Duty Factor Research Articles

Temperature gradients in targets at low energy high-intensity ion implantation

This paper is devoted to the study of the gradient temperature field dynamics and distribution in the metal targets irradiated with high-intensity beams of gas ions. The investigations concerned ion implantation modes with the ion beam current density from several tens of mA/cm2 up to A/cm2 were presented. The ion beam power was varied due to the change of ion energy in the range from 0.6 to several keV and the pulse duty factor in the range of 0.2–0.8. The integral temperature of the target was measured with an electrically isolated thermocouple. To measure the dynamic change in the local temperature on the irradiated surface of target a high-temperature pulsed pyrometer KLEIBER 740-LO was used. Analysis of the experimental data obtained with the use of electrically isolated thermocouple, pulsed pyrometer, and numerical simulation revealed the presence of significant gradient temperature fields both over the surface and along the depth of targets irradiated by high-intensity ion beams.

J-PARC H- ion source and space-charge neutralized LEBT for 100-mA high energy and high duty factor LINACs.

In July 2019, a design beam of 8.3 × 1013 protons/pulse, whose 25 Hz operation produced the design beam power of 1 MW, was accelerated for 10.5 h by using the J-PARC 3 GeV rapid cycling synchrotron. During the operation, a J-PARC H- ion source and a 400 MeV linear accelerator (LINAC) were operated with the design beam duty factor (BDF) of 1.25% (0.5 ms × 25 Hz) and ejected beam intensities of 58 mA and 50 mA, respectively. Furthermore, as expected from the transverse emittances measured in an H- ion source test-stand, they were successfully operated with the BDF of 1.5% (0.6 ms × 25 Hz) and ejected beam intensities of 72 mA and 60 mA, respectively. In the operation, the beam pulse accelerated by the J-PARC radio-frequency quadrupole LINAC (RFQ) had a rapid rise-time of about 10 µs and an excellent flatness with a slow variation of ±0.2%. A flat beam pulse was produced by the predicted 100% space-charge neutralization (SCN) in the upstream half of the J-PARC low-energy beam transport (LEBT) with a vacuum pressure of 3.6 × 10-4 Pa and the unpredicted high and almost constant SCN of about 69% in the downstream half of the LEBT with a vacuum pressure of 2.8 × 10-5 Pa. The rapid rise-time was produced by the preformed 100% SCN with a preceding 100 µs 40 keV beam, which was not accelerated by the RFQ due to the low energy outside the RFQ acceptance. In the test-stand operated with the terminal voltage of 62 kV and BDF of 5% (1 ms × 50 Hz), the transverse emittances of a 100-mA beam were also measured to be suitable for the RFQs of high energy LINACs. A 100-mA high energy and high duty factor LINAC could be realized with this source since the transverse emittances were further improved by about 8% with the shortest beam extractor in the test-stand.

A Comparative Study of EDD and PM-EDD in Producing Holes in Inconel 718 Alloy

In recent times, aerospace, chemical industries and nuclear plant have usually used Inconel 718 alloy because of its excellent mechanical and chemical properties at elevated temperatures. It falls under the category of difficult-to-cut materials due to its high toughness, poor thermal conductivity and high hardness. The set-ups for electric discharge drilling (EDD) and powder-mixed electric discharge drilling (PM-EDD) were developed, and experiments were conducted on them separately. This research shows a comparative study amid producing holes by EDD and PM-EDD in Inconel 718 alloy workpiece with copper tool electrode. SiC was used as an abrasive powder because of its better thermal conductivity in order to get properly mixed with dielectric in a separate tank. Output response was assessed in the form of material removal rate, under the influence of discharge current, duty factor, pulse-on-time and tool speed, as the input parameters.

Controlling liquid crystal alignment by micro-patterned substrates

We propose a method of controlling the liquid crystal alignment at rubbed polyimide substrates by patterning them periodically with the focused ion beam. The pattern duty factor sets the alignment conditions which determine the light phase retardation that can be precisely varied in a range from zero to that of the background. The method opens up opportunities for creating tunable optical devices.

