选择性激光烧结聚苯乙烯粉末成形温度场的数值模拟研究

本文以聚苯乙烯材料为例，对SLS成形三维瞬态温度场的分布变化进行数值模拟计算。计算模型中，考虑了材料的热物性参数随温度变化的情况和激光光强分布不均匀的因素。计算结果表明：烧结过程可以分为两个阶段：第一阶段是光照期的热量输入加热阶段，在该阶段内，光照表面的温度迅速升高，使材料处于过热状态，甚至超过材料的分解点，这一阶段完成粉末表面的致密化，但粉床内部的致密效果不是特别明显；第二阶段是光照结束之后的热量传输阶段，在该阶段内，表面材料吸收的热量向四周扩散，一部分通过对流和辐射换热方式散失到周围环境中，另一部分通过热传导的方式向粉床内部传输，促进粉床内部的烧结，这一阶段粉床内部的致密程度显著提高。

Studies on numerical simulations of temperature field in selective laser sintering of polystyrene powders

Numerical simulations of three-dimensional temperature distribution in selective laser sintering of powders are reported.The factors that the material thermal physical properties vary with the temperature and that the distribution of laser intensity across the beam diameter is un-uniform had been taken into account in the computation model.The simulation result shows that the sintering process can be divided mainly into two stages.In the first stage when the laser beam is on,the focused light of the laser is absorbed into the powder and converted into heat as it contacts the powder surface.The temperature at the powder bed surface increases rapidly,even exceed the decompose temperature.The densification at the powder surface increases rapidly but almost no change in the bed.In the second stage when the laser beam moves away,the thermal energy that the material had absorbed from the laser beam transform to the surrounding.Some of them lost from the powder bed surface by convection and radiation,the other is conducted into the powder bed,which promote the sintering in the powder bed.The densification in the powder bed increases markedly.