Electric Current Pulses Research Articles

Eliminating reversible hydrogen embrittlement in high-strength martensitic steel by an electric current pulse

Hydrogen embrittlement has been a great issue in ultrahigh-strength automotive steel applications. Few studies on solving hydrogen embrittlement have been conducted in terms of removing hydrogen, and most studies focus on improving the resistance to hydrogen embrittlement through microalloying. In this study, an electric pulse was used to solve hydrogen embrittlement by removing hydrogen at 120 Hz (frequency), 180 μs (duration), and 200 A (current intensity). The temperature of the samples reached 105 °C under these parameters. Compared with the samples heat treated at the same temperature, the precharged samples processed by electric pulses had a lower hydrogen content and less ductility loss. Moreover, electric pulse processing can also reduce the approximate equilibrium concentration of hydrogen compared with heat treatment. This is due to the introduction of electrical free energy, which reduces the barrier to hydrogen diffusion, and pulsed electric current also accelerates the hydrogen diffusion.

The Convergence Model of Brain Reward Circuitry: Implications for Relief of Treatment-Resistant Depression by Deep-Brain Stimulation of the Medial Forebrain Bundle

Deep-brain stimulation of the medial forebrain bundle (MFB) can provide effective, enduring relief of treatment-resistant depression. Panksepp provided an explanatory framework: the MFB constitutes the core of the neural circuitry subserving the anticipation and pursuit of rewards: the “SEEKING” system. On that view, the SEEKING system is hypoactive in depressed individuals; background electrical stimulation of the MFB alleviates symptoms by normalizing activity. Panksepp attributed intracranial self-stimulation to excitation of the SEEKING system in which the ascending projections of midbrain dopamine neurons are an essential component. In parallel with Panksepp’s qualitative work, intracranial self-stimulation has long been studied quantitatively by psychophysical means. That work argues that the predominant directly stimulated substrate for MFB self-stimulation are myelinated, non-dopaminergic fibers, more readily excited by brief electrical current pulses than the thin, unmyelinated axons of the midbrain dopamine neurons. The series-circuit hypothesis reconciles this view with the evidence implicating dopamine in MFB self-stimulation as follows: direct activation of myelinated MFB fibers is rewarding due to their trans-synaptic activation of midbrain dopamine neurons. A recent study in which rats worked for optogenetic stimulation of midbrain dopamine neurons challenges the series-circuit hypothesis and provides a new model of intracranial self-stimulation in which the myelinated non-dopaminergic neurons and the midbrain dopamine projections access the behavioral final common path for reward seeking via separate, converging routes. We explore the potential implications of this convergence model for the interpretation of the antidepressant effect of MFB stimulation. We also discuss the consistent finding that psychomotor stimulants, which boost dopaminergic neurotransmission, fail to provide a monotherapy for depression. We propose that non-dopaminergic MFB components may contribute to the therapeutic effect in parallel to, in synergy with, or even instead of, a dopaminergic component.

Modeling dynamic recrystallization behavior of Al-Zn-Mg-Cu alloy during electroshock assisted tension based on cellular automata

Electroshock assisted forming of high-strength aluminum alloy is a new type of plasticizing manufacturing method. To study the dynamic recrystallization (DRX) behavior of Al-Zn-Mg-Cu alloy during low-frequency electroshock assisted tension, a cellular automata (CA) model coupled electro-thermal-mechanical multi-field effect was proposed on the Matlab platform. In the established CA model, the effect of additional driving force generated by the electric pulse on the dynamic recrystallization nucleation and growth has been innovatively taken into account. The grain diameters obtained by the above CA model are consistent with that obtained by the electron back scatter diffraction (EBSD) tests, which verified the accuracy of the model. The effects of current density and electrical pulse period on grain morphology, average grain diameter, DRX fraction, and grain size distribution were analyzed. Additionally, the optimal parameters of electroshock assisted tensile (current density of 30 A·mm−2, pulse period of 5 s) were predicted by the CA method. At this time, the DRX fraction increased to 45.79% and the fracture elongation of unidirectional tensile specimen increased by 21.74%.