Effect of Mass-Center Position of Spinal Segment on Dynamic Performances of Quadruped Bounding with a Flexible-Articulated Spine

Driven by the layout design of devices arranged on the spine of quadruped robot which has a symmetry spine with a flexible joint, we explore the effect of mass-center position of spinal segment (MCPSS) on dynamic performances of quadruped bounding. A simplified model is introduced with MCPSS set as an independent parameter. Periodically quadruped bounding motions are generated to calculate different dynamic performances related to different MCPSS at the low, medium, and high horizontal speeds, respectively. The results indicate MCPSS corresponding to the optimal or suboptimal dynamic performances mainly gather at two positions: the hip joint and the geometric center of spinal segment. MCPSS near the hip joint leads to the largest stride period, stride length, and spinal oscillation-margin at all speeds. The smallest duty factor can also be obtained at the medium and high speeds. These improved inherent characteristics offer advantages in leg-orientation control and fast movement effectively. MCPSS near the geometric center of spinal segment brings the best self-stability, the smallest mass-center vertical fluctuation, and the smallest maximum foot-end force at all speeds, which should greatly enhance resistances to vertical jitters and reduce torque-demands of joint-drivers. This study should give useful suggestions to robot designs in reality.

Enhancing process capabilities of electric discharge machining for nonconductive ceramics

The application of nonconductive ceramic materials is growing in engineering and manufacturing field due to their properties such as high hardness, low thermal conductivity, and resistance to oxidation. But fabricating structures from such materials are difficult and most of the traditional machining techniques are not appropriate. The electrical discharge machining has become a popular machining process for machining nonconducting oxide and nonoxide ceramics such as alumina, silicon nitrides, SiAlON, and zirconium. In the present study, a technique to machine the nonconductive SiAlON ceramic, having resistivity of the order of 100000 Ω-cm is developed. An assistive electrode technique along with graphite powder mixed specially made dielectric mixture of hydrocarbon fluids was used for the electrical discharge machining process. The experiments were conducted according to the Taguchi design and analysis of variance using signal-to-noise ratios showcasing significant parameters and their optimal values for material removal, electrode wear, and size overcut achieved after electrical discharge machining. For multiparameter optimization, the grey relational analysis was carried out for response parameters with suitable weights. Analysis of variance on the grey relational grade showed discharge current, duty factor, and additive percentage as most significant parameters. As the central aim of this research is material removal, the significant parameters found for material removal rate were further used for response surface methodology and their optimum values as central design values for experimentation. A second-order response model was formulated to estimate the machining performance. To validate the study, confirmation experiments were carried out and predicted results have been found to be in good agreement with experimental findings. Based on the experimental investigations, it can be said that a novel and efficient technique has been developed to machine the high resistivity ceramics. The scanning electron microscopic images confirmed that material is removed mostly by spalling and no significant cracks are visible.

Optimization of Process Parameters in Micro-Electrochemical Discharge Machining by Using Grey Relational Analysis

Micro-electrochemical discharge machining is hybrid machining process which is based on combined principle of electro discharge machining and electro chemical machining. It is suitable for machining of both conductive as well as non-conductive materials. In this study a micro hole drilled on Ti-6Al-4V as work piece by varying machining parameters like electrolyte concentration, voltage and duty factor at three different levels. Orthogonal array L9 considered for design and performing experiments. The Grey relation analysis (GRA) was performed to optimize the output parameters i.e. material removal rate (MRR) and hole tapper angle (HTA). The result reveals that voltage was the most significant factor for both MRR and HTA followed by electrolyte concentration and duty factor. The maximum MRR and minimum taper angle are 1.50 mg/min and 0.98 ° obtained respectively. The GRA show optimal machining parameters at electrolyte concentration 3M, voltage 40 V and duty factor 25% respectively.

Novel deuteron RFQ design with trapezoidal electrodes and double dipole four-vane structure

RFQ-based neutron sources for various applications are being developed and constructed worldwide. To simplify RFQ structure and increase the effective shunt impedance, some novel design strategies have been investigated, including trapezoidal electrode modulations, the double dipole (DD) RFQ structure and use of an internal buncher dynamics strategy. Trapezoidal modulations based on 2TERM profiles are proposed to compensate for the variation of inter-vane capacitance, which helps to simplify rf electromagnetic design and field tuning. The double dipole (DD) four-vane structure increases mode separation without adding other equipment by modifying the RFQ undercut scheme. Furthermore, the entrance gap electric field between endplate and electrodes is designed as a longitudinal buncher, which makes the RFQ bunching section much shorter. By applying these considerations, a novel RFQ has been designed. It operates at 162.5 MHz with a duty factor of 1%, and can accelerate the 10 mA deuteron beam to 1.5 MeV. We have reduced the length of electrodes from 2.2 m to 1.8 m while maintaining transmission efficiency above 98.5%. The rf electromagnetic design has been carried out to fulfill the requirements of the resonant frequency, flat longitudinal field distribution and field tuning.

