Abstract
Due to rapid solidification of melted powders in metal additive manufacturing processes and high thermal gradients, large residual stresses are created in the build. This can lead to undesired distortions as well as crack initiation. The main aim of this work is to optimize the Additive Manufacturing (AM) process parameters by finite element modelling of the entire process to minimize the resulting residual stresses and distortions. We focus on two most important metal AM processes: (a) Laser Direct Energy Deposition (LDED) and (b) Selective Laser Melting (SLM). The ABAQUS AM module is employed to simulate both processes as it provides an automated interface allowing the user to define event data, such as element activation and heat input, as a function of both position and time to achieve process simulation of complex 3D parts. For the LDED processes, thin wall components are simulated, and residual stresses predictions are compared with both FIB-DIC and XRD measurement results at different scales. For the SLM process, overhanging structures with different support thicknesses are simulated and compared with experimental part distortion after support removal. It is shown that the support thickness together with selected process and material properties play a key role in resulting distortions.
Highlights
Over the last decade, Additive manufacturing (AM) technology has been established as a viable and cost-effective alternative to traditional subtractive metallic manufacturing processes, resulting in innovative design opportunities for complex parts
The results show that the automated AM module is a valuable tool for analyzing the influence of geometry, material properties and process parameters on distortion and residual stresses
It is obvious that a suitable time incrementation for the Goldak approach is necessary for detailed local residual stress investigations as in the case of Laser Direct Energy Deposition (LDED) simulations in Section 4.2, while investigations of macroscopic deformations, such as for the Selective Laser Melting (SLM) studies in Section 4.3, may be captured by a coarse mesh approach with point-wise heating
Summary
Additive manufacturing (AM) technology has been established as a viable and cost-effective alternative to traditional subtractive metallic manufacturing processes, resulting in innovative design opportunities for complex parts. Due to the rapid solidification of melted metal powders and high thermal gradients of non-uniform surface heating in the metal AM processes, significant residual stresses are created within the part as well as the build platform [4,5,6]. As a result, these stresses lead to distortions of the build part and possibly crack initiation, propagation and complete failure during printing, if their magnitudes are above the yield strength or tensile strength, respectively [7]. As an alternative, numerical simulation of the entire AM process to capture the residual stress evolution during printing has become an important topic for the AM research community
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