Abstract
A cobalt‐catalyzed, N,O‐bidentate directing group‐assisted C−H bond functionalization of benzamides with maleimides was developed for the facile access to isoindolone spirosuccinimides in ...good to excellent yields. This C−H bond activation and spirocyclization employing pyridine N‐oxide as directing group provided very good substrate scope and tolerated various functional groups. Furthermore, the mechanistic investigation revealed that the C−H bond activation is the rate‐determining step of this reaction.
The use of superalloy Inconel 718 is increasing in most of the sophisticated applications like aircraft engines, industrial gas turbines, rocket engines, space vehicles, submarines, etc. Hence, ...in-depth understanding of this material helps to determine the ability of this material to withstand severe conditions of stress, temperature, corrosion, and controls its longevity and reliability. In the present work, an attempt has been made to study the relationship of degree of work hardening and tool life as a function of cutting parameters like cutting speed, feed, depth of cut, untreated tungsten carbide and postcryogenic-treated tool. Work hardening and tool life are the major factors which need to be controlled/improved to enhance the machinability characteristics of superalloy Inconel 718. A significant performance in tool life was observed due to cryogenic treatment given to tungsten carbide tool. Moreover, it was observed that optimized cutting parameters not only minimized/controlled work hardening characteristics but also improved tool life while high-speed machining of Inconel 718.
Magnesium/Teflon/Viton or MTV based pyrotechnic composition has been the most preferred composition for decoy flares against conventional heat-seeking missiles for more than four decades. MTV flares ...of standard configurations are available globally but the details of their manufacturing process including compacting pressure and compressive strength of the flare pellets have not been explicitly defined. The pellets are sub-assembly of the flares dispensed in flight and are critical for successful operations of the decoy flares. Hence, in the present paper, an attempt has been made to optimize the process parameters namely charge mass (A), applied load (B) and dwell time (C) which are responsible for performance variation of compacted standard configuration cylindrical pellets of 50 mm diameter. Each of the process parameters has been considered for three levels. L
27
array has been selected to represent these parameters and their interactions. The Taguchi robust experimental method arrived at the optimal result as A1B3C3 (100 g of charge mass, 78.48 KN of applied load and 20 s of dwell time). Analysis of Variance (ANOVA) highlighted that applied load followed by charge mass significantly influenced the density of the pellets. Finally, general regression equation was derived with R
2
value of 0.936 and validated with experimental results.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Magnesium/Teflon/Viton or MTV pyrotechnic composition has been widely preferred to prepare decoy flares as countermeasures against heat seeking Infra-red (IR) missiles. Though MTV for military ...applications are available in the global market, the manufacturing process and performance characteristics of these flares have not been explicitly defined. The pellets which are an essential sub-assembly of the flares need to be extensively studied to develop these flares for military applications. The study paper attempts to optimise the density of compacted 50 mm diameter cylindrical pellets. The pyrotechnic composition is initially subjected to various sensitivity tests namely impact, friction and spark to assess the threshold values of initiation of this composition. Three levels of process parameters for pelleting have been considered and L
27
array has been selected to represent the process parameters namely charge mass (A), applied load (B), dwell time (C) and their interactions. The Taguchi robust experiment method arrived at the optimal result as A1B3C3 (100 g of charge mass, 8 tons of applied load and 20 s of dwell time). Analysis of Variance (ANOVA) highlighted that parameters A and B significantly influenced the density of the pellets. Finally, general regression equation was derived with R
2
value of 0.94.
In the present research, an experimental and numerical investigation has been performed to study initial pressure rise in multi grain solid rocket motor. A cluster of seven uninhibited tubular grains ...of double base propellant is analysed to get near neutral pressure in rocket motor. It is experimentally observed that in some static firings initial pressure rise in first 100 ms is higher than the predicted value of ∼7.5 MPa. The average pressure in the rocket motor is ∼7 MPa and total burning time of these grains is ∼2 s. ANSYS software is used for numerical analysis to investigate the effects of various % openings of nozzle end (NE) metal grid on pressure rise in the rocket motor with and without peripheral opening. The analysed results are compared with experiments. It is found that, as the %opening of NE metal grid increases, the initial pressure in the rocket motor decreases. The peripheral opening is also important to reduce pressure rise in rocket motor. This study helps in reducing the initial pressure rise in the combustion chamber which is essential for safe working of the rocket motor.
