Search results for: Wire Electric Discharge Machining

Authors: Mohammad Hossain Validad

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Background and Aim: Epidemic keratoconjunctivitis is a type of conjunctivitis caused by adenoviruses that can spread rapidly through direct and indirect contact. The aim of this study was to evaluate the therapeutic effects of Povidone-Iodine 0.4% and 0.2% in improving the symptoms and signs of patients with epidemic keratoconjunctivitis. Materials and Methods: In this clinical trial study, 60 patients with a mean age of 27.8±8.4 years who were eligible for inclusion criteria were randomly divided into three groups. The first group received eye drops of Povidone-Iodine 0.4% and betamethasone 0.1%, the second group received PovidoneIodine 0.2% and betamethasone 0.1% and the third group received betamethasone 0.1%. Follow-ups were on the first, fourth, seventh and tenth days after starting treatment. Parameters examined at each examination were hyperaemia, mucopurulent discharge, eyelid edema, hemorrhage, and subepithelial infiltration. Results: The results showed that mucopurulent discharge on the fourth day of the examination (P = 0.005) and the seventh day of the examination (P = 0.001) were significantly different in the three treatment groups. Sub-epithelial infiltration on the tenth day after treatment did not show a significant difference in the 3 groups (P = 0.287). Conclusion: Based on the results of this study, Povidone-Iodine is more effective in relieving some of signs of EKC, such as reduced mucopurulent discharge than steroids alone.

Keywords: EKC, topical bethadine, adenovirus, sub epithelial opacity

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Authors: Tayyibah Khanam, Mohammad Saad Alam, Sanchari Deb, Yasser Rafat

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Electric vehicles are considered as viable replacements to gasoline cars since they help in reducing harmful emissions and stimulate power generation through renewable energy sources, hence contributing to sustainability. However, one of the significant obstacles in the mass deployment of electric vehicles is the charging time anxiety among users and, thus, the subsequent large waiting times for available chargers at charging stations. Data analytics, on the other hand, has revolutionized the decision-making tasks of management and operating systems since its arrival. In this paper, we attempt to optimize the choice of EV charging stations for users in their vicinity by minimizing the time taken to reach the charging stations and the waiting times for available chargers. Time taken to travel to the charging station is calculated by the Google Maps API and the waiting times are predicted by polynomial regression of the historical data stored. The proposed framework utilizes real-time data and historical data from all operating charging stations in the city and assists the user in finding the best suitable charging station for their current situation and can be implemented in a mobile phone application. The algorithm successfully predicts the most optimal choice of a charging station and the minimum required time for various sample data sets.

Keywords: charging data, electric vehicles, machine learning, waiting times

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Authors: Siming Wang, Qing Ni, Yu Wu, Ruihai Xu, Hong Ye

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Porous electric heaters, compared to conventional electric heaters, exhibit excellent heating performance due to their large specific surface area. Porous electric heaters employ porous metallic materials or conductive porous ceramics as the heating element. The former attains a low heating power with a fixed current due to the low electrical resistivity of metal. Although the latter can bypass the inherent challenges of porous metallic materials, the fabrication process of the conductive porous ceramics is complicated and high cost. This work proposed a porous ceramic electric heater with dielectric honeycomb ceramic as a substrate and surface conductive coating as a heating element. The conductive coating was prepared by the sol-gel method using silica sol and methyl trimethoxysilane as raw materials and graphite powder as conductive fillers. The conductive mechanism and degradation reason of the conductive coating was studied by electrical resistivity and thermal stability analysis. The heating performance of the proposed heater was experimentally investigated by heating air and deionized water. The results indicate that the electron transfer is achieved by forming the conductive network through the contact of the graphite flakes. With 30 wt% of graphite, the electrical resistivity of the conductive coating can be as low as 0.88 Ω∙cm. The conductive coating exhibits good electrical stability up to 500°C but degrades beyond 600°C due to the formation of many cracks in the coating caused by the weight loss and thermal expansion. The results also show that the working medium has a great influence on the volume power density of the heater. With air under natural convection as the working medium, the volume power density attains 640.85 kW/m3, which can be increased by 5 times when using deionized water as the working medium. The proposed honeycomb ceramic electric heater has the advantages of the simple fabrication method, low cost, and high volume power density, demonstrating great potential in the fluid heating field.

Keywords: conductive coating, honeycomb ceramic electric heater, high specific surface area, high volume power density

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Authors: Afsane Amiri

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Electric Vehicle (EV) technology is expected to take a major share in the light-vehicle market in the coming decades. Charging of EVs will put an extra burden on the distribution grid and in some cases adjustments will need to be made. In this paper a review of different plug-in and vehicle to grid (V2G) capable vehicles are given along with their power electronics topologies. The economic implication of charging the vehicle or sending power back to the utility is described in brief.

Keywords: energy storage system, battery unit, cost, optimal sizing, plug-in electric vehicles (PEVs), smart grid

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Authors: P. Treyer, M. Kujda, H. Urs

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The purpose of this paper is to digitally compensate for the apparent discharge time constant of the coaxial cable so that the current step response is flat and can be used to calibrate current transducers using the convolution method. For proper use of convolution, the step response record length is required to be at least the same as the waveform duration to be evaluated. The current step generator based on the cable discharge is compared to the Blumlein generator. Moreover, the influence of each component of the system on the performance of the step is described, which allows building the appropriate measurement set-up. In the end, the calibration of current viewing resistors dedicated to high current impulse is computed.

