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王彪, 王姝予, 熊宇凯, 赵建锋, 康国政, 张旭. 梯度晶粒结构材料拉伸断裂行为的晶体塑性有限元模拟. 力学学报, 待出版. DOI: 10.6052/0459-1879-24-149
引用本文: 王彪, 王姝予, 熊宇凯, 赵建锋, 康国政, 张旭. 梯度晶粒结构材料拉伸断裂行为的晶体塑性有限元模拟. 力学学报, 待出版. DOI: 10.6052/0459-1879-24-149
Wang Biao, Wang Shuyu, Xiong Yukai, Zhao Jianfeng, Kang Guozheng, Zhang Xu. Crystal plastic finite element simulation of tensile fracture behavior of gradient-grained materials. Chinese Journal of Theoretical and Applied Mechanics, in press. DOI: 10.6052/0459-1879-24-149
Citation: Wang Biao, Wang Shuyu, Xiong Yukai, Zhao Jianfeng, Kang Guozheng, Zhang Xu. Crystal plastic finite element simulation of tensile fracture behavior of gradient-grained materials. Chinese Journal of Theoretical and Applied Mechanics, in press. DOI: 10.6052/0459-1879-24-149

梯度晶粒结构材料拉伸断裂行为的晶体塑性有限元模拟

CRYSTAL PLASTIC FINITE ELEMENT SIMULATION OF TENSILE FRACTURE BEHAVIOR OF GRADIENT-GRAINED MATERIALS

  • 摘要: 梯度晶粒结构材料通过在材料内部构筑由纳米晶、细晶渐进过渡至粗晶的微结构, 使其展现出诸多优异的力学性能, 如高强度、高韧性和抗疲劳性等. 工程材料在长期服役过程中, 不可避免会发生疲劳和断裂, 严重威胁材料的服役安全和使用寿命. 相关实验研究报道了纳米晶材料具有沿晶断裂的特点, 且抗断裂性能与晶粒尺寸相关, 然而梯度晶粒结构材料具有复杂的晶粒尺寸分布, 其断裂机理仍需进一步揭示. 为此, 基于晶体塑性有限元方法, 将Cohesive单元植入有限元模型的多晶晶界处, 分别模拟了均匀晶粒结构铜和梯度晶粒结构铜的单拉力学性能, 并研究了预制裂纹对梯度晶粒结构材料裂纹扩展的影响. 结果表明, 所提出的晶体塑性本构模型结合晶界损伤机制可以有效模拟梯度晶粒结构材料的塑性变形以及裂纹扩展过程. 在单轴拉伸变形下, 梯度晶粒结构材料展现了应力与塑性应变的梯度分布特征. 一方面, 由于晶粒尺寸效应, 尽管基体细晶区具有相对较低的流动应力, 但是表层纳米晶强度高. 此外, 由于应变硬化能力的不同, 尽管纳米晶区域表现出较低的塑性应变, 但细晶区域呈现较高的塑性变形能力. 因此, 梯度晶粒结构通过强度与应变硬化能力的差异, 有效地优化了强度与韧性的协同作用, 从而增强了抵抗裂纹扩展的能力. 纳米晶区域预制裂纹对梯度晶粒结构材料的强度影响较大, 因此抑制纳米晶区域的裂纹萌生有助于晶粒结构材料的安全服役.

     

    Abstract: Gradient-grain structure materials exhibit many excellent mechanical properties, such as high strength, high toughness and fatigue resistance, by constructing microstructures from nanocrystals and fine crystals to coarse crystals in the interior of the materials. Engineering materials will inevitably suffer fatigue and fracture during long-term service, which seriously threatens the service safety and service life of materials. It has been reported that the nanocrystalline materials have the characteristics of intergranular fracture, and the fracture resistance is related to the grain size, but the gradient-grain structure materials have a complex grain size distribution, and the fracture mechanism needs to be further revealed. Therefore, based on the crystal plastic finite element method, a Cohesive element is implanted on the polycrystalline grain boundary of the finite element model. The single tensile properties of homogeneous-grain structure copper and gradient-grain structure copper are simulated respectively, and the effect of precast crack on crack propagation of gradient-grain structure materials is studied. The results show that the proposed crystal plastic constitutive model combined with the grain boundary damage mechanism can effectively simulate the plastic deformation and crack propagation of gradient-grain structure materials. The gradient-grain structure materials exhibit the gradient distribution of stress and plastic strain under uniaxial tensile deformation. On the one hand, due to the effect of grain size, the surface nanocrystalline strength is high although the flow stress in the fine-grained region of the matrix is relatively low. In addition, due to the difference in strain hardening capacity, although the nanocrystalline region shows a lower plastic strain, the fine-grained region shows a higher plastic deformation capacity. Therefore, the gradient-grain structure effectively optimizes the synergistic effect of strength and toughness through the difference of strength and strain hardening ability, thus enhancing the ability to resist crack propagation. The precast crack in the nanocrystalline region has a great influence on the strength of gradient-grain structure materials, so restraining the crack initiation in the nanocrystalline region is conducive to the safe service of grain structure materials.

     

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