Abstract:

In order to acquire the heating-cooling process of laser molten pool and the mutual effect of sintering layers in multi-layer powder sintering, factors such as heat conduction, heat radiation, heat convecting and changeable thermophysical property parameters were taken into account comprehensively, the 3D transient state FEM of the temperature field of multi-layer thin-wall metal parts formed by DMLS was established based on ANSYS. The APDL (ANSYS Parametric Design Language) was used to carry out thermal resource moving and the technique of birth/death for element was used to simulate the process of material addition. The simulation results show that with the present process parameters ,sintering depth is over 0.15mm,sintering width is about 0.61mm, sintered part is jointed tight with substrate and within the inter-layers; the thermal gradient along z direction within the sintered part is absolutely predominant compared with that along x direction, so heat dissipates mainly along z direction during cooling process. At last the sintering experiment was carried out, it indicates that experimental result agrees with the previous simulation result well.

Key words: direct metal laser sintering (DMLS), multi-layer sintering simulation, transient temperature field, technique of birth/death for element

摘要：

为掌握多层粉末烧结过程中激光熔池的加热冷却规律以及各烧结层之间的相互影响，综合考虑热传导、热辐射和热对流以及材料的高度非线性，基于ANSYS平台建立了多层金属薄壁件的三维温度场有限元模型，利用APDL语言编程实现模拟中激光热源的移动，采用“单元生死”技术描述粉末材料动态增长过程。模拟结果表明：在现有工艺参数下，烧结获得的熔深在0.15mm以上，熔宽在0.61mm左右，烧结成形件与基体以及层层之间搭接牢固；成形件中，与x方向的热梯度相比，z方向热梯度占绝对优势，这说明成形件在冷却过程中热量的散失以堆积方向为主。将模拟结果与实验结果进行了对比，实验结果较好地验证了模拟结果。

关键词: DMLS, 多层烧结模拟, 瞬态温度场, 单元生死技术