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Browsing Scopus by Department "Fraunhofer-Einrichtung für Additive Produktionstechnologien IAPT"
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Publication3D-Scannen beim roboterbasierten Auftragschweißen( 2022)
;Akramyar, ChabirRobot-based additive manufacturing enables the production of large and resource-efficient parts layer-by-layer. Instabilities of the process induce the necessity of geometrical sensing for close-loop control and quality assurance. The use presupposes a calibration of the sensor-based robotic system. In this paper the existing concepts will be presented and adapted. -
PublicationA study on XFEM simulation of tensile, fracture toughness, and fatigue crack growth behavior of Al 2024 alloy through fatigue crack growth rate models using genetic algorithm( 2023)
;Gairola, Saurabh ;Rengaswamy, JayaganthanVerma, RavirajThis study aims to numerically validate and simulate the fatigue crack growth rate (FCGR), tensile, and fracture toughness properties of T3 and T351 tempered aerospace grade Al 2024 alloy. The extended finite element method (XFEM) coupled with a genetic algorithm (GA) was used to predict FCGR behavior in the framework of an in-house developed MATLAB code. The numerical simulation was performed using three different FCGR models, i.e., Paris, Forman, and Nasgro. The FCGR prediction ability of simulation models was improved and compared further using GA. The Nasgro model with genetically optimized parameters shows the highest FCGR prediction accuracy compared to other FCGR models. The critical stress intensity factor and von Mises stress distribution under static loading were also predicted for C(T) specimen. A similar XFEM approach was used for analyzing the tensile behavior using a center cracked specimen at the gage section of a dog bone-shaped specimen. -
PublicationComparison of iPad Pro®’s LiDAR and TrueDepth Capabilities with an Industrial 3D Scanning Solution( 2021)
;Vogt, Maximilian ;Rips, AdrianEmmelmann, ClausToday’s smart devices come equipped with powerful hard- and software-enabling professional use cases. The latest hardware by Apple utilizes LiDAR and TrueDepth, which offer the capability of 3D scanning. Devices equipped with these camera systems allow manufacturers to obtain 3D data from their customers at low costs, which potentially enables time-efficient mass customization and product differentiation strategies. However, the utilization is limited by the scanning accuracy. To determine the potential application of LiDAR and TrueDepth as a 3D scanning solution, in this paper an evaluation was performed. For this purpose, different Lego bricks were scanned with the technologies and an industrial 3D scanner. The results were compared according to shape and position tolerances. Even though the industrial 3D scanner consistently delivered more accurate results, the accuracy of the smart device technologies may already be sufficient, depending on the application. -
PublicationDesign guidelines for metal binder jetting( 2023)
;Blunk, HeikoSeibel, ArthurIn addition to the general advantages of additive manufacturing technologies, such as the resource-efficient production of highly complex components, the metal binder jetting (MBJ) process enables a more cost-effective manufacturing of metal additive components. However, the design freedoms gained by additive manufacturing, and MBJ in particular, are also accompanied by new design restrictions for component design. While a large number of design guidelines are already available for the established additive manufacturing processes, the metal binder jetting process imposes additional requirements on component design, which are currently only inadequately covered in the literature. Therefore, this paper presents the development and derivation of first design rules for the metal binder jetting process using martensitic stainless steel (17–4 PH). In this way, the paper also provides a methodology for deriving guidelines regardless of the material. In total, 13 guidelines have emerged from this, which in part both confirm existing guidelines, but also extend them. -
PublicationDevelopment and assessment of a methodology for abstraction of topology optimization results to enable the substitution of optimized beams( 2023)
