Effect of Layer Orientation on Fracture Dynamics Using a 3D Image Construction Technique

Layer orientation is a critical parameter in the additive manufacturing method. This process parameter significantly influences the material’s mechanical behavior and fracture mechanics. In this study, we investigated the effect of layer orientation on fracture dynamics using a three-dimensional (3D) image reconstruction approach based on the Depth from Defocus (DFD) technique. The DFD method was employed to capture high-resolution defocused image sequences that enable building an accurate reconstruction of surface topology and evolving crack geometry in three dimensions. The specimens contain numerous voids formed during the AM fabrication process and dynamic high-strain-rate impact. The voids play a pivotal role in the specimen's crack propagation mechanics.

Objective: The research aims to develop an understanding of the presence of voids in the tension and compression zones of a fractured specimen.

Method: The test specimens were produced by a selective laser melting process in the metal additive manufacturing method for AlSi10Mg, an aluminum alloy. There were two layer orientations used, horizontal and vertical layer directions, for making the specimens at a global energy density of 37.1 J/mm³. The specimens were prepared according to the ASTM A370 Charpy V-notch standard. The fracture in the specimen was created by the Charpy testing, and the Charpy-tested specimens were investigated to understand the fracture dynamics of the materials. There were three zones identified in the fracture surface of the tested specimens: tension, neutral, and compression (as Type - I fracture mechanics), using a box counting method. The voids of the three zones were studied by using a digital microscope and the DFD method. The collected data were analyzed using statistical methods.

Finding: The layer orientation has an effect on the void quantity and size in the tension and compression zones of the specimens.