Department of Mechanical engineering
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Item Wear of silicon carbide wheel during grinding of intermetallic titanium aluminide(Inder Science, 2020-02) Mathew, Nitin TomAn experimental investigation is reported on the wear of silicon carbide wheel and its influence on the wheel topography and grinding behaviour during the surface grinding of high performance intermetallic gamma titianium aluminide. The radial wear of the wheel was characterised by initial transient state followed by a steady state wear regime and finally a steel rise in wear rate. The initial transient region progressed up to a radial wear of 40 μm. The normal and tangential forces remained approximately constant up to about 25 μm wheel wear and subsequently progressively increased to a maximum at 60 μm wear. The specific energy began approximately at about u = 140 J/mm3 and started progressing beyond radial wear of 25 μm and increased up to 600 J/mm3 at wear of 60 μm. There was high initial roughness value with the fresh wheel with a progressive decrease with continued grinding. There was noticeable increase in roughness value after a radial wear of 60 μm. With the progress of wear there was presence of surface burns, chatter marks and cracking. The presence of blue oxide discoloration was observed during the visual inspection signifying the generation of reasonably high temperatureItem Drilling of titanium aluminide at different aspect ratio under dry and wet conditions(Elsevier, 2016-10) Mathew, Nitin TomTo increase the wide use of intermetallic titanium aluminides for various fields of engineering application, a broad understanding of the machinability of these material is essential. The present work is focussed on the drilling of this intermetallic alloy at low and high aspect ratio under dry and wet environments. The machinability in dry and wet conditions were assessed based on the thrust force, torque, burr formation, surface quality, tool condition and chip morphology. The supply of cutting fluid is found to be effective in reducing the thrust force and torque and producing quality surface. Burr, being an important factor in drilling have also been studied, and the findings show the presence of uniform burr with and without roll back in dry and wet condition respectively. Surface defects formed and their intensity during both the machining environments were analysed. Built up edge formation on the drill tool was detected in all cutting conditions. The transformation of chip shape as the depth of hole progresses is also detailed in the present work. Furthermore, the study demonstrates the feasibility of drilling titanium aluminide in dry and wet environment. The overall results indicate that dry environment is not viable for high aspect ratio drilling.Item Environmentally friendly drilling of intermetallic titanium aluminide at different aspect ratio(Elsevier, 2017-01) Mathew, Nitin TomThere is an increasing attempt to implement green manufacturing in almost all fields of engineering. Minimum quantity lubrication is considered as a relevant and promising candidate in promoting environmentally friendly machining since it bridges the gap between dry and wet condition. It can keep the work material temperature lower than those in a dry environment by reducing the frictional heat generated during the machining processes and deliver certain amount of cooling effect in the tool-workpiece contact region. The present work is focussed on the drilling of this intermetallic titanium aluminide alloy at low and high aspect ratio under minimum quantity lubrication environment and is compared with dry and wet environments. The feasibility of using minimum quantity lubrication is evaluated based on the thrust force and torque. Burr, being an important factor in drilling have also been studied, and the findings show the presence of uniform burr in minimum quantity lubrication condition. In a complex process like drilling, chip flow is restricted only through the flutes and hence there occurs transformation of chip shape, chip thickening and changes in force and torque as the depth of hole progresses. In order to study these changes peck drilling was adopted and the depth at which the transformation of chip shape occurs is identified.Item Selection of Nd:YAG laser beam micro-drilling parameters using multi-criteria decision making methods(Elsevier, 2019-11) Bhattacharyya, SuvanjanMulti criteria decision making methods and response surface methodology based approaches are invariably utilized in improvement of quality in several manufacturing industries. This paper presents the technique to determine optimal process parameters during micro-drilling using Nd:YAG laser source on gamma titanium aluminide alloy using fuzzy-TOPSIS (fuzzy-technique for order preference by similarity to ideal solution) and RSM (response surface methodology) together. A new alloy, Gamma-titanium aluminide (Ti-44.5, Al-2, Cr-2, Nb-0.3B (at%)) has been chosen for experimentation. This material possesses desirable qualities like very high hardness, high strength temperature resistant, high yield stress and ultimate strength in tension, good creep, very low density, resistance to oxidation etc., found applications in technologically advanced industries like spacecrafts, aerospace, nuclear power plants, electronics, automobiles etc. A model has been developed which can be used for decision making in identifying the optimum laser parameters like lamp current, pulse frequency, air pressure and thickness of the workpiece, which affect several quality aspects of micro-machined job such as hole circularity at entry, hole circularity at exit and taper of drilled hole. Triangular fuzzy numbers are being utilized to calculate weighting factor of each machining criterion. Also, the combination of most desirable factor levels has been obtained using a fuzzy-TOPSIS method.