Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
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Item Prediction of secondary dendrite arm spacing in squeeze casting using fuzzy logic based approaches(De Gruyter Open Ltd, 2015) Gowdru Chandrashekarappa, M.G.C.; Krishna, K.; Parappagoudar, M.B.The quality of the squeeze castings is significantly affected by secondary dendrite arm spacing, which is influenced by squeeze cast input parameters. The relationships of secondary dendrite arm spacing with the input parameters, namely time delay, pressure duration, squeeze pressure, pouring and die temperatures are complex in nature. The present research work focuses on the development of input-output relationships using fuzzy logic approach. In fuzzy logic approach, squeeze cast process variables are expressed as a function of input parameters and secondary dendrite arm spacing is expressed as an output parameter. It is important to note that two fuzzy logic based approaches have been developed for the said problem. The first approach deals with the manually constructed mamdani based fuzzy system and the second approach deals with automatic evolution of the Takagi and Sugeno's fuzzy system. It is important to note that the performance of the developed models is tested for both linear and non-linear type membership functions. In addition the developed models were compared with the ten test cases which are different from those of training data. The developed fuzzy systems eliminates the need of a number of trials in selection of most influential squeeze cast process parameters. This will reduce time and cost of trial experimentations. The results showed that, all the developed models can be effectively used for making prediction. Further, the present research work will help foundrymen to select parameters in squeeze casting to obtain the desired quality casting without much of time and resource consuming. © by M.B. Parappagoudarb 2015.Item Influence of Ni-P Coated SiC and Laser Scan Speed on the Microstructure and Mechanical Properties of IN625 Metal Matrix Composites(Springer US, 2015) Sateesh, N.H.; Kumar, G.C.M.; Krishna, K.Nickel based Inconel-625 (IN625) metal matrix composites (MMCs) were prepared using pre-heated nickel phosphide (Ni-P) coated silicon carbide (SiC) reinforcement particles by Direct Metal Laser Sintering (DMLS) additive manufacturing process under inert nitrogen atmosphere to obtain interface influences on MMCs. The distribution of SiC particles and microstructures were characterized using optical and scanning electron micrographs, and the mechanical behaviours were thoroughly examined. The results clearly reveal that the interface integrity between the SiC particles and the IN625 matrix, the mixed powders flowability, the SiC ceramic particles and laser beam interaction, and the hardness, and tensile characteristics of the DMLS processed MMCs were improved effectively by the use of Ni-P coated SiC particles. © 2015, Springer New York.Item Characterization of short E-glass fiber reinforcedgraphite and bronze filled epoxy matrix composites(Iran University of Science and Technology Narmak Teheran 16844, 2016) Patil, N.; Krishna, K.The mechanical characterization of short E- glass fiber reinforced, graphite and sintered bronze filled epoxy composite was carried out in this study. The aim of the present study was to develop tribological engineering material. In this study the flexural strength, theoretical and experimental density, Hardness and Impact strength of composites was investigated experimentally. The results showed that the increased percentage of graphite (10 to 15%Vol) and Eglass fiber (10 to 15%Vol) enhanced flexural strength (149 MPa) of the composite and the maximum flexural modulus (13.3 GPa and 13.1 GPa) was obtained for composite C2 and C5 respectively. Maximum hardness (84 on L scale) and impact energy (90 Joule) was obtained for the composite C6 with increased percentage of glass fiber and graphite filler. The metallurgical electron microscopic images were discussed to interpret the effect of graphite and sintered bronze on mechanical characterization of composite. © 2016, Iran University of Science and Technology. All rights reserved.Item Design and development of microneedle array-based electrode for bio-potential measurement(Inderscience Publishers, 2017) Balashanmugam, N.; Naveen, K.; Krishna, K.; Mohan Kumar, G.C.Conventional wet electrodes used in bio-potential measurement like EEG, ECG, etc., require the need for conductivity gel application on skin to wet the surface so that more contact area exist between skin and electrode resulting in better signal acquisition. Wet electrodes have certain drawbacks like the gel tends to underperform within one to two hours after application due to reasons like body heat. To overcome this drawbacks, dry electrodes are being developed which can be classified into two types; one penetrating skin and the other not. Both this type of electrodes has the advantages and limitations. The major drawback of filament type non-penetrating dry electrodes is that if the interest is in acquiring signals during motion, these electrodes tend to move relative to the skin resulting in noisy signal where as the microneedle can overcome this drawback by being continuously in contact with skin in all circumstances. In present work we have used micromachining technique to fabricate PMMA microneedle array. The study involves design of microneedle array, fabrication and mechanical testing of microneedles for skin insertion. It was found that for skin insertion upto 150 ?m microneedles 7.5 N load was required and microneedles were structurally stable at this load. © © 2017 Inderscience Enterprises Ltd.Item Effect of cusn filler on tribological performance of glass fiber-epoxy composite(IAEME Publication, 2017) Patil, N.; Krishna, K.The aim of this research work was to design polymer matrix composite material for sleeve bearing application. The friction and wear performance of short glass fiber reinforced epoxy (CY230,) filled