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Abstract：
Polyamide 12 (PA12) is vastly utilized in many additive manufacturing methods, such as Selective Laser Sintering (SLS), and a better understanding of its mechanical behaviors promotes available knowledge on the behaviors of 3D-printed parts made from this polymer. In this paper, SLS-produced standard tensile specimens are studied under monotonic and cyclic tension tests, as well as stress relaxation experiments, and the obtained force-displacement responses are shown to be consistent with a hyper-viscoelastic material model. This finding is also observed in typical pantographic structures produced by the same manufacturing parameters. To propose a constitutive model for predicting these behaviors, the convolution integral of a strain-dependent function and a time-dependent function is developed where the material parameters are determined with the use of both short-term and long-term responses of the specimens. Numerical results of the presented model for standard test specimens are shown to be in good agreements with the experimental ones under various loading conditions. To prove the capabilities of the proposed model in studying any SLS-produced part, finite element implementation of the constitutive equations is shown to provide numerical results in agreement with the empirical findings for tensile loading of the 3D-printed pantographic structure.
摘要：
聚酰胺12（PA12）在许多增材制造方法中得到了广泛的应用，如选择性激光烧结(SLS)，并且更好地了解其力学行为可以促进对由这种聚合物制成的3D打印部件的行为的可用知识。在本文中,在单调和循环拉伸试验下研究了SLS生产的标准拉伸试样，以及应力松弛实验，所获得的力-位移响应与超粘弹性材料模型一致。在由相同的制造参数生产的典型的缩放结构中也观察到该发现。为了提出一个预测这些行为的本构模型，建立了应变相关函数和时间相关函数的卷积积分，其中使用样品的短期和长期响应来确定材料参数。在各种载荷条件下，所提出的标准试样模型的数值结果表明与实验结果吻合良好。为了证明所提出的模型在研究任何SLS生产的零件方面的能力，本构方程的有限元实现表明，数值结果与3D打印缩放结构的拉伸载荷的经验结果一致。