Subcutaneous priming of protein-functionalized chitosan scaffolds improves function following spinal cord injury.

Strategies using neural stem cells (NSCs) to aid regeneration following spinal cord injury (SCI) show much promise, but challenges remain regarding implementation and efficacy. In this work, we explored the use of an NSC-seeded scaffold consisting of covalently immobilized interferon-γ and rat NSCs within a hydrogel matrix (methacrylamide chitosan). We placed the scaffolds within the subcutaneous environment of rats, allowing them to incubate for 4 weeks in order to prime them for regeneration prior to being transplanted into a right lateral hemisection SCI model in the same animal. We found that subcutaneous priming reduced the lineage commitment of encapsulated NSCs, as observed by increased nestin expression and decreased NeuN expression. When combined with intracellular σ peptide administration (which reduces inhibition from the glial scar), subcutaneous maturation improved functional outcomes, which were assessed by BBB score and quantitative gait parameters (fore and hind limb duty factor imbalance, right and left paw placement accuracy). Although we did not observe any direct reconnection of the transplanted cells with the host tissue, we did observe neurofilament fibers extending from the host tissue into the scaffold. Importantly, the mechanism for improved functional outcomes is likely an increase in trophic support from subcutaneously maturing the scaffold, which is enhanced by the administration of ISP.

EDM ASSISTED BY MAGNETIC FIELD FOR ARMOURED STEEL

The present paper presents a study on the performance of electrical discharge machining (EDM) assisted by magnetic field for armoured steel (HV500). Response surface methodology (RSM) has been utilized to model, analyze and determine the optimal parameters setting in the EDM process assisted by magnetic field. The process performance criteria such as; material removal rate (MRR), tool wear rate (TWR), were evaluated. Peak current, magnetic flux density, duty factor, and dielectric fluid pressure have been considered the main factors affecting EDM assisted by magnetic field performance. RSM was employed to develop the experimental models. The EDM process assisted by magnetic field process has proved its adequacy to machine armoured steel alloy under acceptable metal removal rate and minimum tool wear rate. The metal removal rate generally increases with the increase of the magnetic flux density and peak current value. The effect of duty factor was limited and dielectric fluid pressure has a moderate effect. Further, the minimum tool wear rate has been obtained at the parametric combination of higher magnetic flux density and higher duty factor when machined by EDM assisted by magnetic field with copper electrodes. It has also been clarified that the effect of magnetic flux density was limited on metal removal rate with graphite electrodes. It has also been found that the minimum tool wear rate was obtained at the parametric combination of higher magnetic flux density, higher peak current and lower duty factor, when machined by EDM assisted by magnetic field, with graphite electrodes.

Optimization of Surface Topography of Electro- Discharge Machined Super Alloy Inconel 825: Using TOPSIS Integrated with Taguchi Philosophy

The aim of this research work is to find the optimum combination of input process parameters such as Peak Current(I P ), Open Voltage(V g ), Pulse-On-Time(T on ) & Duty Factor(τ) for machining of Inconel 825 on EDM using copper electrode. The experiment has been designed on 4 levels 4 factors i.e. L 16 orthogonal array. The output response parameters studied were Metal Removal Rate (MRR), Electrode Wear Rate (EWR) and Surface Roughness (R a ). During our study we have used Taguchi method to identify the proper control factors to obtain the optimum results of the process.

Keep calm and hang on: EMG activation in the forelimb musculature of three-toed sloths (Bradypus variegatus).

Sloths exhibit below branch locomotion whereby their limbs are loaded in tension to support the body weight. Suspensory behaviors require both strength and fatigue resistance from the limb flexors; however, skeletal muscle mass of sloths is reduced compared with other arboreal mammals. Although suspensory locomotion demands that muscles are active to counteract the pull of gravity, it is possible that sloths minimize muscle activation and/or selectively recruit slow motor units to maintain support, thus indicating neuromuscular specializations to conserve energy. Electromyography (EMG) was evaluated in a sample of three-toed sloths (Bradypus variegatus; N=6) to test this hypothesis. EMG was recorded at 2000 Hz via fine-wire electrodes implanted into two suites of four muscles in the left forelimb while sloths performed suspensory hanging (SH), suspensory walking (SW) and vertical climbing (VC). All muscles were minimally active for SH. During SW and VC, sloths moved slowly (duty factor: 0.83) and activation patterns were consistent between behaviors; the flexors were activated early and for a large percentage of limb contact, whereas the extensors were activated for shorter burst durations on average and showed biphasic (contact and swing) activity. Muscle activities were maximal for the elbow flexors and lowest for the carpal/digital flexors, and overall activity was significantly greater for SW and VC compared with SH. Wavelet analysis indicated high mean EMG frequencies from the myoelectric intensity spectra coupled with low burst intensities for SH, although the opposite pattern occurred for SW and VC, with the shoulder flexors and elbow flexor, m. brachioradialis, having extremely low mean EMG frequencies that are consistent with recruitment of slow fibers. Collectively, these findings support the hypothesis and suggest that sloths may selectively recruit smaller, fast motor units for suspensory postures but have the ability to offset the cost of force production by recruitment of large, slow motor units during locomotion.

