结晶对PLA熔融沉积过程的残余应力影响  

Effect of Crystallization on the Residual Stresses during Fused Deposition Modeling of PLA

作　　者：于康 朱琦 李晗侨 张卿卿 屠大维[1] YU Kang;ZHU Qi;LI Hanqiao;ZHANG Qingqing;TU Dawei(School of Mechatronic&Automation Engineering,Shanghai University,Shanghai University,Shanghai 200444,China;Corporate Technology,Siemens Ltd.,Beijing 100102,China)

机构地区：[1]上海大学机电工程与自动化学院,上海200444 [2]西门子中国研究院,北京100102

出　　处：《塑料》2022年第3期108-114,共7页Plastics

基　　金：上海市青年科技英才扬帆计划(18YF1408400)。

摘　　要：熔融沉积成型(FDM)已被广泛应用于工业生产和日常生活中。聚乳酸(PLA)作为热塑性材料,其结晶过程对制件的残余应力影响较大。因此,建立了PLA的多场耦合FDM工艺动态仿真模型,将整个动态模型分为热传导分析、非等温结晶动力学以及残余应力形成3个部分。利用温度场和翘曲实验验证了模型的准确性,通过有限元方法计算分析了不同冷却速度情况下PLA的结晶动力学对制件内部平面残余应力的影响。在缓慢冷却的结晶情况下,由于结晶放热,PLA内部温度急剧上升,热膨胀应力大于结晶收缩应力,整体平面应力呈现拉伸状态,最大应力值约为5 MPa。在快速冷却的非结晶状态下,PLA内部为热收缩应力,稳定平均值为1.5 MPa。最终分析结果表明,在热塑材料FDM过程中,结晶能够提高结构刚度,但会导致某些区域出现断裂,而非结晶状态下的打印过程中会发生翘曲变形。Fused Deposition Modeling(FDM)had been widely used in daily life and industries.Being the representative thermoplastic in the type manufacturing process,PLA was influenced by the crystallization kinetics which had a significant impact on the residual stresses generated in the final printed parts.A dynamic multi-field coupling simulation model was established based on PLA.The entire model was divided into three parts:heat transfer analysis part,non-isothermal crystallization part,and residual stress calculation part.The model was first verified by online temperature measurement and warpage experiment.Then through the finite element simulation,the influence of the crystallization of the PLA on the plane residual stress was analyzed by comparing between slow and rapid cooling situations.At slow cooling case,the temperature rose sharply due to the exothermal behavior of crystallization.The thermal expansion induced stress was greater than the crystallization induced stress,and the overall plane stress was under tensile state with a maximum value at about 5 MPa.For non-crystallization case under rapid cooling,the average stress was 1.5 MPa under contraction.Finally,the analysis showed that during the FDM process of thermoplastics,the structure stiffness could be improved by crystallization with potential fracture risks in a certain area.In contrast,warpage will take place during FDM process without crystallization.

关 键 词：熔融沉积成型 热塑性材料 结晶动力学 多场耦合仿真 残余应力 

分 类 号：TQ323.4[化学工程—合成树脂塑料工业] TP391.9[自动化与计算机技术—计算机应用技术]