多组元金属粉末激光选区烧结热力耦合有限元应力场分析

Thermal-mechanical Coupling Finite Element Analysis of Stress Field in Selective Laser Sintering of Multi-component Metal Powder

根据金属粉末激光选区烧结的特点,采用ANSYS有限元软件中的间接热力耦合方法,建立了多组元金属粉末激光选区烧结应力场分析模型。利用生死单元技术,模拟了烧结材料由粉末态转变为高温液态继而转变为连续实体的过程。通过该计算模型,可以掌握激光选区烧结成形过程以及冷却过程中应力场随时间的变化规律,探索烧结件翘曲变形的机理及其影响因素。结果表明,烧结件与基板结合层处σz、τzx、τzy的过大是造成烧结件翘曲变形的主要原因。通过实验验证,模拟分析结果与实际相吻合。经过讨论,提出了通过改善烧结件散热状况、提高基板预热温度、精选基板材质等措施可以有效避免金属粉末激光选区烧结件翘曲变形。

According to the characteristics of selective laser sintering （SLS）, a finite element model for analyzing the stress field in SLS process of a multi--component metal powder system was established by using an indirect thermal--mechanical coupling method. A successive transformation of the sintering material from the powder to the high--temperature liquid phase and, afterwards, to the continuous solids was simulated by using a ＂birth and death＂ element technique of the ANSYS software. The stress field at different time in the sintered part and the base plate can be calculated by the finite element model. The mechanism and the influencing factors of the warping in the sintered parts were discussed. The results show that the σz,τzx,τxy between the sintered part and the base plate are the main cause of the sintered warping. The simulation results show a good agreement with the experimental ones. The analysis shows that the warping and cracking of the sintered part, which is induced by thermal stress, can be efficiently alleviated by optimizing the geometrical structure of the part to be built, enhancing the pre--heating temperature, and well choosing the building substrate.