Markus Bambach

Last Name

Bambach

First Name

Markus

ORCID

0000-0002-8790-0807

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09706 - Bambach, Markus / Bambach, Markus

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Publications1 - 10 of 166

Analysis and compensation of shrinkage and distortion in wire-arc additive manufacturing of thin-walled curved hollow sections
Nguyen, Lam; Buhl, Johannes; Israr, Rameez; et al. (2021)
Additive Manufacturing
Curved hollow sections are used in numerous applications from lightweight space frames to pipings in process engineering. In conventional manufacturing, such structures are produced mainly by metal forming or casting. Despite ongoing efforts in rapid tooling technologies for casting and flexible forming processes, there is a demand for dieless manufacturing of curved hollow structures, as this would allow to produce parts with greatly reduced lead-times, e.g., as on-demand spare parts and on construction sites using mobile equipment. Wire-arc additive manufacturing (WAAM) processes with multi-axis deposition can be used in this case. This process typically draws upon the gas metal arc welding (GMAW) process with cold metal transfer (CMT) technology. Thin-walled metal parts produced by WAAM may show deviations to the target geometry due to material shrinkage and distortion, which may entail tedious trial-and-error compensation. This study analyses shrinkage and distortion in curved hollow sections with different cross sections and curvature radii both experimentally and with a thermo-mechanical finite element model. Based on these findings, a novel method for the compensation of shrinkage and distortion for thin-walled hollow parts is put forward and validated. The correction method draws upon the geometrical deviations that occur when the part is produced based on the CAD geometry, and computes a correction to the CAD geometry, which is used to define the welding path for a part with improved accuracy. The results show that the geometry of the manufactured part can be corrected to tolerances in the range of the waviness of the surface by applying the proposed correction.
Study on the effect of wear models in tool wear simulation using hybrid SPH-FEM method
Zhang, Nanyuan; Klippel, Hagen; Kneubühler, Fabian; et al. (2023)
Procedia CIRP ~ 19th CIRP Conference on Modeling of Machining Operations
The prediction of the tool wear progression using numerical methods has been widely studied in recent years, and various wear models considering different wear mechanisms have been implemented in the simulation work. Typically, these wear models take the physical fields such as contact pressure, sliding velocity and temperature at the tool-workpiece interface into account and are applied either individually or in combinations into the wear simulation. However, how and to what extent the physical parameters in these models affect the generated wear profiles have not been explored in detail in the simulation. In this paper, the behaviors of several typical wear models are studied by simulating the tool wear of cutting Ti6Al4V using a hybrid SPH-FEM method. Considering different combinations of physical contact parameters in the wear model, the simulated wear progression is discussed, and the resulting worn tool geometry is qualitatively compared to the experimental result. Furthermore, insights into the calibration of wear models are proposed.
Structural behavior of a wire arc additively manufactured steel eye bar for the repair of a historic high-tech facade
Brenner, Matthias; Silvestru, Vlad-Alexandru; Studer, Patrick; et al. (2026)
Structures
The practice of early demolition and replacement of building facades in the architecture, engineering, and construction (AEC) industry, particularly metal facades, raises significant sustainability and preservation concerns ranging from the loss of valuable materials, increased carbon emissions, and the erosion of architectural heritage. This research focuses on innovative metal facade structures from the second half of the 20th century that are particularly vulnerable due to their novel construction techniques and materials. It examines a possible repair scenario using the facade construction of the CLA research facility at ETH Zurich as a case study, illustrating the challenges of repairing a complex metal facade that is not protected by conservation regulations but is treated as a listed building. The research explores the potential of digital fabrication, specifically Wire-and-Arc Additive Manufacturing (WAAM), as a viable solution for producing the bespoke replacement parts needed to repair such facade structures. The paper illustrates the production and testing of the printed specimens under compressive and tensile loading, focusing on force-displacement curves, strain distributions, and failure modes. A total of eight specimens are tested, four in tension and four in compression. The experimental results show a ductile behavior of the WAAM parts, and a significantly higher load-bearing capacity than is necessary for transferring the forces occurring in the considered facade. The experimental results are then compared with those obtained from calculations according to existing standards. A porosity analysis is performed on two test specimens, subjected to compressive and tensile loading. The study demonstrates that WAAM, with its capability for mass customization and rapid material deposition, is a viable method for producing high-quality, on-demand components that meet the stringent requirements of facade preservation.
