Magnetic Pulse Research Articles

Design of the Working Coil to reduce of the Compressive Deformation of the Inner Tube in Magnetic Pulse Tubular Welding

Design of the Working Coil to reduce of the Compressive Deformation of the Inner Tube in Magnetic Pulse Tubular Welding

Development and Performance Evaluation of a Microcontroller Pulsed Magnetic Field Technique for Assisting Cellular Foods Freezing

Cellular foods have a short shelf-life due to the high water content and activity of microorganisms. Their water content is known to be magnetized when they are exposed to electromagnetic field, which is beneficial to their freezing. Although, magnetized water contained in cellular foods benefits freezing, but pulsed magnetic field technique available generates irregular wave patterns that are not promising to modern days freezing market. Therefore, the current study focuses on development and performance evaluation of a microcontroller pulsed magnetic field (MPMF) device for assisting cellular foods freezing. The MPMF technology consists of four main components including the magnetic field treatment chamber (120 mm x 90 mm x 60 mm), four electromagnets, and a step down transformer, a rectifier, capacitors, diodes, and a timer. The technology was operated at a voltage range and current of 2, 5, 7, 9, 11, 13 V, and 2.00, 12.60, 20.70, 28.60, 34.90, 38.60 A, respectively. The performance evaluation carried out on the machine includes magnetic field strengths and wave patterns. The results showed that the magnetic field strength varies between 9.15 to 42.96 T, and the wave patterns obtained were regular and satisfactorily. It is hope that the information on the development and evaluation of MPMF technique for assisting cellular foods freezing will be useful for the food industry

Formation mechanism for the interface between Cu and Sn formed by magnetic pulse welding

The formation of interfacial intermetallic compounds (IMCs) such as Cu6Sn5, Cu3Sn or platelet-shaped Ag3Sn which are formed in reflow soldering process will directly destroy the soldering reliability. Magnetic pulse welding (MPW), as a solid state welding technique can effectively restrain or even impede the formation of interfacial IMCs. In this paper, Cu and Sn dissimilar metals were welded by MPW under the discharge energy from 17 to 31 kJ. The typical wavy interface and metal jet flow were found in all samples. When the discharge energy reached 31 kJ, a typical gradient nanograined (GNG) interface has been observed to undergo an evolution from a sub-micron secondary solid solution of Cu6.26Sn5 IMCs to a nanoscale secondary solid solution of Cu81Sn22 IMCs, followed by the formation of nanoscale equiaxed α-Cu grains, and ultimately leading to the deformed elongated nanoscale α-Cu grains. This discontinuous distribution of the aforementioned phases occurs specifically at the interface of the 23 kJ_1.5 mm sample. In contrast, when subjected to a discharge energy of 17 kJ, there were no indications of a secondary solid solution of Cu6.26Sn5 IMCs or elongated nanoscale α-Cu grains. However, a discontinuous secondary solid solution of Cu81Sn22 IMCs was observed to form at the Cu/Sn interface under these conditions. Based on these findings, the utilization of microprojection welding (MPW) techniques involving Cu and Sn-based solder in the microscale is anticipated to serve as a highly efficient and automated technology within the field of electronic micropackaging.

Propagation dynamics of the Bloch-type domain wall on CoFeB nanostripes driven by a nanosecond magnetic pulse

Despite the abundance of research on the dynamics of magnetic domain walls (DW) on thin-film media, in-depth discussions regarding the behavior around the so-called Walker breakdown phenomenon are still scarce. In this work, propagation dynamics of the Bloch-type DW on CoFeB nanostripes with perpendicular anisotropy driven by a nanosecond magnetic pulse are investigated using micromagnetic simulation. It is found that on smaller nanostripes, the Walker breakdown corresponds with the oscillatory motion of the DW. On larger nanostripes, the formation of a Bloch-line with previously unreported behavior can be observed for magnetic pulses above HWB. Using a nanosecond field pulse instead of a continuous external field may allow for more direct control over the oscillatory DW motion and nucleation of the Bloch-line. A deeper understanding of the dynamics of the Bloch-type DW and its correlation to the applied nanosecond pulse may lead to better control of the DW for future spintronic devices.

