Low Discharge Energy Research Articles

To investigate the effect of discharge energy and addition of nano-powder on processing of micro slots using EDM assisted µ-milling operation

ABSTRACT Micro-electric Discharge-Milling (µ-ED-M) is a non-contact process that uses an electrical spark to remove the material from a submerged workpiece with an electrode in a dielectric. The present paper focuses on optimizing process energizing (Capacitor, Voltage) and process stabilizing (Tool Travel Speed, Nano-Powder) parameters for controlling the size and surface characteristics of micro-crater. The present work focuses on the effect of nano-powder concerning dimensional aspects and surface characteristics at high and low capacitance levels. A µ-slot has been generated on the copper material by a tungsten carbide electrode. The experimentation is performed with two capacitor levels and three voltage and tool travel speed levels using full factorial design technique using with and without mixing of nano-powder in dielectric. The desirability functional multi-objective optimization approach is used to analyze the MRR, TWR, Width, and Depth. Field emission scanning electron microscopy (FESEM), non-contact optical profilometer, and x-ray diffraction (XRD) techniques are used to analyze the surface morphology of machined surfaces. The ANOVA is used to optimize the results; at low discharge energy, tool travel speed contributes 41% and promotes a higher thickness of recast layer 12.7 µm, whereas high discharge energy and nano-powder concentration contribute approx.—36% with 8.56 µm of recast layer.

Polypropylene nanocomposite film with enhanced energy storage performance via a continuous preparation

Dielectric polymers have been extensively employed in renewable energy conversion, hybrid electric vehicle, and high voltage direct current transmission systems, owing to their excellent electrical insulation, processability, and self-healing capability. However, the challenge lies in their relatively low dielectric constant (εr) and limited discharge energy density (Ue), which hinder the advancement of integrated power modules. Despite numerous efforts aimed at enhancing Ue, the fabrication of scalable dielectric film with both enhanced Ue and high charge–discharge efficiency (η) remains a major obstacle. Herein, the polypropylene-based films with BaTiO3@PP-g-MAH (BTO@PP-g-MAH) core–shell nanoparticles are prepared through a continuous melt extrusion process. The resulting nanocomposite film, incorporated with 5 wt% BTO@PP-g-MAH, exhibits an impressive Ue of 5.15 J cm−3 and achieves a high η of 93.2 % at 433 MV m−1, along with excellent cycle dielectric stability. Such enhancements in εr and Ue are ascribed to the improved interfacial polarization facilitated by BaTiO3 nanoparticles and the enhanced interface binding achieved through the PP-g-MAH shell layers. Furthermore, the enhancement of electric breakdown strength (Eb) is comprehensively investigated based on electrical breakdown mechanism and electromechanical breakdown model. This study demonstrates a novel strategy to prepare nanocomposite dielectric films that are compatible with commercial capacitor fabrication process.

Performance of pulsed plasma thruster at low discharge energy

As the size of satellites scales down, low-power and compact propulsion systems such as the pulsed plasma thruster (PPT) are needed for stabilizing these miniature satellites in orbit. Most PPT systems are operated at 2 J or more of discharge energy. In this work, the performance of a PPT with a side-fed, tongue-flared electrode configuration operated within a lower discharge energy range of 0.5‒2.5 J has been investigated. Ablation and charring of the polytetrafluoroethylene propellant surface were analyzed through field-effect scanning electron microscopy imaging and energy-dispersive X-ray spectroscopy. When the discharge energy fell below 2 J, inconsistencies occurred in the specific impulse and the thrust efficiency due to the measurement of the low mass bit. At energy 2 J, the performance parameters are compared with other PPT systems of similar configuration and discussed in depth.