Keywords: Blumlein generator, cable attenuation, convolution, current step generator

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Authors: Ramin Rezaei, Terry Ng, Abdollah Afjeh

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Near wake development of a wind turbine affects the aerodynamic loads on the tower and the wind turbine. Design considerations of both isolated wind turbines and wind farms must include unsteady wake flow conditions under which the turbines must operate. The consequent aerodynamic loads could lead to over design of wind turbines and adversely affect the cost of wind turbines and, in turn, the cost of energy produced by wind turbines. Reducing the weight of turbine rotors is particularly desirable since larger wind turbine rotors can be utilized without significantly increasing the cost of the supporting structure. Larger rotor diameters produce larger swept areas and consequently greater energy production from the wind thereby reducing the levelized cost of wind energy. To understand the development and structure of the near tower wake of a wind turbine, an experimental study was conducted to describe the flow field of the near wake for both upwind and downwind turbines. The study was conducted under controlled environment of a wind tunnel using a scaled model of a turbine. The NREL 5 MW reference wind turbine was used as a baseline design and was modified as necessary to design and build upwind and downwind scaled wind turbine models. This paper presents the results of the wind tunnel study using turbine models to quantify the near wake of upwind and downwind wind turbine configurations for various lengths of tower-to-turbine spacing. The variations of mean velocity and turbulence are measured using a computer-controlled, traversing hot wire probe. Additionally, smoke flow visualizations were conducted to qualitatively study the wake. The results show a more rapid dissipation of the near wake for an upwind configuration. The results can readily be incorporated into low fidelity system level turbine simulation tools to more accurately account for the wake on the aerodynamic loads of a upwind and downwind turbines.

Keywords: hot wire anemometry, near wake, upwind and downwind turbine. Hot wire anemometry, near wake, upwind and downwind turbine

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Authors: Mazen Al-Bulaihed, Nissar Wani, Abdulrahman Al-Arainy, Yasin Khan

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Partial Discharge (PD) measurements are widely used for diagnostic purposes in electrical equipment used in power systems. The main cause of these measurements is to prevent large power failures as cables are prone to aging, which usually results in embrittlement, cracking and eventual failure of the insulating and sheathing materials, exposing the conductor and risking a potential short circuit, a likely cause of the electrical fire. Many distribution networks rely heavily on medium voltage (MV) power cables. The presence of joints in these networks is a vital part of serving the consumer demand for electricity continuously. Such measurements become even more important when the extent of dependence increases. Moreover, it is known that the partial discharge in joints and termination are difficult to track and are the most crucial point of failures in large power systems. This paper discusses the diagnostic techniques of four samples of XLPE insulated cable joints, each included with a different type of defect. Experiments were carried out by measuring PD and tanδ at very low frequency applied high voltage. The results show the importance of combining PD and tanδ for effective cable assessment.

Keywords: partial discharge, tan delta, very low frequency, XLPE cable

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Authors: Hany Mohamed Abdu, Mohamed Hassan Gadallah, El-Giushi Mokhtar, Yehia Mahmoud Ismail

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Laser beam cutting is one nontraditional machining process. This paper optimizes the parameters of Laser beam cutting machining parameters of Stainless steel (316L) by considering the effect of input parameters viz. power, oxygen pressure, frequency and cutting speed. Statistical design of experiments are carried in three different levels and process responses such as 'Average kerf taper (Ta)' and 'Surface Roughness (Ra)' are measured accordingly. A quadratic mathematical model (RSM) for each of the responses is developed as a function of the process parameters. Responses predicted by the models (as per Taguchi’s L27 OA) are employed to search for an optimal parametric combination to achieve desired yield of the process. RSM models are developed for mean responses, S/N ratio, and standard deviation of responses. Optimization models are formulated as single objective problem subject to process constraints. Models are formulated based on Analysis of Variance (ANOVA) using MATLAB environment. Optimum solutions are compared with Taguchi Methodology results.

Keywords: optimization, laser cutting, robust design, kerf width, Taguchi method, RSM and DOE

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Authors: Prateek Saxena, Sanjeev Singh, Julius Roy

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The security of the power distribution grid remains a paramount to the utility professionals while enhancing and making it more efficient. The most serious threat to the system can be maintaining the transformers, as the load is ever increasing with the addition of elements like electric vehicles. In this paper, intelligent transformer monitoring and grid management has been proposed. The engineering is done to use the evolving data from the smart meter for grid analytics and diagnostics for preventive maintenance. The two-tier architecture for hardware and software integration is coupled to form a robust system for the smart grid. The proposal also presents interoperable meter standards for easy integration. Distribution transformer analytics based on real-time data benefits utilities preventing outages, protects the revenue loss, improves the return on asset and reduces overall maintenance cost by predictive monitoring.

