This work presents the wire-EDM of WC-Co composite and optimization of process parameters using an integrated technique of response surface methodology (RSM), Vise Kriterijumska Optimizacija ...Kompromisno Resenje (VIKOR) and artificial bee colony (ABC) algorithm to obtain the best set of machinability indicators. Wire feed (WF), servo voltage (SV), pulse off-time (Pon) and pulse on-time (Poff) are the variable process parameters, whereas root mean square roughness (Rq), average surface roughness (Ra) and material removal rate (MRR) are the machinability indicators considered in the present work. A total of twenty nine experiments have been conducted based on Box Behnken design (BBD) technique of response surface methodology. VIKOR has been used for normalization of responses and followed by solving empirical models using ABC algorithm to obtain optimized process parameters setting. WF-12 m/min, SV-65V, Pon-116 µs, Poff-20 µs are the optimum wire-EDM parameters obtained by intelligent RSM-VIKOR-ABC technique that produced best values of Ra-4.51 µm, Rq-5.64 µm, MRR-0.061 mm3 /min simultaneously. The validation test confirmed an improvement up to 15% in the response characteristics which proved the effectiveness of this novel hybrid technique for optimization. The optimum parameter setting is for ready industrial reference to attain best surface quality and process productivity for WC-Co composite machining by wire-EDM.
Shape memory alloys are important biomaterials but difficult-to-machine (DTM). Their machining needs to be done using intelligent techniques to obtain a better machinability. Hybrid optimization is ...one of such techniques which can do modelling and optimization of machining parameters for the best values of machinability indicators. Wire electric discharge machining (WEDM) of shape memory alloy has been found as a prominent alternate to the conventional machining techniques, however it needs the assistance of intelligent techniques to machine such materials to get the optimum values of machinability indicators. In this paper, WEDM of shape memory alloy Ni55.8Ti is reported. WEDM has been done by varying four process parameters i.e. servo voltage SV, pulse-on time Pon, pulse-off time Poff, and wire feed rate WF using Taguchi L16 robust design of experiment technique. A hybrid optimization technique TOPSIS-Fuzzy-PSO has been successfully used to optimize these parameters (SV-50V; Pon-1µs; Poff-17 µs; WF-4 m/min) for the best possible values of material removal rate (MRR)- 0.049 g/min, maximum roughness- 11.45 µm, and recast layer- 22.10 µm simultaneously.
Manufacturing of miniature gears with good accuracy and quality, and at low cost is a challenging task for traditional manufacturing processes. Wire-cut electric discharge machining (WEDM) has the ...capacity to machine any conductive material to fabricate typical shaped products like gears with high level of accuracy and quality. In present research, stainless steel (SS) alloy 316 is used to fabricate miniature gears by WEDM. The experimental array is designed according to Response Surface Methodology (RSM) based central composite face centered (CCFC). Four input parameters namely servo feed (SF), duty factor (DF), servo voltage (SV) and wire feed (WF) with three levels each are used for experimental array to investigate the process performance in terms of cutting rate (CR), and product i.e. gear quality in terms of mean roughness depth (Rz) and dimensional deviation (DD). After WEDM parameter optimization, confirmation experiments are performed at the parametric setting by considering equal importance to all response variables. A very close agreement between the experimental and predicted values have been observed.
The rotor or impeller is a rotational and key part of a pump and compressor. This article presents the detailed development process of a rotor of small size constructed from an EN8 steel cylindrical ...blank using a novel technique based on a computer numerical control engraving milling machine (CNC-EMM) equipped with a 4 mm tungsten carbide end mill cutter. We fabricated a total of twenty-eight stepped rotors following the Box-Behnken Design (BBD) DoE technique at fourteen distinct combinations of CNC-EMM variable parameters, namely rotational speed, feed, and plunge feed. Average roughness '
', an important surface quality indicator, has been considered and presented in this article, as a quality measure for the fabricated rotors. Feed and plunge feed have been identified as the most influencing variable parameters as per an analysis of variance (ANOVA) test. The lowest average roughness value obtained by this process for the rotor blade was 0.11 µm. A micrograph obtained from a field-emission scanning electron microscope (FE-SEM) showed a uniform and accurate tooth profile along with burr formation at corner edges. This study claims to establish engraving milling as a viable alternative to other manufacturing processes used for rotor blades. The findings of this study are useful to scholars, engineers, and researchers who are exploring new ways to fabricate mechanical parts and components.
