Fakultät für MaschinenbauFrei zugängliche Publikationen aus der Fakultät für Maschinenbauhttps://www.repo.uni-hannover.de/handle/123456789/62024-03-19T01:24:37Z2024-03-19T01:24:37ZQuantum algorithms for process parallel flexible job shop schedulingDenkena, BerendSchinkel, FritzPirnay, JonathanWilmsmeier, Sörenhttps://www.repo.uni-hannover.de/handle/123456789/167662024-03-18T08:10:51Z2021-01-01T00:00:00ZQuantum algorithms for process parallel flexible job shop scheduling
Denkena, Berend; Schinkel, Fritz; Pirnay, Jonathan; Wilmsmeier, Sören
Flexible Job Shop Scheduling is one of the most difficult optimization problems known. In addition, modern production planning and control strategies require continuous and process-parallel optimization of machine allocation and processing sequences. Therefore, this paper presents a new method for process parallel Flexible Job Shop Scheduling using the concept of quantum computing based optimization. A scientific benchmark and the application to a realistic use-case demonstrates the good performance and practicability of this new approach. A managerial insight shows how the approach for process parallel flexible job shop scheduling can be integrated in existing production planning and control IT-infrastructure.
2021-01-01T00:00:00ZOn the Microstructural and Cyclic Mechanical Properties of Pure Iron Processed by Electron Beam MeltingTorrent, Christof Johannes JaimeWackenrohr, SteffenRichter, JuliaSobrero, César ErnestoDegener, SebastianKrooß, PhilippMaier, Hans JürgenNiendorf, Thomashttps://www.repo.uni-hannover.de/handle/123456789/167592024-03-18T08:01:12Z2021-01-01T00:00:00ZOn the Microstructural and Cyclic Mechanical Properties of Pure Iron Processed by Electron Beam Melting
Torrent, Christof Johannes Jaime; Wackenrohr, Steffen; Richter, Julia; Sobrero, César Ernesto; Degener, Sebastian; Krooß, Philipp; Maier, Hans Jürgen; Niendorf, Thomas
Additive manufacturing (AM) processes such as electron beam melting (EBM) are characterized by unprecedented design freedom. Topology optimization and design of the microstructure of metallic materials are enabled by rapid progress in this field. The latter is of highest importance as many applications demand appropriate mechanical as well as functional material properties. For instance, biodegradable implants have to meet mechanical properties of human bone and at the same time guarantee adequate cytocompatibility and degradation rate. In this field, pure iron has come into focus in recent studies due to its low toxicity. Hierarchical microstructures resulting from the EBM solidification processes and intrinsic heat treatment, respectively, allow for an adjustment of the degradation behavior and may promote enhanced fatigue strength. Herein, commercially pure iron (cp-Fe) is processed by EBM. Microstructural analysis as well as an evaluation of the cyclic mechanical material properties are conducted. The results are compared to a hot-rolled (HR) reference material. A contradiction observed as the EBM-processed cp-Fe (EBM Fe) shows lower ultimate tensile strength under monotonic loading but improved fatigue properties compared to the HR Fe. It is revealed that such a unique behavior originates from prevailing microstructural features in the EBM as-built condition.
2021-01-01T00:00:00ZStrategies for residual stress adjustment in bulk metal formingFranceschi, A.Stahl, J.Kock, C.Selbmann, R.Ortmann-Ishkina, S.Jobst, A.Merklein, M.Kuhfuß, B.Bergmann, M.Behrens, B.-A.Volk, W.Groche, P.https://www.repo.uni-hannover.de/handle/123456789/167382024-03-17T19:21:04Z2021-01-01T00:00:00ZStrategies for residual stress adjustment in bulk metal forming
Franceschi, A.; Stahl, J.; Kock, C.; Selbmann, R.; Ortmann-Ishkina, S.; Jobst, A.; Merklein, M.; Kuhfuß, B.; Bergmann, M.; Behrens, B.-A.; Volk, W.; Groche, P.
The family of bulk forming technologies comprises processes characterised by a complex three-dimensional stress and strain state. Besides shape and material properties, also residual stresses are modified during a bulk metal forming process. The state of residual stresses affects important properties, like fatigue behaviour and corrosion resistance. An adjustment of the residual stresses is possible through subsequent process steps such as heat treatments or mechanical surface modification technologies, like shot peening and deep rolling. However, these additional manufacturing steps involve supplementary costs, longer manufacturing times and harmful effects on the product quality. Therefore, an optimized strategy consists in a targeted introduction of residual stresses during the forming processes. To enable this approach, a fundamental understanding of the underlying mechanisms of residual stress generation in dependence of the forming parameters is necessary. The current state of the art is reviewed in this paper. Strategies for the manipulation of the residual stresses in different bulk forming processes are classified according to the underlying principles of process modification.
2021-01-01T00:00:00ZDevelopment of a numerical compensation framework for geometrical deviations in bulk metal forming exploiting a surrogate model and computed compatible stressesScandola, LorenzoBüdenbender, ChristophTill, MichaelMaier, DanielOtt, MichaelBehrens, Bernd-ArnoVolk, Wolframhttps://www.repo.uni-hannover.de/handle/123456789/167362024-03-17T16:12:06Z2021-01-01T00:00:00ZDevelopment of a numerical compensation framework for geometrical deviations in bulk metal forming exploiting a surrogate model and computed compatible stresses
Scandola, Lorenzo; Büdenbender, Christoph; Till, Michael; Maier, Daniel; Ott, Michael; Behrens, Bernd-Arno; Volk, Wolfram
The optimal design of the tools in bulk metal forming is a crucial task in the early design phase and greatly affects the final accuracy of the parts. The process of tool geometry assessment is resource- and time-consuming, as it consists of experience-based procedures. In this paper, a compensation method is developed with the aim to reduce geometrical deviations in hot forged parts. In order to simplify the transition process between the discrete finite-element (FE) mesh and the computer-aided-design (CAD) geometry, a strategy featuring an equivalent surrogate model is proposed. The deviations are evaluated on a reduced set of reference points on the nominal geometry and transferred to the FE nodes. The compensation approach represents a modification of the displacement-compatible spring-forward method (DC-SF), which consists of two elastic FE analyses. The compatible stress originating the deviations is estimated and subsequently applied to the original nominal geometry. After stress relaxation, an updated nominal geometry of the part is obtained, whose surfaces represent the compensated tools. The compensation method is verified by means of finite element simulations and the robustness of the algorithm is demonstrated with an additional test geometry. Finally, the compensation strategy is validated experimentally.
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