Pulse Current Parameters Research Articles

Investigation of arc spot splitting behavior on aluminum, titanium, and their alloy cathodes under different gas flows

This paper presents an experimental study on the spot splitting behavior of aluminum, titanium, and their alloy cathodes during electric arc discharge. Utilizing high-speed digital cameras, we dynamically captured the splitting motion of cathode arc spots and analyzed their behavior under different pressures of argon, nitrogen, and oxygen. The study also examined the effects of pulsed arc current parameters on spot splitting. We observed a ringlike expansion of pulsed arc spots during splitting, with aluminum cathodes showing better performance than titanium in promoting spot splitting and stabilizing the subsequent motion of the split spots. Oxygen was found to enhance spot splitting more effectively than nitrogen. Furthermore, the parameters of the pulsed arc can control the extent of spot splitting and expansion. These findings provide valuable insights for optimizing arc parameter control in metal film deposition processes.

Microscopic characteristics and properties of co-based coating by pulse current-assisted laser cladding on high carbon steel

Laser cladding has the advantages of a short processing cycle and good processing quality, and has been extensively researched in the field of rail property enhancement. The current study focuses mostly on enhancing the mechanical properties of rails by altering the laser process parameters and using complicated materials. However, the enhancement of mechanical properties such as corrosion and friction resistance by laser cladding is limited. As an effective metallurgical processing method, pulse current can be used to control the microstructure and improve the mechanical properties by altering the solidification process of the metal. In this paper, the effects of pulse current parameters (pulse current frequency, current peak, and duty cycle) on microscopic characteristics, such as microstructure number of pores, and microhardness, as well as mechanical properties, such as wear and corrosion resistance, of stellite-6 coatings created by pulse current-assisted laser cladding (PC-ALC), on the U71Mn substrate were investigated. The results showed that the electromagnetic action of the current refined the grains and reduced the number of pores in the PC-ALC coating. The degree of grain fineness increased, then decreased, as the current intensity increased. When compared with the microhardness without pulse current, the average hardness of the HAZ and coating rose by 49.7 % and 167 %, respectively. The results showed a positive link between corrosion resistance and current frequency, but a negative correlation between corrosion resistance and current peak. The corrosion resistance was improved by increasing the current duty cycle from 25 % to 50 %. The wear resistance of coatings was positively related to microhardness, and the coating reached the wear stabilization stage with a friction loss of about 0.5 %. The tests indicated that PC-ALC coatings had good corrosion and friction resistance for rail repair, extending their service life.

MICRO- AND NANO-ENGINEERING OF SEMICONDUCTOR COMPOUNDS AND METAL STRUCTURES BASED ON ELECTROCHEMICAL TECHNOLOGIES

This paper aims to address the challenges of micro- and nano-engineering semiconductor compounds and fabricating metal-semiconductor nanocomposite materials by developing theoretical concepts for the application of electrochemical nanostructuring technologies to semiconductor substrates. It includes identifying the technological conditions for controlled electrochemical etching to create nanostructured semiconductor templates with wide bandgaps, such as III-V semiconductors (InP, GaAs, GaN) and II-VI compounds (CdSe, ZnSe, ZnxCd1-xS). The study also demonstrates the conditions for electrochemical metal deposition in porous semiconductor templates and investigates the laws and mechanisms of metal deposition depending on the composition of the semiconductor substrates and current pulse parameters. Additionally, the paper addresses the conditions for electrochemical etching of semiconductor substrates to produce nanowire networks with directed alignment to the substrate surface, instead of merely producing porous layers. A comprehensive investigation of the properties of the developed nanostructures and materials is proposed to demonstrate their applicability in nanoelectronic, optoelectronic, and photonic devices.

