基于SPH方法的激光选区熔化数值模拟研究

Numerical simulation of selective laser melting based on SPH method

激光选区熔化是一种常用的增材制造技术,其成形过程涉及传热、熔化、熔池流动及快速凝固等复杂的多物理现象,发展多层多道粉床熔化的数值算法具有重要的科学意义和广阔的工程应用价值.本文基于光滑粒子动力学(SPH)方法,建立了粉末尺度多物理场熔池动力学数值模型,实现了激光选区熔化多层多道的三维SPH数值模拟.首先,针对SPH方法难以实现多层铺粉的问题,提出了一种将SPH表面粒子转化为界面网格的技术,并实现了多层粉末床的铺设;其次,针对单道能量密度以及多道扫描间距对熔道成形的影响展开讨论;最后,通过对比不同工况对应的熔道成形质量,得到了单层的最优工况,并将其用于多层模拟.本文工作弥补了目前SPH方法在粉末尺度金属增材制造数值模拟方面的不足,可为粉末尺度金属增材制造缺陷分析、过程优化及工艺参数与产品性能的关联提供可靠的仿真工具.

The selective laser melting(SLM)is a common additive manufacturing technology.SLM formation involves complex multiphysical phenomena,such as heat transfer,melting,molten flow,and solidification.The development of a numerical method for modeling multitrack powder melting in SLM has important scientific significance and broad application prospects.In this paper,a powder-scale multiphysics numerical model of molten pool dynamics is established using the SPH method.For the first time,the three-dimensional SPH simulation of multilayer multitrack SLM has been realized.First,a key technique for transforming SPH surface particles into interface meshes is proposed,and the multilayer powder bed is realized.Then,the effects of energy density and laser hatch spacing on molten formation are discussed.The optimal simulation condition of a single layer is obtained and further used in multilayer simulation.This work makes up for the deficiency in SPH simulation of powder-scale metal additive manufacturing and can provide a reliable simulation tool for defect analysis,process optimization,and the correlation between process parameters and product performance.