Current Sheet Evolution in a Planar Inductive Pulsed Plasma Thruster

Abstract The evolution of the current sheet is fundamental to the understanding and operation of planar inductive pulsed plasma thrusters. Methods for experimentally determining the time-varying mutual inductance and plasma resistance associated with the current sheet are presented. From these, time-histories of the resistive heating in and electromagnetic acceleration of the sheet are found. Analysis of experimental data obtained from a compact, low discharge energy inductive pulsed plasma thruster shows that current sheet evolution is well described by three phases: ionization, formation, and acceleration. Evidence is provided for the plasma current and resistive heating becoming localized near the upstream edge of the current sheet as the sheet forms. The influence of initial propellant density and pre-ionization on the characteristics of the sheet are examined. Both higher propellant densities and increased pre-ionization are found to produce current sheets which exhibit greater magnetic impermeability. Higher densities cause the sheet to form closer to the coil face, improving coupling, while stronger pre-ionization leads to more rapid resistive heating, causing the sheet to form earlier in time.

Three-stage hybrid NSD/DC plasma assisted n-C5H12/O2/N2 ignition: Improved energy efficiency and reduced NOx/N2O emissions

This work presents a three-stage hybrid nanosecond discharge (NSD) and direct current (DC) discharge assisted n-C5H12/O2/N2 ignition with lower discharge energy and higher energy efficiency. The reaction rate coefficients between O2(a1Δg) and n-C5H12 are updated by mass/Master equation simulation. The promotive ignition enhancement via reaction channel O2(a1Δg) + n-C5H12 → C5H10 + H2O2 in the hybrid NSD/DC discharge is demonstrated. The results show that the ignition delay time of the three-stage hybrid plasma assisted ignition is 1–2 orders of magnitude shorter than that of the two-stage hybrid discharge when the reduced electric field strength in the DC discharge stage is over 10 Td. Meanwhile, the plasma-enhanced energy efficiency of three-stage hybrid discharge increases. This improved efficiency on ignition enhancement is due to the kinetic enhancement by the electronically excited species and radicals (O2(a1Δg), O(1D), N2(B) and O). The kinetic and thermal effects by plasma are effectively intergated to enhance ignition. However, more discharge energy deposited in the vibrationally excited states N2(v) in the two-stage hybrid discharge is less efficient on ignition enhancement due to the thermal contribution via vibrational-translational relaxation. In the aspect of NOx/N2O emissions, reduction efficiency of the three-stage hybrid discharge is two times higher than that of the two-stage hybrid discharge. By controlling the N/N(2D) production pathway e + N2 → e + N + N(2D), the three-stage hybrid discharge reduces NOx and N2O production by 61.1 % and 90 %, respectively. The results show that the ignition delay time is non-monotonically dependent on the discharge pulse number. There exist optimal pulse number, reduced electric field and effective threshold power density of DC discharge to achieve maximum ignition enhancement and low NOx/N2O emissions. This study provides valuable insights into the use of NSD/DC hybrid discharge technology in advanced engines to achieve energy-efficient ignition enhancement and reduce NOx/N2O emissions.

Powder-Mixed Micro-Electro-Discharge Machining-Induced Surface Modification of Titanium Alloy for Antibacterial Properties

The powder-mixed electro-discharge machining (PM-EDM) technique has shown its advantages in forming surfaces and depositing elements on the machined surface. Moreover, using hydroxyapatite (HA) powder in PM-EDM enhances the biocompatibility of the implant’s surfaces. Ti-6Al-4V alloy has tremendous advantages in biocompatibility over other metallic biomaterials in bone replacement surgeries. However, the increasing demand for orthopedical implants is leading to a more significant number of implant surgeries, increasing the number of patients with failed implants. A significant portion of implant failures are due to bacterial inflammation. Despite that, there is a lack of current research investigating the antibacterial properties of Ti-6Al-4V alloys. This paper focuses on studying the performance of HA PMEDM on Ti-6Al-4V alloy and its effects on antibacterial properties. By changing the capacitance (1 nF, 10 nF and 100 nF), gap voltage (90 V, 100 V and 110 V) and HA powder concentration (0 g/L, 5 g/L and 10 g/L), machining performance metrics such as material removal rate (MRR), overcut, crater size and hardness were examined through the HA PM micro-EDM (PM-μ-EDM) technique. Furthermore, the surface roughness, contact angle, and antibacterial properties of HA PM micro-wire EDM (PM-μ-WEDM)-treated surfaces were evaluated. The antibacterial tests were conducted for Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Bacillus subtilis bacteria. The key results showed a correlation between the discharge energy and powder concentration with the antibacterial properties of the modified surfaces. The modified surfaces exhibited reduced biofilm formation under low discharge energy and a 0 g/L powder concentration, resulting in a 0.273 μm roughness. This pattern persisted with high discharge energy and a 10 g/L powder concentration, where the roughness measured 1.832 μm. Therefore, it is possible to optimize the antibacterial properties of the surface through its roughness.

