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摘要: 通过单轴压缩实验、径向压缩（巴西圆盘）实验和冷模模压实验建立了基于密度相关修正Drucker-Prager Cap（DPC）的Ti-6Al-4V粉末压制本构模型，利用ABAQUS有限元仿真软件的二次开发用户子程序USDFLD对该本构模型进行了模拟验证。综合考虑压制过程中实验装置变形对实验数据的影响，通过空压校正实验控制实验误差，建立了更加准确的修正DPC模型。结果表明：修正DPC本构模型可很好地应用于Ti-6Al-4V粉末压制过程的仿真模拟；当上模冲压力较小时（< 50 MPa），模壁摩擦系数随上模冲压力的增加逐渐减小，当上模冲压力较大时（>50 MPa），模壁摩擦系数随上模冲压力的增加而基本趋于稳定。
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关键词:
- Ti-6Al-4V粉末 /
- Drucker-Prager Cap模型 /
- 粉末压制 /
- 数值模拟
Abstract: The density-dependent modified Drucker-Prager Cap (DPC) constitutive model of Ti-6Al-4V powders for cold die compaction was established by uniaxial compression test, diametrical compression test (Brazilian disc experiment), and die compression test in this paper, the constitutive model was verified by the user subroutine USDFLD in secondary development based on finite element software ABAQUS. Considering the influence of device deformation on experimental data in compaction process, the experimental error was controlled by calibration experiment, and the more accurate modified DPC model was established. The results show that, the modified DPC model of Ti-6Al-4V powders for cold die compaction can be accurately used in the simulation analysis of Ti-6Al-4V powders compaction. In addition, the wall friction decreases gradually with the increase of the top punch pressure when the top punch pressure is lower than 50 MPa; while the wall friction tends to be stable with the increase of the top punch pressure, when the top punch pressure is higher than 50 MPa.-
Key words:
- Ti-6Al-4V powders /
- Drucker-Prager Cap model /
- powder compaction /
- numerical modeling
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图 1 压坯压缩强度测量实验：（a）单轴压缩实验；（b）巴西圆盘实验
Figure 1. Compression strength tests of the powder compacts: (a) uniaxial compression test; (b) diametrical compression test
图 3 修正DPC模型及模压实验加载路径
Figure 3. Modified DPC model and the loading path of die compaction test
图 4 剪切破坏面确定实验：（1）单轴拉伸实验；（2）剪切实验；（3）巴西圆盘实验；（4）单轴压缩实验
Figure 4. Determination of shear failure surface: (1) uniaxial tension test; (2) pure shear test; (3) diametrical compression test; (4) uniaxial compression test
图 5 压坯压缩强度与相对密度关系：（a）单轴压缩强度；（b）径向压缩强度
Figure 5. Compression strength change with relative density of powder compacts: (a) axial compression strength; (b) radial tensile strength
图 6 空压校正实验：（a）整个模压装置的力–位移曲线；（b）模压实验原始数据与修正数据的力–位移曲线
Figure 6. Die compaction tests without powders: (a) force–displacement response of the whole testing system; (b) force–displacement curves with the raw and corrected data for powder compact
图 7 修正DPC模型参数、弹性参数与相对密度的关系以及摩擦系数与上模冲压力的关系：（a）内聚力，d；（b）摩擦角，β；（c）演化参数，pa；（d）静态屈服应力，pb；（e）偏心距，R；（f）弹性模量，E；（g）泊松比，υ；（h）摩擦系数，μ
Figure 7. Relationship of modified DPC model parameters, elastic properties, and relative density and the variation of friction coefficient with top punch pressure: (a) cohesion, d; (b) friction angle, β; (c) evolution parameter, pa; (d) hydrostatic yield stress, pb; (e) cap excentricity, R; (f) Young's modulus, E; (g) Poisson's ratio, υ; (h) friction coefficient, μ
图 8 有限元模型及模拟实验：（a）组装模型；（b）划分网格模型；（c）加载完毕模型；（d）卸载完毕模型
Figure 8. Finite element model and simulation experiment: (a) assembled model; (b) model with meshes; (c) model after loading; (d) model after unloading
图 9 生坯相对密度分布云图：（a）加载完毕；（b）卸载完毕
Figure 9. Relative density distribution of green: (a) after loading; (b) after unloading
表 1 Ti–6Al–4V粉末化学成分表（质量分数）
Table 1. Chemical composition of Ti–6Al–4V powders
% Al V Fe C N H O Ti 6.00 3.90 0.05 0.02 0.180 0.039 0.20 余量 
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