With the development of lightweight and precision, joining of small-diameter metal tubes, such as aluminum (AA) and stainless steel (SS), is increasingly required in high-end equipment manufacturing industries such as automobiles. Limited space and significant property differences make it difficult to obtain reliable bonding between small-diameter AA and SS tubes. Under such severe geometric constraints, conventional impact welding techniques often face challenges related to insufficient loading efficiency and process instability. This work investigates underwater electrical explosion welding (UEEW) as a feasible solid-state joining approach for the small-diameter AA and SS dissimilar metal tubes. An UEEW experimental platform was set up to achieve controllable underwater electrical explosion. The 9-mm-diameter SS 304 tube and 7-mm-diameter AA6063 tube welding experiments were carried out at discharge energies of 1.75, 2.52, 3.43, and 4.48 kJ. Well-bonded tubular joints were achieved when the discharge energy was 2.52 kJ, corresponding to a discharge energy condition derived from the impact loading requirement associated with the welding window. SEM and EDS were used to analyze the bonding interface. The results show the presence of wavy and vortex structures at the bonding interface with localized elemental diffusion, and intermetallic compounds have been found in some areas. These results demonstrate that underwater electrical explosion can provide effective impact loading for joining small-diameter dissimilar metal tubes and verify the feasibility of UEEW for tubular joining under limited geometric scales.

The rapid expansion of the nuclear power industry has intensified the demands for composite components including zircaloy and stainless steel. Driver-assisted electromagnetic pulse welding (EMPW) is a promising welding method for the fabrication of these composite components, where the driver thickness is one of the key parameters. However, current studies have not yet provided a sufficient insight of the thickness modification on the energy transfer process and welding effect. In this study, the basic principles and energy transfer process of copper-ring-driver-assisted EMPW are systematically explored. An index is proposed to quantify and predict the effect of driver thickness on the dynamic performance, where the local maximum is obtained when the thickness is equal to the skin depth of driver material. To reveal the spatial-temporal distribution of electromagnetic parameters, a multifield coupled finite-element simulation model is set. Based on the model, the energy transfer efficiency is calculated, where the optimized effect is found with driver thickness of 0.7mm. Experiments of copper-driver-assisted EMPW are conducted subsequently with different discharge voltages and driver thicknesses for welding zircaloy tube and stainless steel rod. Mechanical properties and microstructural characterization show that, within the selected parameters, welding effect of the zircaloy-stainless steel joint are optimal with 0.7-mm driver thickness, supporting the numerical analysis. This work provides a reference for the optimization of the EMPW technology in the field of nuclear power.

The connection quality of multi-layer workpieces such as tabs and busbars is key to lithium-ion batteries. Electromagnetic pulse welding, as a solid-state welding technology, can be used for welding these workpieces for lithium-ion batteries. However, the gaskets required for electromagnetic pulse welding are inconvenient to place and remove in the multi-layer structure. This work proposed an electromagnetic pulse welding method based on a double H-type welding coil and gradient through hole. The flyer was used to weld the busbar by the Lorentz force through the gradient through a hole, and each Cu tab was connected at the same time. When the discharge voltage was 11 kV, the metallurgical bonding of 1 mm-thick Al flyer, 6 layers of 0.3 mm-thick Cu tabs, and 1 mm-thick Al busbar was realized. Scanning electron microscopy and energy dispersive spectroscopy analysis were carried out from the welding interface perpendicular to the welding direction and parallel to the welding direction. The results showed that the typical electromagnetic pulse welding morphology was formed in the welding interfaces. Different from the welding interface parallel to the welding direction, complex transient zones and some defects were found in the welding interface perpendicular to the welding direction. The metal jet generated by the impact between the flyer and the busbar formed an intermetallic compounds transition zone with Cu tabs. The tensile test showed that the bonding strength of the electromagnetic pulse welding joint was good.

