Image analysis characterization of periodic porous materials produced by additive manufacturing

A method is proposed for evaluating the geometrical parameters of metallic cellular structures produced by additive manufacturing. It is based on the segmentation and the skeletonization of plane images of the specimens. The medial axis transform is the key operator used to quantify the geometry of the structure. The analysis discriminates the struts and the nodes by modeling the latter as polygons. The average thickness, length, and orientation of the struts are individually estimated. The method is implemented as a program that can process multiple images almost automatically. It was validated on a CAD model, and then applied to several Ti6Al4V specimens manufactured by Direct Metal Laser Sintering with varying geometrical parameters. The irregularities of the specimens are readily put into evidence thanks to the comprehensiveness of the measurements. It is concluded that the process is orthotropic with respect to the laser beam. In particular, the struts parallel to the laser beam tend to be thinner than perpendicular ones. The extension of the method to other geometries is discussed. (C) 2015 Elsevier Ltd. All rights reserved.