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基于表面效应三维纳米多孔金属力学性能的有限元分析

FINITE ELEMENT ANALYSIS OF MECHANICAL PROPERTIES OF THREE-DIMENSIONAL NANOPOROUS METALS BASED ON SURFACE EFFECTS

  • 摘要: 纳米多孔金属是一类包含大量纳米尺度孔洞的金属材料, 孔洞突出的表面效应, 使得其具有比传统多孔金属更为优异的力学性能. 相对于理论和分子动力学仿真, 有限元方法更适用于复杂结构模型, 但受限于理论难度, 以往研究仍将纳米多孔金属模型简化为较为简单的二维结构, 因此无法真实刻画纳米多孔金属的力学性能. 为此, 基于Gurtin-Murdoch表面理论, 成功构建计入纳米表面效应的有限元表面单元, 并考虑微观结构非均匀性, 发展面向一般三维纳米多孔金属力学行为的有限元计算模型, 将计算得到的纳米孔附近应力分布与参考文献进行对比分析, 验证了所构建有限元模型的有效性. 通过对包含单球孔和随机多球孔的纳米多孔金属进行单轴拉伸和单轴压缩模拟, 揭示了孔隙率、孔洞数量和表面参数对纳米多孔金属杨氏模量、压缩屈服强度和吸能性的影响规律. 结果表明: 所构建的有限元模型可准确捕捉纳米孔附近应力分布, 相对于表面拉梅常数, 纳米多孔金属的杨氏模量显著依赖于孔洞表面残余应力和加载方向. 所构建的有限元模型为纳米多孔金属力学性能预测提供科学依据.

     

    Abstract: Nanoporous metals are a type of metallic material that contain a large number of nanoscale pores. These materials are characterized by their outstanding surface effects and exhibit superior mechanical properties compared to traditional porous metals. Compared with theoretical and molecular dynamics simulations, finite element methods are more suitable for complex structural models. However, limited by theoretical difficulties, previous research has often simplified the models of nanoporous metals into relatively simple two-dimensional structures, which cannot provide an accurate depiction of their mechanical properties. Therefore, this study employs the principle of minimum energy and the surface theory of nano-materials to develop a finite element surface element that considers the surface effect of nanoporous materials. By considering the non-uniformity of the microscopic structure, we further develop a finite element computational model that enables the analysis of the mechanical behavior of three-dimensional nanoporous metal materials. We verify the effectiveness of our developed finite element model by comparing the calculated stress distribution near the nano-pores with the reference literature. Using the developed computational model, we perform single-axis tension and compression simulations on nanoporous metal materials containing either single spherical pores or random multiple spherical pores, and investigate the influence of porosity, pore quantity, and surface parameters on the Young's modulus, yield strength, and energy absorption capacity of nanoporous metals. Our results demonstrate that the developed finite element model can accurately capture the stress distribution near the nano-pores. Furthermore, our findings indicate that the Young's modulus of nanoporous metals significantly depends on the residual stress on the pore surface and the loading direction, rather than the surface Lamé constant. In summary, the developed finite element model provides a scientific evidence for the mechanical performance prediction of nanoporous metals.

     

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