Department of Mechanical engineering

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Author: search.filters.author.Sharma, AnujSubject: search.filters.subject.Molecular dynamics simulation (MDS)

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    Molecular dynamics simulation of mechanical polishing
    (Inder Science, 2019-07) Sharma, Anuj
    Mechanical polishing, a nano-finishing process is extensively used for generating smooth surfaces on engineering materials. The mechanism of mechanical polishing is extremely complex due to its random nature of material removal at atomic scale. The need for a better understanding of the process at atomic scale is therefore necessary. Hence, molecular dynamics simulation (MDS) was carried out to understand the behaviour of material removal on two different types of engineering materials viz. aluminium and silicon. In the present work, material removal of rough asperities was modelled and simulated by abrading them with abrasive particles. It was observed that the nanometric abrasion occurs through adhesion de-bonding principle, recoverable phase transformation occurs during the nanometric abrasion on aluminium, and the non-crystalline debris formation during polishing of silicon as brittle crystalline structures. In addition, other attributes are also discussed such as force, stress, chemical stability, effect of abrasive particle, and temperature.
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    A molecular dynamics simulation of wear mechanism of diamond tool in nanoscale cutting of copper beryllium
    (Springer, 2019-01) Sharma, Anuj
    In the present study, molecular dynamics simulation (MDS) is employed to study the wear mechanism of single crystal diamond tool during nanocutting of copper beryllium (CuBe). Two edge configurations, i.e., both sharp and worn out tools, are chosen to study the tool and workpiece interaction during the nanocutting of CuBe. Further, the study involves the experimental characterization techniques viz. scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy to confirm the simulation results. The results of the molecular dynamics simulation (MDS) show that the presence of Be as a hard particle in workpiece material influences the cutting forces which subsequently causes degradation of the sharp edge of the diamond tool. Furthermore, the carbon (C) atoms removed from the tool react with Be particles and as a result, it causes the formation of beryllium carbide (BeC). Beryllium interaction with the blunt edge configuration of the tool causes amorphization at the tool edge. Raman spectroscopy of the used diamond tool on CuBe reveals the similar phenomena of amorphization of the diamond at the tool edge. Moreover, surface generation is dependent on the tool edge condition as blunt edge tool leads to smoother surface compared to the surface generated by sharp edge configuration.
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    Investigation of tool-workpiece interaction in nanoscale cutting: a molecular dynamics study
    (Inder Science, 2019) Roy, Tribeni; Sharma, Anuj
    Ductile and brittle materials differ in their physical and mechanical properties and pose distinct interaction with the cutting tool while nano-machining. It is thus imperative to analyse the mechanism of material removal and tool-workpiece interaction. Towards this, molecular dynamics simulation (MDS) is carried out to study the diamond tool and workpiece interaction in the nanoscale cutting of Cu (ductile material) and Si (brittle material). Results show that material removal in Cu takes place through shear deformation by dislocations formation and their propagation while in case of Si, it takes place through phase transformation of the material in cutting zone. Force analysis of both the materials shows that machinability of Cu in nanoscale cutting is better compared to Si. Furthermore, tool wear while machining of Si with sharp edge tool is due to chipping whereas radial distribution function reveals that graphitisation of the round edge tool occurs during machining of Si.
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    Molecular dynamics study on the effect of discharge on adjacent craters on micro EDMed surface
    (Elsevier, 2018-04) Roy, Tribeni; Sharma, Anuj
    Using molecular dynamics simulation (MDS), investigation was carried out to understand the mechanism of material removal during the formation of overlapping craters on surfaces obtained by micro electrical discharge machining (MEDM) and their effect on the crater surface. Apart from overlapping craters, two other cases were also considered viz. craters separated by a finite distance and craters coinciding at the periphery since these two will mostly occur during initial phase of machining. In all cases, the material removal was due to melting and vaporisation; it was also observed that the amount of material removal by vaporisation increased from 36% (approx.) in 1st discharge to 44% (approx.) in the 2nd discharge due to ease of vaporising the amorphous layer formed after the 1st discharge. Moreover, final crater size viz. depth and diameter obtained in the 1st crater measured at the end of MDS was relatively less as compared to 2nd crater. The increase in crater depth and diameter increased with reduction in distance between discharges. The increase in diameter of 2nd crater with respect to 1st crater for all the three cases was observed both during MDS and on the actual surface generated by MEDM.