In the present study, the mathematical prediction with the Paul‐Mukunda model is carried out for maximum pressure rise with erosive burning in multi‐grain solid rocket propellant. For this study, a ...cluster of 7 tubular solid double‐base propellant grains is selected. The erosive burning model has given a fair idea of the maximum pressure rise in rocket motors. The maximum pressure rise due to the erosive burning effect is quite a lot higher than without the erosive burning effect. The erosive burning model helps in studying maximum pressure rise for various configurations of propellant grains. It is found that lowering the outer diameter (OD) of propellant grains is giving low maximum pressure in rocket motor in comparison to increasing the inner diameter (ID) of propellant grains. Ap/At (port area to throat area) ratio is maintained same for both the cases. Although in both the cases predicted maximum flow velocity of propellant gases is almost same. It shows that keeping the same Ap/At ratio and erosive burning effect, the maximum pressure is reduced significantly by lowering OD of propellant grains than increasing the ID of the propellant grains in rocket motor. This study will help to reduce the maximum pressure rise in rocket motors for safe working.
Infra-red decoy flares constituting of Magnesium, Teflon and Viton or MTV, is the most widely acceptable off-board counter measures among majority of the defence forces across the world. These flares ...are essentially pyrotechnic compositions operating in the range of 3–5µm wavelength owing to the selective emission of the combustion products (MgO, MgF
2
and oxides of carbon namely CO and CO
2
). However, literature on manufacturing techniques and performance characteristics of standard configurations flare pellets developed and supplied by few firms globally is somewhat restricted. Hence, this study is an attempt to evaluate the performance of mechanically pressed 50 mm diameter cylindrical MTV pellets. While varying the process parameters viz. charge mass and applied load for pelleting, the cross-sectional area of the pellets and dwell time of applied load have been maintained constant. With increase in applied load, elastic/brittle fracture of the particles occur which increases surface area of contacts between particles. The optimum density was achieved at 8 tons of load. Similarly, the improvement in density with increase in charge mass was observed till L/D ratio of unity was achieved. SEM images confirmed the increase in contact surfaces and reduction in size of particles owing to elastic/brittle fracture. With increase in applied load, the available surface area decreased and there was a conspicuous increase in burn time. With increase in charge mass, the quantity of pyrotechnic mixture available for burning increased leading to increase in burn time.
There are two primary objectives of this study to design the titanium-based novel ENi-P composite coatings on naval grade AH36 steel through Taguchi DOE with the addition of Zwitterionic surfactant ...and identify the most significant factor which contributes to the enhancement of microhardness in the fabricated coatings. The L9 composite coatings are developed by varying bath temperature, pH, wt% of C14-SB and TiO
2
nanoparticles in the electroless bath. Each coatings elemental composition is investigated using SEM and EDAX analysis. XRD peaks are matched with the peaks of Nickel, Phosphorous and Titanium contents in the deposits. The ANOVA and the S/N ratio were deduced and utilised to formulate the optimal combination of parameters for enhancing microhardness in the coatings. The predicted optimal coatings were validated with a confirmation run and achieved 54.66% microhardness enhancement compared with the initial condition and 196.4% improvement achieved with the substrate material AH36 steel. This experimental work proves its first kind of titanium-based ENi-P coating over the marine grade AH36 steel substrate closely associated with defence applications.
This study aims to analyse and forecast the significance of input process parameters to obtain a better ENi-P-TiO
2
coated surface using artificial neural networks (ANN). By varying the four process ...parameters with the Taguchi L9 design, forty-five numbers of AH36 steel specimens are coated with ENi-P-TiO
2
composites, and their microhardness values are determined. The ANN model was formulated using the input and output data obtained from the 45 specimens. The optimal design was developed based on mean squared error (MSE) and
R
2
values. The experimentally measured values were compared with their predicted values to determine the ANN model’s predictability. The efficiency of the ANN model is evaluated with an
R
2
value of 0.959 and an MSE value of 34.563 4. The authors have concluded that the developed model is suitable for designing and predicting ENi-P-TiO
2
composite coatings to avoid extensive experimentation with economic production. Scanning Electron Microscope (SEM) and X-ray diffraction analysis (XRD) are also utilised to compare the base metal and optimal coated surface.
Dry machining is sometimes less effective when higher machining efficiency, better surface finish quality, and severe cutting conditions are required. For these situations, semi-dry operations ...utilizing very small amount of cutting fluids called minimum quantity lubrication is expected to become a powerful tool and played a significant role in a number of practical applications. It has been observed from the literature survey that a systematic research work has to be carried out to determine the optimum quantity of lubricant with appropriate cutting conditions for achieving better machinability characteristics of a material. Hence, an attempt has been made in this paper to enhance the machinability characteristics in high speed turning of superalloy Inconel 718 using quantity of lubricant, delivery pressure at the nozzle, frequency of pulses, direction of application of cutting fluid, cutting speed, and feed rate as the process parameters. Results indicated that the use of optimized minimum quantity lubrication parameters under pulsed jet mode leads to lower cutting force, cutting temperature, and flank wear.
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