The main direction of research is computational mechanics and optimal control of dynamical systems. Efficient technologies for structural mechanics and optimal control simulations are developed, facing contemporary life science and engineering questions. The problems under investigation consider flexible multibody dynamics, coupled problems, biomechanics, and robot dynamics as well as the optimization and optimal control of their dynamics including non-smooth or mixed-integer variants and multiobjective optimization. Furthermore, (human) motion is captured and investigated in our motion analysis laboratory and the measured data in analyzed directly and in simulations.
- Biomechanics (natural or impaired human movements and athleticâ€™s high performance, human hand grasping)
- Biological and artificial muscles models
- Phase-field models for fracture
- Multiscale and multirate systems with dynamics on various times
Electromechanically coupled beam models for stacked dielectric elastomer actuators
(Third Party Funds Single)Term: 1. January 2020 - 31. December 2022
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
Stacked dielectric elastomer actuators bear analogy to the behaviour of human muscles in terms of contracting in length direction when stimulated. They are suitable for point-by-point application of a force. Therefore, dielectric elastomers allow for a sophisticated, efficient and noiseless actuation of systems. However, the use of elastic actuators is also accompanied by new control challenges. As the computational cost for solving optimal control problems is significantly affected by the number of model degrees of freedom, reduced and problem specific actuator models are superior to general but cost-intensive finite element models.
Joint Training on Numerical Modelling of Highly Flexible Structures for Industrial Applications
(Third Party Funds Single)Term: 1. October 2019 - 30. September 2023
Funding source: EU - 8. Rahmenprogramm - Horizon 2020
URL: https://thread-etn.euHighly flexible slender structures like yarns, cables, hoses or ropes are essential parts of high-performance engineering systems. The complex response of such structures in real operational conditions is far beyond the capabilities of current modelling tools that are at the core of modern product development cycles.
Addressing this requires a new generation of brilliant scientists. Marie Skłodowska-Curie funding of the THREAD project will bring together young mechanical engineers and mathematicians who will develop mechanical models and numerical methods for designing highly flexible slender structures, and support the development of future virtual prototyping tools for products where such structures have a key role in functional system performance.
THREAD is a unique network of universities, research organisations and industry which by addressing fundamental modelling problems will ultimately enable the field to better meet the needs of different industries. A group of 14 Early Stage Researchers (ESRs) will receive comprehensive training covering state-of-the-art research topics along the modeling of highly flexible slender structures for industrial applications as well as valuable transferable skills. They will benefit from close cooperation with twelve industrial partner organisations implementing a comprehensive programme of research secondments and contributing their experience.
High order variational integrators for continuum mechanics, constrained mechanical systems and optimal control
(Own Funds)Term: since 15. August 2019
Teilprojekt P2 - Atomistics of Crack-Heterogeneity Interactions
(Third Party Funds Group – Sub project)Overall project: Skalenübergreifende Bruchvorgänge: Integration von Mechanik, Materialwissenschaften, Mathematik, Chemie und Physik (FRASCAL)
Term: 2. January 2019 - 30. June 2023
Funding source: DFG / Graduiertenkolleg (GRK)
The fracture of a brittle solid is crucially determined by material heterogeneities directly at the crack front where the stress field diverges and the usual homogenization strategies are no longer applicable. While this problem has attracted significant interest, currently no consistent theory that relates local changes in properties to the local fracture behavior and macroscopic failure criteria exists. In contrast to the long-range elastic interactions, the direct interaction of the crack front with heterogeneities cannot be described by continuum methods but requires an atomistic treatment.
The aim of this project is to study the influence of various types of heterogeneities on the energy dissipation mechanisms in different classes of materials.
Teilprojekt P9 - Adaptive Dynamic Fracture Simulation
(Third Party Funds Group – Sub project)Overall project: Fracture across Scales: Integrating Mechanics, Materials Science, Mathematics, Chemistry, and Physics (FRASCAL)
Term: 2. January 2019 - 30. June 2023
Funding source: DFG / Graduiertenkolleg (GRK)
In the simulation of continuum mechanical problems of materials with heterogeneities caused e.g. by a grained structure on a smaller scale compared to the overall dimension of the system, or by the propagation of discontinuities like cracks, the spatial meshes for finite element simulations are typically consisting of coarse elements to save computational costs in regions where less deformation is expected, as well as finely discretised areas to be able to resolve discontinuities and small scale phenomena in an accurate way. For transient problems, spatial mesh adaption has been the topic of intensive research and many strategies are available, which refine or coarsen the spatial mesh according to different criteria. However, the standard is to use the same time step for all degrees of freedom and adaptive time step controls are usually applied to the complete system.