Dynamics of the transition resistance of Al–(Ti, Ni, Mo)–Si type contacts under conditions of non-stationary electrical loads

This paper analyses the behavioral features of ohmic contacts under the conditions of traditional isothermal annealing. The purpose of this paper is to study the value change of the semiconductor contact resistance when applying electric current pulses of different powers. For the experiments, structures were formed of metal-sublayer-semiconductor wafer Al–(Ti, Ni, Mo)–Si. The quality control of the deposited films was carried out microscopically by the four-probe method. The presented results indicate the solid-phase interaction of components during diffusion annealing Si–Me–Al thin-film systems. This rearrangement of atoms, which occurs with grain-boundary diffusion, significantly affects the electrical and thermal characteristics of the formed contacts. The novelty of the paper is that the optimal parameters of a rectangular current pulse were selected, which made it possible to reduce the value of the transition resistance by 1.6 times.

Novel combinatorial microstructures in Ti-6Al-4V alloy achieved by an electric-current-pulse treatment

Abstract An electric-current-pulse (ECP) treatment was employed to rapidly heat a dogbone-shaped Ti-6Al-4V sheet. After the treatment, the alloy was modified from a single micrometer-sized structure to a shape-associated combinatorial counterpart. Coexisting with the original equiaxed coarsegrained α-Ti and the intergranular β-Ti, two kinds of novel ultrafine structures, nanometer-sized lamellar twins of β-Ti martensites and refined bimodal structure have been produced in the different parts of the bulk sample. Formation of the novel microstructures during the ECP treatment was systematically investigated. This work demonstrated that the ECP rapid heating treatment is a promising method to tailor the microstructures of the metallic alloys basically by designing the shape-associated distribution of the current density and offer a new possibility for improving the conventional alloys.

Regulating the recrystallized grain to induce strong cube texture in oriented silicon steel

• Cube texture contains two easy magnetization direction 〈001〉 parallel to rolling and transverse direction respectively, which is the most ideal magnetic texture suitable not only for transformers but also for rotating machines. In this study, strong cube texture with ODF density of 50.73 mrd was successfully obtained by controlling orientation using pulsed electric current in finished oriented silicon steel. • To transform from Goss to cube texture in oriented silicon steel, cross cold rolling process intentionally “created” metastable deformed cube orientation in oriented silicon steel. • The effects of Joule heating and heating rate on the cube recrystallization texture were distinguished, which fills a significant gap in our knowledge of the mechanism of pulse electric current induced texture transformation. • This idea of current-controlled texture is worthy of popularization in more materials and the realization of electromagnetic field to crystal orientation selection is an interesting topic. Cube texture contains two easy magnetization directions 〈001〉 parallel to rolling and transverse direction, respectively, which is the most ideal magnetic texture suitable not only for transformers but also for rotating machines. In this study, a strong cube texture with ODF density of 50.73 mrd was successfully obtained by regulating the recrystallized grain orientation using cross-rolling and pulsed electric current, compared to conventional thermal annealing (the average cube texture intensity is ~10 mrd in lots of latest studies). Cross cold rolling process intentionally “created” metastable deformed cube orientation in oriented silicon steel and the specific recrystallization texture rotation path was identified under pulsed electric current in 5 min: {114}<261>→{114}<151>→{114}<041>→{001}<150>→{001}<010>. The cube-oriented grains were induced by pulsed electric current (800 °C) and rapid heating (51.9 °C/s, 750 °C), while the cube grains were observed in the annealed samples at the high temperature (1060 °C). Recrystallized grain size of pulsed samples is about twice that of the annealed sample. This phenomenon is considered that the concurrent effects of electron wind force and Joule heating affected the nucleation, growth and rotation of cube grains by reducing the nuclear barrier, producing higher grain boundary mobility and structural evolution towards a state with lower electrical resistance. This idea of current-controlled texture is worthy of popularization in more materials and the realization of an electromagnetic field to crystal orientation selection is an interesting topic.

