Articles written in Sadhana

    • Machining performance of Ti6Al4V under dry environment, pressurized air supply and water-MQL: analysis of machininginduced vibration signals and captured thermographs


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      In the present investigation, machining performance of Ti6Al4V is studied under dry environment, pressurized air supply and distilled water based Minimum Quantity Lubrication (MQL). Machining (turning) performance is assessed in purview of cutting force (tangential component) magnitude, tool-tip temperature,width of tool flank wear progression, morphology of evolved chips and severity of vibrations at varied cutting speeds as well as cooling media. Characteristic features of spatial temperature distribution profile (at the vicinity of tool-tip) as influenced by varied cooling media are studied with the help of thermographs of the cutting zone. Mechanisms of cutting tool wear are studied as well. It is experienced that amongst three cutting environments tested, application of water-MQL is beneficial for machining of Ti6Al4V at low cutting speed. Severity of vibrations gets 50.39% reduced during machining under water-MQL than dry condition. Consequently, as compared to dry machining, water-MQL causes 79% reduced tool flank wear and 82% reduced crater wear at low cutting speed. Under water-MQL, reduced tool-tip temperature (66% reduced than dry condition) suppresses severity of tool wear. In comparison with high cutting speed, performance of water-MQL is found much better at low cutting speed. ‘Unaffected zones’ are identified at the worn-out tool rake face under water-MQL. High amplitude of vibration (maximum absolute mean value) causes low chip-segmentation ratio. On the contrary, chip reduction coefficient gets truncated with decrement in vibration amplitude. Vibration amplitude has positiveinfluence on degree of chip-curl.

    • Machinability of Inconel 825 under nano-Al2O3 based nanofluid minimum quantity lubrication


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      In the present work, turning performance of Inconel 825 superalloy is studied under Nanofluid Minimum Quantity Lubrication (NFMQL). Nanofluid used is nano-Al2O3 dispersed distilled water. The tool insert used in this study is PVD multi-layered (TiN/ TiCN/ TiN) coated cermet. The following machiningperformance indicators: tangential cutting force, tool-tip temperature, wear morphologies of the tool insert, macro/ micro-morphologies of chips produced, etc. are studied. It is observed that dry machining environment causes vibration signals of random nature whose frequency and amplitude of acceleration are highly timevariant. On the contrary, periodic vibration signal with lower amplitude of acceleration is detected in case of NFMQL machining. Consequently, NFMQL exhibits lower cutting force, reduced tool-tip temperature, and less severe tool wear than that of dry machining. NFMQL produces thinner chips with shorter segmentation spacing and wider shear angle than dry machining.

    • Parametric studies of fused filament fabrication towards fabrication of 2D auxetic metamaterial cellular structure followed by auxeticity simulation


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      As compared to conventional materials, auxetic metamaterials correspond to cellular structures with low density and better mechanical properties. Mechanical properties of auxetic metamaterials are influenced by both the base material and the geometry (topology) of the unit cell. The high strength-to-weight ratio and tunable mechanical properties of auxetic structures make them suitable for wide engineering applications. In this work, auxetic behavior of novel chiral honeycomb structures (anti-tetra chiral) is studied using Finite Element Method(FEM). In addition, fabrication of a few tensile specimens is carried out by Fused Filament Fabrication (FFF). FFF is an efficient rapid prototyping technology which offers design freedom to fabricate complex geometrical structures (difficult or impossible to manufacture through conventional routes). Several FFF parameters do influence part quality and process performance. In order to study effects of process parameters on part quality (tensile strength, roughness, material consumption) and build time, tensile specimens are fabricated at different build orientations and build styles (dense and sparse). Fractured surface morphologies are observed through scanning electron microscopy to understand the bonding pattern between the layers of FFF parts. Finally, anappropriate combination of FFF parameters is determined through Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) to ensure the maximum part tensile strength, the minimum part surface roughnessand the minimum build timing. Finally, an auxetic anti-tetra chiral candidate specimen of ABS plastic is built through FFF. From finite element simulation, the Poisson’s ratio of anti-tetra chiral 2D structure is found to be close to -1. Poisson’s ratio of anti-tetra chiral 2D honeycomb is found insensitive to the dimensionless topological parameter (i.e. ratio of ligament length-to-node radius). It is experienced that part tensile strength decreases with increase in build orientation angle as well as the air gap (from ‘dense’ to ‘sparse’ building style). The build time of FFF parts depends on the height of the part along the build direction. FFF part fabricated using ‘dense’ build style at 45° build orientation exhibits the best quality and corresponds to the minimum fabricationtime.

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