Computational study of pulse current and thermal stress on thermoelectric cooler

The thermal performance of a Peltier thermoelectric cooler (TEC) can be enhanced by multi-staging, modifying the geometry of the thermoelement, and using new material with improved thermoelectric properties. This study utilizes COMSOL multiphysics to simulate thermomechanical analyses of various geometries of thermoelectric coolers under pulse current conditions. This investigation explores the influence of pulse current parameters, such as pulse width, pulse ratio, and hot-side convective heat transfer coefficient, on a thermoelectric cooler with different leg geometries. Additionally, the impact of the TEC cold-side temperature, hot-side temperature, and thermal stress on both sides is discussed. The results indicate that TEC leg shapes, such as pin and trapezoid, exhibit the minimum cold-side temperature. Increasing the pulse ratio leads to a decrease in the cold-side temperature and an increase in the hot-side temperature. A notable improvement in the cold-side temperature is also observed with higher pulse ratios, with the pin geometry achieving a minimum cold-side temperature of 276 K. Furthermore, the cooling load affects the temperature on both sides of the TEC. These findings provide valuable insights for optimizing thermoelectric coolers for electronic cooling applications using pulse current methods.

A novel framework for low-temperature fast charging of lithium-ion batteries without lithium plating

This paper proposes a novel framework for low-temperature fast charging of lithium-ion batteries (LIBs) without lithium plating. The framework includes three key components: modeling, constraints, and strategy design. In the modeling phase, a new electro-thermal coupled model is introduced, which integrates both frequency-domain and time-domain electro-thermal coupled models. They optimize the bidirectional pulsed current (BPC) heating parameters and charging current, respectively. Terminal voltage boundaries and lithium plating serve as constraints. Terminal voltage is confined within upper and lower limits to prevent battery overcharge and overdischarge. Lithium plating avoidance entails setting a minimum frequency for BPC heating. During charging, lithium plating is mitigated by maintaining negative potential above 0 V. To obtain calculated negative electrode potential, a three-electrode battery is employed to calibrate the electro-thermal coupled model parameters. Subsequently, a novel low-temperature fast charging strategy is devised. This strategy enables intelligent switching between BPC heating and charging, while also synergistically optimizing BPC heating parameters and charging current. The strategy also achieves optimization of both charging speed and energy consumption. Charging the battery SOC from 0.2 to 0.9 in 42 min at −10 °C, without triggering lithium plating, is feasible with this proposed strategy. Compared to strategies focusing solely on current amplitude optimization, heating followed by charging, and traditional methods, this heating strategy exhibits the highest charging speed.

DAC phase and amplitude noise experimental studies in RZ, NRZ and RF modes

Amplitude and duration of pulses generated by current cells of multimode DAC may differ in real DACs. In this case the problem arises of current pulse parameters defining, their relationship with frequency domain response and noise parameters of DAC, which can be experimentally determined. The article describes the measurements of frequency domain response, phase noise and amplitude noise of multimode DAC output signal in RZ, NRZ and RF (mixed) mode. Phase noise and amplitude noise of multimode DAC in RZ and RF modes calculation uses experimental data obtained in RZ mode. Measurement and consequent calculation of AD9739 DAC phase and amplitude noise confirmed the theoretical analysis.

Study of the microstructure evolution of alloy structural steel and inhomogeneity effect of the microscale pulsed currents during current-assisted plane strain compressions by modeling a novel cellular automata method

The current-assisted forming process is considered to be a novel process that utilizes the electroplasticity effect to reduce the deformation resistance of difficult-to-deform metals and to refine the grain size while improving the mechanical properties of the part. However, the lack of understanding of the mechanisms by which pulsed current affects grain refinement still makes it difficult to experimentally develop analytical or empirical models of the relationship between grain size, pulse current parameters, and deformation amount. It will seriously hinder the further development and application of the current-assisted forming process. To reveal the mechanism of grain refinement coupling with electroplasticity, a series of Electron Back Scattering Diffraction observation tests were carried out after current-assisted plane strain compressions. The results show that the grain orientation spread value of the pulse current condition is lower than that of the non-current condition, while the refined grain area percentage is higher than that of the non-current condition. Based on the microstructure observation results, a cellular automata model for grain refinement is proposed. This consists of a dislocation density evolution, sub-grains generation, grain fragmentation, and a grain orientation rotation algorithm. To study the electroplasticity of the grain refinement process, the cellular automata model is also embedded with a finite difference numerical algorithm for solving the microscopic current density distribution of the model. The cellular automata model simulation results show that the error of grain size accuracy of this cellular automata model under non-current and pulse current conditions is 10.48% and 8.55%, respectively. It shows that the model can accurately characterize the grain refinement behavior of the current-assisted plane strain compression. The simulation results reveal the deep mechanism of pulsed current promotion on grain refinement, i.e., an inhomogeneous microstructure leads to uneven distribution of pulse current density. The inhomogeneous current distribution will further increase the grain refinement rate in the coarse-grained regions, thus increasing the proportion of the refined grain regions in the microstructure and leading to a relatively more homogeneous microstructure under pulse current conditions. The cellular automata model accurately reveals the mechanism of electroplasticity on the grain refinement. The model will serve as a crucial theoretical reference in designing current-assisted forming process routes to ensure excellent microstructure and properties in manufactured parts. It will enhance the widespread utilization of current-assisted forming process.

