Showing papers by "Amitava Ghosh published in 2017"

Grinding of Ti-6Al-4V Under Small Quantity Cooling Lubrication Environment Using Alumina and MWCNT Nanofluids

Abstract: Ti-6Al-4V is a difficult-to-grind material as chips tend to adhere to the grit materials of an abrasive wheel due to its chemical affinity. In the present work, it has been attempted to improve the grindability by application of small quantity cooling lubrication (SQCL) technology using nanofluids, namely, multiwalled carbon nanotube (MWCNT) and alumina nanofluid. The suitability of nanofluids was experimentally evaluated in reciprocating surface grinding using a vitrified SiC wheel. Substantial improvement in grindability under the influence of MWCNT nanofluid (SQCL) could be achieved compared to soluble oil (flood). Reduction of specific grinding forces and specific energy was observed due to the combined effect of superior heat dissipation and lubrication abilities; when the latter one was realized through on-site rolling of MWCNT strands, inter-tubular slip and solid lubrication of the film adhered onto the wheel surface. These outperforming characteristics of MWCNT nanofluid helped in retaini...

Interfacial reaction and wetting behavior of active Ag-Cu filler alloys on surface of cBN grits and its influence on failure patterns of brazed joint

Abstract: Cubic boron nitride (cBN) abrasive grits are often brazed on steel to produce monolayer grinding wheels. Establishing a strong cBN brazement is a challenge. In the current work, performance of three different active Ag-Cu alloys have been investigated in-depth considering microstructure of alloys, interfacial reaction phase formation and wetting capability of the reaction product towards the alloy. In the current study, all three alloys contain Ti as active element but with different wt%. One of alloys was so chosen that Indium (In) was present as an additional alloying element, which is responsible for its low liquidus temperature, high Young's modulus and good ductility. Segregation of Ti towards the interface was critically examined. To evaluate joint strength, a miniature twin-ring grinding wheel was produced with these alloys. Interestingly, the alloy containing higher Ti, which required higher brazing temp, resulted in intense reaction but with inferior joint strength. On the other hand, the very presence of indium in Ag-Cu alloy, containing low wt% of Ti not only lowered the brazing temperature but also led to effective wetting and higher joint strength. Failure pattern indicates the prevalence of high residual stress at the bond level for the alloy containing the highest percentage of titanium.

Study of micro ball end mill geometry and measurement of cutting edge radius

Abstract: Cutting edge radius plays an important role in conventional micro machining process, as it is of the same order as uncut chip thickness. Therefore it is important to measure the edge radius accurately. There is no recommended methodology, as of now, to measure edge radius of a ball end mill. An attempt is made in this paper to study edge radius of ball end mill at normal and transverse planes on a virtual ball end mill generated using kinematic relations in CAD environment. In the present study, non-destructive methods using confocal microscope and stereo microscope are used to measure edge radius. These measurements capture the edge radius on the transverse plane. For confirmation, the tool sectioned in the transverse plane by a low speed diamond saw is examined under scanning electron microscope and the radius is assessed using suitable software. Among the non-contact approaches proposed in this work, confocal method appeared to be more reliable considering the reproducibility aspect.

Impact of intra-bond orbital hybridization and morphology of diamond coatings on machining performance of coated end mill cutters

Abstract: The current study analyses machining performance of diamond coated end mills in the light of coating morphology, difference in intra-bond orbital hybridization, wettability and anti-frictional characteristics. Three different classes of diamond coatings, including a new generation nanocrystalline (NCD) coating, were chosen so that they do contain different intensity of sp 2 and sp 3 hybridisation in C C covalent bonding. The machining experiments were carried out in slot machining mode accomplished by two-fluted endmills and on aluminium and a silicon-free aluminium alloy, AA2024. sp 2 -rich hydrogenated DLC coating demonstrated outperformance in anti-frictional characteristics over its counter parts when tested against a sliding aluminium disc. The tribological performance of the sp 3 -rich NCD coating was superior to the sp 3 -hybridized microcrystalline diamond coating (MCD) but could not excel H-DLC coating. The difference in the hybridization level did not influence wettability towards the molten aluminium. However, the end mills having new generation NCD coating outperformed its counterparts at high speed machining conditions, establishing the supremacy over H-DLC coating, even over the MCD coating. The coating morphology including roughness played the most influencing role in favour of the machining performance, considering the ability to arrest built up layer (BUL) formation and to produce high surface finish of the machined work-surface.

An Experimental Evaluation of Solid Lubricant Based Nanofluids in Small Quantity Cooling and Lubrication during Grinding

Abstract: Small quantity cooling lubrication (SQCL) with commercially available metal working fluids (MWF) and nanofluids has been attempted successfully in machining and grinding. Solid lubricants also provided some benefits in grinding of metallic alloys. However, there are very few studies using molybdenum di-sulphide (MoS2) and hexagonal boron nitride (hBN) dispersed nanofluids applied in SQCL mode in grinding. The aim of the present work is to experimentally study improvement in grinding of EN31 steel using alumina grinding wheel with aqueous MoS2 and hBN nanofluids. The grinding study is supported by detailed tribometry at 1 m/s sliding speed to reveal the possible reasons behind such improvement. MoS2 dispersed nanofluids provided minimum coefficient of friction in ball-on-disc test. It also provided the maximum reduction in specific grinding energy and improvement in surface finish with respect to flood cooling. hBN dispersed nanofluids could not match the performance of MoS2 dispersed nanofluids both in ball-on-disc and grinding experiments.

