissivity of molten oxides using a combination of immiscible molten oxides and liquid metals. We can determine the normal spectral emissivity of molten oxide from the ratio of the normal spectral radiance of molten oxides and liquid metals. using a commercially available pyrometer combined with an electromagnetic levitation system. In the present study, we measured the normal spectral emissivity of a molten oxide sample from SiO2-CaOFeO (SCF) ternary system and FeO using liquid Fe as the reference liquid metal. The normal spectral emissivity of the molten SCF sample with the composition of SiO2:CaO:FeO = 20:20:60 mass % was determined to be 0.78 * 0.01 and that of molten FeO to be 0.68 * 0.03. Based on these results. we have discussed the relationship between the normal spectral emissivity and the electrical conductivity of molten oxides. [ABSTRACT FROM AUTHOR]

The applicability of the dual-wavelength reflectance-ratio (DWR) method to emissivity-free radiation thermometry of electromagnetically levitated high-temperature liquid metals was investigated. To establish the measurement technique, the DWR method was applied to liquid Ni levitated in a static magnetic field, which suppresses the surface oscillation and the translational motion. In a previous study, temperature of the levitated liquid metals measured by DWR showed deviations of about 95 K to 175 K from the temperature measured by a calibrated pyrometer. Since this discrepancy could be attributed to the imperfect contribution of the auxiliary light. the effect of the optical setup of the auxiliary light on the temperature measurement was investigated in this study. By using a reflecting collimator for the auxiliary optical system and adopting the radiance ratio determined considering the geometrical arrangement of the measurement system. the difference between temperature of liquid Ni kept near its melting temperature (Tm = 1728 K) measured using DWR and the temperature measured by a pyrometer calibrated using the melting point of Ni was 12 Kon average and the standard deviation in the temperature measurement was 25 K (n = 5). [ABSTRACT FROM AUTHOR]

The normal spectral emissivity at 807 and 940 nm and heat capacity at constant pressure of Pd-Fe melts were measured under electromagnetic levitation with a static magnetic field. The samples were made of Fe of mass purity 99.9985%. The present emissivity of Fe melts was relatively low compared with previously reported data using Fe with purity lower than 99.95% mass purity. The spectral emission of the Fe melts was ana- Iyzed u sing their nornial spectral emissivity obtained from the Drude model. The excess heat capacity of Pd-Fe melts was evaluated from the measured heat capacity of Pd-Fe melts. Applying the Lupis-Elliot rule. we concluded from the obtained excess heat capacity that the enthalpy of mixing and excess entropy of the Pd-Fe melts should be negative. The composition dependence of the enthalpy of mixing, excess entropy. and excess Gibbs energy of Pd-Fe melts were evaluated using data obtained in this study and the literature. [ABSTRACT FROM AUTHOR]

Recently, demand for thin steel plates has increased. In the manufacturing of thin steel plates, surface quality deterioration due to contact between the rollers and steel plate involved is problematic. We are investigating magnetic levitation conveyance to propose a noncontact conveyance system using electromagnets. However, the magnetic levitation of thin steel plates is unstable because of the deflection in the range where the electromagnetic force is not affected. Therefore, to improve the levitation stability, we are investigating a bending magnetic levitation system in which a thin steel plate is bent during magnetic levitation but not deformed plastically. In this study, a dynamic analysis using the finite difference method is performed to understand the behavior of a thin steel plate during magnetic levitation. In the dynamic analysis, vibration is evaluated based on the displacement standard deviation. The dynamic simulation visualizes the dynamic behavior of a levitated flexible steel plate. [ABSTRACT FROM AUTHOR]

Systematical experimental data on density. molar volume and the sun face tension, measured in electromagnetic levitation, has been summarized for the liquid Ti-V system. The optical dilatometry method as well as the oscillating drop technique have been employed to investigate the temperature- and compositional dependence. A linear decrease in density and surface tension with increasing temperature has been observed for all investigated compositions. Pure Vanadium shows hereby the highest density and surface tension while pure titanium shows the lowest density and surface tension respectively. Therefore, the density and surface tension decrease with increasing titanium content, however not linear. Since no excess quantities were available, simple models could be employed to cover the complete liquid Ti-V system. Experimental data as well as the corresponding linear fits are presented. [ABSTRACT FROM AUTHOR]

