激光熔融八边形双棱锥与Kelvin混合点阵结构的力学性能及变形机理

Mechanical properties and deformation mechanism of laser melting octagonal double pyramid and Kelvin hybrid lattice structure

摘要

点阵结构因其优异的力学性能，在航天器轻量化结构和缓冲吸能装置上展现出广阔的应用前景。本工作提出基于八边形双棱锥结构和Kelvin结构的混合结构1，并通过拉伸处理得到长宽高比为2∶2∶3的混合结构2，采用选区激光熔融制备对应的点阵结构。通过实验和仿真系统地研究混合结构的力学性能、吸能特性及变形机理。结果表明：混合结构的力学性能和吸能性能均得到显著增强；当相对密度相同时，混合结构1的吸能效率提升15.7%，混合结构2的比强度和比吸能分别提升93%和92%。在变形机制方面，混合结构1均匀坍塌，呈现出以弯曲为主导的变形机制；混合结构2则是全程自下而上逐层坍塌。为了进一步改善混合结构变形机制和提高力学性能，对混合结构的几何参数进行优化，发现改变内外杆件直径比例λ可以实现对混合结构的调整优化。λ=0.75时，混合结构1的综合性能最优，其比强度和比吸能分别提高21%和10%。

Abstract

Due to their excellent mechanical properties，dot matrix structures show a broad application prospect for spacecraft lightweight structures and cushioning energy absorbing devices. In this paper，two hybrid structures based on octagonal bipyramidal structure and Kelvin structure are proposed，and the corresponding dot matrix structures are prepared by selected laser melting. The mechanical properties，energy-absorption characteristics and deformation mechanisms of the hybrid structures are systematically investigated through experiments and simulation. It shows that the mechanical and energy-absorbing properties of the hybrid structures are significantly enhanced；when the relative density is the same，the energy-absorbing efficiency of the hybrid structure 1 is increased by 15.7%，and the specific strength and specific energy-absorption of the hybrid structure 2 are increased by 93% and 92%，respectively. In terms of the deformation mechanism，the hybrid structure 1 uniformly collapses，which shows a bending-dominant deformation mechanism；while the hybrid structure 2 collapses layer by layer throughout the whole process from bottom to top. In order to further improve the deformation mechanism and enhance the mechanical properties of the hybrid structure，the geometric parameters of the hybrid structures are investigated. It is found that adjusting the ratio of inner and outer rod diameters can realize optimization of the hybrid structure. When λ = 0.75，comprehensive performance of hybrid structure 1 is best，with in its specific strength and specific energy absorption increasing by 21% and 10% respectively.

关键词

选区激光熔融 / 混合点阵 / 力学性能 / 能量吸收 / 几何参数优化

Key words

selected laser melting / hybrid lattice / mechanical property / energy absorption / geometric parameter optimization

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基金资助

机械传动与制造工程湖北省重点实验室开放基金项目(MTMEOF2021B05)