Structural investigations of Fe-Zr-Si-Cu metallic glass with low glass-forming ability produced in laser powder bed fusion technology
Szczepanski, Łukasz; Bambach, Markus; Jensch, Felix; et al. (2021)
Materials & Design
Fe-based metallic glasses (MG) have become the subject of extensive research in recent years due to their favorable mechanical and magnetic properties. In particular, the production of this type of materials in Laser Powder Bed Fusion (LPBF), also known as Selective Laser Melting (SLM) technology, is a kind of breakthrough, as it has become possible to produce elements of any shape. An important factor influencing the properties of the manufactured parts is their microstructure. For metallic glass Fe79Zr6Si14Cu1 with low glass-forming ability, produced in SLM technology, tests were carried out in the field of structural X-ray diffraction, Scanning Electron Microscopy, and Transmission Electron Microscopy. In addition, porosity analysis was compared with process parameters such as laser power and scanning speed. The paper shows that the fusion line comprises a solid solution α-Fe(Si) and low fraction of intermetallic Fe23Zr6 and FeZr2 phases. Furthermore, in the melt pool area, a nanometric α-Fe(Si) phase and an amorphous matrix was observed. The presented research results of the Fe79Zr6Si14Cu1 alloy produced for the first time in SLM technology will undoubtendly contribute to further optimization of parameters for elements produced in Additive Manufacturing technology using Fe-based MG.
Directed energy deposition of Inconel 718 powder, cold and hot wire using a six-beam direct diode laser set-up
Bambach, Markus; Sizova, Irina; Kies, Fabian; et al. (2021)
Additive Manufacturing
This study puts forward a new set-up for directed energy deposition (DED) with a six-beam direct diode laser head. The set-up implements three process variants, i.e. cold and hot wire as well as powder DED. The differences in the material behavior of INCONEL® alloy 718 (IN718) during additive manufacturing using the three processes is analyzed with respect to dilution, penetration into the base material, as well as solidification microstructure, second phase particles and texture. The results confirm that all three processes allow for defect-free DED of IN718, and that the hot wire process facilitates high-deposition rates with low dilution, whereas the cold wire and powder processes yield different dilution and penetration. The differences of the three process variants motivate to apply these processes interchangeably on the same part depending on the desired local microstructures, textures and thus, properties. The fundamental correlation between the processing conditions of the novel set-up used and the material behavior during DED is discussed.
Investigation by operando synchrotron X-ray diffraction of the phase transformation in 316L-IN625 multi-material direct energy deposition
Martin, Noémie; Denoréaz, Thomas; Bambach, Markus; et al. (2025)
Journal of Materials Research and Technology
Stainless steel 316L is widely used and frequently studied in additive manufacturing. Although designed to be fully austenitic, its microstructure, grain morphology, and phase composition vary with different processes and parameters, sometimes displaying a significant fraction of ferrite. Simulations and ex-situ observations suggest that cooling rates, solidification velocities, and local chemical composition gradients play key roles, but no experimental observations could validate that hypothesis and determine the role of each factor. This study uses operando synchrotron X-ray diffraction and ex-situ observations to examine the solidification process of 316L deposited via wire-based laser direct energy deposition, both pure and on Inconel 625, a bi-material combination also common in literature and industry. Real-time diffraction data revealed the formation and the evolution during the cooling of the BCC and FCC phases, along with the temperature profiles. EBSD and feritscope measurements confirmed that ferrite is retained in the microstructure. The results validate that in the case of laser DED, the primary BCC solidification of 316L is determined by a competition between chemical composition and solidification velocity, while the cooling rates influences the phase retention. This study sets a precedent for operando investigations of commercial additive manufacturing processes in medium energy synchrotron X-ray radiation, and contributes to the understanding of the solidification modes of 316L deposited by laser DED.
End-to-end path planning for homogeneous temperature fields in additive manufacturing
Sideris, Iason; Duncan, Stephen; Fabbri, Maicol; et al. (2024)
Journal of Materials Processing Technology
