激光粉末床熔融成形仿生梯度多孔结构弯曲性能

Bending Properties of Graded Bio-Inspired Porous Structures Fabricated by Laser Powder Bed Fusion

梯度材料结构具有优异的力学性能和能量吸收性能,在航空航天、医学植入体、吸能结构等方面具有广阔的应用前景。通过模仿竹子梯度结构,提出了一种梯度极小曲面多孔结构设计方法,并基于该方法设计了线性梯度Gyroid结构和拓扑密度梯度Gyroid结构。利用激光粉末床熔融技术制备了上述多孔结构,并通过弯曲试验和数字图像相关技术对比研究了均匀结构与梯度结构的弯曲性能差异。研究结果表明,Gyroid均匀多孔结构的弯曲弹性模量与孔隙率呈现线性函数关系,且在80%~85%之间具有弯曲断裂临界孔隙率;而线性梯度多孔结构则具有类似竹子的非对称性弯曲行为,当孔隙率以70%→90%形式分布时具有最高的挠曲韧性且无弯曲断裂现象,而以90%→70%形式分布时则具有最高的弯曲强度,比80%Gyroid均匀结构弯曲强度高出36.08%;基于拓扑优化密度云的梯度Gyroid结构具有最优的弯曲弹性模量。本研究工作验证了孔隙率梯度分布模式会改变结构的弯曲变形和断裂模式,可以通过合理的梯度结构设计获得轻质高强抗弯结构。

The graded material structure has broad application prospects in aerospace,medical implants,energyabsorbing structures,etc.for its excellent mechanical properties and energy absorption.A graded minimal surface porous structure design method is proposed by imitating the structure of bamboo with graded structure,and linearly graded Gyroid structures and topological density graded Gyroid structures were designed based on this method.The porous structures were manufactured by laser powder bed fusion technology,and the bending properties of the uniform structure and graded structure were analyzed by bending test and digital image correlation technology.The experimental results show that the bending elastic modulus of the Gyroid porous structure is a linear function of porosity,and the critical porosity of bending fracture is between 80%and 85%.The linear graded porous structure has the asymmetric bending behavior like bamboo,and it has the highest bending toughness and no bending fracture when the porosity is distributed in the form of 70%→90%,while it has the highest bending strength when the porosity is distributed in the form of 90%→70%,which is 36.08%higher than the bending strength of the uniform Gyroid structure with porosity of 80%.It is demonstrated that bending deformation and fracture mode can be adjusted by the graded distribution mode of porosity.A structure with lightweight and high bending strength can be obtained by the reasonably graded structure design.