Material extrusion (ME), an extrusion-based rapid prototyping technique, has been extensively studied to manufacture final functional products, whose forming quality is significantly influenced by the melt flow behavior (MFB) inside the extrusion liquefier. Applied vibration has a great potential to improve the MFB, and thereby promote the forming quality of the built product. To reveal the mechanism, a dynamic model of the melt flow behavior (DMMFB) is established based on fluid dynamics, Tanner nonlinear constitutive equation and Newton’s power law equation. The MFB, i.e., pressure drop, shear stress and apparent viscosity, is investigated without and with different vibration applied. The corresponding finite element analysis (FEA) is then carried out. From the comparison between DMMFB and FEA results, it is concluded that the proposed model is reliable. When vibration is applied onto the extrusion liquefier, the time-domain MFB will change periodically. Its effective value decreases significantly, and further decreases with the increase of vibration frequency or amplitude. This paper provides the theoretical basis to improve the MFB by applied vibration, and thereby to enhance the forming quality of ME products.

中文翻译：

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振动场下材料挤出增材制造中聚乳酸熔体流动行为的理论和计算分析

材料挤压（ME）是一种基于挤压的快速成型技术，已被广泛研究以制造最终的功能产品，其最终成型质量受挤压液化器内部的熔体流动行为（MFB）显着影响。施加的振动具有改善MFB的巨大潜力，从而提高了成型产品的成型质量。为了揭示机理，基于流体动力学，Tanner非线性本构方程和牛顿幂定律方程建立了熔体流动行为的动力学模型。在未施加振动和施加不同振动的情况下，对MFB（即压降，剪切应力和表观粘度）进行了研究。然后进行相应的有限元分析（FEA）。通过DMMFB和FEA结果的比较，结论表明该模型是可靠的。当振动施加到挤出液化器上时，时域MFB将定期更改。其有效值显着降低，并随着振动频率或振幅的增加而进一步降低。本文为通过施加振动来改善MFB，从而提高ME产品的成型质量提供了理论基础。