针对SLS快速成型产生的结构内部缺陷问题，利用检测与统计手段建立基于试验数据的仿真预测。对同一多孔结构的CAD模型，提出了设置两种打印方向进行多次成型制备，通过CT分层扫描技术，对3D打印结构进行微结构检测，可以发现微结构中存在缺口、翘曲、孔洞为主的缺陷，其几何方向与打印方向具有一致性。利用三维图像重建模型技术，统计微结构缺陷的几何参数概率分布，研究SLS打印工艺参数对缺陷几何参数统计规律的影响，发现样品放置方向设置为45°时容易引起结构发生翘曲，设置为0°时孔洞容易形成。基于统计建立具有随机缺陷的数值仿真模型，分析随机缺陷引起力学宏观刚度和渗透率、微观应力的性能误差，结果表明随机缺陷使结构刚度变小，使得最大微观应力变动非常大。通过压缩试验验证了宏观刚度数值模拟结果。本研究中关于SLS几何缺陷的统计数据也适用于其他多孔结构的分析和数值计算，对研究SLS打印工艺引起微结构缺陷，及评估对力学性能影响具有重要价值。
文聘
,
叶红玲
,
杨庆生
. 激光选区烧结马氏体时效钢多孔框架的微结构缺陷及力学性能影响分析[J]. 机械工程学报, 2018
, 54(17)
: 173
-180
.
DOI: 10.3901/JME.2018.17.173
The product manufactured by selective laser sintering (SLS), usually applied in high value engineering products including an airplane, medical support and so on, and needs a careful assessment and analysis of the defects. Defects induced during the 3D printing metals by SLS process are difficult to be predicted and eliminated. The aim of this study is to observe and obtain the statistics of defects so as to utilize the numerical predictions to quantify the variation in the mechanical properties by considering statistical nature of the defects. Specifically one cellular structure is fabricated several times as variation of building directions in two different ways. After manufacturing, the Computed Tomography (CT) technology is used to observe the microstructure in order to evaluate the performance of printed structure. In the raw material of managing steel, the geometrical defects are characterized and categorized into three main groups, i.e. notch, kink and hole. It is found that the directions of above defects are put along with the direction of printing. By reconstruction of CT images, the 3D model of printed structure is built and the parametrization of those geometrical defects and statistics are done. It is also found that when the printing angle is set at 45°, the kink is of most probable to be formed while the notch is likely to be formed at 0°. Based on those statistics data, microstructures including defects are built with random parameters. The macroscopic properties are analyzed to obtain the variation from mean value in macroscopic stiffness, permeability and micro stress. Variation turned out to be huge of micro stress but small in macro stiffness. The numerical result is validated via compression test of macroscopic stiffness for printed specimens. This study can contribute to validation of numerical models and obtained statistics is also applicable in other 3D printed structure.
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