Numerical Evaluation of Advanced Laser Control Strategies Influence on Residual Stresses for Laser Powder Bed Fusion Sys
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TECHNICAL ARTICLE
Numerical Evaluation of Advanced Laser Control Strategies Influence on Residual Stresses for Laser Powder Bed Fusion Systems Massimo Carraturo1 · Brandon Lane2 · Ho Yeung2 · Stefan Kollmannsberger3 · Alessandro Reali1 · Ferdinando Auricchio1 Received: 3 September 2020 / Accepted: 3 November 2020 © The Author(s) 2020
Abstract Process-dependent residual stresses are one of the main burdens to a widespread adoption of laser powder bed fusion technology in industry. Residual stresses are directly influenced by process parameters, such as laser path, laser power, and speed. In this work, the influence of various scan speed and laser power control strategies on residual stresses is investigated. A set of nine different laser scan patterns is printed by means of a selective laser melting process on a bare plate of nickel superalloy 625 (IN625). A finite element model is experimentally validated comparing the simulated melt pool areas with high-speed thermal camera in situ measurements. Finite element analysis is then used to evaluate residual stresses for the nine different laser scan control strategies, in order to identify the strategy which minimizes the residual stress magnitude. Numerical results show that a constant power density scan strategy appears the most effective to reduce residual stresses in the considered domain. Keywords Selective laser melting · Finite cell method · Residual stress · Thermo-mechanical analysis · Inconel 625
Introduction Laser powder bed fusion (LPBF) or selective laser melting (SLM) is an additive manufacturing (AM) technology where freeform parts are produced by means of a layer-by-layer process. A layer of metal powder is spread over a build plate and a highly localized laser beam selectively melts metal powder particles following a predefined scan strategy. During this process, each material point undergoes rapid melting–solidification cycles generating residual stresses, i.e., stresses which remain in the material at equilibrium. The residual stresses generated during an LPBF process can severely affect the fatigue behavior of the component [1]. Moreover, they might lead to crack generation or large part distortions in the final * Massimo Carraturo [email protected] 1
Department of Civil Engineering and Architecture, University of Pavia, via Ferrata 3, 27100 Pavia, Italy
2
Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
3
Chair of Computational Modeling and Simulation, Technische Universität München, Arcisstr. 21, 80333 München, Germany
artifact [2]. Nowadays, the presence of process-dependent residual stresses is one of the main limitations to a widespread adoption of LPBF technology in industrial applications [3]. As thoroughly investigated in the recent literature review of Bartlett and Li [2] on residual stress generation in LPBF processes, direct changes in the energy input generate large variations in the residual stress magnitude since they alter heat transfer conditions and coo
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