Keywords: electric vehicle charging, transformer monitoring, data analytics, intelligent grid

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Authors: Chia-Chia Chang, Jhen-Ting Huang, Hu-Cheng Weng, An-Ya Lo

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This study developed a simple hierarchical porous carbon (HPC) synthesis process and used for supercapacitor application. In which, mesopore provides huge specific surface area, meanwhile, macropore provides excellent mass transfer. Thus the hierarchical porous electrode improves the charge-discharge performance. On the other hand, cerium oxide (CeO2) have also got a lot research attention owing to its rich in content, low in price, environmentally friendly, good catalytic properties, and easy preparation. Besides, a rapid redox reaction occurs between trivalent cerium and tetravalent cerium releases oxygen atom and increase the conductivity. In order to prevent CeO2 from disintegration under long-term charge-discharge operation, the CeO2 carbon porous materials were was integrated as composite material in this study. For in the ex-situ analysis, scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM) analysis were adopted to identify the surface morphology, crystal structure, and microstructure of the composite. 77K Nitrogen adsorption-desorption analysis was used to analyze the porosity of each specimen. For the in-situ test, cyclic voltammetry (CV) and chronopotentiometry (CP) were conducted by potentiostat to understand the charge and discharge properties. Ragone plot was drawn to further analyze the resistance properties. Based on above analyses, the effect of macropores/mespores and the CeO2/HPC ratios on charge-discharge performance were investigated. As a result, the capacitance can be greatly enhanced by 2.6 times higher than pristine mesoporous carbon electrode.

Keywords: hierarchical porous carbon, cerium oxide, supercapacitor

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Authors: John Yahng, Hansraj Riteesh Bookun

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Objective: This was a retrospective cross-sectional study evaluating the safety of discharge on the first postoperative day following carotid surgery - principally carotid endarterectomy. Methods: Between January 2010 to October 2017, 252 patients with mean age of 72 years, underwent carotid surgery by seven surgeons. Their medical records were consulted and their operative as well as complication timelines were databased. Descriptive statistics were used to analyse pooled responses and our indicator variables. The statistical package used was STATA 13. Results: There were 183 males (73%) and the comorbid burden was as follows: ischaemic heart disease (54%), diabetes (38%), hypertension (92%), stage 4 kidney impairment (5%) and current or ex-smoking (77%). The main indications were transient ischaemic attacks (42%), stroke (31%), asymptomatic carotid disease (16%) and amaurosis fugax (8%). 247 carotid endarterectomies (109 with patch arterioplasty, 88 with eversion and transection technique, 50 with endarterectomy only) were performed. 2 carotid bypasses, 1 embolectomy, 1 thrombectomy with patch arterioplasty and 1 excision of a carotid body tumour were also performed. 92% of the cases were performed under general anaesthesia. A shunt was used in 29% of cases. The mean length of stay was 5.1 ± 3.7days with the range of 2 to 22 days. No patient was discharged on day 1. The mean time from admission to surgery was 1.4 ± 2.8 days, ranging from 0 to 19 days. The mean time from surgery to discharge was 2.7 ± 2.0 days with the of range 0 to 14 days. 36 complications were encountered over this period, with 12 failed repairs (5 major strokes, 2 minor strokes, 3 transient ischaemic attacks, 1 cerebral bleed, 1 occluded graft), 11 bleeding episodes requiring a return to the operating theatre, 5 adverse cardiac events, 3 cranial nerve injuries, 2 respiratory complications, 2 wound complications and 1 acute kidney injury. There were no deaths. 17 complications occurred on postoperative day 0, 11 on postoperative day 1, 6 on postoperative day 2 and 2 on postoperative day 3. 78% of all complications happened before the second postoperative day. Out of the complications which occurred on the second or third postoperative day, 4 (1.6%) were bleeding episodes, 1 (0.4%) failed repair , 1 respiratory complication (0.4%) and 1 wound complication (0.4%). Conclusion: Although it has been common practice to discharge patients on the second postoperative day following carotid endarterectomy, we find here that discharge on the first operative day is safe. The overall complication rate is low and most complications are captured before the second postoperative day. We suggest that patients having an uneventful first 24 hours post surgery be discharged on the first day. This should reduce hospital length of stay and the health economic burden.

Keywords: carotid, complication, discharge, surgery

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Authors: Ursula D. C. Resende, Fabiano S. Bicalho, Sandro T. M. Gonçalves

