均质与变密度增材制造Ti6Al4V合金极小曲面力学性能与吸能特性研究

Mechanical Properties and Energy Absorption Characteristics of Ti6Al4V Alloy TPMS Fabricated by Homogeneous and Variable Density Additive Manufacturing

摘要:

基于金刚石型极小曲面（D-TPMS）点阵结构，采用了线性梯度壁厚的调控方法，设计了均质以及变密度的2类极小曲面点阵结构模型，并采用选择性激光熔化技术进行制备。通过实验分析了相对密度、打印方向以及模型类型对力学性能与吸能特性的影响规律，并采用有限元方法验证了变密度点阵结构的应力分布和破坏机制。结果表明：均质极小曲面点阵结构的破坏形式为45^o剪切断裂，且发生在塑性变形初期；变密度极小曲面点阵结构的破坏形式为层间坍塌，整体结构具有较为优异的承载及吸能能力。当极小曲面点阵结构的相对密度为0.275时，均质极小曲面点阵结构的极限抗压强度可达193.8 MPa，发生破坏时变形量为7.7%，累计吸能值为11.76 MJ/m³，而变密度极小曲面点阵结构的极限抗压强度可达221.4 MPa，在变形量为50%时仍保持结构完整，累计吸能值可达77.52 MJ/m³，是均质结构的6.59倍。因此，变密度极小曲面点阵结构具有良好的吸能效果与优异的承载性能，在防撞吸能领域具有较大应用前景。

Abstract:

Based on the diamond-type triply periodic minimal surface (D-TPMS) lattice structures, two types of TPMS lattice structure models of homogeneous and variable density were designed and prepared by the regulation method of linear gradient wall thickness and selective laser melting technology. The effects of relative density, printing direction and model type on the mechanical properties and energy absorption characteristics were analyzed, and the stress distribution and damage mechanism of the variable-density lattice structures were verified by the finite element method. The results show that the damage of the homogeneous TPMS lattice structure is 45^o shear fracture, which occurs at the early stage of plastic deformation; the damage of the variable density TPMS lattice structure is interlayer collapse, and the overall structure has excellent load bearing and energy absorption capacity. When the relative density of the TPMS lattice structure is 0.275, the ultimate compressive strength of the homogeneous TPMS lattice structure is up to 193.8 MPa, the deformation amount is 7.7%, and the cumulative value of energy absorption is 11.76 MJ/m³, whereas the ultimate compressive strength of the variable-density TPMS lattice structure is up to 221.4 MPa, and the structure is still intact when the deformation amount is 50%, and the cumulative value of energy absorption is up to 77.52 MJ/m³, which is 6.59 times higher than that of the homogeneous structure. It is demonstrated that the variable-density TPMS lattice structure has good energy absorption effect and excellent load-bearing performance, which has a significant application prospect in the field of collision avoidance and energy absorption.