Department of Mechanical engineering

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Author: search.filters.author.Sharma, AnujSubject: search.filters.subject.Micro electrical discharge machining (MEDM)

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    Molecular dynamics simulation of single discharge and dimensionless correlation with actual material removal in micro electrical discharge machining
    (Taylor & Francis, 2019-06) Roy, Tribeni; Sharma, Anuj
    Shorter time pulses and length scales in micro EDM (MEDM) makes it difficult to observe the material removal phenomena taking place at very small zone during discharge. Since numerical or analytical model considers material to be uniform/isotropic, it cannot predict the discrete effects viz. crystal structure distortion due to discharge. Also, little attention has been given to the mechanism of material removal in MEDM at the atomistic level. Therefore, to understand the behaviour of material removal and crystal structure distortion due to single spark in MEDM, MD simulations have been carried out. Based on MD simulations, it was found that the percentage of material removed by vaporisation (∼40%) was higher at spark energies used in this model as compared to spark energies used by Wong et al. (20% at 23.50 µJ). Conversion from FCC crystal structure to amorphous was observed at the top surface of crater in both cases; the one with higher spark energy has marginally higher distortion indicating higher amorphisation. A new method is proposed based on which a dimensionless correlation was obtained between results of MDS and experiments which relates the ratio of specific material removal at higher spark energy to that at lower energy for both MDS and experiments
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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.