Electromagnetic Levitation in reduced gravity has demonstrated great utility in the measurement of thermophysical properties and the study of solidification of metallic melts. Internal flow in the liquid metal samples is a critical parameter in many of these experiments. For example, turbulent flow in the sample prevents measurement of viscosity by the oscillating droplet method, as the measured damping of oscillations is a property of the flow and not of the fluid. In solidification, it has been demonstrated that internal flow changes the lifetime of the metastable phase in stainless steels by almost two orders of magnitude over the experimentally accessible range. For these experiments, the flow was quantified by CFD models: however, these models require as an experimental input whether the flow is laminar or turbulent. To date, the only study of the transition to turbulence in EML comes from experiments on the Space Shuttle in 1997 on MSL-1 TEMPUS on a palladium-silicon alloy. On each melting cycle, tracer particles reveal the laminar or turbulent nature of the flow. However, this phenomenon was only noticed and examined after the flight, so observations are available only for a very narrow range of conditions. As these results were the only ones available, they have been boldly extrapolated to conditions far from the original experiment. Furthermore, while evidence from measurements on germanium shows that the positioner alone can drive turbulent flow, there are no available measurements of the turbulent transition in positioner-dominated flows. On a more fundamental level, EML flows are constrained by the free surface of the drop, like the walls of internal flows. However, the free surface of the EML drop does not support shear stresses, unlike the walls in internal flows. Better quantification of the transition to turbulence iii EML flows may lead to insights into the nature of turbulence and turbulent transition. Closing this gap requires a combination of experiments and models that will quantify the turbulent transition over as wide a range of experimental conditions as possible in ISS-EML. Modeling results are presented here; experiments are planned for ISS-EML Batch 4, estimated for 2024. [ABSTRACT FROM AUTHOR]

The solidification of Inconel 718 alloy (IN718) from undercooled liquid is studied. The solidification kinetics is evaluated in melted and undercooled droplets processed using the electromagnetic levitation (EML) technique by the temperature–time profiles and solid/liquid (S/L) interface movement during recalescence. The kinetics is monitored in real time by special pyrometrical measurements and high-speed digital camera. It is shown that the growth velocity of γ-phase (the primary phase in IN718), the final crystalline microstructure (dendritic and grained), and the mechanical properties (microhardness) are strongly dependent on the initial undercooling ΔT at which the samples started to solidify with the originating γ-phase. Particularly, with the increase in undercooling, the secondary dendrite arm spacing decreases from 28 μm to 5 μm. At small and intermediate ranges of undercooling, the solidified droplets have a dendritic crystalline microstructure. At higher undercooling values reached in the experiment, ΔT>160 K (namely, for samples solidified with ΔT=170 K and ΔT=263 K), fine crystalline grains are observed instead of the dendritic structure of solidified drops. Such change in the crystalline morphology is qualitatively consistent with the behavior of crystal growth kinetics which exhibits the change from the power law to linear law at ΔT≈160 K in the velocity–undercooling relationship (measured by the advancement of the recalescence front in solidifying droplets). Study of the local mechanical properties shows that the microhardness increases with the increase in the γ″-phase within interdendritic spacing. The obtained data are the basis for testing the theoretical and computational of multicomponent alloy samples.

This paper presents the results of a comprehensive study of the pull-in phenomenon in the hybrid levitation microactuator (HLMA), in which square-shaped proof masses (PMs) of different sizes, namely, length sides of 2.8 and 3.2 mm and thicknesses of 25 and 10 μm were electromagnetically levitated. The pull-in actuation of the square-shaped PMs was performed by the electrostatic force generated by the set of energized electrodes and acting on the bottom surface of the PMs along the vertical direction. The pull-in parameters, such as pull-in displacements and the corresponding applied pull-in voltages, were measured with the developed setup. The experimental measurements showed that the pull-in actuation is nonlinearly dependent on the size and mass of the PMs and a levitation height. In particular, it was found that PMs levitated within a height range from 140 to 170 μm can be stably displaced within a range of 30 μm. The results of measurements were extensively simulated with the developed analytical model by means of the quasi-FEM method. The direct comparison of the results of simulation and measurements showed a very good agreement between the theory and experiments. [ABSTRACT FROM AUTHOR]