Dissolved Gas Analysis of Transformer: An Approach Based on ML and MCDM

In the electric power business, power transformers are one of the most common and expensive components. The conventional diagnostic tool for understanding insulation incipient failures is the dissolved gas analysis (DGA) of transformers. Nonetheless, interpreting DGA fault gases remains a significant difficulty for engineers. Along with offline methods, a number of computational approaches have been created for DGA fault classification. Still there exist significant hurdles in applying those methods for DGA fault classification. To establish an effective fault classification system, very diversified and massive DGA data sets of in-service transformers were collected from various utilities for this study. The dataset consists of 3147 instances with four classes: No fault, Thermal fault, Low energy discharge and high energy discharge. Models were built using various machine learning approaches like Quadratic Discriminant Analysis (QDA), Gradient Boosting (GB), Extra Trees (ET), Light Gradient Boosting Machine(LGBM), Random Forest (RF), K Nearest Neighbors (KNN), Naive Bayes (NB), Decision Tree (DT), Ada Boost (AB), Logistic Regression (LR), Linear Discriminant Analysis (LDA), Ridge Classifier, and SVM - Linear Kernel. The proposed work adopts Analytic Hierarchy Process (AHP) technique for the estimation of weights of the criteria. Based on the generated weights, the performance of the various classifiers is assessed and ranked using Multi-Objective Optimization based on the Ratio Analysis (MOORA) approach. QDA is selected as the best classifier model by the proposed technique.

Polycaprolactone/hydroxyapatite coating on spark generated Mg surfaces to promote anticorrosion and interfacial adhesion strength

Surface coatings have been widely accepted to tailor the degradation rate of Mg alloys for bioimplant applications. Nevertheless, poor adhesion strength resulting in debonding and delamination compromises their corrosion resistance. In the present study, Polycaprolactone/Hydroxyapatite (PCL/HA) coatings have been developed on different textured Mg surfaces obtained under optimized low discharge energy (LDE) and high discharge energy (HDE) conditions of wire electric discharge machining (WEDM). Since discharge energy influences the surface texture of WEDMed Mg alloy, coating on LDE treated surface (LDEedcoated) and coating on the fine-polished surface (Polcoated) showed homogeneous and defect-free coating morphology with contact angles (CA) of 87.85°, 94.05° with simulated body Fluid (SBF) while coating on HDE treated surface (HDEedcoated) displayed spatial defects, lowering the CA. On the LDEedcoated sample, physical anchoring, H2 bonding, and electrostatic interactions combinedly improved the coating's adhesion strength to 9.91 N, 4.5 times higher than the polished counterpart. LDEedcoated samples significantly suppressed the Icorr to 9.74 × 10−9 A/cm2, resulting in 75 % and 99.8 % higher corrosion inhibition efficiency (ηc) after 24 h compared to Polcoated and HDEedcoated samples. After 7 days of in-vitro immersion, the hydrogen evolution rate (HER) of the LDEedcoated sample (0.034 mL/cm2/day) was nearly 2.8 and 35 times lower than Polcoated and HDEedcoated samples, respectively. Superior anticorrosion performance and Ca-P rich apatite growth on LDEedcoated samples significantly improved the cellular viability of L929 cells. WEDM treatments at LDE settings offer a facile method for the preparation of 'substrate-anchored' coating systems with enhanced interfacial adhesion and anticorrosion performance on Mg alloys for clinical translation.