with graphite (C,) and sintered bronze (CuSn) were investigated by pin on disc wear test. The thermal analysis was also carried by TGA (Thermo Gravimetric Analysis,) to study stability of designed composites. It was observed that the friction coefficient and wear was significant at the start of the test. As the normal load, sliding distance and sliding velocity increased it was considerably reduced. Fillers and fiber separation might have led to initial high wear and later-on lubricating film developed on pin surface might helped in reducing friction coefficient and wear. © IAEME Publication.Item Synthesis of high hardness IR optical coating using diamond-like carbon by PECVD at room temperature(Elsevier Ltd, 2017) Krishna, K.; Varade, A.; Niranjan Reddy, K.; Dhan, S.; Chellamalai, M.; Balashanmugam, N.; Krishna, P.Diamond-like Carbon (DLC) for IR antireflective properties is currently being used in the coating of germanium based IR optics. These DLC coatings offer better wear resistance as compared to traditional anti-reflective (AR) coatings. The current work emphasizes the development of IR optics using germanium substrate coated with DLC which typically covers IR transmission in wavelength regions like 3–7 ?m and 9–15 ?m. In order to study IR transmission, an optimum film thickness of DLC was calculated and coated on a double sided polished germanium substrate. DLC was coated on a single side of a germanium substrate, as well as on both sides of germanium. DLC has been deposited using Radio Frequency Plasma Enhanced Chemical Vapour Deposition (RF-PECVD) at room temperature without the use of any intermediary buffer layers required for adhesion and high hardness values were achieved at room temperature as compared to existing literature. The transmission of IR through DLC coated germanium windows was measured using Fourier Transform Infra-Red (FTIR) spectroscopy. A comparison between transmission through a single side and double sided DLC coating on germanium has been demonstrated. The hardness of the film was measured using nanoindentation. Scratch test was also performed using nanoindentation. Adhesion and salt spray tests were performed as per MIL standards. With double sided DLC coating, a peak transmission value of 93% is achieved in 3–7 ?m and the average hardness of DLC is measured to be 32.74 GPa. © 2017 Elsevier B.V.Item Synthesis of high hardness, low COF diamond-like carbon using RF-PECVD at room temperature and evaluating its structure using electron microscopy(Elsevier Ltd, 2017) Krishna, K.; Varade, A.; Reddy, N.; Dhan, S.; Chellamalai, M.; Krishna, P.; Balashanmugam, N.Diamond-like carbon (DLC) coatings have been deposited on Silicon wafers using a Radio Frequency based Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) at room temperature. Experiments were carried out using a flow rate of 100 sccm and 300 sccm of acetylene (C2H2) gas and the bias voltage was varied from 300 to 450 V for DLC deposition. Scanning electron microscope (SEM) and transmission electron microscope (TEM) has been used to study the structure and morphology of the DLC coating. TEM results of DLC coatings deposited at 100 sccm C2H2 flow suggest that some crystalline features of diamond are present in the disordered matrix of DLC. Mechanical properties of DLC coatings were studied using a nanoindenter. The results indicate that the hardest DLC film is obtained at 100 sccm flow rate of C2H2 deposited at 450 V bias voltage of about 32.25 GPa. The results also indicate that the lowest coefficient of friction (COF) of about 0.04 in DLC film is obtained at 300 sccm flow rate of C2H2 deposited at 400 V bias voltage. COF is found to be lower in high C2H2 flow rate, wherever relatively softer DLC was deposited. © 2017 Elsevier B.V.Item Optimal sizing and stacking sequence of composite skid landing gear of a helicopter(IAEME Publication, 2018) Ramesh Kumar, K.R.; Krishna, K.; Nagarathna, H.S.In this paper, the design and optimization of skid landing gear for landing performance and gear strength. The composite skid landing gear is designed to replace usual aluminium 7075 skid landing gear using Kelvar49 epoxy, High modulus (HM) carbon/epoxy and AS4/8552 epoxy composites. A formulation and solution technique using a particle swarm algorithm (PSA) for design optimization of composite skid landing gear is obtainable. The reason of using PSA is to optimize and weight minimization of skid landing gear by considering the constraints such as angle of orientation, ply stacking sequence and ply thickness, taking aluminium alloy 7075 as base metal. The weight savings of the both composite skid landing gear have been calculated. © 2018 IAEME Publication.Item Chemical characterization and source apportionment of ambient PM10 in Hubli-Dharwad region, Karnataka, India(World Research Association, 2021) Navalgund, N.; Keshava, J.; Krishna, K.; Srinikethan, S.; Sampagaon, N.; Manoj, K.; Aishwaraya, S.In India, particulate matter (PM10) shows very strong persistence and very high levels in most of the tier-II cities along with metropolitan cities and other cities of the world. The present work was to study air pollution (PM10) in Hubli-Dharwad, a tier-II city of Karnataka, India. The mean mass concentration for PM10 varied from 260-410 ppm, substantially higher than guidelines of CPCB. Seasonal variations of these pollutants indicated that higher concentrations of pollutants were observed in summer than in winter seasons with air quality index (AQI) as 211 in summer. The source apportionment study using positive matrix factorization (PMF5) indicated the presence of heavy metals in the atmosphere. Out of 4 identified factors, motor vehicles contributed vastly (38.8%), dust (16.4%), industrial emission (19.8%) and biomass burning (25.0%). This study has found that the source apportionment has distinct regional and seasonal characteristics. Such studies are essential for the Government to make region specific control strategies for particulate pollution in India. © 2021 World Research Association. All rights reserved.