;Röver, Tim ;Bader, Maximilian ;Asami, Karim ;Emmelmann, ClausKelbassa, IngomarImproving mechanical topology optimization (TO) results by substituting biomimetic beams is one possibility to achieve designs of mechanical components that are highly sustainable and show good mechanical performance. Because of their geometric complexity, such designs were found to be well-suited for production by laser additive manufacturing. One obstacle of incorporating biomimetics beams in TO designs is the lack of detailed design methodologies. Röver et al. [“Methodology for integrating biomimetic beams in abstracted topology optimization results,” in Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition. Volume 4: Biomedical and Biotechnology; Design, Systems, and Complexity Columbus, OH, 30 October-3 November (ASME, New York, 2022)] proposed a corresponding design concept. Building on their concept, we present in this work a detailed methodology for abstraction of TO results to a design consisting of ball nodes and cylindrical beams. Using such an auxiliary design, the internal forces and moments of the beams can be evaluated to allow for the substitution of suitable biomimetic beams to generate biomimetic component designs in a next step. We present a skeletonization algorithm based on the potential field approach. Using the skeletonization and an additional analysis of the dimensions of the beams in the TO result, the algorithm develops an auxiliary design of the original TO result. The final algorithm was applied to three common TO results to obtain one auxiliary component design each. The developed algorithm was found to generate abstractions that were well-suited for use in the methodology proposed in Röver et al. [“Methodology for integrating biomimetic beams in abstracted topology optimization results,” in Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition. Volume 4: Biomedical and Biotechnology; Design, Systems, and Complexity Columbus, OH, 30 October-3 November (ASME, New York, 2022)], because internal forces and moments in the abstracted beams could be evaluated with less effort. Therefore, our work contributes to a detailed design methodology for biomimetic mechanical components in the field of design for additive manufacturing. -
PublicationEffect of DED process parameters on distortion and residual stress state of additively manufactured Ti-6Al-4V components during machining( 2022)
;Romanenko, Denys ;Prakash, Vishnuu Jothi ;Kuhn, Tobias ;Moeller, Carsten ;Hintze, WolfgangEmmelmann, ClausOne of the major challenges in high-deposition rate Directed Energy Deposition processes is the resultant residual stresses generated during material deposition, often leading to distortion and poor material characteristics. Important part families suitable for DED process in aerospace sector are thin-wall components, characterized by a large base surface area with rib-like strengthening structures. Here, the substrate plate can be designed to be a part of the final component. The integration of substrate plate into final component results in possible deformation due to residual stress release during machining. This paper therefore investigates the effect of various powder-based Laser Metal Deposition process parameters and strategies on the residual stress state of the additively manufactured Ti-6Al-4V components and the resulting stress release during machining process. The analysis has been carried out during the machining process by including in-process strain measurements of the substrate. The embraced layer removal method allows the determination of machining zone specific stress release mapping, based on an analytical and FEM-model. Hence, the initial residual stress state of the builds was calculated, which revealed that although the heat treatment resolved most of the residual stresses, also in heat treated parts residues were identified depending on the part clamping during the treatment. Furthermore, the study revealed that the significant residual stresses are present in the layers close to the substrate. -
PublicationHDPE@UHMWPE Powders for Power Bed Fusion Based Additive Manufacturing( 2022)
;Wencke, Y.L. ;Proes, FriedrichLuinstra, G.A.Commercial UHMWPE powder of 60 µm size (d50) embossed with 2–5 wt% of nanosilica is used as a support for the preparation of core–shell HDPE@silica@UHMWPE particles. The HDPE shell is generated by polymerization of ethylene in toluene slurry after treatment of the silica@UHMWPE with a methyl aluminoxane activated bisimine pyridine iron complex. Heat pressing the powder gives a solid material with identifiable original UHMWPE particles and a layer from fusion of UHMWPE and the surrounding HDPE shell; the properties match those of the UHMWPE base material. The powder flow properties of the HDPE@silica@UHMWPE are insufficient for a powder bed fusion process, a value for the flow function between 2 and 3 is measured in a ring shear tester. Additivation with nanosilica helps to overcome the insufficient flowability and allows the material to be recoated in a power bed fusion system. Laser sintering gives evidence for a substantial mixing and welding of the HDPE shells and UHMWPE. Caking at the surface of the built parts hinders the manufacturing of isolated parts. Further additivation with carbon black reduces the caking; however, the welding within the HDPE@silica@UHMWPE material is much less strong. -