Pulsed power systems require compact high-voltage pulse generators with high current capability, where series–parallel configurations of semiconductor switches are inevitable. However, voltage imbalance in series devices and current mismatch in parallel branches significantly degrade system reliability under high-current pulsed conditions. In this work, a high-current solid-state Marx pulse generator based on a series–parallel IGBT configuration is proposed with a coordinated voltage balancing and current sharing strategy. A passive RC snubber is employed to suppress dynamic voltage imbalance, while a coupled inductor is introduced to mitigate transient and steady-state current mismatch. Simulation and experimental results demonstrate that the prototype achieves a peak output of 5 kV and 1000 A with adjustable pulse widths of 2–10 μs. The current imbalance degree is reduced from 45.8% to 3.1%, indicating significantly improved current sharing performance. The proposed method provides an effective and scalable solution for high-current pulsed power applications.

High-voltage ultrashort pulses with fast-rising edges have great prospects in the fields of biomedical, food sterilization, military weapons, and so on. It is hard to balance high-voltage and fast-rising edge requirements in the development of ultrashort pulse generators. This article proposed a novel high-voltage ultrashort pulse generator with a subnanosecond rising edge based on the diode opening switch (DOS) and the avalanche transistor module (ATM). By analyzing the output characteristics of DOS through the 1-D Poisson equation, the factors affecting the rising edge and amplitude in the circuit were determined, thereby determining the parameters of the DOS circuit. A pulse rising edge sharpening circuit has been designed based on the characteristics of avalanche transistor collector-emitter fast voltage rise rate conduction. The microstrip transmission line is designed as a sharpening capacitor to increase the voltage rise rate of energy. Furthermore, a PSPICE circuit simulation model was built to study the sharpening effect of ATM and the influence factors. Compared to existing DOS circuits with a rising edge of 3.1 ns, the prototype pulse generator developed in this article generates ATM-based ultrashort pulses with a rising edge of 0.6 ns and an amplitude of 4.2 kV and realizes an increase in output amplitude and a shortening of the rising edge at the same time.

This study aims to addresses the challenge of electromagnetic pulse welding (EMPW) laminated workpieces (tabs and busbar of lithium-ion batteries (LIBs)) for electric vehicles (EVs), where the tabs and busbar are normally stacked closely together without enough standoff distance that required for EMPW. We propose a novel EMPW method for laminated workpieces based on a gradient through-hole (GTH) structure without standoff distance. When the discharge energy was 15.75 kJ, a 1 mm-thick Al sheet (driver sheet), four layers 0.3 mm-thick Al sheets (tabs), and a 1 mm-thick Cu sheet (busbar) were successfully welded. The mechanical properties and contact resistance of the EMPW welded joint were tested. The influence of discharge energy on the mechanical properties of the joint was also investigated. Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), Electron Backscattered Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were used to characterize and analyze the bonding interface microstructure. The results show that a wavy interface is found between the driver sheet and the busbar. The AlCu intermetallic compounds are found, and grain refinement and element interdiffusion occur at the interface. There is no obvious boundary between each layer of tab. Compared with the straight through-hole (STH) structure, the EMPW welded joint obtained by the GTH structure achieves a larger contact surface area, better mechanical properties, and better electrical properties. This study provides a new EMPW method for welding laminated workpieces of the LIBs.

