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孔隙结构对3D打印多孔钨力学性能的影响

Influence of pore structure on mechanical properties of 3D printing porous tungsten

  • 摘要: 利用ANSYS有限元软件设计了正方体和三棱锥两种孔隙结构的多孔钨。研究发现,当分别承受点、线和面载荷时,正方体和三棱锥骨架单元受力不均匀。当骨架单元分别承受面和线载荷时,有支撑的棱柱处应力较小,没有支撑的棱柱处应力较大,并引起了较大的变形量。当骨架单元承受点载荷时,其应力和变形量均在加载处最大。采用选区激光熔化技术制备两种孔隙结构的高孔隙率多孔钨,分析了孔隙形状和尺寸对其力学性能的影响。结果表明,两种多孔钨的宏观形貌与其设计结构无明显差别,由于骨架棱柱(边)上易悬垂和粘粉导致孔隙率较设计值有所降低。预设孔隙率为50%和80%的正方体多孔钨抗拉强度分别为127.4 MPa和55.8 MPa,抗压强度分别为667.1 MPa和213.0 MPa,冲击韧性分别为6.764 J/cm2和4.492 J/cm2,硬度值相差不大。预设50%和80%孔隙率的三棱锥多孔钨抗压强度分别为231.1 MPa和65.3 MPa,冲击韧性均为2.030 J/cm2,硬度与正方体骨架相同。正方体和三棱锥多孔钨的拉伸和压缩断口形貌均呈现出典型的准解理脆性断裂特征。

     

    Abstract: The porous tungsten with the cube and triangular pyramid shape was designed by ANSYS finite element analysis in this paper. In the results, when the point, line, and plane loads are applied, respectively, the stress on the cube and triangular pyramid skeleton units is uneven. When the skeleton unit is subjected to the plane and line loads, respectively, the stress at the supported struts is relatively small, while the stress at the unsupported struts is relatively large, causing a large amount of deformation. When the skeleton unit is subjected to the point load, the stress and deformation are both the maximum at the loading point. The porous tungsten in the shape of cube and triangular pyramid with high porosity was fabricated by selective laser melting (SLM) technique, and the effects of pore shape and size on the mechanical properties were investigated. The results show that the macrostructure of these skeleton structure is not significantly different from the designed structure, but the porosity is lower than that of the designed value, because of the hanging and sticky powders on the skeleton struts. The tensile strength of cube skeleton with 50% and 80% porosity is 127.4 MPa and 55.8 MPa, the compressive strength is 667.1 MPa and 213.0 MPa, the impact toughness is 6.764 and 4.492 J·cm−2. The compressive strength of the triangular pyramid skeleton with 50% and 80% porosity is 231.1 MPa and 65.3 MPa, the impact toughness is 2.030 J·cm−2, and the hardness is similar as that of the cube skeleton. The tensile and compressive fracture morphology of the cube and triangular porous tungsten show the typical quasi-cleavage brittle fracture.

     

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