Joule Heating Current Research Articles

Machine learning-based self-sensing of the stiffness of shape memory coil actuator.

Self-sensing actuation (SSA) assists in sensing the vital property of the shape memory coil which can be used to monitor and control the actuation in smart equipment as well as robotics. The stiffness characteristic of the shape memory coil (SMC) is sensed during actuation which plays a significant role in development of intelligent robotics in defense systems. The electrical property of SMC such as electrical resistance changes due to martensitic phase transformation which is further used to sense the mechanical properties such as strain, stress, temperature, length, and force of the equipment. Nowadays electrical properties are used to sense the stiffness of the shape memory coil. As of now, there is no well-established analytical model to predict the stiffness of SMC during actuation accurately. Therefore, a soft model based on machine learning is proposed in this paper for autosensing of the stiffness in SMC. The experimental facility has been developed for the collection of data with respect to diverse Joule heating currents. To determine the experimental data values of stiffness and electrical resistance of SMC is a cumbersome task. Hence, we have proposed an automated method to predict the stiffness of the SMC using soft computing-based methods. The Classical Polynomial and Bayesian optimization-based Feedforward Neural Network (FFNN) models are developed for analyzing the stiffness of the SMC. It is found that the hybrid FFNN model outperforms the other ML-based model by attaining 95.2650% accuracy. The FFNN model is also able to explain almost all the predicted stiffness values which are experimentally recorded.

Preparation of MgB2 superconducting wires by the rapid heating and quenching method

In order to reduce the long-term annealing process and prevent excessive grain growth, we attempted to fabricate MgB2 superconducting wires by the rapid heating and quenching (RHQ) method. In this paper, we have successfully prepared MgB2 superconductive wires with self-made RHQ equipment, and the effect of various Joule heating currents on the properties of MgB2 was investigated. The XRD results showed that the sample had relatively strongest diffraction peaks and least heterogenous peaks when the loading heating current was 350 A, so the superconducting transition temperature (Tc) could reach 38.5 K. Because the MgB2 phase particles were small and uniformly distributed, there was a good critical current density (Jc). That is, in the self-field, the Jc value of the 350 A sample reached up to 1.39 × 105 A/cm2, and the downward trend was the flattest. When the magnetic field was 7 T, the critical current density was still as high as 300 A/cm2.

Improved safety and mechanical characterizations of thick lithium-ion battery electrodes structured with porous metal current collectors

Porous metal current collectors enable the fabrication of thick electrode structures with improved safety margins and unique mechanical properties. Interpenetrating phase composite LiCoO2 cathodes and graphite anodes with large active material loadings are formed using advanced slurry processing techniques with a submersible ultrasonic horn. Full cells with 600 μm thick electrodes demonstrate high aerial capacity of 16.7 mAh.cm−2, improving energy density by 22% with respect to volume versus reference cells using traditional laminate composite electrode stacks. External shorting and nail penetration testing show notably suppressed joule heating currents, limiting peak temperature accrued to just 25% of the reference. Shear testing and three-point bending of individual electrodes and stack assemblies elucidate the greater role of the binder phase in the mechanical response, and that extensive characteristics such as thickness can be more influential than the intensive properties of the materials. Optimization of electrode thicknesses to balance rate capability with abuse safety is discussed, and opportunities for multifunctional application as load-bearing structural components are considered. Improved battery safety characteristics are demonstrated by reorienting the inherent components of the cell, without altering the chemical make-up, emphasizing the profound influence of structural design.

Effect of Joule heating current on phase formation and superconducting properties based on Nb3Al for applications in nuclear fusion magnet energy

With extremely high critical current density (Jc) and excellent strain tolerance, Nb3Al superconductor is considered as an alternative to Nb3Sn for application of high-field magnets. However, owing to their complex structure, Nb3Al superconducting wires can hardly meet the requirement of engineering application at present. In this work, we have reported the manufacture of a single core-structured jelly-roll Nb3Al precursor long wire. While using homemade rapid heating and quenching (RHQ) equipment, we have successfully carried out RHQ heat-treatment of Nb3Al wire samples with various heating conditions, especially the effect of the Joule heating currents by rapid heating, quenching and transformation (RHQT) method on the phase formation and the superconducting properties of the wires were investigated.

Surface chemical reaction enhanced by Joule heating current

Surface chemical reaction enhanced by Joule heating current

Structural, magnetic, and magnetostriction behaviors during the nanocrystallization of the amorphous Ni5Fe68.5Si13.5B9Nb3Cu1 alloy

The changes in the magnetic properties (coercive field and saturation magnetostriction) of Ni5Fe68.5Cu1Nb3Si13.5B9 amorphous alloy after thermal treatment are reported. In order to develop a nanocrystalline structure, the thermal annealing was carried out by Joule heating currents of 1.7 and 1.8 A during different annealing times. Additionally, a microstructural characterization of the treated samples was performed by x-ray diffraction, determining the partial volume of the two, crystalline grains and residual amorphous matrix, existing phases. They seem to be correlated to the softening of the nanocrystallized samples in comparison to the as-cast one.