Summary: This paper highlights the design, electromagnetic analysis, system modelling, set‐up fabrication, and finally control of an attraction type lab developed levitation prototype. The objectives of this work are parameters' evaluation, for example, force, inductance, and current‐air‐gap characteristics using a novel analytical model, electromagnetic results, and practical experiments. The FE model has been built using standard packages. A novel permeance function‐based approach is developed for the analytical evaluation of parameters. These are verified by actual experiments too with excellent correlation between the sets of results. Agreement between analytical and practical values also show that the modelling is perfect and reliable which further leads to accurate design, fabrication, and implementation of the controller. A simple but reliable controller has been designed, analyzed, and implemented. The performances have been significantly improved. Finally, the steel object has been successfully and steadily levitated in robust condition. [ABSTRACT FROM AUTHOR]

The effects of temperature and phosphorus addition on the surface tension of molten CuP alloys were measured by the oscillating droplet method using the electromagnetic levitation technique. We successfully measured the accurate surface tension of molten samples that were sufficiently above the liquidus temperature. The surface tension of liquid copper was determined in its pure state, which is free from any contamination, such as oxygen adsorption and chemical reaction with the supporting material. The surface tension of the molten sample was decreased as phosphorus addition was increased. The surface tension of molten CuP alloys was well expressed as functions of temperature and phosphorus activity from the measurement results using the Szyszkowski model. Furthermore, the enthalpy and entropy changes in phosphorus adsorption on liquid copper were also estimated. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation (EML) was employed for studying the velocity and morphology of the solidification front as a function of undercooling of metallic materials. The limitation of the EML technique with respect to low melting alloys that emit outside the visible light spectrum was overcome by employing state-of-the-art high-speed mid-wavelength infrared cameras (MWIR cameras) with a photon detector. Due to the additional thermography contrast provided by the emission contrast of the solid and liquid phases, conductor, and semi-conductor, the pattern formation of Al-based alloys was studied in detail, revealing information on the nucleation, phase selection during solidification, and the influence of convection. [ABSTRACT FROM AUTHOR]

Purpose. The purpose of this work is the formation of conceptual approaches to the construction of an effective integrated system of simultaneous synchronized control of the movement and suspension of a maglev vehicle – a magnetoplane. Methodology. The paper uses a technique for simultaneous control of the movement and suspension of a maglev vehicle with the mutually coordinated application of both levitation methods, electromagnetic and electrodynamic, through individual control of the energy supply of each track coil. Findings. The conceptual control principles of a traction-levitation system in a hybrid mode of its operation are substantiated. The interaction of a track structure with a vehicle on an electrodynamic suspension with a linear drive is disclosed and the features of the implementation of the power unit are highlighted. Originality. It is shown that a significant improvement in maglev technology can be achieved due to the mutually coordinated combination of electromagnetic and electrodynamic methods of magnetic levitation and the use of a fundamentally different architecture for constructing a MAGLEV track. It is constructed not from long sections with three-phase power windings, but from discrete ones, they are also linear engine traction coils, and a component (load) of a solar track power plant located along the overpass. The power plant includes a photovoltaic module (solar battery) that converts solar energy into electricity, a storage device and an inverter. This construction makes possible independent supply of each travel coil and its autonomous control with the ability to switch to traction or levitation mode. The control concept is that each track coil can participate both in the creation of a static suspension due to the interaction of the magnetic field of the onboard superconducting magnet and the magnetic field of the track coils when a certain amount of direct current is applied to them, as well as the dynamic suspension provided during the train movement as a result of the interaction of the magnetic field of the onboard superconducting magnet and the magnetic fields created in the track coils by currents induced in them when the magnetic fields of the onboard superconducting magnet intersect. Practical value. The results are of practical value, as the use of such complex control system of the suspension and the magnetic plane movement will significantly improve the quality of MAGLEV technology, increase the efficiency and reliability of high-speed land transport based on electrodynamics levitation using superconducting magnets.