Influence of Wear Pattern of Graphite Electrode on EDM Geometric Accuracy of Slot Machining

EDM is an effective method for deep and narrow slot machining. The high aspect ratio blind slot can be machined with jump motion and vibration assistance. The decrease in machining accuracy and actual depth caused by electrode consumption in this process are currently common problems. Using oil-based working fluids, graphite electrodes have different wear and deposition patterns under different conditions. This study aims to control the final geometric accuracy of deep and narrow slot machining by optimizing electrical parameters. Experiments using orthogonal design were conducted with a 20×1×20mm narrow slot. The combined influences of parameters on the electrode geometry evolution are concluded. The peak current and duty factor are the main factors affecting the pattern of electrode tip geometry. Experiments were carried out to analyse the wear pattern corresponding to different levels of these two factors. The locations where deposition and wear are prone to occur are found to be the edge of the electrode tip. Parameters combinations capable of stably maintaining the shape of the electrode end are found. The results showed the feasibility of adjusting the tip wear pattern. Thus the final geometric precision of the slot machining can be controlled by adopting apposite parameters.

Optimization of backpropagation neural network-based models in EDM process using particle swarm optimization and simulated annealing algorithms

In the present study, artificial neural network (ANN) along with heuristic algorithms, namely particle swarm optimization (PSO) and simulated annealing (SA), has been employed to carry out the modeling and optimization procedure of electrical discharge machining (EDM) process on AISI2312 hot worked steel parts. Surface roughness (SR), tool wear rate (TWR) and material removal rate (MRR) are the process quality measures considered as process output characteristics. Determination of a process variables (pulse on and off time, current, voltage and duty factor) combination to minimize TWR and SR and maximize MRR independently (as single objective) and also simultaneously (as multi-criteria) optimization is the main objective of this study. The experimental data are gathered using Taguchi L36 orthogonal array based on design of experiments approach. Next, the output measures are used to develop the ANN model. Furthermore, the architecture of the ANN has been modified using PSO algorithm. At the last step, in order to determine the best set of process output variables values for a desired set of process quality measures, the developed ANN model is embedded into proposed heuristic algorithms (SA and PSO) with which their derived results have been compared. It is evident that the proposed optimization procedure is quite efficient in modeling (with less than 1% error) and optimization (less than 4 and 7 percent error for single- and multi-objective optimizations, respectively) of EDM process variables.

Upgrading the LANSCE accelerator with a SNS RF-driven H- ion source.

The LANSCE accelerator is currently powered by a filament-driven, biased converter-type H- ion source that operates at 10%, the highest plasma duty factor for this type of source, using only ∼2.2 SCCM of H2. The ion source needs to be replaced every 4 weeks, which takes up to 4 days. The measured negative beam current of 12-16 mA falls below the desired 24 mA acceptance of the LANCSE accelerator. The SNS (Spallation Neutron Source) RF-driven, H- ion source injects ∼50 mA of H- beam into the SNS accelerator at 60 Hz with a 6% duty factor and an availability of >99.5% but requires ∼30 SCCM of H2. Up to 7 A h of H- have been produced during the 14-weeks-long source service cycles, which is unprecedented for small emittance, high-current, pulsed H- ion sources. The emittance of the SNS source is slightly smaller than the emittance of the LANSCE source. The SNS source also features unrivaled low Cs consumption and can be installed and started up in <12 h. LANSCE and SNS are working toward the use of SNS H- ion sources on the LANSCE accelerator because they could (a) fill the LANSCE accelerator to its capacity, (b) decrease the source replacement time by a factor of up to 7, and (c) increase source lifetime by a factor of about 4. This paper discusses some of the challenges that emerge when trying to match a different H- source into an existing injector with significantly different characteristics and operating regimes.