Efficient pretreatment of spent LiFePO4 cathode sheets requires selective separation of cathode coatings from aluminum foil while minimizing foil over-fragmentation. In this study, high-voltage pulsed discharge (HVPD) was employed as a physical pretreatment method to selectively delaminate cathode coatings from aluminum foil. Owing to the mechanical contrast between brittle cathode coatings and ductile aluminum foil, shock-wave loading induces selective interfacial failure and distinct fragmentation behaviors. A mechanically bounded stress window was established to rationalize the separation behavior and identify the voltage range for selective delamination. Experimentally, cathode powders were enriched in the fine fraction (<2 mm), whereas Al foil was concentrated in the coarse fraction (>2 mm). Under the tested HVPD configuration (140 mu F total capacitance, 10 mm electrode gap, and two pulses per batch), the best separation performance was obtained at 5 kV, corresponding to a separation efficiency of 98.84%. XRD and XPS analyses indicated no detectable changes in the crystal structure or chemical states of the recovered materials. Electrochemical tests further confirmed that the recovered LFP retained its electrochemical performance after HVPD treatment. An indicative gate-to-gate comparison further showed that HVPD required relatively low energy input (approximate to 1.72 MJ kg-1) and exhibited favorable process intensity compared with representative thermochemical and direct recycling routes. These results demonstrate the potential of HVPD as a controllable physical pretreatment route for selective recycling of spent LFP cathode sheets.

In recent years, the prevalence of modern flight data sensing systems, represented by quick access recorder (QAR), has made it viable to improve flight safety by analyzing massive flight parameters. However, the existing studies predominantly concentrate on predefined safety events, where the expert-annotated data are highly scarce and imbalanced. In this article, we address this issue by uncovering abnormal flight patterns from tremendous unlabeled data to discover potential and unexpected safety risks. To this end, we propose DUVET, a reconstruction-based dual view enhanced transformer model for flight data anomaly detection, which plays a vital role in aviation safety monitoring. Specifically, DUVET adopts patching and channel independence techniques to reduce model parameters and improve transformer's computational efficiency while preserving its semantic representation capacity. Based on the observation that flight safety risks usually relate to both long-term trend and short-term patterns, we creatively propose flight trend-aware attention and bell attention mechanisms to capture both global and local dependencies, enhancing the model reconstruction ability. We evaluate DUVET on six public real-world datasets and one QAR dataset, demonstrating that DUVET achieves the state-of-the-art performance in general time-series anomaly detection task. Further experiments on the QAR dataset show that DUVET meets key criteria of anomaly detection for flight safety in terms of stability, training efficiency and detection accuracy. Case study shows that DUVET can effectively uncover hidden flight safety risks.

The field-shaper is a key component in the electromagnetic pulse welding (EMPW) of tubular workpieces. However, during a single welding process, the metallurgical bonding occurs only at the corresponding edges of the field-shaper working area, resulting in a small welding zone. Thus, this paper proposed a kind of split-type field-shaper to extend the welding zone. Numerical analysis was used to analyze the distribution law of magnetic parameters and the kinetic behavior. AA1060 tubes and T2 copper rods were conducted with the split-type field-shaper and conventional field-shaper in the experiments. The mechanical property and microcosmic structure of joints were examined through Universal testing machine, Scanning Electron Microscopy and Energy Dispersive Spectroscopy. The findings revealed that the magnetic induction intensity and electromagnetic force under the split-type field-shaper were greater than those under the conventional field-shaper, and the collision angle and velocity were also larger. The width of the welding zone of the EMPW fabricated by split-type field-shaper increased by 26.6

Existing Electromagnetic Pulse Welding (EMPW) technology is only suitable for thin metal sheets around 1 mmthick. This study proposes an EMPW technique based on pulse current synergistic eddy current. This method directs pulse current through 1060 Al and T2 Cu plates to enhance Lorentz force, thereby increasing collision velocity. A simulation model is constructed, analyzing electromagnetic and motion parameters. The results indicate that at a discharge voltage of 15 kV, the tensile strengths of the 3 mm and 4 mm thick joints were 6373.72 N and 3009.24 N, respectively, with bond interface lengths of 3768 mu m and 2628 mu m.

