Development, numerical simulation and experimental characterization of selective laser melting (SLM) microstructures with deliberately introduced dissipation
Mechanics
Final Report Abstract
Vibration-sensitive tools, such as long and slim boring bars, typically have a short lifespan due to increased loading. While active dampers are cost-intensive and space-consuming, passive damping systems can be integrated directly into the tool This can be done, for example, through additive manufacturing (AM) via powder bed fusion of metals using a laser beam (PBF-LB/M). The presented project aimed to develop novel concepts for additively manufactured microstructures with controllable dissipation. The following concepts were considered: Concept 1: Enclosed cavities filled with loose metal powder Concept 2: Coherent, porous metal phases filled with viscous oil Concept 3: Lightweight lattice structures infiltrated with a highly dissipative low-density material Concept 4: Smart microstructures with built-in micro-friction elements. A novel setup for modal analysis, including an automated impulse hammer, was built at the iwb to perform experimental studies. For concept 1, significant influencing factors, such as the particle packing density within the component, were identified. In concept 3, SS316L lattice structures with an epoxy resin filling combined a high structural stiffness with the desired dissipative behavior. For concept 4, an improved damping behavior could be achieved after modifying the gap dimensions in micro-friction elements. Concept 2 was abandoned after initial feasibility studies because the PBF- LB/M process could not produce stable and coherent pore structures. Concept 1 turned out to offer the highest damping potential. Since the underlying physics was not adequately understood initially, the numerical studies were focused on this concept. To perform these numerical studies, a novel modeling approach for solid structures with enclosed powder cavities has been developed at LNM, coupling the finite element method (FEM) and the discrete element method (DEM) at the solid-powder interface. Based on this modeling approach, inter-particle sliding friction induced by cavity-deformation was identified as a fundamental physical dissipation mechanism, in contrast to existing damping strategies exploiting particle collisions. Moreover, a strong dependence of the dissipation on the oscillation frequency, the oscillation mode, and the packing density, along with the existence of an optimal powder packing density, could be demonstrated. To enable powder layers with these optimal packing densities in PBF-LB/M, novel powder spreading strategies were proposed and successfully validated in additional simulations. In summary, the results of this project contribute significantly to reducing vibrations via additively manufactured, integrated damping approaches instead of cost-intensive and space-consuming external devices.
Publications
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Physics‐based modeling and predictive simulation of powder bed fusion additive manufacturing across length scales. GAMM-Mitteilungen, 44(3).
Meier, Christoph; Fuchs, Sebastian L.; Much, Nils; Nitzler, Jonas; Penny, Ryan W.; Praegla, Patrick M.; Proell, Sebastian D.; Sun, Yushen; Weissbach, Reimar; Schreter, Magdalena; Hodge, Neil E.; John, Hart A. & Wall, Wolfgang A.
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Dämpfende Strukturen in der Additiven Fertigung. Zeitschrift für wirtschaftlichen Fabrikbetrieb, 118(7-8), 492-496.
Mair, Thomas; Wenzler, David; Praegla, Patrick & Zäh, Michael F.
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Experimental Investigations of the Influence of Filler Materials on the Dynamic Structural Behavior of a Lattice Structure Manufactured by PBF-LB/M. Procedia CIRP, 120, 1004-1009.
Mair, T.; Baehr, S.; Fuerbacher, J. & Zaeh, M.F.
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Additively manufactured structures with powder inclusions for controllable dissipation: The critical influence of packing density. Powder Technology, 437, 119587.
Praegla, Patrick M.; Mair, Thomas; Wimmer, Andreas; Fuchs, Sebastian L.; Zaeh, Michael F.; Wall, Wolfgang A. & Meier, Christoph
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Exploration of improved, roller-based spreading strategies for cohesive powders in additive manufacturing via coupled DEM-FEM simulations. Powder Technology, 443, 119956.
Weissbach, Reimar; Praegla, Patrick M.; Wall, Wolfgang A.; Hart, A. John & Meier, Christoph
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Quantitative analysis of thin metal powder layers via transmission X-ray imaging and discrete element simulation: Blade-based spreading approaches. Powder Technology, 432, 119106.
Penny, Ryan W.; Oropeza, Daniel; Praegla, Patrick M.; Weissbach, Reimar; Meier, Christoph; Wall, Wolfgang A. & John, Hart A.
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Quantitative analysis of thin metal powder layers via transmission X-ray imaging and discrete element simulation: Roller-based spreading approaches. Powder Technology, 432, 119105.
Penny, Ryan W.; Oropeza, Daniel; Weissbach, Reimar; Praegla, Patrick M.; Meier, Christoph; Wall, Wolfgang A. & Hart, A. John