The aim of this project is to investigate the kinetics of heterogeneous, e.g. cracked material, in several steps by developing suitable combinations of spatial and temporal mesh adaption strategies.
Fracture across Scales: Integrating Mechanics, Materials Science, Mathematics, Chemistry, and Physics (FRASCAL)
(Third Party Funds Group – Overall project)Term: 1. January 2019 - 30. June 2023
Funding source: DFG / Graduiertenkolleg (GRK)
The RTG aims to improve understanding of fracture in brittle heterogeneous materials by developing simulation methods able to capture the multiscale nature of failure. With i) its rooting in different scientific disciplines, ii) its focus on the influence of heterogeneities on fracture at different length and time scales as well as iii) its integration of highly specialised approaches into a “holistic” concept, the RTG addresses a truly challenging cross-sectional topic in mechanics of materials. Although various simulation approaches describing fracture exist for particular types of materials and specific time and length scales, an integrated and overarching approach that is able to capture fracture processes in different – and in particular heterogeneous – materials at various length and time resolutions is still lacking. Thus, we propose an RTG consisting of interdisciplinary experts from mechanics, materials science, mathematics, chemistry, and physics that will develop the necessary methodology to investigate the mechanisms underlying brittle fracture and how they are influenced by heterogeneities in various materials. The insights obtained together with the methodological framework will allow tailoring and optimising materials against fracture. The RTG will cover a representative spectrum of brittle materials and their composites, together with granular and porous materials. We will study these at length and time scales relevant to science and engineering, ranging from sub-atomic via atomic and molecular over mesoscale to macroscopic dimensions. Our modelling approaches and simulation tools are based on concepts from quantum mechanics, molecular mechanics, mesoscopic approaches, and continuum mechanics. These will be integrated into an overall framework which will represent an important step towards a virtual laboratory eventually complementing and minimising extensive and expensive experimental testing of materials and components. Within the RTG, young researchers under the supervision of experienced PAs will perform cutting-edge research on challenging scientific aspects of fracture. The RTG will foster synergies in research and advanced education and is intended to become a key element in FAU‘s interdisciplinary research areas “New Materials and Processes” and “Modelling–Simulation–Optimisation”.
- Phutane, U., Roller, M., & Leyendecker, S. (2022). Optimal control simulations of two-finger grasps. Mechanism and Machine Theory, 167. https://dx.doi.org/10.1016/j.mechmachtheory.2021.104508
- Holz, D., Duong, M.T., Martonová, D., Alkassar, M., & Leyendecker, S. (2021). A Transmural Path Model Improves The Definition of The Orthotropic Tissue Structure in Heart Simulations. Journal of Biomechanical Science and Engineering. https://dx.doi.org/10.1115/1.4052219
- Holz, D., Duong, M.T., Martonová, D., Alkassar, M., & Leyendecker, S. (2021). Discontinuous Galerkin-based approach to define orthotropic tissue structure in computational heart models. In Proceedings of the International Conference on Computational Biomechanics. Paris, FR.
- Huang, D., & Leyendecker, S. (2021). Modelling of Electromechanical Coupling in Geometrically Exact Beam Dynamics. In Proceedings of the 14th WCCM-ECCOMAS Congress 2020. online: Scipedia.
- Leitz, T., Sato Martin de Almagro, R., & Leyendecker, S. (2021). Multisymplectic Galerkin Lie group variational integrators for geometrically exact beam dynamics based on unit dual quaternion interpolation — no shear locking. Computer Methods in Applied Mechanics and Engineering, 374, 113475. https://dx.doi.org/10.1016/j.cma.2020.113475
- Leyendecker, S., Penner, J., & Phutane, U. (2021). Geometric numerical integration in simulation and optimal control of biomechanical motion. In Proceedings of the Invited lecture, GAMM Annual Meeting. Kassel, DE.
- Lohmayer, M., Kotyczka, P., & Leyendecker, S. (2021). Generic and Port-Hamiltonian structures for complex systems. In Proceedings of the Joint European Thermodynamics Conference, conference talk. Prague, CZ.