Investigation on a sustainable composite method of glass microstructures fabrication—Electrochemical discharge milling and grinding (ECDM-G)

Glass structures with microchannel morphology play an important role in the fields of biology, medicine and MEMS. The non-traditional machining methods currently used to machining glass have problems such as excessive energy consumption, poor sustainability, and harmful to operators and the environment. To achieve precision, efficient, green, sustainable production and save resources, a novel composite machining method of electrochemical discharge milling and grinding (ECDM-G) was proposed in this paper. Compared with tranditional electrochemical discharge machining, lower discharge energy is applied, and KH2PO4 solution is used as electrolyte instead of alkaline solution, thus realizing energy-saving and green machining. Compared with mechanical grinding, tool wear is reduced and the sustainability of machining is improved. In the theoretical part, the heat conduction process of electrochemical discharge was simulated and the softening effect of workpiece material was analyzed. Furthermore, the matching mathematical model between electrochemical discharge energy and material removal by grinding was established. So as to accurately control the energy and avoid waste. In the experiment part, the key parameters were determined through the Plackett-Burman experiment, and then the Box-Behnken experiment was conducted on the key parameters and the Response Surface Methodology (RSM) was used to obtain the optimal combination of machining parameters. Compared with mechanical grinding, the problems of edge collapse and breakage are solved. The overcut is reduced by 35.1%, the edge damage is reduced by 42.2%, the surface morphology is improved and the surface roughness value is reduced by 47.7%. Compared with ECDM, the problems of heat affected zone and thermal defects are solved. The overcut is reduced by 49.1%, the edge damage is reduced by 56.6%, the surface feather morphology is removed and the surface roughness value is reduced by 74.9%. The machining stability and consistency of ECDM-G method are analyzed by machining array microchannels. Finally, with the optimized machining parameters, the microfluidic chip with typical microchannel structure was fabricated by ECDM-G, and the tool electrode has no severe wear after machining the long path complex structure, which proves that ECDM-G can be an energy-saving, sustainable and effective method for machining precision glass microstructures with high quality, and further shows that ECDM-G has industrial application prospects in the manufacturing of key biological and medical components.

Crosslinking modification and hydrogen bonding synergy to achieve high breakdown strength and energy density of PMMA-co-GMA/PVDF dielectric composite films.

Polymer-based dielectric materials have been used in film capacitors due to their rapid charge-discharge rate, lightness, and low cost. Nevertheless, the energy storage properties of these dielectric films were limited by their weak polarization ability and low discharge energy density. Herein, the solution casting method was used to prepare all-organic crosslinked composite films using linear methyl methacrylate-co-glycidyl methacrylate (MG) as the matrix and ferroelectric poly(vinylidene fluoride) (PVDF) as the organic filler. The crosslinked MG networks can enhance the breakdown strength, restrain dielectric loss, and keep high discharge efficiency. What's more, the presence of PVDF can compensate for the low electrical displacement, improve the permittivity, and overcome the brittleness of the crosslinked films. The optimal all-organic crosslinked dielectric film exhibited an ultrahigh breakdown strength of 800 MV m-1 and a high efficiency of 77.4%. The maximum energy density of the composite film reached up to 12.1 J cm-3, which was nearly 120% higher than the energy density of 5.6 J cm-3 of the pure MG film. The enhancement in energy storage properties is ascribed to the synergistic effects of chemical crosslinking and hydrogen bonding. This study offers a feasible method for all-organic polymer films to fabricate energy storage equipment.

