@inproceedings{KeskinSwobodaFlassigetal., author = {Keskin, Akin and Swoboda, Marius and Flassig, Peter Michael and Dutta, Amit Kumar and Bestle, Dieter}, title = {Accelerated Industrial Blade Design Based on Multi-Objective Optimization Using Surrogate Model Methodology}, series = {Proceedings of the ASME Turbo Expo 2008, presented at the 2008 ASME Turbo Expo, June 9 - 13, 2008, Berlin, Germany, Vol 6., Part C}, booktitle = {Proceedings of the ASME Turbo Expo 2008, presented at the 2008 ASME Turbo Expo, June 9 - 13, 2008, Berlin, Germany, Vol 6., Part C}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-4316-1}, pages = {2339 -- 2349}, language = {en} } @inproceedings{KeskinDuttaBestle, author = {Keskin, Akin and Dutta, Amit Kumar and Bestle, Dieter}, title = {Modern Compressor Aerodynamic Blading Process using Multi-objective Optimization}, series = {Proceedings of the ASME Turbo Expo 2006, presented at the 2006 ASME Turbo Expo, May 6 - 11, 2006, Barcelona, Spain, Vol. 6, Part B}, booktitle = {Proceedings of the ASME Turbo Expo 2006, presented at the 2006 ASME Turbo Expo, May 6 - 11, 2006, Barcelona, Spain, Vol. 6, Part B}, publisher = {ASME}, address = {New York, NY}, isbn = {0-7918-4241-X}, pages = {1209 -- 1216}, language = {en} } @inproceedings{KeskinBestle, author = {Keskin, Akin and Bestle, Dieter}, title = {A Method for Using Multi-objective Optimization within the Rolls-Royce meanline Prediction Process}, language = {en} } @inproceedings{DuttaFlassigBestleetal., author = {Dutta, Amit Kumar and Flassig, Peter Michael and Bestle, Dieter and Keskin, Akin and Swoboda, Marius}, title = {Validierung optimierter Verdichterschaufeln mit Hilfe der 3D-CFD}, series = {Deutscher Luft- und Raumfahrtkongress 2008, Darmstadt, 23. bis 25. September 2008, Bd. 2}, booktitle = {Deutscher Luft- und Raumfahrtkongress 2008, Darmstadt, 23. bis 25. September 2008, Bd. 2}, publisher = {Dt. Ges. f{\"u}r Luft- und Raumfahrt}, address = {Bonn}, pages = {1023 -- 1033}, language = {de} } @inproceedings{KeskinPrzewoznyGraeseletal., author = {Keskin, Akin and Przewozny, Hans and Gr{\"a}sel, J{\"u}rgen and Saxer, Andre and Swoboda, Marius}, title = {A full parametric model for turbo machinery blade design and optimisation}, language = {en} } @inproceedings{BestleKeskinOtto, author = {Bestle, Dieter and Keskin, Akin and Otto, Dierk}, title = {Process Integration and Automation for optimal Design}, language = {en} } @inproceedings{KoberKuehhornKaestneretal., author = {Kober, Markus and K{\"u}hhorn, Arnold and K{\"a}stner, Benjamin and Keskin, Akin}, title = {Evaluation of the Stress and Displacement Behavior of Different LS-Dyna Element Types in Combination with Different Anti-Hourglassing Formulations and Initial Element Deformations}, series = {Kurzfassungen der Vortr{\"a}ge, 13. LS-DYNA Forum 2014, 6. - 8. Oktober 2014, Bamberg}, booktitle = {Kurzfassungen der Vortr{\"a}ge, 13. LS-DYNA Forum 2014, 6. - 8. Oktober 2014, Bamberg}, publisher = {DYNAmore GmbH}, address = {Stuttgart}, isbn = {978-3-9816215-1-8}, language = {en} } @inproceedings{KoberKuehhornStelldingeretal., author = {Kober, Markus and K{\"u}hhorn, Arnold and Stelldinger, Enrico and Keskin, Akin}, title = {Identification of Stiffness Parameters of a Simplified Aero-Engine Mount System by Using a Higher Fidelity Model of the Mount System}, series = {Kurzfassungen der Vortr{\"a}ge, 13. LS-DYNA Forum 2014, 6. - 8. Oktober 2014, Bamberg}, booktitle = {Kurzfassungen der Vortr{\"a}ge, 13. LS-DYNA Forum 2014, 6. - 8. Oktober 2014, Bamberg}, publisher = {DYNAmore GmbH}, address = {Stuttgart}, isbn = {978-3-9816215-1-8}, language = {en} } @inproceedings{KoberKuehhornKeskin, author = {Kober, Markus and K{\"u}hhorn, Arnold and Keskin, Akin}, title = {Implicit Time Integration Schemes for the FEM Simulation of Fast Rotating Structures}, series = {WCCM XII \& APCOM VI (World Congress on Computational Mechanics \& Asia Pacific Congress on Computational Mechanics), Seoul, South Korea, 23.-29. Juli 2016}, booktitle = {WCCM XII \& APCOM VI (World Congress on Computational Mechanics \& Asia Pacific Congress on Computational Mechanics), Seoul, South Korea, 23.