Abstract
Additive manufacturing (AM) is the term for a number of processes for joining materials to build physical components from a digital 3D model. AM has multiple advantages over other construction techniques, such as freeform, customization, and waste reduction. However, AM components have been evaluated by destructive and non-destructive testing and have shown mechanical issues, such as reduced resistance, anisotropy and voids. The build direction affects the mechanical properties of the built part, including voids of different characteristics. The aim of this work is an extended analysis of void shape by means of X-ray computed tomography (CT) applied to fused deposition modeling (FDM) samples. Furthermore, a relation between the tensile mechanical properties and digital void measurements is established. The results of this work demonstrate that void characteristics such as quantity, size, sphericity and compactness show no obvious variations between the samples. However, the angle between the main void axis and the mechanical load axis α shows a relation for FDM components: when its mean value μ(α) is around 80 (degrees) the yield strength and Young’s modulus are reduced. These results lead to the formulation of a novel criterion that predicts the mechanical behavior of AM components.
Highlights
IntroductionAdditive manufacturing (AM) is classified by seven general processes: material extrusion (ME), direct energy deposition (DED), material jetting (MJ), powder bed fusion (PBF), vat photopolymerization (VP), binder jetting (BJ), and sheet lamination (SL) [1]
According to the standard ASTM D638 type 1 [74], five pieces of each orientation were tested using a velocity of 5 mm/min
In this research five samples in three different directions: flat, edge, and upright were built by material extrusion (ME)/fused deposition modeling (FDM) technology and tensile tested
Summary
AM is classified by seven general processes: material extrusion (ME), direct energy deposition (DED), material jetting (MJ), powder bed fusion (PBF), vat photopolymerization (VP), binder jetting (BJ), and sheet lamination (SL) [1]. From these processes and their combinations with others manufacturing processes, different technologies have been developed. AM advantages include the possibility to manufacture freeform complex components that would otherwise be impossible to build with subtractive manufacturing processes, and product customization and personalization by reducing mass, amount of assemblies, and material waste in order to improve the supply chain operability [2,3,4,5,6]. AM has shown disadvantages: the presence of voids and inclusions due to the lack of material union or recrystallization [7]; mechanical anisotropy as a consequence of the layer-by-layer build characteristics; reduced resistance against external forces; surface inconsistencies, such as the stair-stepping effect and witness marks from support material removal; and residual stresses caused when the material is heated unevenly [5,6,8,9,10,11,12]
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