PublicationInfluence of temperature and beam size on weld track shape in laser powder bed fusion of pure copper using near-infrared laser system( 2024)
;Bauch, AlexanderHerzog, DirkAdditive manufacturing of copper using laser powder bed fusion enables the production of highly complex components with excellent heat and electrical conductivity. However, the processing of copper by means of near-infrared laser radiation, which is commonly used, is challenging due to its high reflectivity. Nevertheless, it has been demonstrated that high densities and electrical conductivities can be achieved using high-power laser systems. In order to process pure copper with reliable quality with different machines, it is essential to understand the conditions at which a continuous weld track is formed. For this purpose, weld tracks with varying laser power and scan speeds were welded on a copper substrate plate with an applied powder layer. The preheating temperature of the substrate plate and the beam size were varied to test different process conditions. The melt pool depths and widths were measured, and a relationship was elaborated. Based on these results, cube samples with discrete weld tracks on top were manufactured. The melt pool depth was measured and compared with the predicted melt pool depth to investigate the transferability of the elaborated relationship from the substrate to process conditions. It was found that with rising preheating temperature and for larger beam diameters at the same peak intensity, the weld width and weld depths increase. Furthermore, continuous weld tracks formed reliably in the keyhole welding regime. A good agreement between the weld depth of weld tracks on the substrate and the elaborated relationship was revealed. However, the weld tracks were shallower than predicted. -
PublicationLaser beam powder bed fusion of novel biomedical titanium/niobium/tantalum alloys: Powder synthesis, microstructure evolution and mechanical properties( 2023)
;Johannsen, Jan ;Lauhoff, Christian ;Stenzel, Melanie ;Schnitter, Christoph ;Niendorf, ThomasWeinmann, MarkusThe synthesis of spherical titanium/niobium/tantalum (TNT) alloy powders, namely Ti-20Nb-6Ta, Ti-27Nb-6Ta, Ti-35Nb-6Ta, and Ti-22Nb-19Ta (in wt-%) by electrode induction melting gas atomization is reported. The powder materials are characterized in detail using X-ray diffraction and scanning electron microscopy. Their processability via laser beam powder bed fusion (PBF-LB/M) is proven, and microstructure as well as mechanical properties of the additively manufactured specimens are assessed. All powders feature a dendrite-type microstructure with Nb/Ta-rich dendritic and Ti-rich inter-dendritic phases. Crystal structures of the powders are strongly composition-dependent. Nb- and Ta-rich Ti-35Nb-6Ta and Ti-22Nb-19Ta feature a body-centered cubic lattice, whereas Ti-rich Ti-20Nb-6Ta and Ti-27Nb-6Ta powders are characterized by multi-phase microstructures, consisting of non-equilibrium martensitic phases. Processing by PBF-LB/M causes significant changes in their microstructures: the dendrite-type morphologies vanish, and the formation of microstructures with a homogeneous element distribution can be observed in all additively manufactured parts. Ultimate tensile strength (UTS) as well as elongation at fracture are assessed by tensile testing. UTS values are found to be in a range from 651 MPa (Ti-35Nb-6Ta) to 802 MPa (Ti-20Nb-6Ta); strain-to-failure is between 21.3 % (Ti-35Nb-6Ta) and 31.7 % (Ti-22Nb-19Ta). Ductile fracture behavior is seen for all TNT alloys investigated. -
PublicationMethodology for Integrating Biomimetic Beams in Abstracted Topology Optimization Results( 2022)