-29. Juli 2016}, abstract = {Due to the demand of more and more detailed FEM simulation results of whole aero-engine models, the number of DOF of such models (Fig. 1) increases dramatically. Although the available computational power for the solution of such highly nonlinear, dynamic boundary value problems also increased during the last years, the overall computational time of these high-fidelity models for the simulation of a few milliseconds of the running engine is in the order of several weeks even on high performance clusters with thousands of CPU cores. Typically, for such highly dynamic FEM computations explicit time integration schemes are used in order to solve the equations of motion. To keep such a numerical integration stable, the time step size may not exceed a certain critical time step size. Unfortunately, the critical time step size of an explicit time integration algorithm for the engine models under consideration is in the order of 10-8. This means that the simulation of a running engine over a time span of a few seconds results in a computational time of several years with clusters, which are available nowadays. Therefore, implicit time integration schemes, which are unconditionally stable and allow much bigger time steps, have to be used. Since in an implicit integration, in contrast to an explicit one, an equilibrium iteration is always necessary, the computational costs for an implicit time step are much higher than for an explicit time step. Almost all commercial FE codes use the classical Newmark implicit time integration scheme. It will be shown that this algorithm fails especially for the simulation of fast rotating structures if bigger time steps are used. This is demonstrated at the example of academic examples as well as for more realistic rotor models. To overcome the problems of the Newmark integration, a 3-Point-Newmark- Euler-Backward integration scheme [1,2] has been selected, which consists of alternating Newmark and 3-Point-Euler-Backward steps. The additional interpolation information for the Euler-step is provided by the previous Newmark step. This integration procedure has been implemented and successfully applied to the FEM simulation of fast rotating structures, which will be also demonstrated during the presentation.}, language = {en} } @inproceedings{KoberKuehhornKeskin, author = {Kober, Markus and K{\"u}hhorn, Arnold and Keskin, Akin}, title = {Instability problems in implicit transient FEM simulations of fast rotating elastic structures - Description of the phenomenon and possible solutions}, series = {Proceedings of NAFEMS DACH Conference 2018, Bamberg, May 14-16, 2018}, booktitle = {Proceedings of NAFEMS DACH Conference 2018, Bamberg, May 14-16, 2018}, publisher = {NAFEMS Deutschland, {\"O}sterreich, Schweiz GmbH}, address = {Grafing}, isbn = {978-1-910643-14-3}, pages = {48 -- 52}, language = {en} } @inproceedings{KoberKuehhornKeskin, author = {Kober, Markus and K{\"u}hhorn, Arnold and Keskin, Akin}, title = {Optimization of Newmark-Euler Time-Integration Parameters for a Stable and Efficient Implicit Simulation of Rotating Elastic Structures}, series = {Proceedings of 15th German LS-DYNA Forum}, booktitle = {Proceedings of 15th German LS-DYNA Forum}, publisher = {DYNAmore GmbH}, address = {Stuttgart}, isbn = {978-3-9816215-5-6}, pages = {235 -- 238}, language = {en} } @inproceedings{KoberKuehhornKeskinetal., author = {Kober, Markus and K{\"u}hhorn, Arnold and Keskin, Akin and Singh, Kai Navtej}, title = {Challenges and opportunities of thermomechanical FEM simulations of high fidelity aero-engine models by implicit time-integration}, series = {Proceedings of ISABE 2017, ISABE-2017-22568, Manchester, September 3.-8., 2017}, booktitle = {Proceedings of ISABE 2017, ISABE-2017-22568, Manchester, September 3.