Моделирование дислокационного электропластического эффекта в монокристалле методом молекулярной динамики

The electro-plastic effect is a decrease in the resistance of metal crystals to deformation under the influence of a high-density pulsed electric current. Applying this effect allows deformation processing of relatively brittle metals without a sharp increase in temperature while reducing the probability of temperature negatively affecting the material. The paper discusses the influence of the electro-plastic effect on the change in the deforming force and the dislocations dynamics for a two-dimensional single crystal model based on the molecular dynamics method using the Morse potential. The authors propose a model implementing the electro-plastic effect by increasing the total kinetic energy of the system not uniformly over the entire crystal volume but depending on the potential energy of atoms. It is accepted that as a result of the electric current pulse traveling, the atom’s kinetic energy increases proportionally to the third degree of their potential energy. Atoms near defects have higher potential energy; therefore, the temperature will grow to a greater extent in the areas of defects, increasing their mobility. The authors simulated the motion of dislocations under the influence of shear stresses and temperature, considering the electric current pulse effect on the system. The paper describes the dependence of yield strength on temperature without taking into account the electro-plastic effect and then with it. The authors plotted the graphs of the dependence of the system’s kinetic energy on the frequency and the power of current pulses. The study shows that the electro-plastic effect sharply reduces the yield strength of a crystal, increasing the temperature in the system. It is caused by the fact that, besides general heating, the system is subjected to local heating of atoms near defects, which facilitates their motion.

Exchange spring-like inhomogeneous states in a ferromagnetic wire with current

Transverse structure of magnetization in a ferromagnetic film induced by magnetic field of electric current has been analyzed. Two steps of arising exchange spring evolution are shown. The first one (weak current) is gradual twisting of magnetization aside from the wire axis. Above some critical current the transient area is compressed and localized near the middle plane. In presence of additional conductive layer the transient structure becomes asymmetric resulting to non-zero lateral component of the net magnetization. It is shown also that the mentioned asymmetry can provide additional displacement of domain walls after the electric current pulses. Keywords: spintronics, domain wall dynamics, exchange spring, ferromagnet.

Multi-Channel, Actively Shielded, Power Efficient MRI Z-Gradient Cylindrical Coil Design Using Target-Field Method

Gradient coils are essential for MRI where fast and large electrical current pulses are typically applied to conventional, single-channel gradient coils, particularly for high-performance gradient applications. However, these pulses result in significant power losses and heating of the coil. We investigate the design of power-efficient multi-channel Z-gradient coils operating in the conventional mode comparing them to conventional single-channel coils designed using similar dimensions and alike DC performance characteristics. The power-efficiencies of thirteen different two-channel configurations having various section lengths for two different dimensions are analyzed. The current density of each section is approximated by Fourier series expansion where a linear equation relating the desired target field and current density is formulated and then solved. A stream function is derived from the obtained current density and then used to extract the final winding patterns of each section using a particular track width and a specific number of turns. The design process involves optimizing the current driving each channel, the distribution of coil windings, and the section size. Similarly, the performance of three-channel coils is also investigated. Results show that a power dissipation reduction of 17-28% and ~23% can be achieved using two- and three-channel coils, respectively. Moreover, we showed that multi-channel coils may have a slightly better shielding efficiency compared to conventional coils. A new methodology for designing two- and three-channel coils is presented where an advantage in terms of power efficiency can be gained depending on design parameters, coil’s dimensions, number of turns, and other metrics.

Increasing the fatigue resistance of aircraft parts magnetically impulse hardening

The results of fatigue tests of samples made of D16T aluminum alloy, treated by magnetic-pulse hardening (MPH) and the passage of a high-voltage pulsed electric current, are presented. It is shown that MPT increases the cyclic durability of samples by 2...2.5 times, regardless of the considered modes and hardening schemes during fatigue tests with loading by symmetric cantilever bending. However, there is a slight increase in fatigue life dissipation after this treatment. Passing a high-voltage pulse current through the sample increases the cyclic life by 1.9-2.4 times at a stress amplitude of fatigue tests of 320 MPa.

