Quasi-static and dynamic behavior of additively manufactured lattice structures with hybrid topologies
Quasi-static and dynamic behavior of additively manufactured lattice structures with hybrid topologies
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DOI：
10.1016/j.addma.2021.102466
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发表时间：
2021-12-01
影响因子：
11
通讯作者：
Hazeli, Kavan
中科院分区：
文献类型：
--
作者：
Barnes, Baxter;Babamiri, Behzad Bahrami;Hazeli, Kavan
当具有不同机械行为（例如，弯曲与拉伸为主）的不同晶胞拓扑结构被并入单个混合晶格结构（LS）中时，出现了关于支柱内的局部应力的分辨率以及局部应变状态作为结果如何支配结构的全局响应的问题。为了理解混合LS的力学，本研究使用实验和建模数据的组合来研究在不同加载方向和应变率下局部应力状态与混合增材制造晶格结构（AMLS）的全局行为之间的关系。本研究中的混合AMLS由两种不同的单元格拓扑结构组成，按交替行堆叠，并根据该拓扑结构堆叠确定加载方向。结果表明，加载方向的影响的力学行为，作为混合AMLS的流动应力是7%-10%，当加载在堆叠方向比当加载在横向方向时低。这种流动应力的降低是由于较少数量的结构元件支撑水平制造的支柱在堆叠方向上的载荷和拉伸失效。应变速率也影响AMLS的力学行为，因为无论加载方向如何，对于所有混合AMLS，静态平衡后的第一峰值应力在动态加载下比准静态加载高5%-10%。此外，它示出的崩溃机制的拓扑堆叠的顺序的影响。结构剪切带的形成，这导致高达60%的混合AMLS的动态载荷下的流动应力下降，可以通过分离相邻行的剪切带形成拓扑结构与一行的拓扑结构，不形成剪切带的单胞来抑制。最终，确定这些分层结构的性能受到最弱拓扑的限制。即使在横向载荷下，其中第一峰值应力接近较强拓扑结构的峰值应力，随后的流动应力降低的幅度通常与较弱拓扑结构的流动应力降低的幅度更一致。
When different unit cell topologies with distinct mechanical behavior (e.g. bending vs stretching dominated) are incorporated into a single hybrid lattice structure (LS), questions arise about the resolution of local stresses within the struts and how localized states of strain as a result govern the global response of the structure. To understand the mechanics of hybrid LS, this study uses a combination of experimental and modeling data to investigate the relationship between localized states of stress with the global behavior of hybrid additive manufactured lattice structures (AMLS) under different loading directions and strain rates. The hybrid AMLS in this study consist of two different unit cell topologies stacked in alternating rows, with loading directions identified with respect to this topology stacking. It is shown that the loading direction influences the mechanical behavior, as the flow stress of the hybrid AMLS is 7%-10% lower when loaded in the stacking direction than when loaded in the transverse direction. This flow stress decrease is due to a smaller number of structural elements supporting the loading and tensile failure of horizontally-manufactured struts in the stacking direction. The strain rate also influenced the mechanical behavior of the AMLS, as irrespective to the loading direction, for all hybrid AMLS, the first peak stress after static equilibrium is 5%-10% higher under dynamic loading compared to quasi-static loading. Additionally, it is shown that the collapse mechanisms are influenced by the order of the topology stacking. Structural shear band formation, which leads to up to a 60% drop in flow stress under dynamic loading of the hybrid AMLS, can be inhibited by separating adjacent rows of shear band-forming topologies with a row of unit cells of a topology which does not form shear bands. Ultimately, it was determined that the performance of these layered structures is limited by the weakest topology. Even under transverse loading, where the first peak stress approaches that of the stronger topology, the magnitude of the subsequent decrease in flow stress is generally more in line with that of the weaker topology.