Electromagnetic levitation technique was performed to investigate the surface wave phenomenon and microstructure evolution mechanism of undercooled ternary Ti 50 Al 30 Fe 20 alloy. Under the condition of high undercooling, the formation process of surface waves on the levitated alloy surface were directly detected by high-speed camera. The cooling gas provided the external perturbation that promoted surface nucleation, providing the suitable site for surface wave generation. On the rotating semisolid alloy surface, the competition between centrifugal force and surface tension caused the surface wrinkling, leading to the formation of surface waves. The residual liquid phase was solidified in the vortex circulation flow, and the vortex-shape pattern was preserved during rapid solidification. With the increases of undercooling, the microstructure evolved from dendrites and interdendritic lamellar eutectics into uniform anomalous eutectics because of the independent nucleation and competitive growth of (βTi) and TiFe phase. The surface wave was formed only at high undercoolings, indicating this phenomenon was related to the fluidity in eutectic growth. In this case, the uniform microstructure was closer to satisfying the continuum medium hypothesis, and the homogeneous medium reduced the energy damage during wave propagation. In addition, the micromechanical properties were remarkably increased as undercooling rose owing to the microstructural morphology and solute trapping effect. • The formation process of surface waves were directly detected by high-speed camera. • Waves mainly attributed to surface nucleation, semisolid rotation and vortex flow. • Independent nucleation and competitive growth resulted in microstructure evolution. • The micromechanical properties were remarkably increased as undercooling rose. [ABSTRACT FROM AUTHOR]

The non-equilibrium solidification of undercooled Inconel 718 melts has been studied in situ on electromagnetically levitated samples by using high-speed video recording and optical pyrometry. Microstructure and phase constitution of solidified samples were analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscatter diffraction and high-energy X-ray diffraction. Due to containerless sample processing experimental data on phase formation, γ-dendrite growth, and microstructural evolution in Inconel 718 were obtained over a wide range of undercooling Δ T between 20 and 289 K. It has been found that the dendrite growth velocity, extracted from high-speed video records, rises exponentially with increasing undercooling at first. At an undercooling of about 150 K, growth slows down drastically. Furthermore, morphology and size of γ-matrix grains essentially depend on Δ T. They alter from coarse equiaxed to coarse columnar at an undercooling of about 60 K, get refined and equiaxed at undercoolings above 150 K, and become larger and elongated again upon reaching an undercooling of about 250 K. The deviation from equilibrium and trapping of solute atoms in γ-dendrites result in a notable reduction of NbC and Laves fraction, the latter apparently disappearing at Δ T larger than 150 K. [Display omitted] • Inconel 718 melts were solidified in an undercooled state at Δ T between 20 and 289 K. • Growth velocity was determined by using high speed video and optical pyrometry. • Growth velocity rises exponentially and slows down at an undercooling of about 150 K. • Coarse grains get refined at Δ T ≈ 150 K and become larger again at Δ T ≈ 250 K. • Solute trapping at high undercooling results in reduction of NbC and Laves fraction. [ABSTRACT FROM AUTHOR]

There are numerous methods used for measuring the coefficient of thermal expansion of alloys and density change at low temperatures, but it is difficult to accurately measure the volume and density of high-temperature melts, particularly during the process of rapid volume change during material phase transformation. This article proposes a method for measuring and analysing the volume and density changes in high-temperature alloy melts using high-speed photography and computer MATLAB program image analysis technology, which includes the ordinary image threshold segmentation method, the elliptical fitting method, and the local dynamic threshold segmentation method. The ordinary image threshold segmentation method is best suited to samples with clear boundaries; the elliptical fitting method is the simplest and can be used to analyse samples with unclear boundaries; and the local dynamic threshold segmentation method is the most accurate and best suited to samples with unclear boundaries. These techniques will aid in understanding the variations in the volume and density of high-temperature melt samples during the phase transition process.