Synchrotron X-ray operando study and multiphysics modelling of the solidification dynamics of intermetallic phases under electromagnetic pulses

In this paper, we used synchrotron X-ray radiography and tomography to study systematically and in operando conditions the growth dynamics of the primary Al3Ni intermetallic phases in an Al-15wt%Ni alloy in the solidification process with magnetic pulses of up to 1.5 T. The real-time observations clearly revealed the growth dynamics of the intermetallics in time scale from millisecond to minutes, including phase growth instability, side branching, fragmentation and orientation alignment under different magnetic pulse fluxes. A multiphysics numerical model was also developed to calculate the alternating and cyclic Lorentz forces and stresses acting on the Al3Ni phases and the nearby melt due to the applied pulses. Combining the results of the operando experiments and modelling, for the first time, the differential forces between the growing Al3Ni phases and the nearby melt were quantified. The forces can create slip dislocations at the growing crystal front which can further develop into nm and µm crystal steps for initiating phase branching. Furthermore, the magnitudes of the shear stresses are strongly related to the size, morphological and geometric features of the growing Al3Ni phases. Dependent on the magnitude of the shear stresses, phase fragmentation could occur in a single pulse period or in multiple pulse periods via fatigue mechanism. This systematic research work elucidate some of the long-time debated hypotheses concerning intermetallic phases growth instability and phase fragmentation in pulse magnetic fields. The research establishes a robust theoretical framework for quantitative understanding of the intermetallic phase growth dynamics in solidification under pulse magnetic fields.

Thermal–electrical coupling analysis based on solid–liquid phase transition theory of single-turn coil

Single-turn coil (STC) is a destructive pulse magnet aiming at a 100–300 T ultra-high magnetic field. A thermal–electrical coupling model, in which the solid–liquid phase transition process is considered, is proposed. The effects of solid–liquid phase transition on pressure, temperature, and electrical conductivity are investigated. The results show that the compressed and stretched regions coexist simultaneously, and the distribution of both regions changes with time during discharging. Moreover, the region with the highest current density is inside the conductor, since the phase transition reduces the electrical conductivity of the region near the inner surface of STCs. By comparison, the simulation results are highly consistent with the measured data, and the necessity of considering the phase transition process is validated. The results obtained in this work are helpful for understanding the thermodynamic process of STCs during discharge.

Flux jump and mechanical response in inhomogeneous high-temperature superconductor under the pulsed-field magnetization

The high-temperature bulk superconductors with high critical current density are brittle, and can be damaged by large Lorentz forces and thermal stress during magnetization. Several studies have reported the failure of bulk superconductors during flux jumps. In this study, we analyzed the magnetization characteristics and mechanical response of the HTS bulk with inhomogeneous current density along the c-axis. The numerical simulation was consistent with the experimental results presented in the reference. Moreover, a flux jump occurred near the area of the pre-arrangement flux during the second pulsed field magnetization. The maximum temperature is lower than the critical temperature during the flux jump. In the mechanical analysis, the flux jump led to an abrupt change in the maximum stress of the bulk, and the maximum radial stress was significantly higher than the maximum hoop stress during the flux jump. The maximum radial stress increased with decreasing ambient temperature during the flux jump, and the maximum stress area was always near the seeded plane. Subsequently, the magnetization characteristics and mechanical response were studied for different locations of the seeded surface, two concentric superconducting bulks, and non-uniform fields.

Analysis and Design of a Pulsed Power Generator for a Low-Energy Magnetic Pulse Welding System

Magnetic pulse welding (MPW) is a joining method that uses Lorentz force generated from an electromagnetic field. This method not only has the advantage of not causing thermal deformation of the material and no by-products compared to the method of joining by melting by heat but also enables the joining of dissimilar metals rather than the joining of the same metal. Joining dissimilar metals can reduce the weight of mechanical devices and apply them to various fields. Recent research on MPW has focused on the characteristics of bonding according to the material or structure of metal rather than on pulse power research that generates the main factor of operation. However, in the operation of MPW, a Lorentz force is generated by the induced current caused by the electromotive force created in the flyer tube and the external magnetic field in the actuator. Therefore, it is necessary to analyze and optimize the pulse power to improve reliability and to miniaturize the system to expand the MPW utilization range. In this paper, we analyzed MPW operation according to a section of the pulse power output waveform. A condition for obtaining the maximum current in the flyer tube was proposed, and a plateau-shaped waveform was derived as an ideal output waveform capable of maintaining the Lorentz force. Through analysis, the proposed pulse power device is designed as a pulse-forming network (PFN) that generates a plateau output waveform. The design specification is that the circuit of PFN (type E) is designed so that the output waveform is pulse width 10 (μs) and the maximum output current is 100 (kA), and it is verified by simulation.

