Mohit Goenka - Academia.edu (original) (raw)

Papers by Mohit Goenka

An analytical solution for the variation in thermal cycles in a finite thickness workpiece, kept ... more An analytical solution for the variation in thermal cycles in a finite thickness workpiece, kept on different semi-infinite backing materials and irradiated by a stationary and moving laser beam has been derived. The effects of laser beam diameter, scan speed and backing material with heat sink compound in between on thermal cycles have been investigated experimentally. The thermal cycles are recorded using a non-contact type IR pyrometer. Mild steel, stainless steel and aluminium are used as backing materials, considering their heat conduction capacity. The effect of these backing materials on cooling rate, affected heat region and solidification time are studied. The cooling trend from analytical model and experiment has been compared. For experiment, a 1 mm finite AISI 1020 sheet has been used and it is irradiated with a stationary laser beam for 0.9 sec for stationary laser beam by varying spot diameters and keeping the power density constant. For moving laser beam, sample has been irradiated with 3 mm spot diameter by varying scan speed. The study shows that the cooling rate at surface i.e. at z=0, for a sample decreases with increase in laser spot diameter and this trend is maintained for all the six samples considered. Cooling is faster as the thermal conductivity of the backing material, with heat sink compound, increases but for a same backing material, without heat sink compound, it decreases. Cooling rate at z=0 for a finite mild steel sheet is minimum and for semi-infinite mild steel sheet it is maximum. Solidification time or melt pool life time follows the same trend as above, viz. for a given sample it decreases with the decrease in spot diameter. For a given spot diameter, with increase in thermal conductivity of backing plate it decreases. With increase in scan speed the effect of backing plate decreases viz. for higher scan speed value of 3500 mm/min cooling rate across all samples are nearly close by and consecutively the effect of backing plate is not observed. For a range of ~0.7-0.75 Cr value thermal cycle plot from analytical model is in good agreement with the experimental graphs for a moving heat source at non-melting condition. All these have been demonstrated using thermal cycle plots, cooling rate bar plots, and heat affected region plots generated using experimental data.

An analytical solution for the variation in thermal cycles in a finite thickness workpiece, kept ... more An analytical solution for the variation in thermal cycles in a finite thickness workpiece, kept on different semi-infinite backing materials and irradiated by a stationary and moving laser beam has been derived. The effects of laser beam diameter, scan speed and backing material with heat sink compound in between on thermal cycles have been investigated experimentally. The thermal cycles are recorded using a non-contact type IR pyrometer. Mild steel, stainless steel and aluminium are used as backing materials, considering their heat conduction capacity. The effect of these backing materials on cooling rate, affected heat region and solidification time are studied. The cooling trend from analytical model and experiment has been compared. For experiment, a 1 mm finite AISI 1020 sheet has been used and it is irradiated with a stationary laser beam for 0.9 sec for stationary laser beam by varying spot diameters and keeping the power density constant. For moving laser beam, sample has been irradiated with 3 mm spot diameter by varying scan speed. The study shows that the cooling rate at surface i.e. at z=0, for a sample decreases with increase in laser spot diameter and this trend is maintained for all the six samples considered. Cooling is faster as the thermal conductivity of the backing material, with heat sink compound, increases but for a same backing material, without heat sink compound, it decreases. Cooling rate at z=0 for a finite mild steel sheet is minimum and for semi-infinite mild steel sheet it is maximum. Solidification time or melt pool life time follows the same trend as above, viz. for a given sample it decreases with the decrease in spot diameter. For a given spot diameter, with increase in thermal conductivity of backing plate it decreases. With increase in scan speed the effect of backing plate decreases viz. for higher scan speed value of 3500 mm/min cooling rate across all samples are nearly close by and consecutively the effect of backing plate is not observed. For a range of ~0.7-0.75 Cr value thermal cycle plot from analytical model is in good agreement with the experimental graphs for a moving heat source at non-melting condition. All these have been demonstrated using thermal cycle plots, cooling rate bar plots, and heat affected region plots generated using experimental data.