TY - GEN A1 - Imran, Muhammad A1 - Afzal, Muhammad Junaid A1 - Buhl, Johannes A1 - Bambach, Markus A1 - Dunlap, Anthony A1 - Schwedt, Alexander A1 - Aretz, Anke A1 - Wang, Shuhan A1 - Lohmar, Johannes A1 - Hirt, Gerhard T1 - Evaluation of process-induced damage based on dynamic recrystallization during hot caliber rolling T2 - Production Engineering Y1 - 2020 U6 - https://doi.org/10.1007/s11740-019-00932-0 SN - 1863-7353 SN - 0944-6524 VL - 14 IS - 1 SP - 5 EP - 16 ER - TY - BOOK A1 - Bähr, Martin A1 - Buhl, Johannes A1 - Radow, Georg A1 - Schmidt, Johannes A1 - Bambach, Markus A1 - Breuß, Michael A1 - Fügenschuh, Armin T1 - Stable honeycomb structures and temperature based trajectory optimization for wire-arc additive manufacturing Y1 - 2019 U6 - https://doi.org/10.26127/btuopen-5079 CY - Cottbus ER - TY - RPRT A1 - Beisegel, Jesse A1 - Buhl, Johannes A1 - Izar, Rameez A1 - Schmidt, Johannes A1 - Bambach, Markus A1 - Fügenschuh, Armin ED - Fügenschuh, Armin T1 - Mixed-integer programming for additive manufacturing Y1 - 2021 U6 - https://doi.org/10.26127/BTUOpen-5731 CY - Cottbus ER - TY - BOOK A1 - Schmidt, Johannes A1 - Buhl, Johannes A1 - Fügenschuh, Armin T1 - A finite element approach for trajectory optimization in Wire-Arc Additive Manufacturing Y1 - 2021 U6 - https://doi.org/10.26127/BTUOpen-5575 CY - Cottbus ER - TY - GEN A1 - Bähr, Martin A1 - Buhl, Johannes A1 - Radow, Georg A1 - Schmidt, Johannes A1 - Bambach, Markus A1 - Breuß, Michael A1 - Fügenschuh, Armin T1 - Stable honeycomb structures and temperature based trajectory optimization for wire-arc additive manufacturing T2 - Optimization and Engineering N2 - 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. KW - Mixed-integer linear programming KW - Geometric optimization KW - Eikonal equation KW - Heat transmission KW - Additive manufacturing KW - Centroidal Voronoi tesselation Y1 - 2021 U6 - https://doi.org/10.1007/s11081-020-09552-5 SN - 1573-2924 VL - 22 IS - 2 SP - 913 EP - 974 ER - TY - GEN A1 - Bambach, Markus A1 - Fügenschuh, Armin A1 - Buhl, Johannes A1 - Jensch, Felix A1 - Schmidt, Johannes ED - Bambach, Markus T1 - Mathematical Modeling and Optimization for Powder-Based Additive Manufacturing T2 - Procedia Manufacturing; Part of Special issue: 23rd International Conference on Material Forming Y1 - 2020 U6 - https://doi.org/10.1016/j.promfg.2020.04.158 SN - 2351-9789 VL - 47 SP - 1159 EP - 1163 ER - TY - CHAP A1 - Beisegel, Jesse A1 - Buhl, Johannes A1 - Israr, Rameez A1 - Schmidt, Johannes A1 - Bambach, Martin A1 - Fügenschuh, Armin ED - Cristiani, Emiliano ED - Falcone, Maurizio ED - Tozza, Silvia T1 - Mixed-Integer Programming Models for Two Metal Additive Manufacturing Methods T2 - Mathematical Methods for Objects Reconstruction Y1 - 2023 SN - 978-981-9907-75-5 SN - 978-981-9907-76-2 SP - 121 EP - 155 PB - Springer CY - Heidelberg ER - TY - GEN A1 - Israr, Rameez A1 - Buhl, Johannes A1 - Bambach, Markus T1 - A study on power-controlled wire-arc additive manufacturing using a data-driven surrogate model T2 - The International Journal of Advanced Manufacturing Technology N2 - Wire-arc additive manufacturing (WAAM) provides an alternative for the production of various metal products needed in medium to large batch sizes due to its high deposition rates. However, the cyclic heat input in WAAM may cause local overheating. To avoid adverse effects on the performance of the part, interlayer dwelling and active cooling are used, but these measures increase the process time. Alternatively, the temperature during the WAAM process could be controlled by optimizing the welding power. The present work aims at introducing and implementing a novel temperature management approach by adjusting the weld-bead cross-section along with the welding power to reduce the heat accumulation in the WAAM process. The temperature evolution during welding of weld beads of different cross-sections is investigated and a database of the relation between optimal welding power for beads of various sizes and different pre-heating temperatures was established. The numerical results are validated experimentally with a block-shaped geometry. The results show that by the proposed method, the test shape made was welded with lower energy consumption and process time as compared to conventional constant-power WAAM. The proposed approach efficiently manages the thermal input and reduces the need for pausing the process. Hence, the defects related to heat accumulation might be reduced, and the process efficiency increased. Y1 - 2021 U6 - https://doi.org/10.1007/s00170-021-07358-y SN - 1433-3015 SN - 0268-3768 VL - 177 IS - 7-8 SP - 2133 EP - 2147 ER - TY - GEN A1 - Gerold, Stefanie A1 - Buhl, Johannes A1 - Geiger, Sonja M. T1 - How to Enhance Time Wealth? Insights from Changes in Time Use and Working Conditions During the COVID-19 Lockdown in Germany T2 - Social Indicators Research N2 - This paper investigates the changes in time use, working conditions and subjective time wealth during the COVID-19 pandemic in Germany. Our analysis draws on panel data collected before and during the first lockdown among 786 employees. It employs a recently developed scale on time wealth which has been suggested as a comprehensive measure to capture the subjective experience of time. We provide separate analyses according to gender and essential occupation. First-difference regressions are applied to examine how changes in time use and changes in working conditions during the lockdown affected subjective time wealth. Our results show a general growth in time wealth during the lockdown which is, among other factors, driven by a decline in work hours and an increase in sleep duration. We also find positive effects on time wealth from decreased time pressure at work, more autonomy in organising one’s working day, and an improved reconciliation of work and private life. This study contributes to existing research by identifying key aspects how to improve time wealth among employees. Y1 - 2023 U6 - https://doi.org/10.1007/s11205-023-03252-0 SN - 1573-0921 VL - 171 SP - 349 EP - 371 ER - TY - GEN A1 - Nguyen, Lam A1 - Buhl, Johannes A1 - Bambach, Markus ED - Bambach, Markus T1 - Multi-bead Overlapping Models for Tool Path Generation in Wire-Arc Additive Manufacturing Processes T2 - Procedia Manufacturing; Part of Special issue: 23rd International Conference on Material Forming Y1 - 2020 U6 - https://doi.org/10.1016/j.promfg.2020.04.129 SN - 2351-9789 VL - 47 SP - 1123 EP - 1128 ER -