This paper investigated the degradation of wire electrode during electrical discharge machining of SiC reinforced Al-based metal matrix composites (MMCs). MMCs with different size of reinforcements ...(0.7, 3 and 13µm) as well as corresponding matrix material were machined under similar machining conditions to understand the effect of reinforcement size on the degradation of wire. In addition, pulse-on-time and wire tension were varied to understand the effect of machining parameters and interaction between machining parameters and size of the reinforcements. It was found that initial circular shaped wire deformed during the machining process as curved front and rear edges and two straight side edges irrespective of cutting conditions and workpiece materials. The curved edge at the front and straight side edges take part in material removal and experience sever degradations. The final cross-sectional area of the wire after the machining process is decided by balancing two mechanisms: (i) downward flow of highly malleable soft wire material due to high temperature which increases the diameter of wire electrode and (ii) vaporisation of the wire material at higher temperature which reduces the diameter of wire electrode. These complex processes are affected by machining conditions as well as workpiece materials.
•The circular shaped wire deformed to curved front and rear, and straight side edges.•This deformation occurred irrespective of cutting conditions and workpiece materials.•Downward flow of soft wire material increases the diameter of wire electrode.•Vaporisation of wire material reduces the diameter of wire electrode.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
It is a daunting challenge to improve the sustainability of electrical discharge matching (EDM) as well as to make the process environmentally friendly. This paper carried out investigations into the ...role of steam as a dielectric medium during sink (EDM) of aluminum-based metal matrix composite (MMC) and critically compares the outcome with that of widely used hydrocarbon-based dielectrics such as kerosene in terms of output parameters, positive environmental aspect, and cost-effectiveness. The output parameters such as recast layer, material removal rate (MRR), and machined surface characteristics were analyzed in details. The recast layer obtained upon steam dielectric EDM was significantly improved by 37.15% in terms of thickness, bonding with base metal as well as structure and morphology. This favorable development was attributed towards high temperature, low heat spark material erosion, and low conductivity of steam as a dielectric medium. The machined surface upon steam dielectric EDM apparently contained machined debris rather than solidified molten workpiece material and contributed towards minimum roughness by 1.5 times due to high temperature, high pressure, and low viscosity of the steam. It is found that the ongoing cost of sink EDM can be reduced to one-fifth if the hydrocarbon-based dielectric is replaced by steam.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Demand for drilled micro-holes on difficult to machine materials have increased over the past years and non-traditional drilling processes are commonly used to fabricate such micro-holes on difficult ...to machine materials. This research investigates different non-traditional drilling processes, such as electro discharge, laser beam, abrasive water jet, electrochemical and electrochemical discharge drilling methods. Drilling mechanism, material removal rate/machining speed and surface finish have been analysed for every process. These analyses clearly show that vaporisation, melting, chemical dissolution and mechanical erosion are dominant material removal mechanism during non-traditional drilling. The understanding on electro discharge, laser beam and abrasive water jet drilling are more developed than that of electrochemical, electrochemical discharge and hybrid drilling processes.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
To reduce the machining time and energy, it is important to have uninterrupted machining to make the process sustainable. Understanding the factors and mechanism that affect the wire failure is vital ...to reduce machining time to preserve resources and improve sustainability. Therefore, the mechanism of wire electrode rupture during electrical discharge machining (EDM) of Ti-6Al-4V alloy has been investigated in this study. To aid the analysis, electrolyte flushing pressure (7, 10, 15, 18 MPa), wire tension (800, 1100, 1400 and 1700 gf) and pulse-on-time (4, 6, 8 and 10 μsec) were varied to understand the effects of these parameters on wire rupture. The incidents of wire rupture are high at lower flushing pressure and higher wire tension. The influence of pulse-on-time depends on the interaction ns between wire tension and flushing pressure. The wire rupture occurs at instantaneous high temperature due to generation of unwanted arcs when the EDM debris/wastes are not flushed away properly. Higher wire tension may break the wire even at lower temperature in the machining zone. The wire rupture might be very sudden and/or gradual decrease of cross-section of the wire, however, the tips of the broken wire experience necking before fracture which is contributed to associated wire tension and softening by high temperature. The coating of the wire was disrupted and wear-off around the tips of broken wire. Workpiece material was not detected on the tips, however, trace of oxides islands was detected that formed due to high temperature oxidation of wire materials around the broken tips.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The differential, integrated elastic, total and momentum transfer cross sections along with Sherman function for the elastic scattering of electrons and positrons by cadmium atom