Facile In-Situ Electrosynthesis of MnO2/RGO Nanocomposite for Enhancing the Electrochemical Performance of Symmetric Supercapacitors

One-pot galvanostatic reverse pulse electrochemical deposition (RPED) was used to create a supercapacitive electrode made of manganese dioxide/reduced graphene oxide (MnO2/RGO) nanocomposite. Systematic changes of two independent parameters of the reverse pulse current, including times of the anodic and cathodic pulses (ta and tc), were investigated to achieve the desired physicochemical and electrochemical properties. Galvanostatic charge–discharge, cyclic voltammetry, and electrochemical impedance spectroscopy tests were employed to perform electrochemical evaluations. According to the results, the MG50-5 nanocomposite, synthesized at ta = 50 ms, tc = 5 ms, and anodic peak current density of 2 mA cm−2, was selected as the optimal sample. This sample showed the highest specific surface area of 284.6 m2 g−1 and the specific capacitance of 789.0 F g−1 at a current density of 0.5 A g−1. The specific capacitances of the MG50-5 symmetric supercapacitor at current densities of 0.5 and 10 A g−1 were 660.14 and 402.50 F g−1, respectively. Maintaining 84.8 % of the specific capacitance after 5000 consecutive cycles at 4 A g−1 indicated stable cycle performance of the MG50-5 symmetric cell. The MG50-5 symmetric supercapacitor presented the maximum energy density of 22.92 Wh kg−1 at a power density of 156.3 W kg−1 and the maximum power density of 3.125 kW kg−1 at an energy density of 13.97 Wh kg−1. Therefore, optimizing reverse pulse current parameters in the galvanostatic RPED of MnO2/RGO nanocomposite leads to an outstanding electrochemical performance of the fabricated supercapacitors.

Study on pulse current auxiliary heating process of submerged arc welding

During the welding process, temperature filed distribution of weldment is one of the key factors which influence welding quality. In order to improve the mechanical properties of welding joint, a technology for heating process of weldment using auxiliary pulse current was proposed in this article. Firstly, through metallographic experiment, strength experiment and hardness experiment, it was proved that the auxiliary pulse current not only can refine grain size but also improves the mechanical property of the welding joint. Then the paper used ANSYS and its ANSYS Parametric Design Language parametric design language to simulate the welding process with assistant pulse current, and the temperature field, the pulse current density distribution and the time of effective pulse current in the welded joint were obtained. Quantitative analyses were undertaken on the influence laws of auxiliary pulse current parameters on weld temperature field, auxiliary pulse current density distribution and the time of effective pulse current. A new parameter was defined as time-current density (the time integral of current density) to demonstrate the change rule of auxiliary pulse current density distribution with time. Finally, analyzing the reasons for raising the welding quality. There were two reasons for such phenomenon: one was auxiliary pulse current change the state of heat distribution in the weld seam area, the other was that the impulse oscillation of the auxiliary pulse influences the nucleation process of melting region.