Tunable Tesla-Scale Magnetic Attosecond Pulses through Ring-Current Gating.

Coherent control over electron dynamics in atoms and molecules using high-intensity circularly polarized laser pulses gives rise to current loops, resulting in the emission of magnetic fields. We propose, and demonstrate with ab initio calculations, "current-gating" schemes to generate direct or alternating-current magnetic pulses in the infrared spectral region, with highly tunable waveform and frequency, and showing femtosecond-to-attosecond pulse duration. In optimal conditions, the magnetic pulse can be highly isolated from the driving laser and exhibits a high flux density (∼1 T at a few hundred nanometers from the source, with a pulse duration of 787 attoseconds) for application in forefront experiments of ultrafast spectroscopy. Our work paves the way toward the generation of attosecond magnetic fields to probe ultrafast magnetization, chiral responses, and spin dynamics.

Electromagnetic radiation from electrically driven vehicles

The problem of electromagnetic radiation of vehicles exists and worries people, because it is not clear what is the safe level of frequency, intensity, time spent by drivers and passengers in vehicles, etc. The article is devoted to the disclosure of the problems of adverse effects of electromagnetic fields (EMF) and electromagnetic radiation (EMR) of modern hybrid and electric vehicles on drivers, passengers, pedestrians and the environment. The purpose of the study was to investigate the process of occurrence, propagation and impact of negative functions of electromagnetic radiation on biological objects, their propagation speed, flicker, wavelength and frequency, and radiation devices in electric and hybrid vehicles. The methodology of the article is based on the results of research by scientists from around the world and our own research and experiments, the results of which are presented in this article. The results of the scientific work are reviewed from researchers on this topic and their own tests are described The authors point out the need to measure electromagnetic radiation at the stages of their operation, repair and manufacture, since these vehicles running on electric traction generate magnetic fields that can violate electromagnetic safety. This is because electric vehicles have power plants, sensors, control, information and communication systems. Electric currents flowing through electric motors, power circuits, and batteries while driving generate magnetic fields (MFs) in the low frequency ranges (ultra low frequency (ULF), 0.001 - 10 Hz; extremely low frequency (ELF), 10 - 300 Hz).Higher harmonics of the electric field in electric vehicles and hybrid vehicles are generated by various electronic devices on board, information and communication systems. For example, in hybrid vehicles, magnetic pulses of up to 5 kHz are generated when the internal combustion engine is switched to electric mode. In addition, all types of cars generate a low-frequency pulsating magnetic field when the steel wheel disks rotate. The frequency f of this field is determined by the wheel speed and is usually f 20 Hz, but the spectrum also contains harmonics. The scientific novelty is that for the first time the concept of modeling and optimization of electromagnetic hazard assessment of electric vehicles and hybrid vehicles is presented, which has a unified approach to the study of the magnetic field regardless of the structure and design schemes of their power plants at the stage of operation; for the first time methods for assessing important parameters of the magnetic field of electric vehicles and hybrid vehicles at the stage of operation are developed based on the concept of optimal control of the power plant depending on the operating conditions. The practical significance is the originality, which lies in the fact that the authors have considered the problems of determining the moment of occurrence of traffic hazards in various road and transport situations and the technical hazards of various types of electric vehicles and hybrid vehicles.