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The growing demand for cheap and clean energy sources have been motivated by the study and development of distinct technologies and devices able to provide different amounts of energy. In order to supply energy for small loads, the energy from the electromagnetic spectrum can be harvested. This possibility is particularly interesting because this kind of energy is constantly available in the environment and the number of radiofrequency sources is permanently increasing, due to advances in telecommunications services. A rectenna, which is a combination of an antenna and a rectifier circuit, is an equipment that can efficiently perform the electromagnetic energy harvesting. However, since the amount of electromagnetic energy available in the environment is very small, limited values of power can be harvested by the rectenna. Therefore, several technical strategies have been investigated in order to increase this amount of power. In this work, a metamaterial electromagnetic lens is used to improve the electromagnetic energy harvesting. The rectenna investigated was designed and optimized to charge a Li-Ion battery using the electromagnetic energy from an internet Wi-Fi commercial router model TL-WR841HP operating in 2.45 GHz with maximal output power equal to 18 dBm. The rectenna consists of a high directive antenna, a double voltage rectifier circuit and a metamaterial lens. The printed antenna, constituted of two rectangular radiator elements, was projected and optimized by using the Computer Simulation Software (CST) in order to obtain high directivities and values of S11 parameter below -10 dB in 2.45 GHz. The antenna was printed over a double-sided copper fiberglass substrate, FR4, with characterized relative electric permittivity εr = 4.3 and tangent of losses δ = 0.01. The rectifier circuit, which incorporates a circuit for impedance matching and uses the Schottky diode HSMS-2852, was projected and optimized by using Advanced Design Software (ADS) and built over the same FR4 substrate. The metamaterial cell is composed of two Square Split Ring Resonator (S-SRR) and a thin wire in order to operate with negative values of εr and relative magnetic permeability in 2.45 GHz. In order to evaluate the performance of the purposed rectenna two experimental charging tests were performed, one without and other with the metamaterial lens. The result obtained demonstrate that the electromagnetic lens was able to significantly increase the levels of electric current delivered to the battery, approximately 44%.

Keywords: electromagnetic energy harvesting, electromagnetic lens, metamaterial, rectenna

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Authors: Touati Mawloud

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Between electronics and electrical systems has developed a new technology that is power electronics, also called electronic of strong currents, this application covers a very wide range of use particularly in the industrial sector, where direct current engines are frequently used, they control their speed by the use of the converters (DC-DC), which aims to deal with various mechanical disturbances (fillers) or electrical (power). In future, it will play a critical role in transforming the current electric grid into the next generation grid. Existing silicon-based PE devices enable electric grid functionalities such as fault-current limiting and converter devices. Systems of future are envisioned to be highly automated, interactive "smart" grid that can self-adjust to meet the demand for electricity reliability, securely, and economically. Transforming today’s electric grid to the grid of the future will require creating or advancing a number of technologies, tools, and techniques—specifically, the capabilities of power electronics (PE). PE devices provide an interface between electrical system, and electronics system by converting AC to direct current (DC) and vice versa. Solid-state wide Bandgap (WBG), semiconductor electronics (such as silicon carbide [SiC], gallium nitride [GaN], and diamond) are envisioned to improve the reliability and efficiency of the next-generation grid substantially.

Keywords: Power Electronics (PE), electrical system generation electric grid, switching frequencies, converter devices

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Authors: Shane D. Inder, Mehrdad Khamooshi

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Efficient energy storage is a crucial factor in facilitating the uptake of renewable energy resources. Among the many options available for energy storage systems required to balance imbalanced supply and demand cycles, compressed air energy storage (CAES) is a proven technology in grid-scale applications. This paper reviews the current state of micro scale CAES technology and describes a micro-scale advanced adiabatic CAES (A-CAES) system, where heat generated during compression is stored for use in the discharge phase. It will also describe a thermodynamic model, developed in EES (Engineering Equation Solver) to evaluate the performance and critical parameters of the discharge phase of the proposed system. Three configurations are explained including: single turbine without preheater, two turbines with preheaters, and three turbines with preheaters. It is shown that the micro-scale A-CAES is highly dependent upon key parameters including; regulator pressure, air pressure and volume, thermal energy storage temperature and flow rate and the number of turbines. It was found that a micro-scale AA-CAES, when optimized with an appropriate configuration, could deliver energy input to output efficiency of up to 70%.

Keywords: CAES, adiabatic compressed air energy storage, expansion phase, micro generation, thermodynamic

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Authors: Sara Ataei, Mohammad Bagher Oghazian, Mania Radfar

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We describe a patient with hypercalcemia associated with the injection of high doses vitamin D as supplement for a period of six months. A 76-year-old woman had been taking an intramuscular injection of vitamin D 300,000 IU every ten days for six months. She was hospitalized with symptoms of hypercalcemia: chronic constipation, unstable gait, a chronic generalized musculoskeletal pain and increased fatigue. On admission her 25 (OH) vitamin D and Calcium levels were 559 nmol/L and 13.85 mg/dL respectively, and Parathyroid Hormone (PTH) level was 7.1 pg/mL. Immediately she received diuresis therapy with saline and furosemide in conjunction with calcitonin and pamidronate. At discharge her serum calcium level was 11.5 mg/dL. To lower endogenous overproduction of calcitriol, prednisolone 20 mg/day for 10 days was administered at discharge time.

Keywords: vitamin D, hypercalcemia, vitamin D toxicity, parathyroid hormone

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Authors: E. S. Manuylovich, V. A. Astapenko, P. A. Golovinsky

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The dispersion relation binding the constant of propagation and frequency is calculated for silver cone. The evolution of the electric field of ultrashort pulse during its propagation in conical structure is considered. Increasing of electric field during pulse propagation to the top of the cone is observed. Reduction of the pulse duration at a certain distance is observed. The dependence of minimum pulse duration on initial chirp and cone angle is investigated.