Interfacial microstructure and mechanical properties of the Al/Ti joint by magnetic pulse welding

Magnetic pulse welding (MPW) had attracted widespread attention due to its advantages on joining dissimilar metals. In this study, the joints of Al 1060/Ti-6Al-4 V dissimilar at different discharge energies were prepared to characterize the interface microstructure and to evaluate the tensile shear properties. The MPW joint consists of an annular welded zone and a central non-welded zone. The low discharge energies lead to joints with poor quality. A small amount of intermetallic compound (IMC) TiAl3 was formed at the welding interface due to mutual diffusion. With the increase of discharge energy, the failure mode changed from welding zone fracture to base metal fracture at the weaker side (Al side). The welding interface consists of four regions: transition zone, shear wave interface zone, sine wave interface zone and flat interface zone. Element diffusion is accompanied by the formation of dislocations, stacking faults (SFs) and deformation twins, which provides sufficient strain hardening ability for the interface. According to the element distribution and phase composition analysis results in the interface, the sound Al/Ti dissimilar joints are attributed to the wavy pattern in the interface.

Improving the Energy Storage Performance of All-Polymer Composites By Blending PVDF and P(VDF-CTFE).

Organic film capacitors have incredibly high power density and have an irreplaceable position in pulsed power systems, high-voltage power transmission networks and other fields. At present, the energy storage density and energy storage efficiency of organic film capacitors are relatively low, resulting in excessive equipment volume. The performance of organic film capacitors is determined by polymer materials, so it is crucial to develop a polymer composite with high energy storage density and high charge-discharge efficiency. Poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-CTFE)) is incorporated into the polyvinylidene fluoride (PVDF) matrix by solution blending. The successful preparation of the all-polymer composite material solves the problems of low breakdown electric field strength, low discharge energy density, and low charge-discharge efficiency of high-dielectric ferroelectric materials. The discharge energy density of the PVDF/P(VDF-CTFE) (70/30) film is more than twice that of pure PVDF due to the increase of phases α and γ and the decrease of crystallinity. Under the breakdown electric field (380kV mm-1 ), PVDF/P(VDF-CTFE) (70/30) film also has an ultrahigh energy storage efficiency of 64%. The relationship between the structure and properties of composite materials is investigated in this study, which has important implications for the development of capacitors with high energy storage density.

Dual-wafer intergrinding thinning by bipolar-discharge EDM with a capacity-coupled pulse generator considering large gap capacitance and minimization of discharge energy

The noncontact electrical discharge grinding technique has the potential to effectively grind thin, increasingly large-diameter wafers. This study proposes a bipolar electrical discharge machining (bipolar-EDM) method to realize the intergrinding of dual wafers, in which both wafers serve as the working electrode. A capacity-coupled (CC-type) pulse generator generates regular and identical bipolar discharges, ensuring symmetrical and stable removal of both wafers. Thus, both the energy efficiency and wafer thinning yield are doubled. The process characteristics are evaluated through equivalent circuit analysis and experiments, demonstrating that two thinned wafers exhibit high consistency in surface integrity and material removal rate (MRR). Moreover, the dual-wafer system causes an increase in the circuit resistance and gap capacitance, leading to a much lower discharge energy. This is beneficial for precision wafer grinding and thinning by electrical discharge machining (EDM) while keeping damage minimal. As a result, two Φ20 mm 4H–SiC wafers were thinned simultaneously with a maximum thinning rate of 3 μm/min. A mirror-like smooth surface (Ra < 80 nm) was obtained under finishing conditions, demonstrating its capability for precise wafer processing.

