Calculation Of The Phase Transition And The Oxidation Of The Metalplates Under Laser Irradiation Based On Fluid-solid Heat Coupled

In this paper, the temperature field in the metal plate under laser irradiation and subsonicboundary layer flow are studied here by using the computational fluid dynamics method.Taking the oxidation reaction and the convection heat transfer between the target surface andthe tangential gas flow, the distribution of temperature in metal plate is analyzed. The metalplate is melted after a period time of laser irradiation and appears the metal molten pool. Thetwo phase flow field on effects of near-wall tangential airflow has great influence on laserirradiation. Numerical computation is simulated the velocity of gas flow is respectively0,20,40and60m/s.The numerical simulation results show, before the phase transition of the metal plate, thetarget surface temperature rises rapidly in initial0.2s, with a maximum rate of temperature upto5000K/s, and decline gradually in the later period；and back surface temperature begins torise at about0.6s after the irradiation. Heat loss by convection and the quantity of oxidationheat increase with airflow velocity. The average temperature of the target material inside is thehighest, when the irradiation center temperature is1800K and airflow velocity is60m/s; andthe laser loading time is the longest when nitrogen flow velocity is60m/s. The gas highesttemperature decreases with the increasing of gas flow velocity; and its position is more closerto the right end of laser loading. The quantity of oxidation heat is greater than the heat loss byconvection heat transfer under the same gas velocity, so the laser loading time under thecondition of nitrogen flow is longer than air flow.After phase transition of the metal plate, the temperature does not change with gas flowvelocity, but this platform period increases with gas flow velocity increases, and irradiationcenter temperature fluctuation is more larger. The depth and width of the metal molten poolincreases gradually with laser irradiation time. The molten pool is symmetric developmentunder the condition of no flow; but when there is the gas flow. The metal molten pool isdeeper at the upstream side and is wider at the downstream side. The metal liquor is blew out by gas flow from the molten pool and this is helpful for laser loading when the molten pool isshallow. But when the molten pool is deeper, gas flow can only take away part of the metalliquid and the most moves in the molten pool, and it is disadvantage for laser irradiation. Thequantity of oxidation heat is smaller than the heat loss by convection heat transfer as gasvelocity increases and the reason is that the metal liquor is blew out by gas flow. In the wholesimulation calculation, the metal liquid does not vaporize and the target is not penetrated.