Keywords: ultrashort pulses, surface plasmon polariton, dispersion, silver cone

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Authors: T. Mohammed Chikouche, K. Hartani

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Based on the analysis of basic direct torque control, a parallel master slave for four in-wheel permanent magnet synchronous motors (PMSM) fed by two three phase inverters used in electric vehicle is proposed in this paper. A conventional system with multi-inverter and multi-machine comprises a three phase inverter for each machine to be controlled. Another approach consists in using only one three-phase inverter to supply several permanent magnet synchronous machines. A modified direct torque control (DTC) algorithm is used for the control of the bi-machine traction system. Simulation results show that the proposed control strategy is well adapted for the synchronism of this system and provide good speed tracking performance.

Keywords: electric vehicle, multi-machine single-inverter system, multi-machine multi-inverter control, in-wheel motor, master-slave control

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Authors: Wallyson Thomas, Zsombor Fulop, Attila Szilagyi

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Impact dampers are mainly used in the metal-mechanical industry in operations that generate too much vibration in the machining system. Internal turning processes become unstable during the machining of deep holes, in which the tool holder is used with long overhangs (high length-to-diameter ratios). The devices coupled with active dampers, are expensive and require the use of advanced electronics. On the other hand, passive impact dampers (PID – Particle Impact Dampers) are cheaper alternatives that are easier to adapt to the machine’s fixation system, once that, in this last case, a cavity filled with particles is simply added to the structure of the tool holder. The cavity dimensions and the diameter of the spheres are pre-determined. Thus, when passive dampers are employed during the machining process, the vibration is transferred from the tip of the tool to the structure of the boring bar, where it is absorbed by the fixation system. This work proposes to compare the behaviors of a conventional solid boring bar and a boring bar with a passive impact damper in turning while using the highest possible L/D (length-to-diameter ratio) of the tool and an Easy Fix fixation system (also called: Split Bushing Holding System). It is also intended to optimize the impact absorption parameters, as the filling percentage of the cavity and the diameter of the spheres. The test specimens were made of hardened material and machined in a Computer Numerical Control (CNC) lathe. The laboratory tests showed that when the cavity of the boring bar is totally filled with minimally spaced spheres of the largest diameter, the gain in absorption allowed of obtaining, with an L/D equal to 6, the same surface roughness obtained when using the solid boring bar with an L/D equal to 3.4. The use of the passive particle impact damper resulted in, therefore, increased static stiffness and reduced deflexion of the tool.

Keywords: active damper, fixation system, hardened material, passive damper

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Authors: Subrato Saha, Yun-Hyun Cho

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In electric power steering (EPS), spoke type brushless ac (BLAC) motors offer distinct advantages over other electric motor types in terms torque smoothness, reliability and efficiency. This paper deals with the shape optimization of spoke type BLAC motor, in order to reduce cogging torque. This paper examines 3 steps skewing rotor angle, optimizing rotor core edge and rotor overlap length for reducing cogging torque in spoke type BLAC motor. The methods were applied to existing machine designs and their performance was calculated using finite- element analysis (FEA). Prototypes of the machine designs were constructed and experimental results obtained. It is shown that the FEA predicted the cogging torque to be nearly reduce using those methods.

Keywords: EPS, 3-Step skewing, spoke type BLAC, cogging torque, FEA, optimization

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Authors: Shilpa Kumari, Ramakumar Jayachandran

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Machining of aluminium extrusion profiles in the automotive industry has gained much interest in the last decade, particularly due to the higher utilization of aluminum profiles and the weight reduction benefits it brings. Milling is the most common material removal process, where the rotary milling cutter is moved against a workpiece. The physical contact of the milling cutter to the workpiece increases the friction between them, thereby affecting the longevity of the milling tool and also the surface finish of the workpiece. To minimise this issue, the milling process uses cutting fluids or emulsions; however, the use of emulsion in the process has a negative impact on the environment ( such as consumption of water, oils and the used emulsion needs to be treated before disposal) and also on the personal ( may cause respiratory problems, exposure to microbial toxins generated by bacteria in the emulsions on prolonged use) working close to the process. Furthermore, the workpiece also needs to be cleaned after the milling process, which is not adding value to the process, and the cleaning also disperses mist of emulsion in the working environment. Hydro Extrusion is committed to improving the performance of sustainability from its operations, and with the negative impact of using emulsion in the milling process, a new innovative process- Dry Milling was developed to minimise the impact the cutting fluid brings. In this paper, the authors present one application of dry milling in the machining of tensile specimens in the laboratory. Dry milling is an innovative milling process without the use of any cooling/lubrication and has several advantages. Several million tensile tests are carried out in extrusion laboratories worldwide with the wet milling process. The machining of tensile specimens has a significant impact on the reliability of test results. The paper presents the results for different 6xxx alloys with different wall thicknesses of the specimens, which were machined by both dry and wet milling processes. For both different 6xxx alloys and different wall thicknesses, mechanical properties were similar for samples milled using dry and wet milling. Several tensile specimens were prepared using both dry and wet milling to compare the results, and the outcome showed the dry milling process does not affect the reliability of tensile test results.

Keywords: dry milling, tensile testing, wet milling, 6xxx alloy

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Authors: Nilesh Pancholi, Mangal Bhatt

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This paper highlights comparative results of traditional FMECA and multi-factor decision-making approach based on “Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)” for aluminum wire rolling mill plant. The suggested study is carried out to overcome the limitations of FMECA by assigning the scores against each failure modes in crisp values to evaluate the criticalities of the failure modes without uncertainty. The primary findings of the paper are that sudden impact on the rolls seems to be most critical failure cause and high contact stresses due to rolling & sliding action of mesh to be least critical failure cause. It is suggested to modify the current control practices with proper maintenance strategy based on achieved maintainability criticality index (MCI). The outcome of the study will be helpful in deriving optimized maintenance plan to maximize the performance of continuous process industry.

