关键词: 3D打印, 激光选区烧结, 缺陷统计, 随机数值模型

Abstract: 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.

Key words: 3D printing, defect statistics, selective laser sintering, stochastic numerical simulation