Bulk Ti–Al based alloys with an approximate mass of 30 g are first prepared by electromagnetic levitation. The microstructures and the compression properties of Ti‐45%Al‐z%V alloys (z = 4, 8, and 12, atomic percent) at room and high temperatures are studied by experiments. The relationship between V content and the mechanical properties of γ and α2 intermetallics has been investigated by first‐principle calculations. It is clarified that V addition controls the phase contents and the microstructure characteristics. With the increase of V content, the microstructures of Ti‐45%Al‐4%V and Ti‐45%Al‐12%V are dominated by the phase transformations of α → γ and α → α2, respectively. Ti‐45%Al‐4%V alloy is mainly constituted of fine full lamellar γ phase while Ti‐45%Al‐12%V alloy is composed of coarsening lath α2 phase. Besides, the Young's modulus of Ti‐45%Al‐12%V alloy is smaller than that of Ti‐45%Al‐4%V alloy at 300 K, but the yield stress and ultimate compression stress are larger than that of Ti‐45%Al‐4%V alloy. The differences are attributed to the change of the main phase from γ to α2 and the mechanical properties of crystals changed by V addition. In addition, V addition changes the Young's modulus of α2 crystal from isotropy to anisotropy. [ABSTRACT FROM AUTHOR]

Vehicle seats have a significant impact on the comfort of passengers. The development of seats is a field in which scholars are widely concerned. In this study, we add an electromagnetic levitation structure and design a new active seat suspension based on the passive seat suspension. Then, simulation research is carried out based on a C-level road surface combined with integral sliding mode control and state feedback control. The results show that both state feedback control and integral sliding mode control positively affect vehicle seat vibration reduction, and integral sliding mode control has a better anti-interference effect than state feedback control. At the same time, it is proved that the seat suspension has good working characteristics and economy. [ABSTRACT FROM AUTHOR]

One of the most important factors during Laser Powder Bed Fusion is a robust and stable process to generate reproducibly dense and crack-free components with the same homogenous and fine-grained microstructure. Among other factors, surface tension influences the robustness of this process. Three aluminum alloys were investigated by means of 3D laser printing with respect to their ability to form lightweight and high-performance structures. The alloys include two Al-Cr based alloys (Zicromal®: Al-Cr-Zr-Mn, Scancromal®: Al-Cr-Sc-Zr) and an Al-Mg based alloy (Scalmalloy®: Al-Mg-Sc-Mn-Zr). The surface tensions of their liquid melts were measured by means of the oscillating droplet method in electromagnetic levitation. Scalmalloy® exhibited a surface tension that was by 3-8% smaller than the other two alloys, over a temperature range of 500 K above their liquidus temperature; the evaporation analysis showed that Scancromal® exhibits significantly less evaporation compared to the other two alloys by an order of magnitude. During the Laser Powder Bed Fusion process, Scalmalloy® presented the most unstable melt dynamics, and Scancromal® appeared to be more robust and stable with less weld spatters and negligible dust deposition, as evidence from the high-speed video observations. The results support the idea that surface tension and evaporation are potentially crucial factors influencing the melt dynamics and also demonstrate the capability of additive manufacturing that produces customized aluminum alloys for aerospace applications. [ABSTRACT FROM AUTHOR]

To accurately measure the surface tension of liquid titanium free of contamination from chemical reaction with the supporting materials and dissolution of atmospheric oxygen, the measurement was performed by using electromagnetic levitation (EML) and electrostatic levitation (ESL) in consideration of the influence of oxygen partial pressure of the measurement atmosphere, P O 2 . When liquid titanium was maintained at 2000 K under Ar–He gas with P O 2 of 10 Pa flowing at 2 L·min−1 using EML, the surface tension decreased with time due to the dissolution of atmospheric oxygen into the sample. When the P O 2 of the gas was decreased to 10−2 Pa, the oxygen content and the surface tension were confirmed to not vary, even after 120 min. Even though P O 2 further decreased to 10−11 Pa under Ar–He–H2 gas, the surface tension slightly increased with time due to gas phase equilibrium between H2 and H2O that allowed for a continuous dissolution of atmospheric oxygen into the liquid titanium. The surface tension of liquid titanium measured by ESL, which prevents contamination of the sample from supporting materials and the high 10−5 Pa vacuum inhibits the dissolution of oxygen, showed almost the same value as that measured under Ar–He gas at P O 2 of 10−2 Pa by EML. From the measurement results of EML and ESL, the surface tension of the 99.98 mass % pure liquid titanium, free from any contaminations from chemical reactions, with the supporting material and dissolved oxygen was expressed as σ 99.98 % = 1613 − 0.2049 T − 1941 (10−3 N·m−1). [ABSTRACT FROM AUTHOR]