Numerical analysis of heating by a current pulse of a niobium nitride membrane in its longitudinal section

A numerical calculation of the evolution of the temperature distribution in the longitudinal section of a niobium nitride membrane when it is heated by an electric current pulse is performed. Mathematical modeling was carried out on the basis of a two-dimensional initial-boundary value problem for an inhomogeneous heat equation. In the initial boundary value problem, it was taken into account that current and potential contacts to the membrane serve simultaneously as contacts for heat removal. The case was considered for the third from the left and the first from the right initial-boundary value problem. Analysis of the numerical solution showed that effective heat removal from the membrane can be provided by current-carrying and potential clamping contacts made, for example, of beryllium bronze. This makes it possible to study the current-voltage characteristics of superconducting membranes near the critical temperature of the transition to the superconducting state by currents close to the critical density without significant heating.

ЗНЕЗАРАЖЕННЯ ПИТНОЇ ВОДИ ЗА ДОПОМОГОЮ ПЛАЗМИ ЕЛЕКТРИЧНОГО РОЗРЯДУ

For today, taking into account the low efficiency of the disinfection technologies using chlorine-containing compounds and the growing number of chlorine-resistant microorganisms, the question of introducing alternative methods of disinfection in the field of water supply and drainage is relevant. One such alternative method is the treatment of liquids with plasma of electric discharge. This article describes our experiments on the treatment of different types of water from surface sources in Kyiv and water intentionally infected with Escherichia coli (E. coli). The experiments were performed on a laboratory installation with a circulating pump and an ejector-type reactor with integrated electrodes. In the reactor a water-air mixture is formed, in which an electric discharge takes place. The disinfection reactor and at the same time the device for the formation of a heterogeneous water-air environment is an ejector with electrodes inserted into it, which receive pulses of electric current. Discharges initiate a range of different physicochemical phenomena, such as a strong electric field, intense ultraviolet radiation, shock waves of excess pressure and, in particular, the formation of various highly active chemicals such as radicals (OH •, H •, O •) and molecules ( H2O2, H2, O2, O3). All these physicochemical processes occur during the discharge itself, for example, the formation and action of short-lived radicals, as well as the action of relatively long-lived oxidants. The effect of the concentration of microorganisms on the rate and completeness of water disinfection was studied in technical (tap) water with the introduction into the reaction tank of the washoff from two test tubes. This provided an initial concentration of E. coli of 3.4 ∙ 106 CFU / cm3. Water treatment for 30 seconds reduced the concentration of microorganisms by two orders of magnitude (up to 5.4 ∙ 104). After 1 minute of treatment, this figure decreased to 1.7 ∙ 102, and after 3 minutes to 5.2 CFU / cm3, i.e., the treated water corresponded to norms for almost pure water. Experiments have proven the effectiveness of plasma disinfection, even for liquids with a concentration of microorganisms significantly exceeding the maximum allowable concentrations. The content of microorganisms before and after treatment was determined by the method of limiting dilution of samples with subsequent sowing on a nutrient medium in Petri dishes

Substantiating the pulse method for determining the time parameter of fire detectors with a thermoresistive sensing element

This paper substantiates the pulse method for determining the time parameter for fire detectors with a thermoresistive sensing element ‒ the time constant. The method is based on using the Joule-Lenz effect, which manifests itself when an electric current pulse passes through the thermoresistive sensing element of fire detectors. Thermal processes in such a sensing element are described by a mathematical model that belongs to the class of equations of mathematical physics. The solution to the differential equation of this class was derived using the Hankel integral transformation and is represented as a series relative to the Bessel functions. The resulting solution is used to construct a mathematical model of a thermoresistive sensing element in the form of a transfer function, which takes the form of the transfer function of the inertial link. To trigger the thermoresistive sensing element of fire detectors, a single pulse of electric current in the shape of a rectangular triangle is used. The integral Laplace transformation was applied to mathematically describe the response of a thermoresistive sensing element to the thermal effect of such a test influence. To obtain information about the time parameter of fire detectors with a thermoresistive sensing element, the ratio of its output signals is used, which are measured in the a priori defined moments. A two-parametric expression was built to determine the time parameter of fire detectors; a verbal interpretation of the pulse method to determine it was provided. The implementation of this method ensures the invariance of the time parameter of fire detectors with a thermoresistive sensing element relative to the amplitude of a single pulse of an electric current, as well as relative to the parameter that is included in its transfer coefficient.