- Martonová, D., Alkassar, M., Seufert, J., Holz, D., Duong, M.T., Reischl, B.,... Leyendecker, S. (2021). Characterisation of passive mechanical properties in healthy and infarcted rat myocardium. In Proceedings of the GAMM Annual Meeting. Kassel, DE.
- Martonová, D., Alkassar, M., Seufert, J., Holz, D., Duong, M.T., Reischl, B.,... Leyendecker, S. (2021). Passive mechanical properties in healthy and infarcted rat left ventricle characterised via a mixture model. Journal of the Mechanical Behavior of Biomedical Materials, 119. https://dx.doi.org/10.1016/j.jmbbm.2021.104430
- Martonová, D., Holz, D., Duong, M.T., & Leyendecker, S. (2021). Towards the simulation of active cardiac mechanics using a smoothed finite element method. Journal of Biomechanics, 115, 110153. https://dx.doi.org/10.1016/j.jbiomech.2020.110153
- Phutane, U., Liphardt, A.-M., Bräunig, J., Penner, J., Klebl, M., Tascilar, K.,... Leyendecker, S. (2021). Evaluation of Optical and Radar Based Motion Capturing Technologies for Characterizing Hand Movement in Rheumatoid Arthritis — A Pilot Study. Sensors, 21(4). https://dx.doi.org/10.3390/s21041208
- Sato Martin de Almagro, R., Leitz, T., & Leyendecker, S. (2021). Galerkin variational integration of the geometrically exact beam via unit dual quaternion interpolation.
- Scheiterer, E.S., & Leyendecker, S. (2021). Fuzzy forward dynamics of a human leg with a prosthetic foot. In Proceedings of the GAMM Annual Meeting, conference. Kassel, DE.
- Scheiterer, E.S., & Leyendecker, S. (2021). Predeformed geometrically exact beam model for a dynamic-response prosthesis. In Proc. Appl. Math. Mech. (PAMM).
- Stavole, M., Wenger, T., & Leyendecker, S. (2021). Variational formulation and simulation of the 1D wave equation and geometrically exact beam dynamics. In Proceedings of the MaGIC 2021: Workshop on Manifolds and Geometric integration. Bergen and Trondheim, NO.
- Chen, X., Leyendecker, S., & van den Bedem, H. (2020). Kinematic Flexibility Analysis of Active and Inactive Kinase Conformations. In Proc. Appl. Math. Mech. (PAMM).
- Huang, D., & Leyendecker, S. (2020). On computational aspects of electromechanical coupling in geometrically exact beam dynamics. In Proceedings of the Online symposium on flexible multibody system dynamics. Zoom.
- Leyendecker, S. (2020). Geometric numerical integration in simulation and optimal control — and other topics. In Proceedings of the Invited Lecture at Annual Meeting 2020 — Joint Training on Numerical Modelling of Highly Flexible Structures THREAD. Kaiserslautern (Microsoft Teams), DE.
- Lohmayer, M., & Leyendecker, S. (2020). Exergetic Port-Hamiltonian Systems -- a tutorial. In Proceedings of the Student Compact Course -- Variational Methods for Fluids and Solids. Berlin, DE.
- Penner, J., & Leyendecker, S. (2020). Defining Kinematic Chains for Musculoskeletal Optimal Control Simulations via Automatic Differentiation. In Proceedings of the 6th International Digital Human Modeling Symposium (pp. 82 - 90). Skövde, SE.
- Phansalkar, D., & Leyendecker, S. (2020). On numerical challenges with a phase-field model for a mode I fracture. In Proceedings of the 7th GAMM workshop on phase-field modeling. Kaiserslautern, DE.
- Phutane, U., Roller, M., Boebel, A., & Leyendecker, S. (2020). Optimal Control of Grasping Problem Using Postural Synergies. In Proceedings of the 6th International Digital Human Modeling Symposium (pp. 206-213). Skövde, SE.
- Sato Martín de Almagro, R.T., & Leyendecker, S. (2020). Fundamentals of beam theory and flexible multibody dynamics. In Proceedings of the Network wide training — Joint Training on Numerical Modelling of Highly Flexible Structures THREAD. Erlangen (ZOOM), DE.
- Scheiterer, E.S., & Leyendecker, S. (2020). Dynamic analysis of prosthetic structures with polymorphic uncertainty. In Proceedings of the SPP1886 annual meeting 2020, conference.
- Scheiterer, E.S., & Leyendecker, S. (2020). Dynamic analysis of prosthetic structures with polymorphic uncertainty.