单元晶胞尺寸对晶格结构力学性能的影响

Influence of Unit Cell Size on Mechanical Properties of Lattice Structure

为了解具有晶格结构的先进轻质多功能材料的力学性能,以激光选区熔化制备的体心立方单元晶胞晶格结构为例,揭示了单元晶胞尺寸对晶格结构力学性能的影响规律。采用干重法测量晶格结构的质量,通过计算孔隙率确定了单元晶胞尺寸对孔隙率的影响规律;通过压缩实验、压-压疲劳实验及扫描电镜断口形貌图,分析了晶格结构力学性能的演化规律。实验结果表明:所有样品的实际孔隙率均低于设计值,当单元晶胞尺寸为2.5mm时,孔隙率的设计值与实际值偏差最大,为8.2%;当单元晶胞尺寸为7.5mm时,孔隙率的设计值与实际值偏差最小,为1.6%;当单元晶胞尺寸从2.5mm增加到7.5mm,晶格结构的压缩强度降低了41.96%,说明单元晶胞尺寸增加会导致晶格结构抵抗压缩变形的能力变小即塑性变差,断裂模式从塑性断裂向脆性断裂转变且疲劳循环次数减小。此外,单元晶胞尺寸较小时瞬断区断口主要由韧窝组成,而单元晶胞尺寸较大时,瞬断区表现为光滑的平面和少量的韧窝,说明晶格结构更脆。该研究结果可为晶格结构单元晶胞尺寸的设计和选择提供参考。

To understand the mechanical properties of advanced lightweight multifunctional materials with a lattice structure,the body-centered cubic unit cell lattice structure prepared by selective laser melting was taken as an example to reveal the influence of the unit cell size on the mechanical properties of the lattice structure.Firstly,the mass of the lattice structure was measured by the dry weight method,the porosity was calculated,and the influence law of unit cell size on porosity was studied.Then,the evolution law of mechanical properties of lattice structure was studied through compression testing,compression-compression fatigue testing and scanning electron microscope fracture topography.The results showed that the actual porosity of all samples was lower than the design value.When the unit cell size was 2.5 mm,the actual porosity showed a maximum deviation of 8.2%from the design value.However,when the unit cell size was 7.5 mm,the deviation was the smallest(1.6%).As the unit cell size increased from 2.5 mm to 7.5 mm,the compressive strength of the lattice structure decreased by 41.96%,indicating that the ability of the lattice structure to resist compression deformation became smaller,and the plasticity became worse.In addition,the fracture mechanism changed from plastic fracture to brittle fracture,and the number of fatigue cycles decreased.The transient zone was mainly composed of dimples when the unit cell size was small while it displayed a smooth plane and a small amount of dimples when the unit cell size was large,indicating that the lattice structure was more brittle.The research results can provide a reference for the design and selection of the unit cell size of the lattice structure.