Selection of design parameters of working coil for Al/Cu tubular Magnetic Pulse Welding

MPW produces a high Lorentz force for welding through the interaction of magnetic fields between the working coil and outer workpiece. Therefore, the design of the working coil is crucial in the MPW process. In particular, it is important to understand and estimate the distribution of Lorentz force on the outer tube and the stress on the working coil. These factors greatly impact the efficiency of energy delivery and the durability of the process. The purpose of this research was to analyze the effect of coil design parameters on the Lorentz force and stress. The ultimate objective was to optimize these design parameters specifically for welding tubular workpieces; for this, an electromagnetic-mechanical FE-model was developed. The design parameters considered in this study included the angle, radius, and protruding length. The Lorentz force and stress were calculated based on these parameters. Notably, the response surface method (RSM) and sequential quadratic programing (SQP) were utilized to develop a prediction model and optimize the design parameters, respectively. The findings revealed that the protruding length and angle are significant design parameters. Consequently, a working coil was manufactured using the optimized design parameters, leading to a successful Al/Cu joint. These results emphasize the indispensability of optimizing design parameters to achieve high-quality joints.

An innovative coil for magnetic pulse welding of dissimilar sheet metals: Numerical simulation and experiments

Magnetic pulse welding (MPW), as an environmentally friendly room temperature solid-state welding technology, usually involves low energy utilization efficiency, resulting in the need for higher energy to achieve metallurgical welding. This study proposed an innovative coil structure for increasing energy utilization efficiency during MPW. The current signal and structural strength of new coils with different turns were analyzed by numerical simulation. The results show that, different from traditional E-shaped and H-shaped single turn coils, the new structure can achieve nearly n-time amplification of current, which enabling the flyer plate to achieve the critical speed of metallurgical welding at lower energy. The 7-turn coil has higher structural strength and pulse current compared to the other coils in this study. The initial current was amplified 5.2 times by the 7-turn coil and welding of Al-Fe plates was achieved. The microstructures at the welding interface exhibit typical metallurgical features, including wave interfaces, element diffusion layers, and intermetallic compounds. The fracture location of the AA1060 (thickness δ: 0.5)-DP600 joint appeared on the base metal. The fracture morphology of AA5754 (thickness δ: 1.0)-DP600 joint shows that a large amount of aluminum element remains on the DP600 plate. Therefore, the new coil can increase the energy utilization rate during the welding process and achieve stable metallurgical welding of dissimilar materials.

Evolutionary Algorithm to Optimize Process Parameters of Al/Steel Magnetic Pulse Welding

The Magnetic Pulse Welding (MPW) process uses only electromagnetic force to create a solid-state metallurgical bond between a working coil and outer workpiece. The electromagnetic force drives the outer tube to collide with the inner rod, resulting in successful bonding. However, due to the dissimilarity of the MPW joint, only a portion of the interface forms a metallurgical bond, which affects the quality of the joint. Therefore, the purpose of this study is to analyze the effects of process parameters on joint quality through experimental work using RSM. Furthermore, an optimization algorithm is utilized to optimize the process parameters used in magnetic pulse welding. A1070 aluminum and S45C carbon steel were used as the materials, while peak current, gap between working coil and outer tube, and frequency were chosen as the process parameters for MPW. The welding conditions are determined through experimental design. After welding, the maximum load and weld length are measured to analyze the effect of the process parameters, and a prediction model is developed. Specifically, to achieve a high-quality joint, the process parameters are optimized using the Imperialist Competitive Algorithm (ICA) and Genetic Algorithm (GA). The results reveal that the peak current is a significant parameter, and the developed prediction model exhibits high accuracy. Furthermore, the ICA algorithm proves very effective in determining the process parameters for achieving a high-quality Al/Steel MPW joint.

Numerical simulation of macrosegregation phenomenon in Cu-6wt%Ag alloy ingots fabricated by electromagnetic stirring

The development and research of high strength and conductivity materials are essential for the advancement of high-field magnets, including pulsed magnets. This study investigates the effect of electromagnetic fields on the solidification casting of binary Cu-6wt%Ag alloy ingots with diameters of 40 and 160 mm. A 3D numerical simulation is performed utilizing the continuum model with conservation of total momentum, mass, energy, and species. The results indicate that applying electromagnetic stirring (EMS) to small cross-section ingots can cause many randomly distributed small regions with higher segregation degrees inside the ingot, which is not conducive to improving the macrosegregation inside the ingot. For large cross-section ingots without EMS, compared to small cross-section ingots, there is more severe macrosegregation inside the ingot, especially the extreme center segregation with a maximum segregation degree of about 414%. EMS can effectively control macrosegregation within a specific range and eliminate center segregation. When the linear EMS's magnetic induction intensity is set to 0.06 T, the maximum segregation degree near the ingot center can be reduced to less than 260%. Simultaneously, the EMS induced forced convection is also instability, leading to numerous haphazard solute accumulations and depletions, which explains many small segregation regions in the ingot. In terms of improving macrosegregation in large cross-section ingots, Linear EMS has a definite advantage over rotary EMS. It is possible to keep the entire segregation degree in the ingot below 100% when the linear EMS's magnetic induction intensity is set to 0.036 T and the stirring frequency is 4 Hz. The ideal stirring parameters range for linear EMS is to maintain the magnetic induction intensity at around 0.036 T and the stirring frequency in the range of 4–8 Hz.

