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建立了移动光源下三维瞬态、对流 /扩散固、液、糊状区及相变 ,多相区统一的激光熔凝数学模型。该模型主要解决了已往模型必须将固态和液态分开计算然后进行耦合且不能计算糊状区的缺陷 ,这种方法能够反映糊状区的存在及固液相变过程中潜热的吸收和释放的影响且在计算过程中自动跟踪糊状区位置 ,无须人为划分相区。根据数学模型的特点 ,建立了一套固定网格的数值求解方法。通过熔池深度的计算与实验值的比较验证了模型的正确性。进一步研究了表面张力、浮力等驱动力与激光熔池形状几何尺寸的关系。计算结果指出 ,表面张力和浮力驱动熔池内熔体的对流存在一次环流和二次环流。一次环流使熔池变宽、变浅 ,二次环流使熔池底部出现凹坑。实验印证了计算结果
The laser fusion mathematical model of three-dimensional transient, convective / diffusive solid, liquid, paste-like zone and phase transformation and multiphase zone under moving light source was established. The model mainly solves the defects that the former model must separate the solid state and the liquid state and then couple and can not calculate the pasty area. This method can reflect the existence of the pasty area and the absorption and release of the latent heat during the solid-liquid phase transition And in the calculation process automatically track the location of paste-like area, without the need to artificially divided phase area. According to the characteristics of the mathematical model, a set of numerical methods for solving fixed grids is established. The correctness of the model is verified by the comparison between the calculation of the depth of molten pool and the experimental value. The relationship between the driving forces such as surface tension and buoyancy and the geometric shape of the laser pool was further studied. The calculation results show that the surface tension and buoyancy drive the melt flow in the melt pool first and second circulation. A circulation to the pool widening, shallowing, secondary circulation so that the bottom of the puddle pit. The experiment confirms the calculation result