2. Thesis and Dissertations
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Item Modified QUIC Protocol with Congestion Control for Improved Network Performance(National Institute of Technology Karnataka, Surathkal, 2019) Kharat Prashant, Krishnarao; Kulkarni, MuralidharIn a computer communication network, transport layer is responsible for reliable data delivery with guaranteed Quality of Service (QoS). Congestion control mechanism is one of the prime features of transport layer and predominantly responsible for maintaining the performance of network. The main contributions of this thesis are to modify the existing handshaking mechanism of Quick UDP Internet Connections (QUIC) protocol, called modified QUIC (ModQUIC) to reduce control overhead and Congestion Window (cwnd) size update delay. The suggested modification fine tunes the window update mechanism with Acknowledgment (ACK), that results in smooth variation in cwnd growth. Further, it regulates the network traffic which in turn helps to control congestion. In the first phase, we have suggested modification of the existing QUIC protocol called the ModQUIC protocol and its performance has been evaluated with Chromium server-client model testbed. The results and analysis are presented in comparison to QUIC and TCP in terms of performance measures like throughput and delay. Here, the performance has been tested for limited and sufficient link bandwidth in presence of loss, whereas the validation of results have been carried out with the help of linear regression model. In the result analysis, it was evident that ModQUIC achieves a throughput improvement of 35.66% and 51.93% over QUIC and TCP respectively, whereas delay is also reduced to 3% and 5% in comparison to QUIC and TCP. In the second phase, ModQUIC performance is verified in emulated environment using the Mininet for transport layer and browser network. The experimental results of ModQUIC are compared with QUIC, TCP and TCP/HTTP2 based on throughput, delay and fairness. It has been observed that ModQUIC outperforms throughput with an increased speed by minimizing transmission delay and improvised fairness. In addition, specifically for lossy link and low bandwidth, ModQUIC performance is better compared to QUIC and TCP. One of the QUIC features is inbuilt congestion control mechanism, which is responsible for maintaining streaming data. If there is no congestion, regular window size update is carried out as a step by step approach. In next phase of research work, ModQUIC protocol is investigated with CUBIC and Botitleneck Bandwidth Round-trip-propagation (BBR) congestion control mechanisms and suggested use of a decreased value for the factor β = βTCP=n for n flows, which are competing to acquire bottleneck resources, where βTCP is the decrease factor used in TCP. The Chromium server-client testbed experiment results show that the ModQUIC with BBR giver better performance in terms of throughput, delay and datarate. The result analysis actually gives an improvement of 6.8%, 19.06% and 27.9% for the ModQUIC/BBR as compared to ModQUIC/CUBIC, QUIC/BBR and QUIC/CUBIC respectively in terms of throughput. Furthermore, the delay is reduced by 8.02%, 6.56% and 14.38% over ModQUIC/CUBIC, QUIC/BBR and QUIC/CUBIC respectively. The QUIC protocol versions are updating faster and new versions of the same are available for users. In the final contribution of the research work, the performance of QUIC protocol has been tested with respect to congestion control using India’s rapidly growing Internet Service Provider (ISP); Reliance Jio 4G (JioFi) network. This experimental study investigated ModQUIC performance for congestion control mechanisms CUBIC and BBR in JioFi. The experiment is conducted using a testbed, developed with JioFi and Raspberry Pi-3 wireless router along with network emulator; Netem. Furthermore, the QUIC performance is verified with respect to Throughput and Retransmission Ratio (RTR) in which it is observed that overall ModQUIC/BBR performance is better than ModQUIC/CUBIC in the current Internet. We observed that Reliance Jio is an economical solution for the highly populated country like India, but not a contemporary solution to fulfill India’s newly launched digitization project.Item Performance and Emission Characteristics of Vateria Indica Oil as Alternative Fuel for Petrodiesel in CI Engine(National Institute of Technology Karnataka, Surathkal, 2019) Rao, Gangadhara.; Kumar, G. N.; Herbert, Mervin A.Vateria Indica Linn seeds contain nearly 19% oil/fat which can be converted into biodiesel by normal method of esterification followed by transesterification generally adopted for high FFA oils. Biodiesel is a promising alternative fuel for CI engines. In the present work, study of the combustion, performance and emission characteristics of a CI engine fuelled with Vateria Indica biodiesel blends at 180 bar, 200 bar and 220 bar injection pressures (IP) and injection timings at 19obTDC, 23obTDC and 27obTDC (before TDC) is carried out. Blending is done in volumetric ratios of 10%, 15%, 20%, 25% of biodiesel with diesel which are called as B10, B15, B20, B25. Increasing fuel injection pressure promotes atomization, and full penetration into the combustion chamber leading to better