-8., 2017}, publisher = {ISABE}, pages = {10}, language = {en} } @inproceedings{KeskinKoberStelldingeretal., author = {Keskin, Akin and Kober, Markus and Stelldinger, Enrico and K{\"u}hhorn, Arnold and B{\"o}hm, Holger and Hornig, Andreas and Hufenbach, Werner}, title = {On the quantification of errors of a pre-processing effort reducing contact meshing approach : AIAA 2015-0408}, series = {53rd AIAA Aerospace Sciences Meeting 2015, Kissimmee, Florida, USA, 5 - 9 January 2015, held at the AIAA SciTech Forum 2015, vol. 4}, booktitle = {53rd AIAA Aerospace Sciences Meeting 2015, Kissimmee, Florida, USA, 5 - 9 January 2015, held at the AIAA SciTech Forum 2015, vol. 4}, publisher = {Curran}, address = {Red Hook, NY}, isbn = {978-1-5108-0117-2}, doi = {10.2514/6.2015-0408}, pages = {3113 -- 3124}, language = {en} } @inproceedings{KoberKuehhornStelldingeretal., author = {Kober, Markus and K{\"u}hhorn, Arnold and Stelldinger, Enrico and Keskin, Akin}, title = {Considerations About the Necessary Mesh Density of Bearings in Detailed Finite Element Models}, series = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25624}, booktitle = {ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 7B: Structures and Dynamics D{\"u}sseldorf, Germany, June 16-20, 2014, Paper GT2014-25624}, publisher = {ASME}, isbn = {978-0-7918-4577-6}, doi = {10.1115/GT2014-25624}, pages = {8}, abstract = {In order to predict properly the behavior of very complex mechanical models, much focus needs to be done on the level of model details as well as the techniques used to predict component movements based on mechanical and thermal loads. In particular bearings and joints play a significant role in big model assemblies such as aero-engines where most of the structures are modeled by solid elements rather than using traditional shell or beam elements. This approach is very complex and expensive in terms of computational effort however can lead to increased simulation accuracy when done properly. This publication will answer questions related to the modeling techniques required for detailed bearings (not only rotor bearings) and joints of an aero-engine application where these components are not idealized or simplified, i.e. the ball in a ball joint is meshed by solid elements. The investigation will discuss the question about the number of elements needed to mesh a ball joint in such a way that a correct rotation is possible. If the mesh is too coarse, a rotation would be impossible due to the faceting of the rotating parts. It will be shown that a proper rotation depends on a correct relation between the radius of the inner ball, the gap size of the bearing and the number of nodes in the circumferential direction. For this relation an analytical formula has been derived and successfully tested at some examples. Furthermore, some finite element codes offer the possibility of smoothed contact surfaces. These options improve the situation but they might cause issues too. For this reason these smoothed contact options are also considered under the aspects mentioned above. Copyright © 2014 by Rolls-Royce Deutschland Ltd \& Co KG}, language = {en} } @article{BestleKeskin, author = {Bestle, Dieter and Keskin, Akin}, title = {Verbesserter Designprozess f{\"u}r moderne Hochdruckverdichter}, language = {de} } @inproceedings{KeskinSwobodaFlassigetal., author = {Keskin, Akin and Swoboda, Marius and Flassig, Peter Michael and Dutta, Amit Kumar and Bestle, Dieter}, title = {New Optimization Strategy for Rapid industrial Blade Design}, language = {en} } @inproceedings{KeskinDuttaBestle, author = {Keskin, Akin and Dutta, Amit Kumar and Bestle, Dieter}, title = {Alternative Approach for Solving a Multi-Objective Optimization Problem in Aerodynamic Compressor Blade Design}, language = {en} } @inproceedings{KeskinBestle, author = {Keskin, Akin and Bestle, Dieter}, title = {Application of Multi-objective Optimization to Axial Compressor Preliminary Design}, language = {en} } @misc{KoberKuehhornKeskin, author = {Kober, Markus and K{\"u}hhorn, Arnold and Keskin, Akin}, title = {Instabilit{\"a}tsprobleme bei der impliziten transienten FEM-Simulation schnell rotierender elastischer Strukturen - Beschreibung des Ph{\"a}nomens und L{\"o}sungsm{\"o}glichkeiten}, series = {NAFEMS-Online-Magazin}, volume = {48}, journal = {NAFEMS-Online-Magazin}, number = {4}, issn = {2311-522X}, pages = {36 -- 49}, language = {en} } @phdthesis{Keskin, author = {Keskin, Akin}, title = {Process integration and automated multi-objective optimization supporting aerodynamic compressor design}, publisher = {Shaker}, address = {Achen}, isbn = {978-3-8322-5875-7}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-484}, pages = {XII, 138}, language = {en} }