基于晶体塑性的铝合金韧性断裂细观力学研究

发布时间：2018-01-17 17:16

  本文关键词：基于晶体塑性的铝合金韧性断裂细观力学研究　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

  更多相关文章： 晶体塑性 孔洞增长 孔洞聚合 应力三轴度 韧性断裂

【摘要】：韧性断裂是金属材料的重要的非线性行为,加深对韧性断裂的理解在实际工程中有重要意义,如改善金属塑性成型工艺,提高结构完整性评估精度等。众所周知,韧性断裂与微孔洞的形成,增长,聚合的过程有关。材料的韧性断裂受应力状态,孔洞体积分数,孔洞几何尺寸,基体本构响应及温度等众多参数的影响,其中,应力状态对韧性断裂的影响至关重要。目前,已有的韧性断裂研究大都以唯象本构代表材料的非线性行为,对材料韧性断裂过程中微观晶体变形和孔洞扩展的机理缺乏明确考虑。本文对5083-H116铝合金材料提出一个基于晶体塑性力学的细观有限元模型以明确考虑材料中的非线性晶相滑移与孔洞扩展之间的相互作用。有限元分析中,本文选取含单一孔洞的代表性胞元对其施加周期性边界条件,并采用结构化的网格进行有限元离散。本文基于Taylor平均场均匀化方法模拟多晶基体材料的力学响应,将其与实验对比标定了本构模型的材料参数,并将该模型应用于基体材料中。为研究多轴载荷作用下应力状态对单晶含孔洞胞元力学行为的影响,本文发展了一种控制胞元应力三轴度和洛德参数的方法。在三维胞元模型中,本文加入刚硬斜杆来控制代表性胞元总体应力分量之间的比值,进而实现对胞元应力三轴度以及洛德参数的控制。本文在有限元软件中开发了相应的用户子程序并分析了相关参数的影响,最终实现应力状态的控制。在此基础上,本文定量分析了应力三轴度,晶体取向以及洛德参数对孔洞扩展以及孔洞聚合的影响规律,有以下发现:应力三轴度的提高可降低孔洞聚合应变,并改变孔洞扩展趋势;晶体取向对胞元应力应变分布有重要影响;随着应力三轴度的提高,晶体取向的影响减弱;同时,洛德参数对单晶孔洞聚合行为产生重要影响。本文进一步发展了Taylor-Reuss平均场均匀化方法获得含孔洞多晶体材料的力学响应,并将预测结果与传统的采用宏观唯象本构的细观力学模型所得结果以及广为应用的G-T本构模型对比。对比结果验证了本文模型的可靠性,同时这些模型结果之间的区别显示出在分析多晶体材料孔洞扩展行为时对材料的塑性滑移与孔洞之间的相互作用予以明确考虑是很必要的。
[Abstract]:Ductile fracture is an important nonlinear behavior of metal materials. It is of great significance to deepen the understanding of ductile fracture in practical engineering, such as improving metal plastic forming process. It is well known that ductile fracture is related to the formation, growth and polymerization of microvoids. The ductile fracture of materials is subjected to stress state, pore volume fraction, and pore geometry size. The effect of matrix constitutive response and temperature on ductile fracture is very important. At present, most of the researches on ductile fracture represent the nonlinear behavior of materials. The mechanism of microscopic crystal deformation and pore propagation during ductile fracture of materials is not considered clearly. A meso-finite element model based on crystal plastic mechanics is proposed for 5083-H116 aluminum alloy in this paper. The interaction between the nonlinear crystal phase slip and the pore propagation in the material is taken into account. In the finite element analysis. In this paper, periodic boundary conditions are applied to representative cells with a single pore. Based on the Taylor mean field homogenization method, the mechanical response of the polycrystalline matrix is simulated, and the material parameters of the constitutive model are compared with the experimental results. The model is applied to the matrix material. In order to study the effect of stress state on the mechanical behavior of single crystal porous cells under multiaxial loading. In this paper, a method to control the triaxial degree of cellular stress and the Lod parameter is developed. In the three-dimensional cell model, the ratio between the stress components of the representative cell population is controlled by adding rigid and hard skew bars. In this paper, the user subprogram is developed in the finite element software and the influence of the related parameters is analyzed. Finally, the stress state is controlled. On this basis, the effects of stress triaxiality, crystal orientation and Lod parameters on the pore propagation and pore polymerization are quantitatively analyzed. It is found that the increase of stress triaxiality can reduce the pore aggregation strain and change the trend of pore expansion. The crystal orientation has an important effect on the stress and strain distribution of the cell. With the increase of stress triaxiality, the effect of crystal orientation is weakened. At the same time, the Lod parameters have an important effect on the pore polymerization behavior of single crystal. In this paper, the Taylor-Reuss mean field homogenization method is further developed to obtain the mechanical response of porous polycrystalline materials. The prediction results are compared with the results obtained from the traditional meso-mechanical model using macrophenomenological constitutive model and the widely used G-T constitutive model. The comparison results verify the reliability of the model. At the same time, the differences between the results of these models show that it is necessary to consider the interaction between the plastic slip and the pore in the analysis of the pore propagation behavior of polycrystalline materials.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21
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本文编号：1437193