combustion. Blend B25 showed better thermal efficiency of the order of 33.03% and minimum NOX emission of 1047ppm at 220 bar injection pressure and 75% Load. Advancing the injection is proved to be advantageous because of longer residence time and complete combustion with thermal efficiency of the order of 37%, but it also causes higher NOX and soot emissions. Blend is restricted to 25% due to low cetane number of biodiesel which causes severe knocking problem at higher blends. Due to high NOX emission with the blend (B25), NOX mitigation technique like hot EGR is adopted to the extents of 5% and 10%.Finally, it is concluded that blending up to25% can be adopted with 10% EGR at 220 bar injection pressure with 27obTDCinjection timing for better performance, combustion and emission characteristics.Item Computational Modelling of Fluid Flow and Heat Transfer through Metal Foam and Wire Mesh(National Institute of Technology Karnataka, Surathkal, 2019) Kotresha, Banjara.; Gnanasekaran, N.The present research work expounds the numerical investigation of fluid flow and heat transfer through high porosity metallic porous mediums such as metal foam and wire mesh filled in a vertical channel. In the present study the metallic porous mediums are placed on either sides of the heater-plate assembly to enhance the heat transfer. Two different heater assemblies are considered in the present investigation which involves a uniform aluminium plate-heater assembly and a discrete aluminium plate-heater assembly. The present problem is considered as conjugate heat transfer as it involves both solid aluminium plate and fluid flow in the channel. A two dimensional computational domain is selected for the numerical investigation as the vertical channel is symmetrical about the vertical axis. The metal foam/wire mesh region is considered as a homogeneous porous medium with the Darcy Extended Forchheimer model to evaluate the characteristics of fluid flow while the local thermal non-equilibrium heat transfer model is considered for the analysis of heat transfer. The objectives of the present research work are to quantify the effect of pore density, porosity, partially filling thickness, thickness and thermal conductivity of same pore density metal foam, finding out the isothermal condition in discrete heat source system and to determine the interfacial heat transfer coefficient for the wire mesh porous medium in mixed convection and forced convection regimes. Three different filling rates of 40%, 70% and 100% by volume in the vertical channel are also considered for the investigation for the partial filled metallic porous mediums in the vertical channel. The results in terms of Nusselt number, Colburn j factor and overall performance factor are presented and discussed for the cases studied in this research work. This work serves as the current relevance in electronic cooling so as to open up more parametric and optimization studies to develop new class of materials for the enhancement of heat transfer.Item Experimental Investigations on Diamond Burnishing of 17-4 Ph Stainless Steel under Sustainable Cooling Environments(National Institute of Technology Karnataka, Surathkal, 2019) B, Sachin.; S, Narendranath.; Chakradhar, D.The materials which initiate more tool wear, heat, cutting force, and poor surface finish during machining are termed to be difficult-to-cut materials. The precipitation hardenable (PH) stainless steel is one of the interesting family of steels which can attain hardness up to 49 HRC. In these family of stainless steels, 17-4 PH stainless steel has attracted engineers across the world because of its superior corrosion resistance and high strength, which is not possible to find in any of the steel grades. Owing to low thermal conductivity, high strength and admirable wear resistance properties, it has been classified under difficult to cut materials. It is a special type of PH martensitic stainless steel which consists of martensite along with a small quantity of austenite. Compressor blades of steam turbines are subjected to high temperature, vibration, and stress inducement. These issues can cause damage to the engine. Hence, the first set of compressor blades can be manufactured with PH stainless steel to avoid the problems arising due to foreign object damage. Machining of such kind of steels results in poor surface quality and also the production cost is more. Burnishing is one of the preferred secondary finishing operations which is usually performed after machining to achieve the mirror finish of the surface. To achieve the superior surface characteristics of the difficult to cut material, it is preferred to cool the burnishing zone with an appropriate lubricant. Millions of workers throughout the world get affected by working under different kinds of cutting fluids or coolants. Aerosol particles or mist are some of the hazardous elements which will be generated during the application of different types of cutting fluids during machining and which affects the operator’s health. Cryogenic machining has emerged as an alternative cutting fluid in the last two decades. Liquid nitrogen (LN2) will be sprayed at the interface of the tool and workpiece. It is environmental friendly coolant when compared to