Selection of Magnetic Pulse Crimping Process Conditions to Improve Crimped Terminal Quality

The crimping of copper terminals via hand-operated and hydraulic compressors is used to generate a compressive force between a terminal and a wire, generally on a worksite. However, this equipment often causes compression defects because non-uniform pressure is applied to the terminal surface in the radial direction during crimping. When the crimped terminal is connected to electrical parts such as the power transmission system, a low-quality crimped terminal can separate from the wire strands, increasing resistance to current flow through the terminal, energy loss, and the risk of fire due to overheating. For this reason, Magnetic Pulse Crimping (MPC), which can yield highly durable crimped terminals with uniform quality, has recently been developed. This process uses only the magnetic force generated by high electromagnetic interaction between the crimping coil part and the surface of the terminal, without physical contact. The objective of this research was to confirm the superiority of the MPC process over the conventional crimping process and then analyze the effects of the main process parameters, including the crimping length and the charge energy on the crimping part, so that this new process can be applied at worksites. To realize these goals, copper terminals and 35 mm2 copper wire strands were employed, and various types of crimping parts were manufactured under different crimping conditions. In particular, the distribution of electromagnetic force on the crimped parts were analyzed via numerical analysis. The crimping part performance was improved when the MPC process was applied to terminal crimping. In particular, decreasing the crimping length led to increased crimping quality, while increasing the charge energy caused increases in the compression ratio and pullout strength. However, excessively high charge energy caused the edge to break the wire strands; therefore, it is important to select the proper charge energy.

Sensorimotor integration in cranial muscles tested by short- and long-latency afferent inhibition

ObjectiveTo compressively investigate sensorimotor integration in the cranial-cervical muscles in healthy adults. MethodsShort- (SAI) and long-latency afferent (LAI) inhibition were probed in the anterior digastric (AD), the depressor anguli oris (DAO) and upper trapezius (UT) muscles. A transcranial magnetic stimulation pulse over primary motor cortex was preceded by peripheral stimulation delivered to the trigeminal, facial and accessory nerves using interstimulus intervals of 15-25 ms and 100-200 ms for SAI and LAI respectively. ResultsIn the AD, both SAI and LAI were detected following trigeminal nerve stimulation, but not following facial nerve stimulation. In the DAO, SAI was observed only following trigeminal nerve stimulation, while LAI depended only on facial nerve stimulation, only at an intensity suprathreshold for the compound motor action potential (cMAP). In the UT we could only detect LAI following accessory nerve stimulation at an intensity suprathreshold for a cMAP. ConclusionsThe results suggest that integration of sensory inputs with motor output is profoundly influenced by the type of sensory afferent involved and by the functional role played by the target muscle. SignificanceData indicate the importance of taking into account the sensory receptors involved as well as the function of the target muscle when studying sensorimotor integration, both in physiological and neurological conditions.

Transformation sequence of Mg-Si precipitates towards a precipitation of Mn and Cr containing phase governed by the high strain-rate collision during magnetic pulse welding of Al-Mg-Si alloy

