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A Layer-by-Layer Approach for Simulating Residual Stresses in AM
Örebro University, School of Science and Technology.ORCID iD: 0000-0001-6821-5727
Dynamore Nordic, Sweden.
2017 (English)In: 11th European LS-DYNA Conference, 2017Conference paper, Published paper (Refereed)
Abstract [en]

Distortions and residual stresses developed during additive manufacturing(AM) might be so severe that the design does not meet tolerance requirementsor even cracks and fail. Predictions of such distortions andresidual stressesby finite element analysis are therefore preferable performed early during thedesign development in order to reduce such problems. One approach for thiskind of analysis is to apply techniques from welding simulations letting theGoldak heat source move over each layer of the material. However, this iscomputationally most costly and one might also argue how well this actuallyrepresent the AM process. We suggest to simplify this boundary conditionto instead apply the heat layer-by-layer. We mean that this will represent theAM process as well as an approach of using the Goldak heat source and it ismuch more computational efficient than applying Goldaks heat source. Themodel is simply obtained by slicing the geometry in several layers using anin-house script. Then, a volume heat source is applied layer-by-layer, whereeach layer is activated starting from the build plate until the final build layer.Sequentially thermomechanical analysis using LS-Dyna is applied, wherethe heat capacity, conductivity, Youngs modulus, Poissonsratio, expansioncoefficient, yield stress, and the hardening modulus are given as functionsof temperature. The classical heat equation and J2-plasticity with kinematicor isotropic hardening are adopted by using*MATTHERMALCWMand*MATCWM,which makes the activation of the layers straight-forward using the ghostfeature implemented in these material models. After all layers are activatedand heated, a restart of cooling analysis is performed and, finally, the partis cut from the building plate using a third restart analysis. The approachis demonstrated for a benchmark of an open cylinder printed in Inconel 718showing the development of distortions and residual stresses in all stages ofthe AM process from heating during building until the final cut from the buildplate. We suggest that this benchmark can serve as an experimental setup inorder to validate the suggested approach. This is discussedin the paper andis a topic for future work.

Place, publisher, year, edition, pages
2017.
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:oru:diva-83840OAI: oai:DiVA.org:oru-83840DiVA, id: diva2:1448417
Conference
11th European LS-DYNA Conference, Salzburg, Austria, May 9-11, 2017.
Available from: 2020-06-28 Created: 2020-06-28 Last updated: 2025-05-19Bibliographically approved

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