s
have been ...evaluated from the partial wave solution of the Dirac relativistic scattering equations for a projectile-atom complex potential at the energy range 6.4 eV < E < 1.0 keV. For various scattering quantities, a comparison of our results exhibits better agreement with the experimental data than the other available theoretical values.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
The present work investigates the mechanical properties of as-built laser powder bed fusion (L-PBF) Aluminium 7068 alloys, together with microstructural characterization. To achieve this, ...micro-pillar compression (in-situ) was conducted and the state of the materials under compression were correlated with respective stress–strain curves. A cast alloy of similar bulk composition was also investigated, under identical conditions, as a benchmark material. As opposed to the larger spherical grains (about 4 µm) of the cast alloy, the L-PBF alloy exhibited typical ‘melt pool’ meso-structure, combined with refined microstructure induced by rapid cooling and gave rise to sub-micron range grain sizes. The mechanical properties of the L-PBF alloy are anisotropic in nature, due to its bi-modal type meso- and micro-structure. Cross-sectional SEM investigation was carried out on deformed micro-pillars and revealed that there exist numerous slip and shear plane networks that served as load accommodation mechanism during compression.
Graphical abstract
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Display omitted
•Combination of biochar and chemical fertilizer (CF) tested on medicinal herb.•Biochar in combination with CF increased the growth, yield and quality of the herb.•Biochar addition ...enhances soil nutrient availability and enzymatic activities.•CF requirement can be reduced by addition of biochar.•Biochar could be an inexpensive soil amendment for quality medicinal herb production.
Cultivation of medicinal plants by maintaining sustainable environment with low chemical inputs is attempted through a pot culture experiment by integrating the biochar prepared from lemongrass (Cymbopogon flexuosus) distillation waste and chemical fertilizers (CF) in different ratios. The objective was to find out the influence on yield, physiology and quality of Andrographis paniculata (kalmegh) herb and on soil chemical/biological properties. All the growth parameters and yield were significantly influenced by the integrated biochar and CF application. Biochar application, remarkably improved the soil carbon content, cation exchange capacity and nutrients accessibility. However, significantly higher fresh herbage yield (140.8 g plant−1) was recorded in the treatment receiving biochar (5 t ha−1) combined with recommended dose of CF (60:20:40 NPK kg ha−1). The same treatment resulted in higher soil microbial biomass C, fluorescein diacetate hydrolytic, dehydrogenase and alkaline phosphatase activity. Total phenol/flavonoid contents and antioxidant (DPPH and ABTS) activities, were higher in sole biochar treated plant and increased further in combination with CF. Sole application of biochar or CF did not have any significant influence on leaf andrographolide content, however their combination increased the content but the effects were not significant on stem andrographolide. The reduction in stomatal conductance and higher water use efficiency after biochar application indicates it’s potential to mitigate water deficit stress. Results indicate that use of only biochar was not enough to improve the plant growth and soil health. Therefore, to achieve environmentally safe and quality herb production, it is recommended to use combination of biochar and CF which not only improve crop yield and quality but also improves the soil quality.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The aim of this work was to study the effect of the ionic liquids (ILs) with respect to their anion type and the length of alkyl chain as dispersing and coupling agent in carbon nanotube (CNT) filled ...styrene butadiene rubber (SBR)/natural rubber (NR) blends. We characterized the ILs by their surface tensions whereupon their different values explain the different compatibilities of ILs with the rubber components and the filler. The wetting concept was further developed in order to experimentally characterize the effect of the rubber-IL and CNT-IL compatibility on the selective wetting of CNTs in rubber blends. It was found that all the used ILs improved the dispersion of CNTs in rubber blends significantly. During the mixing process the IL layer pre-bound to the CNT surface was replaced mainly by the NR phase and, partly, by the SBR phase. Thus, ILs cannot be used as coupling agent in this rubber blend. For the ILs with surface tension similar to that of CNTs the filler was partly wetted by IL that imparts the mixture a high electrical conductivity directly after the mixing process. This high conductivity can be used for triggering the vulcanization of the blend by means of the Joule heating. The preferential localization of ILs in the rubber matrix - but not in rubber-filler interphase - considerably influences the cross-link behavior of the vulcanizates and thus their final mechanical properties significantly.