Solidification microstructure characteristics of Cu–Pb alloy by ECP treatment

Abstract The effects of high-density electric current pulse (ECP) treatment on the solidification of Cu–37.4 wt% Pb monotectic alloy melt were investigated. Compared to the method of molten glass purification combined with cyclic superheating, ECP treatment created finer microstructures of Cu–Pb alloys, with more homogeneous distribution of the Pb phase in the matrix. This phenomenon can be explained by the cluster theory for liquid metals and the non-equilibrium diffusion theory. First, ECP treatment could cause the fission of larger atomic clusters to increase the undercooling that enabled a large number of smaller clusters to grow and reach the critical nucleation radius. Second, ECP treatment could reduce the diffusion energy barrier to enhance the non-equilibrium diffusion of solute atoms and suppress the segregation of Pb.

TEMPERATURE ERROR WHEN DETERMINING THE TIME PARAMETER OF A FIRE DETECTOR WITH A THERMORESISTIVE SENSITIVE ELEMENT

For fire detectors with a thermoresistive sensing element, a mathematical description of the reaction to the thermal action of an electric current pulse flowing through such a sensing element and having the shape of a right triangle is obtained. The mathematical description is constructed using the Laplace integral transformation and is shown to be a superposition of two Heaviside functions. The parameters of these functions are determined by the transmission coefficient and time constant of the thermoresistive sensitive element of the fire detector and the amplitude and duration of the electric current pulse. It is shown that the ratio of the output signals of the thermoresistive sensitive element of the fire detector at two a priori given moments of time can be used to determine the time parameter of the fire detector. The values ​​of a priori set moments of time, in which the temperature of the thermoresistive sensitive element of the fire detector is determined, are selected under the condition of simplicity of technical implementation. If there is a change in ambient temperature, it leads to a temperature error as a function of the time parameter of the fire detector. For such an error, a mathematical description is obtained in the general case, as well as for the case when the thermal influence on the thermoresistive sensitive element of the fire detector is due to the flow of an electric current pulse in the form of a right triangle. It is shown that the value of the temperature error has a minimum at the values ​​of the ratio of the output signals of the thermoresistive sensitive element of the fire detector at two a priori time points belonging to the range The value of this error does not exceed 4.9% with variations in ambient temperature, the value of which does not exceed 2.0%.

Critical Assessment of the Electric Effect in Electric Arc Welding

This work provides a critical assessment of electric effects on the microstructure evolution at the heat-affected zone in electric arc welding. Electric effects are the interactions between electromagnetic fields and materials’ microstructures. They differ from the arc effect and the Joule heating effect by providing an alternative contribution to nucleation, grain growth, recrystallisation and tempering. The influence of the electric effect on grain size, defects, anisotropic properties, precipitates and residual stress has been examined kinetically and thermodynamically. The use of adaptable electric current densities, pulse durations, pulse frequencies and electrode movements is suggested to achieve desirable microstructures and mechanical properties for the weldments.