All-organic polymer dielectrics prepared via optimization of sequential structure of polystyrene-based copolymers

It is a great challenge to improve simultaneously the permittivity (εr) and breakdown strength of polymer dielectrics. The linear polystyrene (PS) has the advantages of low cost, easy processing and high charge-discharge efficiency (η). However, the low εr and low breakdown strength result in the low discharge energy density (Ue) of PS. For polar liquid crystalline polymer poly[11-((4′-cyano-[1,1′-biphenyl]-4-yl)oxy)undecyl methacrylate] (PCBMA), it shows the merit of high εr, low band gap width and good film-forming property. In this paper, random copolymers P(St-co-CBMA) and block copolymers PS-b-PCBMA were synthesized by radical polymerization and reversible addition-breaking chain transfer polymerization, respectively. The effect of sequential structure on the dielectric behaviors and energy storage properties of polystyrene copolymers is investigated in detail. The experimental results indicate that a high εr value of 5.2 (±0.049), an outstanding Ue of 8.94 J/cm3 and high η of 87.4% at 476 MV/m are achieved in random copolymer P(St-co-CBMA) with the 92 mol% content of CBMA unit because of the strong orientation polarization, deep traps and good film-forming property. This work demonstrates that it is a feasible strategy to obtain high performance polystyrene copolymer dielectrics via tailoring sequential structure between functional monomer and styrene monomer.

Outstanding discharge energy density and efficiency of the bilayer nanocomposite films with BaTiO3-dispersed PVDF polymer and polyetherimide layer

Dielectric polymer nanocomposite films have been widely studied because of their high polarization and electric breakdown strength, leading to high discharge energy density (Ud). However, nanocomposites with high Ud often show low discharge energy efficiency (η). In order to achieve both high Ud and η simultaneously, a series of novel bilayer polymer nanocomposite films composed of pure polyetherimide (PEI) layer and BaTiO3-dispersed poly(1,1-difluoroethylene) (BT/PVDF) layer were prepared by hot-pressing method in this work. The bilayer composites exhibit high η > 84% at 600 MV⋅m−1, which are much larger than most reported values (η < 70%). Specially, the highest η of 84.48% and Ud of 8 J·cm−3 at 600 MV·m−1 were obtained for the bilayer films composed of PEI and 3 vol% BT/PVDF layers, which is promising for pulsed power applications.

Numerical modeling of crater formation during electrical discharge machining of closed cell titanium foam

In this paper, the electrical discharge machining (EDM) is utilized to machine closed cell titanium foam using pure brass tool electrode. Discharge time, current and discharge voltage were taken as input factors. By varying these input factors discharge energy (E) alters. Hence, the effect of E on crater diameter is studied. A numerical simulation model using finite element analysis is developed to forecast the diameter of crater. Scanning electron microscope images were used to measure the experimentally formed crater. The crater diameter grows with the rise in E. The proposed numerical model is in good agreement with experimental results at low discharge energy and over predicts at higher discharge energy. The proposed model forecasts crater diameter with overall error of 5.57%.

A machine learning-based classification model to identify the effectiveness of vibration for μEDM

Micro electro-discharge machining (μEDM) uses electro-thermal energy from repetitive sparks generated between the tool and workpiece to remove material from the latter. However, one of the bottlenecks of μEDM is the phenomenon of short circuits due to the physical contact between the tool and debris (formed during the erosion of the workpiece). Adequate flushing of the debris can be achieved by applying low amplitude high-frequency vibration to the workpiece. This study, however, shows that the application of vibration does not yield beneficial results for the μEDM for all the parametric conditions. This research used an off-the-shelf piezo vibrator as the high-frequency, low amplitude vibration source to the workpiece during the μEDM process. The experiments were conducted with and without vibration with the variation of applied discharge energy and μEDM speed. The samples were characterized using scanning electron microscopes to gather various data related to μEDM outputs. The results of this study revealed that vibration-assisted μEDM becomes less effective as the discharge energy is increased (primarily by increasing the capacitor value of the RC pulse generator). Similarly, the reduction of the occurrence of the short circuit was profound when the low discharge energy level with low voltage and low capacitor setting of the RC Pulse generator was used. The overall scale of the overcut with various discharge energy and μEDM speed varied from 15.5 μm to 42 μm for the conventional μEDM process. However, the scale above slightly reduced to 14.5 μm to 39 μm using an ultrasonic vibration device. Also, the taperness of the machined hole was slightly reduced by applying the vibration device during the μEDM operation (overall average of ∼7%).