A new adaptive-like neural control strategy for motion reference trajectory tracking for a nonlinear electromagnetic suspension dynamic system is introduced. Artificial neural networks, differential flatness and sliding modes are strategically integrated in the presented adaptive neural network control design approach. The robustness and efficiency of the magnetic suspension control system on desired smooth position reference profile tracking can be improved in this fashion. A single levitation control parameter is tuned on-line from a neural adaptive perspective by using information of the reference trajectory tracking error signal only. The sliding mode discontinuous control action is approximated by a neural network-based adaptive continuous control function. Control design is firstly developed from theoretical modelling of the nonlinear physical system. Next, dependency on theoretical modelling of the nonlinear dynamic system is substantially reduced by integrating B-spline neural networks and sliding modes in the electromagnetic levitation control technique. On-line accurate estimation of uncertainty, unmeasured external disturbances and uncertain nonlinearities are conveniently evaded. The effective performance of the robust trajectory tracking levitation control approach is depicted for multiple simulation operating scenarios. The capability of active disturbance suppression is furthermore evidenced. The presented B-spline neural network trajectory tracking control design approach based on sliding modes and differential flatness can be extended to other controllable complex uncertain nonlinear dynamic systems where internal and external disturbances represent a relevant issue. Computer simulations and analytical results demonstrate the effective performance of the new adaptive neural control method.

Temperature dependent isobaric molar heat capacity cP was measured in a containerless way for liquid Ti and two AlTi binary liquid alloys. The technique of electromagnetic levitation was used in combination with laser modulation calorimetry. In all cases, linear temperature dependencies were found: At the corresponding liquidus temperatures, cP equals 49.75(±2.0) J∙K–1mol–1, 57.43 (±2.9) J∙K–1mol–1, and 42.60(±2.2) J∙K–1mol–1, for Ti, Al20Ti80 and Al50Ti50, respectively. The respective temperature coefficients amount to –1.67∙ 10–2 J∙K–2mol–1, –2.73∙10–2 J∙K–2mol–1, and +7.83∙10–2 J∙K–2mol–1. For liquid Ti, there is a good agreement with existing literature data. The results are discussed in relation to the Neumann-Kopp rule. [ABSTRACT FROM AUTHOR]

The hybrid actuator presented in this article is meant to enable stationary and slow dynamic levitation in Maglev applications. The term ‘hybrid’ refers to the design of the actuator, which is a combination of permanent magnets (PM) and electromagnets. This paper presents an analytically computable control algorithm for the said hybrid actuator. The theory of magnetic circuits is summarized shortly and used to derive a cascaded control loop consisting of an inner current controller and an outer air gap controller. Since the uncontrolled hybrid actuator is inherently unstable, the system has to be stabilized. By introducing a PID-controller into the air gap control loop, the unstable behaviour of the uncontrolled system is changed into the system behaviour of a damped harmonic oscillator. The advantage of this approach is that the computed controller parameters of the PID-controller can easily be adjusted, so the system behaviour of damping and eigenfrequency can be selected within a certain range. For the execution of the control algorithm, a microcontroller (MCU) is used and for precise air gap measurement, an eddy current sensor is installed. Finally, the behaviour of the current- and air gap controller is discussed for different measurement results and the adjustable system behaviour of the damped harmonic oscillator is presented.