Electromagnetic pulse welding (EMPW) achieves metallurgical bonding through high-velocity impact and intense plastic flow at the metal interface, making material hardness a critical parameter in joint formation. In this study, the effect of substrate annealing temperature on EMPW performance was investigated by controlling the hardness of magnesium alloy substrates through high-temperature annealing. Substrates were annealed at 0 degrees C, 100 degrees C, 300 degrees C, and 500 degrees C using a muffle furnace, followed by welding with a WD-28 EMPW system. The tensile strength of the resulting Mg - Al joints was measured, and interfacial morphologies were characterized. The results show that higher annealing temperatures led to lower substrate hardness, which significantly improved both the tensile strength and ductility of the joints. The lower threshold of the welding window decreased with increasing annealing temperature, making it easier for the collision point to enter the bonding window and resulting in longer metallurgical bonding lengths. At an annealing temperature of 500 degrees C, the substrate exhibited the lowest hardness (59.5 HV), the longest bonded interface length (690.1 mu m), and the highest tensile strength (3033 N), exceeding that of the base material. These findings demonstrate that substrate annealing plays a crucial role in enhancing weld quality in Mg - Al EMPW.

The valve-side bushing of a converter transformer is a critical component in ultra-high-voltage direct current (UHVDC) systems, making its monitoring through digital twin technology highly significant. However, the complex structure and spatio-temporal nonlinearity of the bushing result in a large computational demand for its digital twin model, which requires an effective order reduction algorithm. This paper proposes a Spatio-temporal Non-uniformity Proper Orthogonal Decomposition (SN-POD) algorithm considering the inhomogeneity of space and time consumption to meet the reduced-order computational requirements of UHV valve-side bushings. This proposed method reduces the calculation time to 10% of the full-order simulation model while controlling the error range of the key research area less than 0.1%. The test results show that this method has good robustness, calculation speed, and accuracy. This research can significantly enhance the computational efficiency of digital twin modeling for valve-side bushings and provide a technical foundation for constructing digital twin models for UHV valve-side bushings.

During the electromagnetic pulse welding (EMPW) process of tubes, the high-speed collision between outer tube and inner tube is easy to cause the shrinkage of inner tube, and it is difficult to form metallurgical bonding. In this work, a dual-coil EMPW method based on the synergies gained from compression coil and expansion coil was proposed, and a three-dimensional simulation model of EMPW process of aluminum alloy tube (outer tube) and stainless-steel tube (inner tube) with coupling the electrical-magnetic-mechanical was established. The distribution pattern of magnetic flux density, induced eddy current, Lorentz force and the movement process of tubes with the effect of dual-coil were analyzed. The results showed that the maximum induced eddy current densities of aluminum alloy and stainless-steel tubes were 7.54 × 1010 A/m3 and 3.31 × 1010 A/m3, respectively. The maximum Lorentz force densities of aluminum alloy and stainless-steel tubes were 8.31 × 1011 N/m3 and 6.59 × 1011 N/m3, respectively. Besides, the maximum collision velocity of the aluminum alloy tube was 772 m/s, while that of the stainless-steel tube was 166 m/s. As the collision velocity decreased and the collision angle increased, the collision velocity and angle match the welding window, indicating that the method is feasible.

Cu is widely used to fabricate highly efficient conductive coatings in the power electronics industry due to its exceptional electrical and ductility. To achieve higher spraying speed and better Cu coating quality, this article deeply studied the method of accelerated plasma spraying (APS) based on electromagnetic pulse welding (EMPW). A multiphysical field simulation model was constructed to study the plasma and Cu powder motion processes. The electromagnetic parameters, temperature, and Cu powder velocity were obtained. The relationship between electrode parameters and the Lorentz force was obtained by combining the plasma equation of motion with numerical analysis. The velocity of the Cu powder motion was obtained through the capture of the spraying process. The findings revealed that the electrode spacing exerted an influence on the plasma motion. The simultaneous impact of the compression shock wave and the Lorentz force propelled the Cu powder, which remained in the solid state, toward the ceramic. The Cu powder speed reached 1024 m/s and the maximum Cu coating thickness of 140 mu m was obtained when the discharge voltage was 5 kV. This study elucidated the mechanism of APS based on EMPW, thereby providing a theoretical foundation for APS in mechanism analysis and future applications.