Research on the influence of pulse current parameters on the tooth filling during current-assisted splitting spinning of small module tooth-shaped part

Current parameters are the main factors influencing the tooth filling of small module tooth-shaped parts (SMTSPs) with characteristics of hollow, thin wall-thickness made of difficult-to-deform metal during current-assisted splitting spinning (CASS). A coupled electrical-thermal-mechanical finite element analysis (FEA) model was established based on the ABAQUS software, and the influence of pulse current parameters, such as current density and duty ratio, on the tooth saturation was investigated. The results show that the tooth saturation increases obviously under pulse current comparing without pulse current, and increases rapidly with the increasing of the current density and duty ratio, but the tooth saturation tends to reach a threshold value when the current density greater than 13.5 A/mm2 and the duty ratio greater than 20%. The relative error of the tooth saturation between simulation and experimental result is less than 2%, which indicates that the established CASS FEA model of SMTSPs is reasonable.

Tuning residual stress in electrodeposited nickel films via pulse current

The pulse current electrodeposition has proved to be effective in the preparation of metal films with a low residual stress, while the formation mechanism of residual stress under the pulse current remains unclear. In this study, in situ measurements of residual stress in electrodeposited nickel films was performed. Nickel films with the lowest average stress were obtained under the frequency of 800 Hz, average current density of 1 A/dm2 and duty cycle of 50%. Based on X-ray diffraction and TEM analysis, the relationship between dislocation density and residual stress was studied, revealing that a high dislocation density contributed to the formation of cross slip, as well as the release of residual stress. Furthermore, charge time of the electric double layer was measured by multi-current step tests, and the possible mechanism for residual stress formation under pulse currents was proposed. The results indicated the stress was modulated by two competing factors: overpotential and fraction of the charge time. The overpotential played a leading role on average stress at low frequency and high current density, while fraction of the charge time played a dominant role at high frequency and low current density (less than 1 A/dm2). Our study provides a valuable insight to understand how pulse current parameters influence the residual stress in electrodeposited nickel films.

The modified GTN model for fracture of nickel-based superalloys considering size effect and healing effect in pulsed current assisted deformation

Gurson-Tvergaard-Needleman (GTN) model is one of the most famous and classical criterions widely used in modelling the ductile fracture process of metal. However, the existence of grain size effect affects the ductile fracture prediction in micro-scaled plastic deformation of nickel-based superalloy ultrathin sheet. In the pulsed current assisted (Pca) forming process, the current has a healing effect on the micro-void of metal due to the existence of local Joule heat, yet the strain has a promotion on the micro-void growth, and the coupled effect between grain size and electrical field is complicated, which makes it difficult to predict the fracture for the traditional GTN model in Pca forming process. To solve this problem, the authors added pulsed current parameters to the GTN model to describe the healing effect of pulsed current on the voids in the material. The parameters of the GTN model were calibrated by the finite element inverse identification method. The modified GTN model was embedded into Abaqus by VUMAT, and the Backward Euler algorithm was employed to integrate the constitutive equation. The validity of the model was verified by comparing the true stress-strain curves with the simulation results and comparing the void volume fraction (VVF) measured by three-dimensional X-ray computerized tomography (3DCT). The model provides a new method for ductile fracture prediction of multiphase alloys under a discontinuous energy field. Meanwhile, it is confirmed that the behaviour of fracture and necking in the Pca forming process is affected by the coupling effect of pulsed current and grain size effect, which provides a new idea for studying the Pca forming process.

Investigation on the effect of nickel and nickel-chromium alloy pulse current plating on copper substrate

ABSTRACT In the present study, nanocrystalline nickel (Ni) and nickel-chromium (Ni-Cr) alloy coatings were developed on copper (Cu) substrate using pulse current. The pulse current parameters include a cycle time of 240 milliseconds at a duty cycle of 0.5 and 4.17 Hz frequency. The surface morphology, texture, hardness, scratch resistance and porosity were investigated for different coatings developed by pulse plating. Energy Dispersive Spectroscopy (EDS) analysis revealed good quality Ni and Ni-Cr alloy coatings developed on the copper substrate. The peak current of the pulse has been observed to have an impact on the coating weight and thickness. The micrographs of the coatings explored under Field Emission Scanning Electron Microscopy (FESEM), depict uniform coatings consisting of fine primary and coarse secondary granules of Ni and Cr. The hard primary and secondary Ni granules deposited on the surface of Cu increase its hardness, corrosion and wear resistance. Further, it was observed that the Ni-Cr alloy plated samples are harder and less porous in nature compared to Ni plated samples.