The thermodynamic description of the fcc phase in the Al-Cu system has been revised, allowing for the prediction of metastable fcc/liquid phase equilibria to undercoolings of -T=421K below the eutectic temperature. Hypoeutectic Al-Cu alloys that are prone to pronouncedmicrosegregation were solidified containerlessly in electromagnetic levitation. Solidus and liquidus concentrations were experimentally determined from highly undercooled samples employing energy-dispersive X-ray analysis. Solid concentrations at a rapidly propagating solid/liquid interface were additionally calculated using a sharp interface model that considers all undercoolings and is based on solvability theory. Modelling results (front velocity versus undercooling) were also corroborated by in situ observation with a high-speed camera. A newly established thermodynamic description of the fcc phase in Al-Cu is compatible with existing CALPHAD-type databases. Inconsistencies of previous descriptions such as a miscibility gap between Al-fcc and Cu-fcc on the Al-rich side, an unrealistic curvature of the solidus line in the same composition range or an azeotropic point near the melting point of Cu, are amended in the new description. The procedure to establish the description of phase equilibria at high undercoolings can be transferred to other alloy systems and is of a general nature. [ABSTRACT FROM AUTHOR]

Temperature-dependent viscosity and its relationship with local atomic packing structure of a liquid Zr56Co28Al16 alloy have been investigated by using an electromagnetic levitation device on board a parabolic flight airplane, together with ab initio molecular dynamics simulations. It is found that viscosity inversely correlates with the fraction of ‘loose’ atoms having larger free volume, indicating that the temperature-dependent viscosity during cooling is statistically related with the fraction of close packing atoms. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation is a unique environment allowing for making non-contact measurements over samples of liquid metals at different temperatures. The electromagnetic coil is the core of the electromagnetic levitation system, and its design defines the amount of energy introduced into the sample as well as the shape and stability of the latter during levitation. In the present work, analytical and numerical modelling for a real electromagnetic inductor is performed and compared with experimental observations. The shape of the experimental electromagnetic coil is assured due to 3D printing of a template which is used for the coil winding. [ABSTRACT FROM AUTHOR]

This paper presents the results of a comprehensive study of the pull-in phenomenon in the hybrid levitation microactuator (HLMA), in which square-shaped proof masses (PMs) of different sizes, namely, length sides of 2.8 and 3.2 mm and thicknesses of 25 and 10 μm were electromagnetically levitated. The pull-in actuation of the square-shaped PMs was performed by the electrostatic force generated by the set of energized electrodes and acting on the bottom surface of the PMs along the vertical direction. The pull-in parameters, such as pull-in displacements and the corresponding applied pull-in voltages, were measured with the developed setup. The experimental measurements showed that the pull-in actuation is nonlinearly dependent on the size and mass of the PMs and a levitation height. In particular, it was found that PMs levitated within a height range from 140 to 170 μm can be stably displaced within a range of 30 μm. The results of measurements were extensively simulated with the developed analytical model by means of the quasi-FEM method. The direct comparison of the results of simulation and measurements showed a very good agreement between the theory and experiments.

A combined simulation method of Magnet/ Simulink was proposed for radial electromagnetic levitation control. Firstly, the model of radial electromagnetic levitation system was built in Magnet software, and the program block diagram of PID control electromagnetic levitation system was built in Simulink. Then the radial electromagnetic levitation system model in Magnet was imported into the control program of Simulink. The radial electromagnetic levitation system Magnet/ Simulink joint simulation control model was established for the PID control simulation of the radial electromagnetic levitation system. The simulation results show that the Magnet/ Simulink co-simulation method can realize the real-time monitoring of the electromagnetic force, rotor velocity, rotor displacement and other parameters in the suspension control process. The co-simulation method of Magnet/ Simulink not only improves the efficiency of electromagnetic levitation control simulation, but also puts forward a new idea to explore the influence of control method or controller parameters on electromagnetic levitation system. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation (EML) was employed for studying the velocity and morphology of the solidification front as a function of undercooling of metallic materials. The limitation of the EML technique with respect to low melting alloys that emit outside the visible light spectrum was overcome by employing state-of-the-art high-speed mid-wavelength infrared cameras (MWIR cameras) with a photon detector. Due to the additional thermography contrast provided by the emission contrast of the solid and liquid phases, conductor, and semi-conductor, the pattern formation of Al-based alloys was studied in detail, revealing information on the nucleation, phase selection during solidification, and the influence of convection.