Electromagnetic pulse welding (EMPW) represents a critical application of pulsed power technology in advanced manufacturing. However, conventional EMPW techniques exhibit relatively low efficiency in converting electromagnetic energy into the kinetic energy of the flyer, often requiring high voltage and large current to achieve reliable metallurgical bonding. To address this limitation, an enhanced EMPW method based on loading loop pulse current is introduced. By injecting an additional pulsed current into the flyer, the current density and resulting Lorentz force density are significantly increased, leading to a higher collision velocity and improved joint quality. A multiphysics finite-element model was established in COMSOL to investigate the distributions of current, magnetic field, Lorentz force, and collision velocity under the influence of the loaded pulse current. Experimental validation was conducted to support the numerical findings. Simulation and experimental results demonstrate that, at a discharge voltage of 7 kV, the proposed method achieves a Lorentz force density of 2.09 x 10(11) N/m(2) and a flyer collision velocity of 224.5 m/s. These values are comparable to those obtained in conventional EMPW at 10 kV, which produces a Lorentz force density of 2.03 x 10(11) N/m(2) and a velocity of 226.7 m/s. Despite comparable welding performance, energy consumption is reduced by approximately 51%, indicating a substantial improvement in the utilization of electromagnetic energy. The proposed approach offers a promising solution for improving energy efficiency in EMPW and supports broader industrial applications of this technology.

The wavy interface is the typical bonding interface in the electromagnetic pulse welding (EMPW) process, and the double-peak wave plays a crucial role in the wavy interface. This study investigates the formation of the double-peak wave structure at the wavy interface during magnesium-aluminum EMPW. A mechanism is proposed for the double-peak wave caused by the secondary Kelvin-Helmholtz (K-H) instability triggered by the second arrival of reflected shock waves at the interface. The multiphysics model was developed to analyze shock wave propagation and perturbation dynamics during the impact process of aluminum and magnesium plates, leading to the formation of the double-peak wave. The results reveal that the shock wave amplitude decreases to 24.5 % of its initial value upon reaching the bonding interface a second time. Despite this attenuation, the second interaction retains sufficient energy to trigger K-H instabilities again. This leads to the primary and double-peak waves evolving concurrently and superimposing, ultimately producing a distinct phenomenon where the minor double-peak wave is distributed atop the primary wave. Moreover, methods involving increased collision velocity and reduced metal plate thickness are proposed to achieve effective regulation of double-peak waves. When the discharge voltage was 15 kV, double-peak waves began to appear, and a large number of double-peak waves appeared when the thickness of the magnesium alloy plate was reduced to 0.2 mm. This study can provide the scientific basis for the formation mechanism and control of the bonding interface in the EMPW process.

Electromagnetic pulse welding (EMPW) technology as a solid-state welding technique, can be used for welding dissimilar metals such as zircaloy and stainless steel. However, both zircaloy and stainless steel belong to low conductivity and deformation difficulty workpieces, making it difficult to generate sufficient electromagnetic force for metal plastic deformation and high-speed collision in transient pulsed strong magnetic fields. In this work, a method for zircaloy—stainless steel (Zr-SS) plates by EMPW based on double H-shaped welding coil and dual drive mode was be proposed. EMPW comprehensive experimental platform was established to conduct Zr-SS welding experiments under the drive of dual aluminum alloy plates. The welding effect of Zr-SS plates joint was analyzed through macroscopic morphology, microscopic characterization, and tensile testing. The results showed that a typical EMPW morphology was formed between zircaloy and stainless steel. The Zr-SS bonding interface included flat interface, wavy interface, and vortex interface. Due to the more intense collision at the vortex interface, Fe(Cr, Zr)2 were discovered. The tensile testing results showed that the bonding strength of EMPW joint was higher than that of the substrate plate (zircaloy). This work can provide experimental basis for the industrial application of low conductivity and deformation difficulty workpieces welded by EMPW.