other conventional coolants. During the burnishing process, because of the pressure created in the burnishing zone, the temperature at that region increases. By the application of LN2, the temperature can be reduced, which results in improved surface integrity of the material.A high-quality finishing of the mechanical parts is necessary to attain the improved fatigue resistance and a low friction ratio. Hence the finishing processes are turned out to be a major drive for industrial innovation all over the globe. Some of the secondary finishing processes such as grinding, lapping, honing, and polishing have been widely used to achieve the super finish of the surface. However, to improve the surface quality and geometrical accuracy of the component, burnishing has been introduced. Burnishing is also one of the well-known secondary finishing process used to improve the functional performance of the component. Diamond burnishing is one of the chipless finishing processes where the spherical tip of the tool made up of natural diamond, slides on the surface of the workpiece which causes plastic deformation. Directly after machining, the workpiece can be diamond burnished to acquire improved surface integrity. It is an economical and compatible process which can be applied on ferrous and nonferrous materials to achieve the mirror-like surface finish. It has a higher level of efficiency when compared to grinding, lapping, and polishing processes. The main objective of this research work is to investigate the influence of process parameters on the surface integrity characteristics while diamond burnishing of 17-4 PH stainless steel under varying working environments. To achieve the best feasible surface integrity properties of the material, the present research work has been classified into four phases. In the first phase, one factor at the time approach (OFATA) was used to find out the influence of control factors such as burnishing speed, burnishing feed and burnishing force on performance characteristics such as surface roughness, surface hardness, surface morphology, surface topography, subsurface microhardness and residual stress using a commercially available diamond burnishing tool. The cryogenic cooling, minimum quantity lubrication (MQL), and dry environments were considered for the study. In the second phase, a novel diamond burnishing tool was designed and fabricated to improve the performance characteristics of the material. To analyze its performance under all the three environments, OFATA was used. Further, the study was extended to investigate the influence of two more process parameters such as the number of tool passes and diamond sphere diameter on the performance characteristics in the cryogenic cooling condition. Inthe third phase, the optimization of process parameters was performed by Taguchi’s Grey Relational Analysis (TGRA). In the fourth phase, a mathematical model was developed for surface roughness and surface hardness by Response Surface Methodology (RSM). The developed regression equation was used to perform multi-objective optimization using genetic algorithm (GA). The optimal process parameters were achieved, which will be beneficial in improving the performance of the component.Item Experimental and Numerical Studies on the Performance of Polyethylene Graphene Based Composite Phase Change Materials for Thermal Energy Storage(National Institute of Technology Karnataka, Surathkal, 2019) Santosh; Gumtapure, Veershetty.; D, Arumuga Perumal.Thermal energy storage domain is filled with composite phase change materials (CPCMs) for thermal performance analysis. The assessment is carried out for different nano additive materials such as copper and Al2O3 with square and rectangular geometric models. The interface morphology is used to understand the flow structure, and two-dimensional energy transport. The flow patterns are depending on the orientation (deep and shallow) of flow domain and initial sub-cooling. The orientation also has significant effect on formation of natural convection currents, heat transfer rate, and melting time. Effects of deep domain orientation (45 ̊, 90 ̊, 135 ̊ and 180 ̊) with different wall heating (base, left, top) conditions are analyzed numerically during melting and solidification processes. As the orientation changes, the heat transfer rate gets influenced significantly and convection currents amplifies. Next, to study the effect of geometry on melting and solidification characteristics, three different geometrical models of square, pentagon and hexagon are considered. Among the three models, hexagon model shown optimum results for both the heating and cooling processes with uniform and smooth variation in liquid fraction and temperature. To achieve the competence in thermophysical properties nanoparticle are blended to base materials (polyethylene). In the present work, linear low-density polyethylene (LLDPE) is blended with functionalized graphene with different concentrations (1, 3 and 5%) and CPCMs are named as CPCM-1, CPCM-2 and CPCM-3 for 1, 3 and 5% respectively. Polyethylene-based composites with optimal concentration (3%) can be utilized for thermal energy storage applications. Higher nanoparticle concentration (5%) emulsifies the molecules and