CAD based simulation of ball end mill manufacturing

Abstract: Geometry of micro ball end mill is quite complex, as helical cutting edges are formed on a hemispherical surface. The edge must have proper rake and clearance faces for effective cutting and appropriate radius to strengthen it. Manufacturers of micro tools do not reveal the details, as they are proprietary in nature. In the present work, a CAD approach is proposed to simulate the generation machining of micro ball end mill using appropriate kinematic relations. Different geometries of micro ball end mill can be generated by the approach proposed in the present work. A critical study of virtual micro ball end mills will be useful to understand their performance. The study allows visualization of the cutting angles and edge radius along different transverse sections, as these geometrical parameters influence mechanics of micro cutting.

A Fuzzy Ranking Approach for a Two-Warehouse Inventory Model for Deteriorating Items with Ramp Type Demand

Abstract: In general, inventory models consider unlimited capacity of warehouses. But in real inventory situations, the capacities of warehouses are limited. So in such cases, to deal with unlimited stocks, one requires additional warehouses. Here a two-warehouse inventory model has been developed for deteriorating items with ramp type demand. Also a corresponding fuzzy model has been developed by considering inventory costs (holding cost, setup cost) and deterioration cost. Subsequently the model has been solved by fuzzy ranking based approach. In both crisp and fuzzy cases, models are being numerically illustrated through examples through a gradient based nonlinear optimization technique (LINGO). Moreover, some sensitivity analysis has been done by taking into consideration the deterioration rate and cost parameters.

The Study of the Impact of Wastewater from Outfall in River Ganga, West Bengal on the Growth and Morphological Parameters of Spinacia Oleracea L.

Abstract: The impact of domestic wastewater from a selected outfall of river Ganga near Dakhineswar, 24 Parganas (N) District, West Bengal, India, had been found on fifteen-days-old Spinacia oleracea L. season wise. An extensive analysis of physicochemical parameters of wastewater before mixing into river showed to exceed its acceptable range in many cases. The accumulation of huge amount of Gram-positive and Gram-negative bacteria had been reported. The range of total coliform and fecal coliform was in between 1.8 × 107 to 2.9 × 107 and 2.4 × 106 to 4.7 × 106, respectively. Mercury level was found to exceed its standard limit 0.01 mg/L. The morphological parameters like stem height, leaf length, leaf width, internodal distance, and petiole length were inhibited by wastewater treatment in comparison with tap water treatment. Along with its morphological growth, 90% reduction in total chlorophyll content and 70% reduction in protein content have also been reported in wastewater treated plants.

Phytochemical investigation and exploration of CNS depressant efficacy of ethanolic root extract of Cyperus kyllinga Endl.

Abstract: Sedative drugs such as diazepam, lorazepam, pentoberbitone, amphetamine derivatives etc., are known to have permanent side effects. However, addiction to such drugs, possibly out of depression, is not uncommon. Similar drugs from plant origin with same efficacy could be a better safe alternative. In this study, we evaluated ethanolic extract of roots of the Cyperus kyllinga Endl. (Nut grass) for central nervous system (CNS) depressant activity (sedative activity) at the dose 20 and 40 mg/kg body wt. when administered i.p. The standard drug used was diazepam. The CNS activity was assayed in two experimental models: locomotor activity using actophtometer and skeletal muscle relaxant test by Rota rod apparatus. The ethanolic extract of the C. kyllinga demonstrated depression of the CNS activities in the mice. Phytochemical preliminary screening of the root extract has revealed the presence of flavonoids, carbohydrates, phenolic compounds, steroids and saponin glycoside.

Monotonicity of strata in the stratification of the cone of totally positive matrices

Abstract: According to a theorem of Bjorner [5], there exists a stratified space whose strata are labeled by the elements of [u, v] for every interval [u, v] in the Bruhat order of a Coxeter group W, and each closed stratum (respectively the boundary of each stratum) has the homology of a ball (respectively of a sphere). In [6], Fomin and Shapiro suggest a natural geometric realization of these stratified spaces for a Weyl group W of a semi-simple Lie group G, and then prove its validity in the case of the symmetric group. The stratified spaces arise as links in the Bruhat decomposition of the totally non-negative part of the unipotent radical of G. In this article, we verify the topological regularity property of the strata formed as a result of Bruhat partial ordering on the elements of theWeyl group (of rank 4) of a semi-simple simply connected algebraic group G which is SL(4,ℝ) in our case here. The Weyl group here is the Coxeter group S 4.