This paper reports the surface quality of a miniature cylindrical titanium rod/bar (MCTB) turned by the wire electrical discharge turning (WEDT) process using a zinc-coated wire of 250 µm diameter. ...The surface quality was mainly evaluated by considering the very important surface roughness parameters, i.e., the mean roughness depth. A Box-Behnken design (BBD) of the response surface methodology (RSM) based on 17 experimental runs was conducted, where the spark duration "
" was found as the most influential parameter affecting the mean roughness depth "
" of the miniature titanium bar. Further, using the grey relational analysis (GRA) technique of optimization, we obtained the least value of "
" 7.42 µm after machining a miniature cylindrical titanium bar with the optimum combination of WEDT's variable parameters:
-0.9 µs,
-30 V, and DOC-0.35 mm. This optimization led to a 37% reduction in the surface roughness
of the MCTB. The tribological characteristics of this MCTB were also found favorable after conducting a wear test. After completing a comparative study, we can claim that our results are better than those of the past research conducted in this area. The findings of this study are beneficial for the micro-turning of cylindrical bars made from a variety of difficult-to-machine materials.
Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), represents a global crisis. Key to SARS-CoV-2 therapeutic development is unraveling the ...mechanisms that drive high infectivity, broad tissue tropism, and severe pathology. Our 2.85-angstrom cryo-electron microscopy structure of SARS-CoV-2 spike (S) glycoprotein reveals that the receptor binding domains tightly bind the essential free fatty acid linoleic acid (LA) in three composite binding pockets. A similar pocket also appears to be present in the highly pathogenic severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV). LA binding stabilizes a locked S conformation, resulting in reduced angiotensin-converting enzyme 2 (ACE2) interaction in vitro
In human cells, LA supplementation synergizes with the COVID-19 drug remdesivir, suppressing SARS-CoV-2 replication. Our structure directly links LA and S, setting the stage for intervention strategies that target LA binding by SARS-CoV-2.
Challenges in developing urban flood resilience in India Gupta, Kapil
Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences,
04/2020, Letnik:
378, Številka:
2168
Journal Article
Recenzirano
Odprti dostop
This note presents a short commentary on the recurring urban flooding in India and the challenges the country faces in implementing sustainable drainage practices and developing urban flood ...resilience. The major incidences of heavy rainfall and the consequent urban flooding and their causes are briefly described. The recent flood disaster management and mitigation measures carried out by the Central, State and Local Government are highlighted. The flood resilience initiatives and challenges are then discussed. The effects of climate change on increased rainfall in shorter durations are now being felt in many Indian cities. The planners are now taking cognizance of this and future flood resilience measures are being planned to incorporate an integrated approach to stormwater management by recommending best management practices in the stormwater manuals. However, a lot still needs to be done to make the cities in India flood resilient. This article is part of the theme issue 'Urban flood resilience'.
•Flank face textured cutting tool found superior than plain tool for dry machining of Mg.•The dimple textures on the flank face of the cutting tool reduces its wear significantly.•Cutting speed is ...the most influencing factor.•Abrasive wear and discontinuous chips were obtained at low-speed machining.
Magnesium alloys have many advantages as lightweight materials for engineering applications, especially in the fields of automotive and aerospace. They undergo extensive cutting or machining while making products out of them. Dry cutting, a sustainable machining method, causes more friction and adhesion at the tool-chip interface. One of the promising solutions to this problem is cutting tool surface texturing, which can reduce tool wear and friction in dry cutting and improve machining performance. This paper aims to investigate the impact of dimple textures (made on the flank face of cutting inserts) on tool wear and chip morphology in the dry machining of AZ31B magnesium alloy. The results show that the cutting speed was the most significant factor affecting tool flank wear, followed by feed rate and cutting depth. The tool wear mechanism was examined using scanning electron microscope (SEM) images and energy dispersive X-ray spectroscopy (EDS) analysis reports, which showed that at low cutting speed, the main wear mechanism was abrasion, while at high speed, it was adhesion. The chips are discontinuous at low cutting speeds, while continuous at high cutting speeds. The dimple textured flank face cutting tools facilitate the dry machining of AZ31B magnesium alloy and contribute to ecological benefits.
This article presents an experimental investigation conducted on wire spark erosion turning of Titanium grade 5 miniature cylindrical bars. Two main output parameters i.e. roundness deviation, a type ...of form error, as an indicator of product quality and material erosion rate as an indicator of productivity, have been focused to measure the success of the machining process. A total of seventeen experiments with two replications based on Box-Behnken design (BBD) of the response surface methodology (RSM) were performed to identify the influence of spark duration ‘Ton’, servo voltage ‘SV’, and depth of cut ‘DOC’ on roundness deviation ‘DR’ and material erosion rate ‘MER’. Grey relational analysis (GRA) based multi-response optimization was carried out to determine the optimum turning condition of WSET with the objectives to minimize roundness deviation and maximize material erosion rate. WSET of Titanium at optimum process parameters resulted in the best values of roundness deviation 15.51 μm and material erosion rate 9.35 mm3/min. The results of validation experiments are much closer to the optimum values of DR and MER with <5% and 2% differences, respectively. Surface morphology investigation confirmed that the surface generated by WSET is fit and suitable for many applications. The results of this work are better than the previous studies and further useful to the researchers for the advanced fabrication of miniature products from difficult-to-machine materials like Titanium.
PDF