generates micelles between themselves. The present work also attempts to address the energy issues by converting recycled plastics into thermal storage materials (TSM). Unfavorable thermophysical properties of plastic make it impractical, but these inadequacies can be amended by blending with additives of superior thermophysical properties such as functionalized graphene (f-Gr) and carbonbased nanoparticles. The experimental results shown energy level enrichment with nanoadditive concentration. Among the TSM, CPCM-2 shows relatively better storage capability due to incorporation of optimum concentration of enhancing material. The solidification process takes place through convection and radiation mode of heat transfer. An energy storage estimation is also performed through characterization, numerical and experimental studies. Thermal energy storage model implementation determines the better utilization of thermal energy for a greener environment.Item Investigation on Elevated Temperature Adhesive Wear Behavior of Microwave Fused Thermal Spray Tribaloy Composite Coatings(National Institute of Technology Karnataka, Surathkal, 2019) C, Durga Prasad; Joladarashi, Sharnappa; Ramesh, M. R.Metallic materials that operate under high speed, high temperature and harsh chemical environments are prone to wear and corrosion degradation. This leads to the failure of metallic components and results in huge economic loss to industries. The amorphous alloy or metallic glasses exhibit superior properties like high hardness, good wear, and corrosion resistance. Metallic glasses eliminate an ordered crystalline structure, hinders plastic deformation. The Co-based amorphous alloy is the best example of bulk metallic glassy structure alloy and presence of primary intermetallic laves phase’s exhibits good mechanical as well as chemical properties. This is mostly employed as coatings because they are too brittle to be used in bulk form. Co-based metallic glass coating depositing on metallic materials could positively eliminate the failure of the working component caused by serious wear and erosion issues. In the present study, CoMoCrSi superalloy powder (Tribaloy-T400) comprising of a primary intermetallic laves phase of Co-rich solid solution has shown better mechanical and tribological properties. Processing of CoMoCrSi feedstock powder is carried out through a high-energy ball milling (HEBM) technique to obtain a higher volume fraction of intermetallic laves phases. The hard phases of 30% Cr3C2, WC-CrC-Ni and WC-12Co are reinforced into milled CoMoCrSi feedstock. The four different feedstock powders CoMoCrSi, CoMoCrSi+30%Cr3C2, CoMoCrSi+30%WC-CrC-Ni and CoMoCrSi+30%WC- 12Co are sprayed on pure titanium grade-15 substrate using High-Velocity-Oxy-Fuel (HVOF) and flame spray methods. The as-sprayed coatings are subjected to post heat treatment to refine their metallurgical and mechanical properties using microwave hybrid heating technique. Characterization of feedstock, as-sprayed and microwave fused coatings is done by using Scanning Electron Microscopy (SEM), Energy dispersive spectroscopy (EDS) and X-ray Diffraction (XRD). Porosity, surface roughness, microhardness, and adhesion strength of as-sprayed and fused coatings are evaluated. The substrate, as-sprayed and microwave fused coatings are subjected to elevated temperature sliding wear test against alumina disc under dry conditions. The test is carried out at 200°C, 400°C, and 600°C temperatures for 10 N and 20 N normal loads. Microwave fused coatings exhibit higher wear resistance than the as-sprayed coatings and substrate. The hard intermetalliclaves phases which are amorphous (bulk metallic glass) in nature strengthen the coatings at high temperatures. Co3Mo2Si, Co7Mo6, Mo3Si, Co3Mo, and Co2Mo3 are the intermetallic laves phases generated in CoMoCrSi feedstock during HEBM process. The coatings produced from HVOF and flame spray process exhibits heterogeneous structure by showing cracks and pores, also cohesive strength between splats is low. The microhardness and adhesion strength of as-sprayed coatings is lower than fused coatings. Microwave fused coatings exhibit homogeneous structure with less porosity, and surface roughness. The posttreated coatings reveals the inter-diffusion of atoms near substrate-coating interface region, these results in formation of metallurgical bonding leads to increase in microhardness and adhesion strength. The as-sprayed coatings exhibits higher wear rate and coefficient of friction due to lower microhardness. The worn surface of as-sprayed coatings reveals detachment of splats with severe deformation results in adhesive wear mechanism. Microwave fused coatings exhibits lower wear rate and coefficient of friction due to higher microhardness obtained from intermetallic laves phases and also formation of homogeneous structure. The fused coatings exhibits tribo-oxide layers during sliding action which is the main phenomenon for improving the wear resistance of the fused composite coatings. CoMoCrSi+WC-12Co composite coating showed better mechanical and tribological properties compared to other types of coatings.Item Experimental Investigation of 3d Printed Syntactic Foam Composites(National Institute of Technology Karnataka, Surathkal, 