Transport properties of long-lengths of RHQT processed Nb/sub 3/Al conductor

A rapid heating and quenching (RHQ) operation along a long-length of jellyroll Nb/Al precursor over 300 m has been established. The J/sub c/ varies sensitively with the joule-heating current (I/sub RHQ/) that determines the temperature from which a precursor wire is quenched, excluding the "plateau" region where the bcc supersaturated-solid solution (Nb(Al)/sub ss/) only forms. The RHQ operation using such a plateau condition can suppress a scatter of J/sub c/ from point to tail of a long-length of wire. The standard deviation of J/sub c/ (4.2 K) at 21 T along a long-length of wire was about 5%, which was less than the variation of J/sub c/ with I/sub RHQ/ in the plateau region (/spl plusmn/7%). The mechanical deformation process needed when incorporating the Cu stabilizer also plays an important role in ensuring uniform heat treatment of the coil that is wound with a long-length of wire and, hence, large heat capacity. Although a temperature ramp-up rate might differ from place to place in the coil, the deformation processing makes such a ramp-up rate insensitive to these critical parameters. The coils using 300.5 m and 254 m lengths of Cu-clad RHQT JR Nb/sub 3/Al conductor generated additional 2.3 T and 3.2 T in bores of 90.2 mm/spl phi/ and 64.6 mm/spl phi/, respectively, indicating that a long-length of RHQT JR Nb/sub 3/Al conductor can be trustworthy for practical coil applications.

Effect of rapid heating, quenching and transformation conditions on the superconducting properties and microstructure of Jelly-Roll processed Nb3Al superconductors

A Jelly-Roll processed Nb3Al superconductor with excellent superconducting properties has been fabricated by the process of rapid heating, quenching and transformation (RHQT). In order to fabricate a long length of wire with homogeneous superconducting properties, the optimization of the RHQT conditions is particularly important because RHQT conditions determine the final microstructure and superconducting properties. In this paper, we have studied the variation of microstructure and superconducting properties with RHQ and transformation annealing conditions, to determine the optimum processing condition. In the study of the RHQ treatment, we found that the RHQ conditions are divided into four regions according to the joule heating current (IRHQ). In the optimum region, the wire is quenched from the temperature in which a bcc solid solution extends to more than 25 at%Al, and the scatter of critical current density (Jc) after transformation annealing is almost negligible. In the study of the deformation and transformation heat treatment, we have found that the deformation of the supersaturated solid solution improves the resultant superconducting properties, and prevents degradation of superconducting properties that occurs when the temperature ramp-up rate is slow.

Temperature behavior of anhysteretic magnetization in granular magnetic systems

Temperature measurements of the anhysteretic magnetization M were performed on nearly-superparamagnetic, granular Cu 90Co 10 submitted to different Joule-heating currents using a VSM. Below about 500 K, the anhysteretic magnetization is fully reversible. All isothermal M( H) curves may be fitted by a superposition of Langevin functions with distributed magnetic moments; however, the reduced magnetization M/ M s is not observed to scale with H/ T; on the contrary, all curves are nearly exactly coincident when plotted against M s/ T. This result is phenomenologically interpreted in terms of an apparent average magnetic moment linearly growing with the ratio T/ M s.

Nanocrystalline Fe73.5 Cu1Nb3Si13.5B9 obtained by direct-current Joule heating. Magnetic and mechanical properties

Nanocrystalline ferromagnetic materials obtained by proper annealing of amorphous ribbons display excellent soft magnetic properties. However, the technological application of these nanostructured ferromagnets is hindered by their high brittleness. Direct-current Joule heating in vacuo is exploited to increase both the magnetic permeability and the ductility of nanocrystalline Fe73.5Cu1Nb3Si13.5B9. The development of the nanostructure in samples submitted to different Joule-heating currents for the same time (t = 60 s) has been analysed by means of X-ray diffraction, and is associated with magnetic permeability and reduced fracture strain measurements. Measurements of electrical resistance performed in the course of the heat treatment allows us to single out an activated process of atomic rearrangement occurring in the amorphous phase. Fracture strain data show that the alloy's embrittlement is mainly to be ascribed to this process rather than to nanocrystallization. It is shown that further improvement in the alloy's ductility can be obtained by inducing fast nanocrystallization in samples submitted to high electrical currents