Inhibition Behavior of Edge Cracking in the AZ31B Magnesium Alloy Cold Rolling Process with Pulsed Electric Current

To solve the edge crack problem of AZ31B magnesium alloy cold rolling, a strong pulsed electric current was introduced to the cold rolling process. The influence of intensity, frequency, width of pulsed electric current and other parameters on edge cracking of AZ31B magnesium alloy plate cold rolling was analyzed based on the principle of a single variable. According to the experimental results, the assistance of pulsed electric current cut down edge cracking and the inhibition effect increased obviously with larger current parameters. When the parameters of pulsed electric current reached 4800 A, 500 Hz, 50 μs, zero edge cracking was achieved. Statistics of edge cracks, rolling load change, and microstructure analysis showed that the current thermal effect was not obvious and non-thermal effect played a more important role in the rolling process under pulse electric current. Edge cracks initiate at the shear bands. The addition of pulse current increases the number of shear bands and presents a blanket structure. Therefore, the amount of strain experienced by a single shear band decrease, which has a positive effect on inhibiting the formation of edge cracks. Furthermore, electroplastic rolling refines the grains and weakens the basal plane. As the current parameter increases, the hardness of the magnesium strip decreases and the yield and tensile strengths increase.

Effect of pulse current parameters on electroplastically assisted dry cutting performance of W93NiFe alloy

Effect of pulse current parameters on electroplastically assisted dry cutting performance of W93NiFe alloy

Effect of Temperature on Current Pulse Characteristics of Negative Corona Discharge Based on Numerical Model

Temperature is an important factor affecting the dynamic processes of corona discharge, since the ionization, attachment, and mobility of charged particles are directly related to temperature. Most existing research has investigated the temperature effect on corona discharge through experimental works. However, they are hard to acquire the corona discharge microphysical processes, which are related to the formation of the current pulse and electromagnetic (EM) wave signals. This article proposes a numerical model with temperature-related transport parameters to study the temperature influence on microphysical processes and current pulses for negative corona. By comparing microphysical quantities such as the effective ionization coefficient, density, and velocity of space charges, the effect of temperature on the current pulse parameters including the rise and fall times, amplitude, and pulsewidth is systematically explained. It shows that as the temperature rises, the current pulse amplitude increases, while the other three parameters decrease. The rise time is dependent on the effective ionization coefficient. The fall time is affected by the velocities of negative and positive ions. The experimental results indicate the simulated current pulses are consistent with the measured ones, proving the effectiveness of the proposed numerical model with temperature variation.

Study of the influence of current pulse parameters on kinematic and energy characteristics of a plasma actuator based on a moving electric arc

In this work, a parametric study of the flow induced during the movement of an arc channel in a transverse constant magnetic field in initially still air is carried out. The analysis of the flow structure, integral energy and kinematic characteristics of the arc acceleration process is carried out. Instantaneous velocity fields in the induced flow were experimentally obtained for the range of discharge current amplitudes from 8 to 160 A and pulse durations from 40 to 380 μs. A parametric study of the flow structure in the wake behind the arc is carried out by the method of two-dimensional numerical simulation in the MHD approximation. In the particular case of a single-mode current pulse, the shape of the current pulse is optimized to maximize the gas momentum in the near-wall region. It is shown that similar conditions for the balance of local acceleration, convective acceleration and viscous forces are observed for the problem of flow past an arc and a cylinder for regimes with a conditionally steady vortex shedding in the wake. In this case, the coincidence of the vortex shedding frequency occurs when the characteristic scale of the streamlined body is chosen equal to half the height of the thermal cavity.