2019) Patil, Balu.; Doddamani, MrityunjayPolymer matrix composites can reduce the structural weight and result in improved fuel efficiency and performance in transportation applications. Thermoplastic matrix composites have been used for semi-structural and engineering applications. In addition to the ease of fabrication using a wide range of forming processes, thermoplastic polymers are recyclable, which is the strong driving force for their current and future applications. Rapid production of high quality components is the key to cost reduction in industrial applications. The present work is the first attempt of manufacturing syntactic foams, hollow particle filled lightweight composites using thermoplastic based fused filament fabrication /fused deposition modeling (FFF/FDM) 3D printing process. High Density Polyethylene (HDPE) is used as the matrix material and fly ash cenospheres as the filler. Development of syntactic foams with cenospheres serves dual purpose of beneficial utilization of industrial waste fly ash and reduction in the component cost. Hollow fly ash cenospheres are blended with HDPE to form cenosphere/HDPE blend and is extruded to filament form and finally fed through 3D printer for printing ecofriendly lightweight syntactic foams. Prior to filament development, thermal degradation, melt flow index (MFI) and rheological properties of cenosphere/HDPE blend are studied. MFI decreased by 39.29, 60.54 and 70.51% with increasing cenospheres content of 20, 40 and 60 vol. % respectively. Rheology study of cenosphere/HDPE blend revealed complex viscosities values are maximum at a lower frequency but decreases with an increasing frequency indicating shear thinning behaviour. Both storage and loss modulus showed an increasing trend with filler content and frequency. Single screw extruder parameters are optimized to develop ecofriendly syntactic foam filament with minimum cenosphere fracture and to obtain homogeneous mixing of constituents. The optimized parameters are used for manufacturing syntactic foams filament with 20, 40 and 60 vol.% cenosphere in HDPE matrix. Further, recycling potential of foam filament is also studied. Density of H40 (HDPE with 40 vol.% ofcenospheres) foams increased in up to two extrusion passes (2X) due to cenosphere breakage and porosity consolidation. Tensile properties of developed filaments are carried out to assess its viability into 3D printer. Tensile modulus and yield strength of neat HDPE filaments increased with each extrusion pass. Specific modulus of 3D printed H40-2X and 3X are 1.6 and 2.6 times higher than the respective filaments, however, fracture strain decreases by up to 40%. For first time extruded (1X) filament with addition of cenosphere density reduces due to intact cenosphere and void formation during extrusion, making it a 3 phase foam material. The void content and weight saving potential increases with increase in filler content and their values are higher for 3D prints than respective filament. Higher filler loading increases filament modulus by 7.72-12.79% as compared to HDPE. Among the foam filaments, H20 composition registered the highest ultimate strength (10.30 MPa) and strain at break (26.20%). Differential scanning calorimeter and X-ray diffraction analysis of neat HDPE and foam filaments crystallinity is used to assess the parametric optimization of 3D printing process. It is observed that addition of cenosphere reduced crystallinity of HDPE. HDPE and foam filaments exhibit lower crystallinity as compared to respective printed material. Coefficient of thermal expansion (CTE) of 3D printed HDPE and its foam is studied to understand warping and shrinkage phenomenon occurring during printing. It is observed that filler addition in HDPE matrix reduces CTE remarkably. Warpage of the specimen is reduced with filler content and print quality is further improvised by optimizing printer speed, layer thickness, print temperature and cooling conditions. Tensile tests are carried out on filaments and printed samples. Cenospheres addition resulted in improved tensile modulus and decreased filament strength. Tensile modulus of printed foams increases with filler content. 3D printed HDPE and foams modulus is better than respective feedstock material (filament). Tensile properties of 3D printed HDPE and foams are compared with injection molded samples. 3D printed HDPE registered higher tensile modulus and fracture strength compared to injection molding. Flexural test is conducted on 3D printed sample in two configurations (topand bottom face of print subjected to the load). Results obtained from both configurations reveals that second configuration has shown better flexural modulus and strength. Neat HDPE print did not show any fracture below 10% strain. Flexural modulus increases with cenosphere content. Highest modulus is exhibited by H60 which is 1.56 times better than neat HDPE print. Raster gaps in 3D prints lowers flexural modulus and strength as compared to fully dense injection molded sample. Quasi-static and regular strain rate compressive response is investigated on prints. Compressive behaviour of 3D printed foams follow similar trend in quasi-static and regular compressive mode as reported in fully dense injection molded two-phase foams. Modulus of neat HDPE is higher for all strain rates as compared to foams. Yield strength shows an increasing trend with strain rate. Highest specific compressive modulus and yield strength is observed for H60 and H20 respectively at 0.1 s-1 among foams. Further, HDPE matrix syntactic foam prints are characterized for their viscoelastic properties by dynamic mechanical analysis. Tests are conducted over 30-125°C temperatures. Storage and loss modulus increase with increasing volume fraction of cenospheres, with a slight difference between HDPE, H20 and H40 vol.