;Röver, Tim ;Lau, Robert ;Lange, Fritz ;Struve, Arnd ;Fuchs, Cedrik ;Bartsch, Katharina ;Seibel, ArthurEmmelmann, ClausThis paper presents a five-step design methodology to generate designs of biomimetic structural components from topology optimization results. In step one, all material allocated by topology optimization is classified as either beam like structures or nodes to generate an auxiliary model consisting of preserved regions, cylindrical beams, and ball nodes, which is an abstraction of the original topology optimization result. In step two, the auxiliary model is exposed to the original boundary conditions in a finite element analysis. Then, internal forces, torsion, and bending moments in all beams of the auxiliary model are identified with respect to both of their ends. In step three, a database is used to find a suitable biomimetic beam for each previously analyzed beam in the auxiliary model. In step four, adapted nodes are designed to connect the biomimetic beams and preserved regions to generate an intermediate biomimetic component design. And in step five, a design iteration and a validation of the final design are performed. The design methodology allows for reproducible biomimetic component designs, a trackable and easily documentable component development process, and the possibility of automating the design process to ultimately save development costs when designing structural components. -
PublicationMobile Refurbishment by Robot-Based Additive Manufacturing( 2022)
;Weber, Julian Ulrich ;Vykhtar, Bohdan ;Fischer, Andre ;Gritz, KarlSchlüter, P.Stationary molding and casting tools with abrasive defect formation can be repaired using Additive Manufacturing technologies. To automate these repair technologies, robot-based process manipulation is a common approach within the industry. Nevertheless, most process integrations into robot systems lead to a stationary deployment of the repair process, limiting the application only for mobile molding and casting tools. Thus, a mobile robot solution is necessary for the automated repair of stationary tools. A concept for such a mobile robot solution was elaborated within this work. System and process requirements were defined based on the repair application. A compact and mobile 6-axis mobile robot system was designed to manipulate a wire-based Laser Metal Deposition (LMD) repair process. Correspondingly, an electronic supply system and a software-based robot control were designed. A prototype system was built up to generate two- and three-dimensional repair structures as a validation of the robot-based mobile LMD process. -
PublicationMonitoring and local gas shielding at laser-based welding of titanium alloys( 2022)
;Vykhtar, Bohdan ;Lingner, Markus ;Richter, AlexanderHoops, FredericInsufficiently shielded joints during laser-based welding of titanium alloys become brittle and result in not loadable connections, which leads to the necessity of gas shielding. Typically, such welding procedures are performed in a shielding gas chamber, which makes the process complex and leads to high gas consumption and gas purging time. To overcome this, a locally acting shielding gas bell was developed, which allows direction-independent laser welding on flat components with an oxygen concentration of less than 20 ppm. Further, the bell extracts fume and continues to cover the material with shielding gas during material cooling. To automate path teaching in welding operations, an optical-based sensor system was developed and integrated into the optical path of the laser. External lighting was integrated into the gas shield bell to improve joint recognition and monitoring. The novel shield gas bell and monitoring system are validated using Ti-6Al-4V welds. -
PublicationNumerical and experimental investigation of the geometry dependent layer-wise evolution of temperature during laser powder bed fusion of Ti-6Al-4V( 2023)
;Li, Gefei ;Ganeriwala, Rishi K. ;Herzog, Dirk ;Bartsch, KatharinaKing, WayneLaser powder bed fusion (L-PBF) is currently the additive manufacturing process with the widest industrial use for metal parts. Yet some hurdles persist on the way to a widespread industrial serial production, with reproducibility of the process and the resulting part properties being a major concern. As the geometry changes, so do the local boundary conditions for heat dissipation. Consequently, the use of global, geometry-independent processing parameters, which are today’s state of the art, may result in varying part properties or even defects. This paper presents a numerical simulation as a method to predict the geometry-dependent temperature evolution during the build. For demonstration, an overhang structure with varying angles towards the build platform was manufactured using Ti-6Al-4V. A calibrated infrared camera was integrated into a commercial L-PBF system to measure the temperature evolution over time for a total build height of 10 mm, and the results are used for validation of the simulation. It is shown that the simulation is capable of predicting the temperature between layers. The deviations between simulation and measurement remain in single digit range for smaller overhang structures (90°, 60° and 45°). For large overhang structures (30°), the simulation tends to over-predict the temperatures up to 15 °C. Experiments with varying process parameters showed the feasibility of energy reduction as compensation of the heat accumulation produced by overhang structures. -