Combined effects of rainfall and flow depth on the resistance characteristics of sheet flow on gentle slopes

Rainfall and sheet flow (SF) on gentle slopes always appear concurrently. However, the combined effects of rainfall and flow depth on SF resistance are still unclear for gentle slopes. In this study, two sets of experiments, namely, upstream inflow with rainfall and upstream inflow only, were conducted to investigate the resistance characteristics of SF on a flat and smooth flume with three gentle slopes (3°, 5° and 7°). The experimental results indicated that in the tests with upstream inflow only, the Darcy–Weisbach resistance (f) and Manning coefficient (n) decreased following a power function with increasing flow depth. When the Reynolds number (Re) was less than 1070, the n and f of the SF in the upstream inflow alone decreased with increasing Re following the power function. Both the n and f of the SF increased with increasing rainfall intensity for the upstream inflow with the rainfall tests. The rainfall significantly affected the f and n of the SF in the low Re zone (Re < 1070), inflow discharge (<0.06 m2 min−1) and flow energy for all inflow with rainfall cases. Under the conditions of upstream inflow with rainfall, both the f and n of the SF decreased with the increase in the ratio between the flow depth and median raindrop diameter (H/D50) in the power function. This result indicated that a deeper flow could dissipate more raindrop energy. In addition, empirical equations among Re, hydraulic slope and H/D50 were established to predict the n and f of the SF for upstream inflow with rainfall tests. This study will be helpful in understanding the combined effects of rainfall and flow depth on SF and could provide a scientific basis for improving hydrological and soil erosion models.

A morphological and textural analysis of Inconel-718 aerospace alloy processed through electrical discharging machining

The Inconel 718 has captured global attention for its huge applications in the aerospace and defense field. However, a limited approach is noticed to investigate this material's responses and morphological features after electrical discharge machining operation. This study wants to offer a more detailed investigating approach, including the analysis of morphological features, recast layer, microhardness, elemental composition, and several textural defects and basic responses. Scanning electron microscopy is used to investigate several textural features, defects, cracks, and recast layers. The findings claim 538 nm–2.168 µm and 14–41 µm variations in crack width and recast thickness, respectively, which increase with pulse current and pulse on-time. However, the low discharge energy can provide better micro-hardness than higher discharge conditions due to having sufficient time for flushing and heat dissipations. The recast surface and the interfaces are, respectively, 7.58%–13.16% and 22.75%–32.74% harder with low discharge condition than the intermediate and higher discharge condition. Moreover, the Energy Dispersive X-ray analysis reported the emigration of 17.81% of carbon and 0.33% of copper from the dielectric and tool during the machining.

Electromagnetic Forming and Perforation of Tubes: Modeling, Simulation, and Validation

Abstract Electromagnetic forming and perforation (EMFP) is an innovative practice where magnetic forces are used for simultaneous forming and perforation operation. This method is complex, which involves a high strain rate as well as high transformation velocities. It is carried out in a short duration of time, and it includes multiple operations, which increases the complexity in understanding the shearing and forming behavior of the material. To understand this behavior, coupled and non-coupled simulation models have been developed and compared with experimental results. Material and failure models are used for simulating the material behavior at a high strain rate. At lower discharge energy, the coupled model failed to capture the initiation of perforation, but numerical results are found 96% in agreement with experimental results. While on the other hand, on the same discharge energy, non-coupled simulation shows 94% agreement and it succeeded in capturing the initiation of perforation. The von-Mises stresses found in all cases are more than 4e+08 Pa which is found higher than the ultimate strength of the material which is resulting in shearing. The failure patterns obtained in finite element analysis (FEA) simulation for both pointed and concave punch perforation show good agreement with general finding in experiments which shows the prediction capability of developed models.