%, at all temperatures. Storage modulus decreased with increasing temperature for neat HDPE and foam prints. Storage and loss modulus decrease with increasing temperature in the range of 30-125°C, while Tan δ increases. Structureproperty correlations of all the investigated properties are presented with the help of exhaustive SEM images to understand underlying mechanisms. Property maps for selected test conditions are presented for comparative analysis between FFF/FDM based 3D printing of eco-friendly lightweight syntactic foam prints and other processing routes used for thermoplastics. This work is an effort towards making wide material choices availability for FFF based 3D printing industries. Finally, the potential for using the optimized parameters of 3D printing is demonstrated by printing several industrial components as a deliverable of of this work.Item Buckling and Dynamic Characteristics of Cenosphere/Epoxy Syntactic Foam Composites and Sandwiches under Mechanical and Thermal Loads(National Institute of Technology Karnataka, Surathkal, 2019) Waddar, Sunil Shankar.; Pitchaimani, Jeyaraj; Doddamani, MrityunjayPolymer matrix composites provide lower weight structures and result in improved efficiency and performance in many transportation engineering applications. Thermosetting polymers reinforced with suitable hollow particle constituents, higher specific properties can be achieved. Development of syntactic foams with cenospheres serves dual purpose of beneficial utilization of industrial waste fly ash and reduction in the component cost in addition to weight reduction. In the present study, LAPOX L-12 epoxy resin is used as the matrix material and fly ash cenospheres in as received and silane modified conditions are used as filler material. Manual stirring method is employed for developing cenosphere/epoxy syntactic foams with as received and surface treated cenospheres in 20, 40 and 60 volume %. Sandwich composites are also prepared using sisal fiber woven fabric reinforced in epoxy as facings and syntactic foam as core. With increasing cenosphere content, density of untreated and silane treated foams decreases in general. Influence of cenosphere surface treatment and volume fraction of cenospheres in epoxy matrix on buckling and dynamic characteristics are experimentally investigated in this work. Buckling and free vibration behavior of cenosphere/epoxy syntactic foams under mechanical and thermal loadings are investigated experimentally in this work. Buckling load is obtained from the load-deflection curve based on the Double Tangent Method (DTM) and Modified Budiansky Criteria (MBC). Further, the influence of axial compression load on the natural frequencies associated with the first three transverse bending modes is analyzed. Finally, the buckling loads predicted using DTM and MBC are compared with the buckling load calculated based on the vibration correlation technique (VCT). It is observed that the buckling loads predicted through the three different methods are in close agreement. Experimental results revealed that the buckling load and natural frequency of syntactic foams increase with cenosphere volume fraction. It is observed that natural frequencies reduce with increase in axial compression load for all the modes. However, rapid increase in the fundamental frequency is observed when the compressive load is near and beyond the criticalbuckling load. It is observed that silane modified cenosphere embedded in epoxy matrix registered superior performance (rise in critical buckling load and natural frequencies to the tune of 23.75 and 11.46% respectively) as compared to untreated ones. Experimental results are compared with the analytical solutions that are derived based on Euler-Bernoulli hypothesis and results are found to be in good agreement. Finally, property map of buckling load as a function of density is presented by extracting values from the available literature. Experimental investigation on deflection behavior of fly ash cenosphere/epoxy syntactic foam under thermal environment (three different heating conditions) is investigated. Three different heating cases (increase-decrease, decrease and decreaseincrease) are considered. Influence of fly ash cenosphere volume fraction and nature of temperature variation on deflection behavior of syntactic foam beam is discussed elaborately. The temperature rise on the test specimens are measured using K-type thermocouples and lateral deflections are measured using Linear variable differential transducer (LVDT). The data is collected with the help of in-built LabVIEW program to plot temperature deflection curve. Results reveal that the syntactic foam beam experience