Keywords: reliability, maintenance, FMECA, TOPSIS, process industry

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Authors: Balkar Singh, Gurpreet Singh, Vivek Aggarwal, Sehijpal Singh

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The present research focused to improve the machinability of Hastelloy C-276 at different machining speeds such as 31, 55, and 79 m/min. The use of CO2 gas and Minimum quantity lubrication (MQL) was applied as coolant and lubrication purposes to enhance the machinability of the superalloy. The output in the form of surface roughness (S.R) and heat generation was monitored under dry, MQL, and MQL-CO2-cooled conditions. The Design of the Experiment was prepared using MINITAB software utilizing Taguchi L-27 orthogonal arrays followed by ANOVA analysis for finding the impact of input variables on output responses. At different speeds and lubrication conditions, different behavioral patterns for Surface Roughness and the temperature was observed. ANOVA analysis depicted that the cooling environment impacted the S.R. majorly (50%) followed by cutting speed (29.84%), feed rate (5.09%), and least through depth of cut (4.95%). On the other side, the temperature was greatly influenced by cutting speed (69.12%), Cryo-MQL (8.09%), feed rate (7.59%), and depth of cut (6.20%). Experimental results revealed that Cryo-MQL cooling enhanced the Surface roughness by 12% compared to MQL condition.

Keywords: Hastelloy C-276, minimum quantity lubrication, olive oil, cryogenic Cooling (CO2)

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Authors: Makoto Hasegawa, Seika Tokumitsu

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Spectra of light beams emitted from white-color LED torches are different from those of conventional electric torches. In order to confirm if white-color LED torches can be used as light sources for popular sunset color demonstrations in spite of such differences, spectra of travelled light beams and scattered light beams with each of a white-color LED torch (composed of a blue LED and yellow-color fluorescent material) and a conventional electric torch as a light source were measured and compared with each other in a 50 cm-long water tank for sunset color demonstration experiments. Suspension liquid was prepared from acryl-emulsion and tap-water in the water tank, and light beams from the white-color LED torch or the conventional electric torch were allowed to travel in this suspension liquid. Sunset-like color was actually observed when the white-color LED torch was used as the light source in sunset color demonstrations. However, the observed colors when viewed with naked eye look slightly different from those obtainable with the conventional electric torch. At the same time, with the white-color LED, changes in colors in short to middle wavelength regions were recognized with careful observations. From those results, white-color LED torches are confirmed to be applicable as light sources in sunset color demonstrations, although certain attentions have to be paid. Further advanced classes will be successfully performed with white-color LED torches as light sources.

Keywords: blue sky demonstration, sunset color demonstration, white LED torch, physics education

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Authors: Jhe-Hao Huang, Kun-Da Wu, Wei-Cheng Shih, Jui-Pin Hung

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This study presented the investigation on the dynamic characteristics of a spindle tool system by experimental and finite element modeling approaches. As well known facts, the machining stability is greatly determined by the dynamic characteristics of the spindle tool system. Therefore, understanding the factors affecting dynamic behavior of a spindle tooling system is a prerequisite in dominating the final machining performance of machine tool system. To this purpose, a physical spindle unit was employed to assess the dynamic characteristics by vibration tests. Then, a three-dimensional finite element model of a high-speed spindle system integrated with tool holder was created to simulate the dynamic behaviors. For modeling the angular contact bearings, a series of spring elements were introduced between the inner and outer rings. The spring constant can be represented by the contact stiffness of the rolling bearing based on Hertz theory. The interface characteristic between spindle nose and tool holder taper can be quantified from the comparison of the measurements and predictions. According to the results obtained from experiments and finite element predictions, the vibration behavior of the spindle is dominated by the bending deformation of the spindle shaft in different modes, which is further determined by the stiffness of the bearings in spindle housing. Also, the spindle unit with tool holder shows a different dynamic behavior from that of spindle without tool holder. This indicates the interface property between tool holder and spindle nose plays an dominance on the dynamic characteristics the spindle tool system. Overall, the dynamic behaviors the spindle with and without tool holder can be successfully investigated through the finite element model proposed in this study. The prediction accuracy is determined by the modeling of the rolling interface of ball bearings in spindles and the interface characteristics between tool holder and spindle nose. Besides, identifications of the interface characteristics of a ball bearing and spindle tool holder are important for the refinement of the spindle tooling system to achieve the optimum machining performance.