This study explores a novel approach to path planning in deposition-based additive manufacturing, integrating the frequently overlooked process-induced temperature fields. Currently, existing approaches either ignore temperature effects entirely or only consider them in small-scale problems due to the high computational cost involved in predicting them and the combinatorial nature of path planning optimization. To address these challenges, the present work proposes an optimization pipeline that involves deriving a reduced order model from a finite volume method model with balanced truncation, using an analytical function to model the heat input and, calculating the steady-state response of the system to an arbitrary path using the Laplace transformation. Then, the optimization is transformed into a sequential decision-making problem and approximated with Monte Carlo tree search. The pipeline is validated through computational and experimental results, demonstrating its efficiency in managing large and complex geometries, as well as its resilience in overcoming the challenges posed by the simulation to reality gap.
Stable honeycomb structures and temperature based trajectory optimization for wire-arc additive manufacturing
Bähr, Martin; Buhl, Johannes; Radow, Georg; et al. (2021)
Optimization and Engineering
We consider two mathematical problems that are connected and occur in the layer-wise production process of a workpiece using wire-arc additive manufacturing. As the first task, we consider the automatic construction of a honeycomb structure, given the boundary of a shape of interest. In doing this, we employ Lloyd’s algorithm in two different realizations. For computing the incorporated Voronoi tesselation we consider the use of a Delaunay triangulation or alternatively, the eikonal equation. We compare and modify these approaches with the aim of combining their respective advantages. Then in the second task, to find an optimal tool path guaranteeing minimal production time and high quality of the workpiece, a mixed-integer linear programming problem is derived. The model takes thermal conduction and radiation during the process into account and aims to minimize temperature gradients inside the material. Its solvability for standard mixed-integer solvers is demonstrated on several test-instances. The results are compared with manufactured workpieces.
Laser powder bed fusion of CuCr1Zr on 316 L: a simplified methodology to unravel the effect of intermixing and energy input in the first interfacial layer
Pellin, Raphael L.; Deillon, Léa; Basu, Indranil; et al. (2025)
Progress in Additive Manufacturing
Multi-material laser powder bed fusion (PBF-LB) enables the fabrication of complex components, but presents challenges in material compatibility at interfaces. This study investigates the interface formation between 316 L steel and CuCr1Zr, a promising combination for heat exchanger applications. A simplified approach is adopted by printing single layers of CuCr1Zr within steel cavities using standard PBF-LB equipment. A process window for the first interfacial layer is established, demonstrating that increased layer thickness (2-4 times the standard) limits intermixing. Despite achieving a 14.2 mm-long interface with only 0.7 % cracking in steel, copper contamination cracking (CCC) remains a critical issue, as revealed by microstructural analyses using Energy-Dispersive X-ray Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD). These findings highlight fundamental limitations in achieving crack-free interfaces over extended lengths, questioning the feasibility of multi-material PBF-LB for certain applications.
Hot workability of a spark plasma sintered intermetallic iron aluminide alloy above and below the order-disorder transition temperature
Emdadi, Aliakbar; Sizova, Irina; Stryzhyboroda, Oleg; et al. (2020)
Procedia Manufacturing ~ 23rd International Conference on Material Forming
The Fe-25Al-1.5Ta alloy has proved to be qualiﬁed for structural applications at and above 600°C due to a superior creep resistance to its binary counterpart. The creep resistance of the Fe-25Al-1.5Ta alloy at 650°C surpasses that of the P92 martensitic-ferritic steel, which is one of the most developed creep resistant alloys for steam turbine applications. From the viewpoint of cost-effectiveness in real-scale forgings, it is important to safely deform the material at as low as possible temperatures. Based on Thermo-Calc computations, the Fe-25Al-1.5Ta alloy shows a B2-to-A2 order-disorder transition at around 860ºC. This paper investigates the hot compression behavior and microstructural evolution of a Fe-25Al-1.5Ta alloy deformed in the disordered A2 (900-1100ºC) and ordered B2 (800-850ºC) regimes. Effects of ordering on plastic deformation, energy dissipation efficiency and instability parameters are identified using the concept of processing maps, and the underlying deformation mechanisms are characterized using scanning electron microscopy and electron back-scattered diffraction. The samples deformed in the A2 disorder region showed no ﬂow instability for the deformation conditions tested, while the specimens deformed in the ordered B2 region revealed a region of flow instability located at 900ºC/1s-1. The observed flow instability region manifests itself in a longitudinal surface crack formed in the samples deformed at 900ºC/1s-1. The change of activation energy of hot deformation and efficiency of energy dissipation are discussed based on the ordering effect and movement of super-dislocations in the B2 regime. The current study identifies processing parameters to safely deform the Fe-25Al-1.5Ta alloy at lower temperatures of 800ºC and at strain rates below 1s-1.

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Markus Bambach

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