High-voltage nanosecond pulse generators with compactness and repetition frequency have become a vital demand in some fields. In this article, the principle of inductive energy storage (IES) is applied to twisted pair wire (TPW), which serves as an energy storage unit for generating nanosecond pulse. As a kind of transmission line, the electromagnetic field constraint of TPW is realized by twisting, so it has greater bent flexibility than a coaxial transmission line, which makes it possess higher 3-D space utilization. Furthermore, an isolated superposition device (ISD) based on TPW is proposed for modular stacking. The inductive isolation effect between adjacent modules produced by ISD can ensure a more efficient power superimposition. Their parameter selection methods are studied and the components are developed accordingly. The application of TPW and ISD with small volumes makes it easy to achieve a compact pulse generator. Experiments of single-module circuits and multimodule superposition are carried out to verify the feasibility. Finally, a compact ten-stage high-voltage nanosecond pulse generator prototype is built, with a voltage amplitude of 10 kV and pulsewidth of 10.6 ns. It can operate at a repetition frequency of 200 kHz.

Electromagnetic pulse welding (EMPW) of zircaloy (Zr) and stainless steel (SS) demonstrates significant potential in nuclear power applications. However, challenges arise due to the low conductivity and high yield strength of both materials. To address these limitations, high-conductivity, lowstrength metals such as copper and aluminum are used as driver components to provide the kinetic energy for collision. The driver thickness directly influences the motion behavior of Zr and SS, affecting the welding effect. In this work, a coupled electrical-magnetic-mechanical simulation model and an experimental platform were developed for Zr-SS EMPW driven by dual copper plates. The copper driver plate thickness was varied at $0.5,1,1.5$, and 2 times the skin depth ($\delta$). The results indicate that while the copper driver plate thickness does not affect the distribution patterns of magnetic flux density, induced eddy current, or Lorentz force within the plate, it affects their magnitudes. As the thickness of the copper driver plate increases, both the induced eddy current and the Lorentz force increase. When driven by $\boldsymbol{\delta}$-thick copper plates, the Zr and SS plates achieve the highest collision speed, facilitating welding conditions. In contrast, plates driven by copper plates of thicknesses $1.5 \delta, 2 \delta$, and $0.5 \delta$ exhibit progressively lower collision speeds, resulting in reduced welding efficiency. When the discharge voltage was 11 kV, welding was not achieved with $0.5 \delta$-thick copper driver plates. Analysis of the successfully welded Zr-SS joints revealed that as the copper driver plate thickness increased, the length of the bonding region and the tensile strength decreased, indicating a reduction in welding effect. The bonding strength of the Zr-SS joint welded with $\boldsymbol{\delta}$ thick copper driver plates exceeded that of the Zr base material, indicating the achievement of effective welding. This study provides valuable insights for the EMPW of metals with low conductivity and high deformation resistance.

Due to high current of 6300A, the bushing adopts a double conduit direct current carrying structure. The current carrying conduit refers to the bushing 60533 of the 170kV/6000A oil paper capacitor transformer supplied, which uses a diameter of the 105 copper tube. The relative error between the root mean square value of voltage meter reading and average value meter reading is much greater than 3%. The method is to divide the capacitor core into three parts, uniformly insert the 1-4 layers of auxiliary plates (small plates) with the length of 300-500mm into the insulation layer between main plates (large plates). it can be seen temperature has significant impact on polarity of interface charges. When experimental temperature is 40 degrees C, charge peak appears at interface 1 and a positive charge peak appears at the interface 2, and the charge amount increases with the time. When experimental temperature was at 80 degrees C, the positive charge peak appeared at interface 1 and the negative charge peak appeared at interface 2. The charge amount reached its maximum value at 5000s, and then showed decreasing trend.