Keywords: contact stiffness, dynamic characteristics, spindle, tool holder interface

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Authors: Soumyajit Koley, Kuladeep Rajamudili, Supriyo Ganguly

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In recent years, iron-based shape-memory alloys have been emerging as an inexpensive alternative to costly Ni-Ti alloy and thus considered suitable for many different applications in civil structures. Fe-17Mn-10Cr-5Si-4Ni-0.5V-0.5C alloy contains 37 wt.% of total solute elements. Such complex multi-component metallurgical system often leads to severe solute segregation and solidification cracking. Wire-arc additive manufacturing (WAAM) of Fe-17Mn-10Cr-5Si-4Ni-0.5V-0.5C alloy was attempted using a cold-wire fed plasma arc torch attached to a 6-axis robot. Self-standing walls were manufactured. However, multiple vertical cracks were observed after deposition of around 15 layers. Microstructural characterization revealed open surfaces of dendrites inside the crack, confirming these cracks as solidification cracks. Machine hammer peening (MHP) process was adopted on each layer to cold work the newly deposited alloy. Effect of MHP traverse speed were varied systematically to attain a window of operation where cracking was completely stopped. Microstructural and textural analysis were carried out further to correlate the peening process to microstructure.MHP helped in many ways. Firstly, a compressive residual stress was induced on each layer which countered the tensile residual stress evolved from solidification process; thus, reducing net tensile stress on the wall along its length. Secondly, significant local plastic deformation from MHP followed by the thermal cycle induced by deposition of next layer resulted into a recovered and recrystallized equiaxed microstructure instead of long columnar grains along the vertical direction. This microstructural change increased the total crack propagation length and thus, the overall toughness. Thirdly, the inter-layer peening significantly reduced the strong cubic {001} crystallographic texture formed along the build direction. Cubic {001} texture promotes easy separation of planes and easy crack propagation. Thus reduction of cubic texture alleviates the chance of cracking.

Keywords: Iron-based shape-memory alloy, wire-arc additive manufacturing, solidification cracking, inter-layer cold working, machine hammer peening

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Authors: Bruno S. Soria, Mauricio R. Policena, Andre J. Souza

Abstract:

The state of the cutting tool is an important factor to consider during machining to achieve a good surface quality. The vibration generated during material cutting can also directly affect the surface quality and life of the cutting tool. In this work, the effect of mechanical broken failure (MBF) on carbide insert tools during face milling of AISI 304 stainless steel was evaluated using three levels of feed rate and two spindle speeds for each tool condition: three carbide inserts have perfect geometry, and three other carbide inserts have MBF. The axial and radial depths remained constant. The cutting forces were determined through a sensory system that consists of a piezoelectric dynamometer and data acquisition system. Discrete Wavelet Transform was used to separate the static part of the signals of force and vibration. The roughness of the machined surface was analyzed for each machining condition. The MBF of the tool increased the intensity and force of vibration and worsened the roughness factors.

Keywords: face milling, stainless steel, tool condition monitoring, wavelet discrete transform

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Authors: Ricardo Torcato, Helder Morais

Abstract:

The manufacture of crystal glass parts is based on obtaining the rough geometry by blowing and/or injection, generally followed by a set of manual finishing operations using cutting and grinding tools. The forming techniques used do not allow the obtainment, with repeatability, of parts with complex shapes and the finishing operations use intensive specialized labor resulting in high cycle times and production costs. This work aims to explore the digital manufacture of crystal glass parts by investigating new subtractive techniques for the automated, flexible finishing of these parts. Finishing operations are essential to respond to customer demands in terms of crystal feel and shine. It is intended to investigate the applicability of different computerized finishing technologies, namely milling and grinding in a CNC machining center with or without ultrasonic assistance, to crystal processing. Research in the field of grinding hard and brittle materials, despite not being extensive, has increased in recent years, and scientific knowledge about the machinability of crystal glass is still very limited. However, it can be said that the unique properties of glass, such as high hardness and very low toughness, make any glass machining technology a very challenging process. This work will measure the performance improvement brought about by the use of ultrasound compared to conventional crystal grinding. This presentation is focused on the mechanical characterization and analysis of the cutting forces in CNC machining of superior crystal glass (Pb ≥ 30%). For the mechanical characterization, the Vickers hardness test provides an estimate of the material hardness (Hv) and the fracture toughness based on cracks that appear in the indentation. Mechanical impulse excitation test estimates the Young’s Modulus, shear modulus and Poisson ratio of the material. For the cutting forces, it a dynamometer was used to measure the forces in the face grinding process. The tests were made based on the Taguchi method to correlate the input parameters (feed rate, tool rotation speed and depth of cut) with the output parameters (surface roughness and cutting forces) to optimize the process (better roughness using the cutting forces that do not compromise the material structure and the tool life) using ANOVA. This study was conducted for conventional grinding and for the ultrasonic grinding process with the same cutting tools. It was possible to determine the optimum cutting parameters for minimum cutting forces and for minimum surface roughness in both grinding processes. Ultrasonic-assisted grinding provides a better surface roughness than conventional grinding.

