Designing additively manufactured lattice structures based on deformation mechanisms
Designing additively manufactured lattice structures based on deformation mechanisms
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DOI：
10.1016/j.addma.2021.102143
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发表时间：
2021-10-01
影响因子：
11
通讯作者：
Hazeli, Kavan
中科院分区：
文献类型：
--
作者：
Babamiri, Behzad Bahrami;Barnes, Baxter;Hazeli, Kavan
增材制造晶格结构（AMLS）的屈服后力学行为是由不同长度尺度上的内在（微观结构）和外在（结构拓扑）性能之间的相互作用决定的。在此，我们引入了一种新的设计优化方法，该方法考虑了控制变形机制的尺度分离和尺寸效应，以实现一定的目标宏观力学响应。新的拓扑设计是通过寻找支撑内部局部应力分布与底层微结构之间的直接关联来指导的。局部应力计算使用支柱水平屈服准则，已校准支柱水平拉伸，压缩和剪切加载实验。因此，在屈服面上考虑了支撑的局部响应，包括拉压不对称、构建方向依赖和尺寸效应，从而能够更准确地表示局部应力状态。精确计算给定微观结构和拓扑组合的应力状态，可以优化给定支柱级微观结构的拓扑结构。通过研究单位胞级变形机制，并通过有限元模拟量化其对整体应力-应变关系的影响，评估了拓扑结构和微观结构之间的相互作用。利用这些关系，可以设计、构建一组新的拓扑，并通过实验进行验证。平均而言，与之前使用本构模型优化的拓扑结构相比，新拓扑结构的能量吸收能力和流动应力分别提高了40%和72%，而本构模型在整个单元胞内都是均匀的。本文的目标是证明同时考虑拓扑结构和微观结构对AMLS力学行为的影响有可能大幅改善关键性能指标，包括极限强度和能量耗散。该方法的独特和新颖之处在于，拓扑优化是在考虑结构微观结构特征和伴随力学行为的异质分布的同时进行的，这导致了与峰值AMLS结构性能相关的新见解。
The post-yield mechanical behavior of additively manufactured lattice structures (AMLS) is governed by the interplay between intrinsic (microstructural) and extrinsic (structural topology) properties at different length scales. Herein, we introduce a novel design optimization approach that accounts for scale separation and size effects, which control deformation mechanisms, to achieve a certain targeted macroscopic mechanical response. The new topological designs are guided by finding a direct correlation between the distribution of local stresses within struts and the underlying microstructures. The local stresses are computed using a strut-level yield criterion that has been calibrated to strut-level tensile, compressive, and shear loading experiments. Therefore, the local response of the struts, including tension-compression asymmetry, build direction dependence, and size effects, are accounted for in the yield surface, enabling a more accurate representation of the local stress state. Accurate calculation of the stress state for a given microstructure and topology combination allows for optimizing the topology for the given strut-level microstructure. The interplay between the topology and microstructure is assessed by investigating the unit cell-level deformation mechanisms and quantifying their influence on the global stress-strain relationship via finite element simulations. Using these relationships, a new set of topologies is designed, built, and validated with experiments. On average, the new topologies demonstrate 40% and 72% improvement in energy absorption capacity and flow stress, respectively, compared to topologies that had been previously optimized using constitutive models, which are homogeneous throughout the unit cell. The goal of the presented article is to demonstrate that simultaneously considering the effects of topology and microstructure on the mechanical behavior of AMLS has the potential to substantially improve key performance metrics, including ultimate strength and energy dissipation. The distinguishing and novel feature of our approach is that the topological optimization is performed while accounting for the heterogeneous distribution of strutlevel microstructural features and concomitant mechanical behavior, which leads to new insights relative to peak AMLS structural performance.