snap-through buckling under thermal environment and is reflected by two bifurcation points in temperature-deflection plot also. It is observed that the time duration for which the syntactic foam beam stays in the first buckled position increases with increase in cenosphere content. Thermal environment induces compressive stresses in the samples causing such snap-through buckling. However, such phenomenon is not observed when the syntactic foam beams are exposed to mechanical compressive loads. Temperature variation across the beam length strongly influences snap-through buckling in syntactic foams in addition to volume fraction of filler content. An experimental study on buckling and dynamic response of cenosphere reinforced epoxy composite (syntactic foam) core sandwich beam with sisal fabric/epoxy composite facings under compressive load is presented. Influence of cenosphere loading and surface modification on critical buckling load and natural frequencies of the sandwich beam under compressive load is presented. The critical buckling load isobtained from the experimental load-deflection data while natural frequencies are obtained by performing experimental modal analysis. Results reveal that natural frequencies and critical buckling load increase significantly with fly ash cenosphere content. It is also observed that surface modified cenospheres enhance natural frequencies and critical buckling load of the sandwich beam under compressive load. Vibration frequencies reduce with increase in compressive load. Fundamental frequency increases exponentially in post-buckling regime. Experimentally obtained load-deflection curve and natural frequencies are compared with finite element analysis wherein results are found to be in good agreement. Buckling behaviour of sandwich composites made of syntactic foam core and sisal fabric/epoxy composite facings subjected to non-uniform heating is investigated. The critical buckling and snap-initiation temperatures are found from the temperaturedeflection plots. It is observed that, the critical buckling temperature increase with the filler content in the core material and surface treatment show slightly higher buckling temperature. The sandwich beams undergo snap-through buckling at higher temperatures due to developed viscoelastic forces. Due to increase in stiffness of the beam with filler content the deflection of the beam found to be less. The sandwich beams showed higher buckling temperatures than the neat syntactic foam samples.Item Studies on End Milling of Maraging Steel Using Cryogenic Treated and PVD Coated Cemented Carbide Inserts Under Dry(National Institute of Technology Karnataka, Surathkal, 2019) Varghese, Vinay; Ramesh, M. R.; Chakradhar, D.Maraging steel MDN 250 is an ultra-high strength steel which is developed to meet the large demand for high strength materials. The high strength of maraging steel is due to the precipitation of intermetallics during aging. Maraging steel finds wide applications in tool dies, a piston rod in heavy vehicles, rocket parts etc. The high strength combined with good hardness makes maraging steel difficult to machine material. Excessive tool wear, high heat generation, high power consumption, larger cutting forces, poor surface quality and/or difficulties in chip formation are some of the difficulties faced while machining difficult to cut materials. It is difficult to overcome these difficulties by the use of conventional cutting methods and tool materials. As the conventional cutting tools cannot withstand the high cutting temperature and cutting forces and results in tool wear while machining these difficult to cut materials. This early failure of cutting tools reduce the surface finish, increase the idle time and production cost. Some of the techniques used to overcome these difficulties are cryogenic treatment of cutting tools, coating of cutting tools, using sustainable cutting fluids like cryogenic liquid nitrogen etc. The cryogenic treatment is a new technique which improves the physical and mechanical properties of existing cutting tool in the most economic and sustainable way. It is reported that cryogenic treatment can improve some of properties of cutting tool like tool life, micro hardness, wear resistance, fatigue life, rupture strength and compressive residual stress. The cryogenic treatment use liquid nitrogen at -196°C for cooling the samples to cryogenic temperature and generally held for 24 hours to improve the properties of cutting tool. The present study investigates the effect of cryogenic treatment of cemented carbide (WC-Co) inserts at the different soaking period of 18 h (CT-18), 24 h (CT-24) and 32 h (CT-32) at a sub-zero temperature of−196 °C. The cryogenically treated inserts exhibited higher tool life, better surface finish and lower cutting forces during machining at different spindle speeds. The optimum soaking time for cryogenic treatment of WC-Co inserts is found to be 24 h (CT-24) beyond which there is no improvement in microhardness and wear resistance. However, as the spindle speed increased the effect of cryogenic treatment diminished. Hence the machining performance of cryogenic treated WC-Co inserts at a soakingvi period of 24 hours under three different environment of dry, wet