Effect of process parameters in the machining of Titanium alloy and high speed steel in powder mixed electrical discharge machining process

Weight reduction is an everlasting challenge in automobile industry, which obviously results in CO2 emission and fuel economy in the vehicles. The quest drives the automobile industry to introduce Titanium in the car engines during 1990s. Among the newer materials used in the vehicle engine, Titanium have been traditionally used due to its strength-weight ratio, corrosion resistant, aesthetic surface appearance and luxurious feeling. But, it poses a stiff challenge in conventional machining due to its hardness and chemical reactivity at elevated temperature. HSS, extensively used in making cutting tool, is equally poses a challenge in its machinability due to its higher hardness. To machine such hardest materials like Titanium and HSS, Powder Mixed Electrical Discharge Machine (PMEDM) can be used. In this study, the EDM process parameters such as current, duty factor and concentration of the Alumina powder mixed dielectric were considered as input parameters and material removal rate (MRR) and tool wear index (TWI) were taken as responses. Taguchi’s L9 orthogonal array was used to optimise the process parameters and main effect plots was used to find the effect of various process parameters on MRR and TWI.

Improving the efficiency of electroosmotic drying of electric motors insulation

The actual problem of electric motors (EM) operation associated with wetting of windings insulation is considered. A new method of EM drying based on electrokinetic phenomenon of electroosmosis was developed at the Department of Electrical Equipment of Vologda State University. It was shown that water molecules can take part in formation of non-mobile hydrated positively charged hydrogen ions. In this case, hydrogen ions become bound, lose their mobility and ability to take part in the process of electroosmotic drying (EOD). EOD efficiency is drastically reduced. It was proved that it is possible to prevent ion hydration, increase their mobility, penetration ability and, thereby, increase the EOD efficiency by applying a pulsed voltage component to the EOD process with a duty factor of 4. As a result, a new EOD method was developed using a pulsed voltage component that increases the speed of EM insulation drying by three times.

Optimization of LiNbO3/Quartz Substrate for High-Frequency Wideband SAW Devices Using Longitudinal Leaky Waves.

Multilayered structures can successfully replace single crystal substrates in high-performance surface acoustic wave (SAW) devices. A combination of high propagation velocity and strong piezoelectric coupling is required for acoustic modes used in wideband high-frequency SAW devices. These characteristics can be achieved simultaneously in SAW devices arranged on a lithium niobate (LN) thin plate bonded to quartz and using longitudinal leaky SAW (LLSAW) if the orientations of both the crystals and the plate thickness are optimized. This article describes an optimization procedure developed to find low-attenuated LLSAWs in layered structures that can be used in LN/quartz applications. The symmetry consideration of two crystals was followed by the optimization of the LN orientation to achieve the largest electromechanical coupling and by an analysis of quartz anisotropy as a crucial factor of the existence of nonattenuated LLSAWs. Finally, the quartz orientation and LN thickness were optimized by a rigorous numerical simulation of resonator admittances and by the extraction of LLSAW attenuation at resonant and antiresonant frequencies. The discovered structures enable the propagation of LLSAWs with velocities in the range of 5400-6000 m/s, electromechanical coupling up to 18%, and negligible attenuation. High Q -factors can be achieved at resonance and antiresonance by the variation of the duty factor in the same layered structure. The specific behavior of the LLSAW attenuation with a variation of the LN thickness and quartz cut angle is illustrated by contour plots for each of the optimal structures discovered.

Modeling of Surface Roughness of AISI 4340 Using Copper-Tungsten Tool in Die Sinking EDM

Abstract The present research focuses on modeling the surface roughness while machining AISI 4340 in a die-sinking EDM process using response surface methodology (RSM) with rotatable central composite design. The four process parameters are peak current, pulse on time, voltage and pulse duty factor having five levels and relation between these parameters and surface roughness was established. The ANOVA results have shown that the proposed model is significant with the present set of parameters level. An increasing trend of surface roughness was achieved with the parameters of EDM

Modeling of Black Layer and Tool Wear in EDM of AISI 4340 using Cu-W electrode

In this research, the modeling of the black layer formed on tool and its influence on tool wear is assessed while machining AISI 4340 in die-sinking EDM. Response surface methodology with rotatable CCD is used with peak current, pulse on duration, voltage and pulse duty factor as process parameters. Tool wear is estimated using the selected set of parameters. The results of ANOVA elucidates that the present model is significant. Pulse duty factor and peak current are found to have crucial significance on tool wear. The SEM images and EDX revealed that the black layer formed on the tool contains silicon, iron and oxygen along with carbon. At higher levels of pulse duty factor, the appearance of black layer is more distinct.