Improvement of low-cycle fatigue life of austenitic stainless steel by multiple high-density pulsed electric currents

This study evaluated the low-cycle fatigue (LCF) life of type 316 austenitic stainless steel to determine the effect of multiple high-density pulsed electric currents (HDPECs). Fatigue properties were analyzed with the fatigue crack growth (FCG) and LCF tests by considering different conditions of multiple HDPECs and its application. The HDPEC densities of 100, 150 and 200 A/mm2 with application numbers from 1 to 17 times were used. The LCF results were assessed by using fatigue models, and the effectiveness of the application methods was examined. Under the HDPEC density of 200 A/mm2, increasing the number of HDPECs during the period of crack propagation is the best way for delaying FCG. Multiple applications of HDPEC caused a decrease in the length and an increase in the depth of striations in the specimen’s fatigue fracture surface, and the degree of ductility was increased thereby leading to the delay in FCG. The proposed conditions pave the way toward improving the LCF life of the material.

Pulsed Electrical Stimulation Enhances Consistency of Directional Migration of Adipose-Derived Stem Cells.

Electrical stimulation is a well-known strategy for regulating cell behavior, both in pathological and physiological processes such as wound healing, tissue regeneration, and embryonic development. Electrotaxis is the directional migration of cells toward the cathode or anode when subjected to electrical stimulation. In this study, we investigated the conditions for enhanced directional migration of electrically stimulated adipose-derived stem cells (ADSCs) during prolonged culture, using a customized agar-salt electrotaxis chamber. Exposure of ADSCs to a 1200 μA electric current for 3 h, followed by cessation of stimulation for 6 h and resumed stimulation for a further 3 h, increased directional cell migration toward the anode without inducing cell death. Moreover, Golgi polarization maintained the direction of polarity parallel to the direction of cell movement. Herein, we demonstrated that a pulsed electric current is sufficient to trigger directional migration of ADSCs in long-term culture while maintaining cell viability.

Stabilization of a nonlinear magnonic bullet coexisting with a Bose-Einstein condensate in a rapidly cooled magnonic system driven by spin-orbit torque

We have recently shown that injection of magnons into a magnetic dielectric via the spin-orbit torque (SOT) effect in the adjacent layer of a heavy metal subjected to the action of short (0.1 $\mu$s) current pulses allows for control of a magnon Bose-Einstein Condensate (BEC). Here, the BEC was formed in the process of rapid cooling (RC), when the electric current heating the sample is abruptly terminated. In the present study, we show that the application of a longer (1.0 $\mu$s) electric current pulse triggers the formation of a nonlinear localized magnonic bullet below the linear magnon spectrum. After pulse termination, the magnon BEC, as before, is formed at the bottom of the linear spectrum, but the nonlinear bullet continues to exist, stabilized for additional 30 ns by the same process of RC-induced magnon condensation. Our results suggest that a stimulated condensation of excess magnons to all highly populated magnonic states occurs.

A seasonal electric barrier blocks invasive adult sea lamprey (Petromyzon marinus) and reduces production of larvae

Sea lamprey (Petromyzon marinus) control is achieved in the Laurentian Great Lakes by applying lamprey-specific pesticides (lampricides) to habitats containing larval sea lamprey. Lampricide treatments cost less and are more effective in watersheds where dams block adult sea lamprey migration and limit larval distribution relative to watersheds with no barriers to migration. However, dams impound water and can block movement of valued fishes, outcomes that are untenable for some stakeholders. Here, a seasonal and non-physical barrier of pulsed direct electrical current was tested to block adult sea lamprey while also monitoring the movement and mortality of non-target fish species. The electric barrier was operated in the Black Mallard River, a tributary to northern Lake Huron, March through August 2016–2018. The electric field blocked adult sea lamprey; 1056 adult sea lamprey were captured downstream of the electric field and two were captured upstream of the electric barrier over the three-year study. In 2018, larval sea lamprey abundance upstream of the barrier was about 50% less than historical averages, and genetic analysis found that roughly 98% of larvae upstream of the barrier were spawned in years prior to barrier installation. When the barrier was electrified, non-target fish species were blocked, and a small percentage (<3%) were killed. This study demonstrated that a seasonally deployed electric barrier can reduce the abundanceoflarval sea lamprey upstream without impounding water, but effects on the movements and survival of other fish species remain a concern.