and cryogenic has been investigated. The machining performance and tool life extended under cooling environments and highest tool life and machining performance is found to be during cryogenic machining. Coatings on the cutting tools are one of the outstanding strategies developed to avoid the difficulties in machining like rapid tool wear and lower tool life. A large number of PVD coatings are developed for the milling operations to have better performance. Aluminium and silicon based coatings find most promising applications in the end milling. Thus aluminium based coatings like AlTiN and AlCrN coatings synthesized by cathodic arc deposition (CAD) and silicon nitride based coatings like TiSiN and TiAlSiN synthesized by magnetron sputtering were studied for end milling performance. The coated tool along with the use of cutting fluid can minimize the tool wear and extend the life of the cutting tool. Also considering the environmental hazards, operator safety, recycling, and the disposal issues, use of conventional cutting fluids should be minimized. The liquid nitrogen is used in the experiment as nitrogen is abundant in the atmosphere and causes a rapid reduction in cutting temperature and quickly evaporates into the atmosphere. The tool life is maximum using AlCrN coated tool (125 min) compared to cryogenic treated and other coated tools at a spindle speed of 270 rpm under cryogenic environment. AlCrN > TiAlSiN > AlTiN > TiSiN > CT-24 is the order of tool life of cutting tools.Item Investigations on Characteristics and Performance of Hard Thin Films Developed by Cathodic Arc Evaporation(National Institute of Technology Karnataka, Surathkal, 2019) Badiger, Pradeep V.; Desai, Vijay H.; Ramesh, M. R.The fretting and adhesive wear behavior of Ti, Al and Fe based thin solid films deposited on MDN121 steel substrate are studied. Plasma-assisted cathodic arc evaporation technique is used to develop TiC-C, Ti/TiN/TiCN/TiN/TiCN, AlCN/AlC and FeCrN coatings. FESEMEDS, nanoindentation and Raman spectroscopy are used to characterize the coatings. The fretting and adhesive wear tracks are investigated using an optical profiler, confocal microscopy and electron microscopy. The diamond-like carbon (DLC) is observed in both the coatings. Developed coatings exhibit better mechanical properties with increase in hardness by 24.5 % in TiC-C and 29.4 % in Ti/TiN/TiCN/TiN/TiCN, 8.70 % in AlCN/AlC and 50.79 % in FeCrN coatings compared to the uncoated SNMG120408 WC substrate. During fretting wear analysis, TiC-C coating is exhibited lower coefficient of friction (COF) compared to Ti-multilayer coating. Similarly, FeCrN coating exhibited lower coefficient of friction (COF) compared to AlCN/AlC coating. The volumetric wear loss of TiC-C monolayer coating is better than the multilayer coating. The volumetric wear loss of FeCrN coating is better than AlCN/AlC coating. The wear surface morphology revealed abrasive form of fretting wear mechanism in all coatings whereas galling failure in the substrate. During adhesive wear analysis, TiC-C coating exhibited lower coefficient of friction (COF) compared to Ti-multilayer coating. Similarly, FeCrN coating exhibited lower coefficient of friction (COF) compared to AlCN/AlC coating. TiC-C, Ti/TiN/TiCN/TiN/TiCN, AlCN/AlC and FeCrN coatings exhibited low friction and high wear resistance. Tungsten carbide cutting tool inserts are coated with customized composition of Ti/TiCN/TiN/TiCN/TiN (multilayer), TiC-C AlCN/AlC and FeCrN (monolayer) thin films using cathodic arc evaporation technique. Quality characteristics of coatings are evaluated using calo and VDI3198 tests. Thickness of the coatings are found to be in the range of 1.1-1.8 µm and adhesion quality of HF1 is attained. Machinability of highly alloyed steel MDN431 is studied using the coatings developed on SNMG120408 inserts. The iiiperformance of coated tool inserts are evaluated using cutting speed (59-118 m/min), feed rate (0.062-0.125 mm/rev) and depth of cut (0.2-0.4 mm) as process parameters in turning MDN431 steel. Experiments are conducted based on full factorial design and regression analysis is used to analyze the cutting forces and surface roughness. Optimization of the process parameters has been done with the combination of desirability approach and PSO technique. Optimum machining condition for least cutting force and least surface roughness are obtained at the condition of Vc=118 m/min, f=0.063 mm/rev and ap=0.2 mm for Ti-multilayer coatings, Vc=59 m/min, f=0.063 mm/rev and ap=0.2 mm for TiCC coatings, Vc=75 m/min, f=0.063 mm/rev and ap=0.3 mm for AlCN/AlC coatings and Vc=118 m/min, f=0.063 mm/rev and ap=0.2 mm for FeCrN coatings. ANN modeling has been adopted in order to improve the coefficients of determination (COD) and capability of predictive regression models. ANN trained model and mathematical regression models predict the responses, which follows the experimental data with minimum absolute error. The predicted results are validated with minimum error and developed models are adequate for further their usage. Tool wear was reduced by 3 times in Ti-multilayer, 3 times in TiC-C, 3.62 times in AlCN/AlC and 1.63times in FeCrN coated tools compared with commercially available uncoated WC-Co inserts (SNMG120408).