Plastic deformation of AZ31B magnesium alloy in the preform and electropulsing treatment process

Magnesium alloys exhibit poor formability at room temperature owing to their hexagonal close-packed crystal structure. In this study, a multi-step preform and electropulsing treatment method was applied to the plastic deformation of AZ31B magnesium alloy to improve its cumulative ductility. The mechanical properties, microstructure, and dislocation evolution were investigated using various parameters. The cumulative elongation of all specimens increased significantly, with the maximum approximately twofold higher for the initial specimens. Although the yield strength decreased after the first step, it increased with the following steps. After electropulsing treatment, the specimens were recrystallized and the dislocations were annihilated. The deformed microstructure caused by preform recovered and the recovery degree was associated with the preform and electropulsing treatment parameters. Therefore, the preform and electropulsing treatment method is effective to enhance the ductility of AZ31B magnesium alloy at room temperature, and a set of appropriate pulse current parameters can achieve satisfactory strength and elongation results. Moreover, the effect of the pulse current on the dislocation mobility and climb mainly accounts for the beneficial restoration during the preform and electropulsing treatment process.

Mechanical Behavior and Constitutive Modeling of the Mg-Zn-Y Alloy in an Electrically Assisted Tensile Test.

The Mg-Zn-Y alloy containing the LPSO phase has excellent mechanical properties and functional application prospects. In an effort to clarify the electrically assisted deformation behavior of the Mg-Zn-Y alloy, electrically assisted tensile tests of Mg98.5Zn0.5Y1 alloy sheets were carried out at different temperatures, current densities, duty ratios, and frequencies. The experimental results showed that, after the pulse current was applied (26.58 A·mm−2), the peak stress of the sample deformed at 200 °C decreased by 8 MPa. The peak stress of the material decreased with the increase in current density. It is noticeable that the changes in duty ratios and frequencies have a small effect on the peak stress and strain. When the current was applied, more recrystallized grains appeared in the alloy and the basal texture was weakened. According to the experimental results, the Arrhenius model was derived based on the Zener–Hollomon parameter. Owing to the appearance of the stacking fault structure (LPSO), the activation energy Q of the Mg98.5Zn0.5Y1 alloy was 389.41 KJ/mol, which is higher than conventional Mg alloys. Moreover, the constitutive equation of the electro plastic effect coupled with temperature and pulse current parameters was established by introducing electrically assisted characteristics. By comparing the experimental and predicted values, the established model can effectively predict the variation trend of flow stress under electrically assisted deformation. Moreover, the constitutive model was incorporated into the UHARD subroutine of ABAQUS software to study the deformation behavior of the Mg98.5Zn0.5Y1 alloy.

Fabrication of a Potential Electrodeposited Nanocomposite for Dental Applications

In the present study, a nanocrystalline Ni-Fe matrix with reinforced TiO2 nanoparticles as a functional nanocomposite material was fabricated by pulsed current electroforming in UV-LIGA (lithography, electroplating, and molding). The influences of TiO2 nanoparticles on the Ni-Fe nanocomposite deposition were also investigated using scanning electron microscopy, transmission electron microscopy, and in vitro cytotoxicity assay. It was found that the Ni-Fe nanocomposite with 5 wt.% TiO2 nanoparticles showed a smooth surface and better dispersion property. When the Ni-Fe nanocomposite is combined with 20 wt.% TiO2, it resulted in congeries of TiO2 nanoparticles. In addition, TiO2 nanoparticles possessed better dispersion properties as performed in pulse current electrodeposition. The microstructure of the electrodeposited Ni-Fe-TiO2 nanocomposite was a FeNi3 phase containing anatase nano-TiO2. Moreover, the electrodeposited Ni-Fe-5 wt.% TiO2 nanocomposite exhibited a smooth surface and structural integrity. Cytotoxicity assay results also proved that the Ni-Fe nanocomposite with different concentrations of TiO2 nanoparticles had good biocompatibility. Therefore, the optimization of pulse current electroforming parameters was successfully applied to fabricate the Ni-Fe-TiO2 nanocomposite, and thus could be used as an endodontic file material for dental applications.