This paper investigates the transformation of Mg-Si precipitates formed at an interface of an Al-Mg-Si alloy joint, welded by the high strain-rate collision during magnetic pulse impact welding. The Transmission Electron Microscopy (TEM) and Energy dispersive X-Ray (EDX) analysis of the precipitates reveal a nucleation of circular shape AlFeMnSiCr precipitate (size of ∼100 nm) from the dissolution of the native β″ (needle-shaped) precipitate. The AlFeMnSiCr phase can also reach a size up to several microns and grows into diverse shapes (rod-shaped, polygonal-shaped, ovoid-shaped). Based on the microstructural characterizations and on observations available in the literature including relevant data of Lodgaard and Ryum, the transformation sequence due to the high-speed collision can be described as follows: β″-Mg-Si (needle-shaped) → β’-Mg2Si (rod-shaped) ‘u-phase’ → Al(MnCrFe)Si (round-shaped) → Al(MnCrFe)Si +(+: Cr; Cu and/or Ni, rod-shaped, polygonal-shaped, ovoid-shaped). The comparison of samples welded at three different impact conditions (low impact intensity, intermediate impact intensity, high impact intensity) shows that the area fraction of the precipitates decreases with the increase of the impact intensity. The identification of the crystal structure of these different precipitates, from the nucleation to the final complete formation of the precipitation, can further enrich the transformation sequence in this paper. The role of the high strain kinematics on the deformation of the Al lattice and on the diffusion rate of alloying elements is also a perspective that can further explain this new observation of precipitation during magnetic pulse welding.

Evaluating the Effectiveness of Magnetic-Pulse Treatment for Healing Continuity Defects in the Metal of Oil and Gas Pipelines

This research paper addresses the issues in evaluating the effectiveness of magnetic-pulse treatment for healing continuity defects in the metal of oil and gas pipelines. A theoretical analysis of the magnetic-pulse action mechanism on continuity defects in the metal was carried out. The results of experimental studies of the effect of magnetic-pulse action on continuity defects of thick-walled samples, cut from used gas pipelines containing microcracks with different geometries, are also presented. The samples were processed under two different technological operating modes of the magnetic-pulse unit: the applied energy was 10 kJ for the first mode and 20 kJ for the second mode. The state of the cracks’ microstructure before and after the magnetic pulse treatment was studied using an optical microscope. As a result of the studies, it was found that magnetic-pulse treatment led to local heating of the crack tips, which was confirmed by the formation of a heat-affected zone in the vicinity of the crack tips. The temperature at the crack tips reached the metal’s melting point at the applied energy of 20 kJ, whereas at the energy of 10 kJ, signs of metal melting were not noted. In the course of the conducted experiments, it was found that the cracks were not completely eliminated after magnetic-pulse treatment; however, the edges of the crack tips melted, with subsequent filling by molten material. Magnetic-pulse treatment resulted in blunting of the crack tips, as their shape became smoother. It was established that the geometry and shape of the crack tip have significant influences on the effectiveness of this technology, as a narrow and sharp crack tip required less energy to reach the metal’s melting point compared to smoother one. The effect of magnetic pulse treatment on the microstructure of pipeline metal and its strength characteristics was also studied. It was found that this treatment leads to structural changes in the area of the crack tip in the form of grain refinement and subsequent strengthening of the pipeline metal.

Effect of the nanopores in the Al-Cu intermetallic phase on nanoindentation instabilities at the Al/Cu interface of a magnetic pulse impact weld

This paper investigates the features of an AlxCuy intermetallic phase produced by the high strain rate collision at an Al/Cu interface during magnetic pulse impact welding. A SEM observation coupled with a EDX analysis reveals a nanoporous Al2Cu phase. A mechanical characterization using a high resolution nanoindentation shows a P-h curve with a pop-in phenomenon which is attributed to the nanoporosity of the Al2Cu phase. As the nanoporosity fraction increases from ∼1 % to ∼6 %, the hardness decreases twofold with a linear tendency. The total cumulative length of pop-ins increases with the nanopores fraction, with a linear tendency also. The critical force of pop-ins is lowered by the porosity content. The curve of highest porosity fraction exhibits the lowest values of critical force. These observations correlate the nanopores to the pop-ins. Compared to the parent metals, the Al2Cu intermetallic phase exhibits a higher hardness in between 4 and 10 GPa.

Modification of the local structure and properties of zinc-substituted hexagonal barium ferrites for microwave devices under magnetic pulsed processing

The results of studies of the effect of magnetic pulse treatment on the local structure and magnetic properties of substituted ferrite for microwave devices are presented. The change in the magnetic properties of ferrites as a result of exposure to them by pulses of a weak magnetic field indicates the possibility of controlling the parameters of ferrites by means of a magnetic field and thereby influence the resonant characteristics of microwave devices based on them.