PublicationRecycling-oriented fabrication of soft robots( 2022)
;Nguyen, Anh MinhSeibel, ArthurClimate change is continuing, and more environmental awareness is required these days. In this context, plastics are a controversial topic. On top of this, a current plastics-based field of research is developing with great interest: soft robotics. Soft robots are generally made of elastomers, for which recycling is rather difficult. An implementation of recycling in soft robotics is still pending. This paper aims to show to what extent three typical materials used in soft robotics (Ecoflex 00-30, Elastosil M4601, and Sylgard 184) can be reintroduced in powder form into the manufacturing process after use and what mechanical properties such recyclates have. -
PublicationSignal processing of airborne acoustic emissions from laser metal deposited structures( 2022)
;Weber, Julian Ulrich ;Knabe, Michael ;Sayilgan, VurgunEmmelmann, ClausLaser Metal Deposition (LMD) is an additive manufacturing process that enables the production of complex structures on existing parts. To reduce the use of costly and energy-intensive produced materials like titanium, these structures can be selectively deposited on favorable but differing substrate materials. However due to differing material characteristics, this results in a high defect potential. Extensive process parameter development and online process monitoring helps to minimize the impact of defect formation. Monitoring of airborne acoustic process emissions can be used to identify critical defects early during the process and gain information about process stability. Two approaches for in-process time-frequency monitoring of the acquired acoustic data were compared within this work: The short time Fast Fourier Transformation and the Continuous Wavelet Transformation. Performance criteria based on detected distinct defect events were defined to evaluate both approaches and define specifications for an Acoustic Emission In-Process Monitoring system. -
PublicationStudy on fatigue crack growth behaviour of DEDed Ti-6Al-4V alloy through XFEM( 2023)
;Verma, Raviraj ;Gairola, SaurabhJayaganthan, R.The mechanical behavoiur of Ti-6Al-4V alloy under cyclic load is essential to understand its crashworthiness, especially for aerospace structural applications. The in-house developed extended finite element (XFEM) based MATLAB code was used to model fatigue crack growth rate (FCGR) in direct energy deposited Ti-6Al-4V alloy. The assumed computational domains such as single-edge, center-edge, and dual-edge cracked square specimens, were loaded under the mode-I scenario to assess FCGR behaviour. The novelty of the work is to analyse and predict all three regimes of "da/dN-ΔK" plot, i.e. threshold-, stable-, and catastrophic-crack growth regimes by using NASGRO empirical phenomenological model, unlike only stable-crack regime of Paris model, which is rare in literature. This phenomenological model was analysed based on the maximum cyclic total strain energy release rate (GT), threshold strain energy release rate (GTH), and quasi-static strain energy release rate (GQS) values. The FCGR behaviour of different computational domains, with respect to varying geometrical configurations, were characterized using microstructure-property correlation. The range of stress intensity factor (ΔK) was also compared with respect to different cracked domains, which is extended further for critical case scenarios for the FCGR prediction. -
PublicationWirtschaftliche Betrachtung von Augmented Reality( 2023)
;Vogt, MaximilianSpatzier, Julian FelixThe shortage of skilled workers as a result of demographic change and the lack of robustness in value chains represent current challenges for industry. In this context, the digitalization of manual operations by using immersive technologies, such as augmented reality (AR), is considered to enhance resilience. This paper presents a holistic methodology to systematically evaluate deployment scenarios of AR-based digital assistance systems economically and demonstrates the approach with use cases in additive manufacturing.