Keywords: CNC machining, crystal glass, cutting forces, hardness

Procedia PDF Downloads 133

Authors: Yong Min You

Abstract:

The study on the torque ripple of Permanent Magnet Synchronous Motors (PMSMs) has been rapidly progressed, which effects on the noise and vibration of the electric vehicle. There are several ways to reduce torque ripple, which are the increase in the number of slots and poles, the notch of the rotor and stator teeth, and the skew of the rotor and stator. However, the conventional methods have the disadvantage in terms of material cost and productivity. The demagnetization characteristic of PMSMs must be attained for electric vehicle application. Due to rare earth supply issue, the demand for Dy-free permanent magnet has been increasing, which can be applied to PMSMs for the electric vehicle. Dy-free permanent magnet has lower the coercivity; the demagnetization characteristic has become more significant. To improve the torque ripple as well as the demagnetization characteristics, which are significant parameters for electric vehicle application, an unequal air-gap model is proposed for a PMSM. A shape optimization is performed to optimize the design variables of an unequal air-gap model. Optimal design variables are the shape of an unequal air-gap and the angle between V-shape magnets. An optimization process is performed by Latin Hypercube Sampling (LHS), Kriging Method, and Genetic Algorithm (GA). Finite element analysis (FEA) is also utilized to analyze the torque and demagnetization characteristics. The torque ripple and the demagnetization temperature of the initial model of 45kW PMSM with unequal air-gap are 10 % and 146.8 degrees, respectively, which are reaching a critical level for electric vehicle application. Therefore, the unequal air-gap model is proposed, and then an optimization process is conducted. Compared to the initial model, the torque ripple of the optimized unequal air-gap model was reduced by 7.7 %. In addition, the demagnetization temperature of the optimized model was also increased by 1.8 % while maintaining the efficiency. From these results, a shape optimized unequal air-gap PMSM has shown the usefulness of an improvement in the torque ripple and demagnetization temperature for the electric vehicle.

Keywords: permanent magnet synchronous motor, optimal design, finite element method, torque ripple

Procedia PDF Downloads 259

Authors: C. Brecher, M. Fey, F. Du Bois-Reymond, S. Neus

Abstract:

Additive manufacturing has emerged into a fast-growing section within the manufacturing technologies. Established machine tool manufacturers, such as DMG MORI, recently presented machine tools combining milling and laser welding. By this, machine tools can realize a higher degree of flexibility and a shorter production time. Still there are challenges that have to be accounted for in terms of maintaining the necessary machining accuracy - especially due to thermal effects arising through the use of high power laser processing units. To study the thermal behavior of laser-integrated machine tools, it is essential to analyze and simulate the thermal behavior of machine components, individual and assembled. This information will help to design a geometrically stable machine tool under the influence of high power laser processes. This paper presents an approach to decrease the loss of machining precision due to thermal impacts. Real effects of laser machining processes are considered and thus enable an optimized design of the machine tool, respective its components, in the early design phase. Core element of this approach is a matched FEM model considering all relevant variables arising, e.g. laser power, angle of laser beam, reflective coefficients and heat transfer coefficient. Hence, a systematic approach to obtain this matched FEM model is essential. Indicating the thermal behavior of structural components as well as predicting the laser beam path, to determine the relevant beam intensity on the structural components, there are the two constituent aspects of the method. To match the model both aspects of the method have to be combined and verified empirically. In this context, an essential machine component of a five axis machine tool, the turn-swivel table, serves as the demonstration object for the verification process. Therefore, a turn-swivel table test bench as well as an experimental set-up to measure the beam propagation were developed and are described in the paper. In addition to the empirical investigation, a simulative approach of the described types of experimental examination is presented. Concluding, it is shown that the method and a good understanding of the two core aspects, the thermo-elastic machine behavior and the laser beam path, as well as their combination helps designers to minimize the loss of precision in the early stages of the design phase.

Keywords: additive manufacturing, laser beam machining, machine tool, thermal effects

Procedia PDF Downloads 245

Authors: Jiahui Song

Abstract:

The use of electric fields with high intensity (~ 100kV/cm or higher) and ultra short pulse durations (nanosecond range) has been a recent development. Most of the studies of electroporation have ignored possible thermal effects because of the small duration of the applied voltage pulses. However, it has been predicted membrane temperature gradients ranging from 0.2×109 to 109 K/m. This research focuses on thermal effects that drive for electroporative enhancements, even though the actual temperature values might not have changed appreciably from their equilibrium levels. The dynamics of pore formation with the application of an externally applied electric field is studied on the basis of molecular dynamics (MD) simulations using the GROMACS package. MD simulations of a lipid layer with constant electric field strength of 0.5 V/nm at 25 °C and 47 °C are implemented to simulate the appropriate thermal effects. The GROMACS provides the force fields for the lipid membranes, which is taken to comprise of dipalmitoyl-phosphatidyl-choline (DPPC) molecules. The water model mimicks the aqueous environment surrounding the membrane. Velocities of water and membrane molecules are generated randomly at each simulation run according to a Maxwellian distribution. The high background electric field is typically used in MD simulations to probe electroporation. It serves as an accelerated test of the pore formation process since low electric fields would take inordinately long simulation time. MD simulation shows no pore is formed in a 1-ns snapshot for a DPPC membrane set at a temperature of 25°C after a 0.5 V/nm electric field is applied. A nano-sized pore is clearly seen in a 0.75-ns snapshot on the same geometry, but with the membrane surfaces kept at temperatures of 47°C. And the pore increases at 1 ns. The MD simulation results suggest the possibility that the increase in temperature can result in different degrees of electrically stimulated bio-effects. The results points to the role of thermal effects in facilitating and accelerating the electroporation process.

Keywords: high-intensity, ultra-short, electroporation, thermal effects, molecular dynamics

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