Filtern
Dokumenttyp
Schlagworte
- DED (4)
- Directed Energy Deposition (3)
- Laser metal deposition (3)
- AM (2)
- Additive manufacturing (2)
- Dimensional accuracy (2)
- Welding simulation (2)
- Additive Manufacturing (1)
- Cimensional Accuracy (1)
- DIC (1)
Organisationseinheit der BAM
Directed energy deposition additive manufactured parts have steep stress gradients and an anisotropic microstructure caused by the rapid thermo-cycles and the layer-upon-layer manufacturing, hence heat treatment can be used to reduce the residual stresses and to restore the microstructure. The numerical simulation is a suitable tool to determine the parameters of the heat treatment process and to reduce the necessary application efforts. The heat treatment simulation calculates the distortion and residual stresses during the process. Validation experiments are necessary to verify the simulation results. This paper presents a 3D coupled thermo-mechanical model of the heat treatment of additive components. A distortion-based validation is conducted to verify the simulation results, using a C-ring shaped specimen geometry. Therefore, the C-ring samples were 3D scanned using a structured light 3D scanner to compare the distortion of the samples with different post-processing histories.
Components distort during directed energy deposition (DED) additive manufacturing (AM) due to the repeated localised heating. Changing the geometry in such a way that distortion causes it to assume the desired shape – a technique called distortion-compensation – is a promising method to reach geometrically accurate parts. Transient numerical simulation can be used to generate the compensated geometries and severely reduce the amount of necessary experimental trials. This publication demonstrates the simulation-based generation of a distortioncompensated DED build for an industrial-scale component. A transient thermo-mechanical approach is extended for large parts and the accuracy is demonstrated against 3d-scans. The calculated distortions are inverted to derive the compensated geometry and the distortions after a single compensation iteration are reduced by over 65%.
In additive manufacturing (AM) Laser Metal Deposition (LMD), parts are built by welding layers of powder feedstock onto a substrate. Applications for steel powders include forging tools and structural components for various industries. For large parts, the choice of tool-paths influences the build-rate, the part performance and the distortions in a highly geometry-dependent manner. With weld-path lengths in the range of hundreds of meters, a reliable, automated tool path generation is essential for the usability of LMD processes.
In this contribution, automated tool-path generation approaches are shown and their results are discussed for arbitrary geometries. The investigated path strategies are the classical approaches: “Zig-zag-” and “contour-parallel-strategies”. After generation, the tool-paths are automatically formatted into g-code for experimental build-up and ASCII for a numerical simulation model. Finally, the tool paths are discussed in regards to volume-fill, microstructure and porosity for the experimental samples.
This work presents a part of the IGF project 18737N “Welding distortion simulation” (FOSTA P1140)
Das DED Auftragschweißen ist ein additives Fertigungsverfahren für Metalle, bei dem das Material schichtweise auf ein Substrat aufgetragen wird. Die schnellen Temperaturzyklen rufen Spannungsgradienten im Bauteil hervor. Der schichtweise Aufbau der Bauteile verursacht eine anisotrope Mikrostruktur. Mittels nachgelagerter Wärmebehandlung können diese Effekte verringert werden. Im anschließenden Schritt der Prozesskette wird das additiv hergestellte Bauteil mittels Drahterodieren von dem Substrat abgetrennt.
In diesem Beitrag wird eine thermo-mechanische Simulation der gesamten Prozesskette vorgestellt, welche den additiven Aufbau, Wärmebehandlung und das Abtrennen vom Substrat beinhaltet. Anstelle der in der Literatur üblichen schichtweisen Modellierungsstrategie für die DED Simulation wird das gesamte Bauteil in einem Stück vernetzt und der vollständig transiente, schichtweise Materialauftrag über Elementgruppen realisiert. Im Gegensatz zu früheren Simulationen muss der nichtlineare Kontakt zwischen den Schichten nicht berücksichtigt werden, was die Rechenzeiten deutlich verkürzt.
Das Modell wurde validiert mittels Abgleiches des Verzugs aus Simulation und Experiment.
Die Proben, bestehend aus DIN 1.4404 (AISI 316L), wurden nach jedem Prozessschritt 3D gescannt um den Verzug zu quantifizieren. Zusätzlich wurden Querschnitte und Härtetests nach Vickers von unterschiedlich behandelten Proben durchgeführt, um den Effekt der Wärmebehandlung auf die Mikrostruktur und die Härte des Bauteils zu untersuchen.
Due to rapid, localized heating and cooling, distortions accumulate in additive manufactured laser metal deposition (LMD) components, leading to a loss of dimensional accuracy or even cracking. Numerical welding simulations allow the prediction of these deviations and their optimization before conducting experiments. To assess the viability of the simulation tool for the use in a predictive manner, comprehensive systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to Cluster these products in new assembly oriented product families for the optimization.
Distortions in Additive Manufacturing (AM) Laser Metal Deposition (LMD) occur in the newly-built component due to rapid heating and solidification and can lead to shape deviations and cracking. This paper presents a novel approach to quantify the distortions experimentally and to use the results in numerical simulation validation. Digital Image Correlation (DIC) is applied together with optical filters to measure in-situ distortions directly on a wall geometry produced with LMD. The wall shows cyclic Expansion and shrinking with the edges bending inward and the top of the sample exhibiting a slight u-shape as residual distortions. Subsequently, a structural Finite Element Analysis (FEA) of the experiment is established, calibrated against experimental temperature profiles and used to predict the in-situ distortions of the sample. A comparison of the experimental and numerical results reveals a good agreement in length direction of the sample and quantitative deviations in height direction, which are attributed to the material model used. The suitability of the novel experimental approach for measurements on an AM sample is shown and the potential for the validated numerical model as a predictive tool to reduce trial-and-error and improve part quality is evaluated.