Display omitted
•Effect of the rubber-ionic liquid and filler-ionic liquid interaction on the CNT dispersion.•Prediction and experimental determination of the selective wetting of CNTs in rubber blends.•Replacement of pre-bound ionic liquid layer on the CNT surface mostly by NR and, partly by SBR.•Improved network formation of CNTs partly wetted by IL.•Joule heating triggered vulcanization of rubber blend by application of an electrical voltage.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The most popular additive manufacturing (AM) technologies to produce titanium alloy parts are electron beam melting (EBM), selective laser melting (SLM) and directed energy deposition (DED). This ...investigation explores mainly these three techniques and compares these three methods comprehensively in terms of microstructure, tensile properties, porosity, surface roughness and residual stress based on the information available in the literature. It was found that the microstructure is affected by the highest temperature generated and the cooling rate which can be tailored by the input variables of the AM processes. The parts produced from EBM have strength comparable to that of conventionally fabricated counterparts. SLM and DED yield superior strength, which can be up to 25% higher than traditionally manufactured products. Due to the presence of larger tensile residual stress, surface roughness and porosity, AM fabricated parts have lower fatigue life compared to those of from traditional methods. EBM parts have slightly lower fracture toughness (i.e., lower fatigue life) than conventionally produced parts while SLM and DED have significantly lower fracture toughness. Annealing, hot isostatic pressing, stress relief and additional machining processes improve the characteristics of parts produced from AM. Ti–6Al–4V alloy parts fabricated via AM may have limited applications despite the high demands in aerospace or biomedical engineering. Since rapid product development using 3D printers leads to significant cost reductions more recently, it is expected that more opportunities may soon be available for the AM of titanium alloys with newer AM processes such as cold spray additive manufacturing (CSAM) and additive friction stir deposition (AFSD).
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
RATIONALE:The rapid induction and orchestration of new blood vessels are critical for tissue repair in response to injury, such as myocardial infarction, and for physiological angiogenic responses, ...such as embryonic development and exercise.
OBJECTIVE:We aimed to identify and characterize microRNAs (miR) that regulate pathological and physiological angiogenesis.
METHODS AND RESULTS:We show that miR-26a regulates pathological and physiological angiogenesis by targeting endothelial cell (EC) bone morphogenic protein/SMAD1 signaling in vitro and in vivo. MiR-26a expression is increased in a model of acute myocardial infarction in mice and in human subjects with acute coronary syndromes. Ectopic expression of miR-26a markedly induced EC cycle arrest and inhibited EC migration, sprouting angiogenesis, and network tube formation in matrigel, whereas blockade of miR-26a had the opposite effects. Mechanistic studies demonstrate that miR-26a inhibits the bone morphogenic protein/SMAD1 signaling pathway in ECs by binding to the SMAD1 3′-untranslated region, an effect that decreased expression of Id1 and increased p21 and p27. In zebrafish, miR-26a overexpression inhibited formation of the caudal vein plexus, a bone morphogenic protein-responsive process, an effect rescued by ectopic SMAD1 expression. In mice, miR-26a overexpression inhibited EC SMAD1 expression and exercise-induced angiogenesis. Furthermore, systemic intravenous administration of an miR-26a inhibitor, locked nucleic acid-anti–miR-26a, increased SMAD1 expression and rapidly induced robust angiogenesis within 2 days, an effect associated with reduced myocardial infarct size and improved heart function.
CONCLUSIONS:These findings establish miR-26a as a regulator of bone morphogenic protein/SMAD1-mediated EC angiogenic responses, and that manipulating miR-26a expression could provide a new target for rapid angiogenic therapy in ischemic disease states.
PDF
