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Item type:Publication, Access status: without files , The role of damping in complex structural dynamics: Data-driven approachesThe Dynamics Group at Hamburg University of Technology has been working on two consecutive research projects supervised by Prof. Norbert Hoffmann within the Priority Programme SPP 1897. The first project ‘Understanding and improving energy dissipation and damping in structures subject to self-excited irregular vibrations’ focused on the chaotic nature of friction-excited dynamics and how properties of those complex vibrations can be leveraged for understanding damping and stability. Within the second project ’Understanding and improving energy dissipation and vibration damping in structures subject to self-excited irregular vibrations - linking data driven approaches with modelling’, data-driven techniques were linked with conventional modeling approaches to arrive at hybrid simulation and identification approaches for damping in complex structural dynamics. The work at hand summarizes central findings and novel approaches that have been published in a number of peer-reviewed journal articles, poses new research questions, and gives an outlook.Publicationtype: Book part18 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Simulation-based design of hybrid particle dampers with application to flexible multibody systemsParticle damping technology is a passive damping technique used to reduce structural vibrations. Either containers attached to the vibrating structure or holes within the vibrating structure are filled with a granular material. By structural vibrations, momentum is transferred to the granular material causing granular interactions. By these interactions, energy dissipation occurs due to inelastic normal collisions and frictional losses. This reduces the structural vibration. Although particle dampers have already been applied to some technical applications, their wide industrial usage is still limited. The main reason for this is the nonlinear damping behavior of this technique and the multitude of influence parameters. Hence, the goal of this project is the development of a new design methodology in form of a toolchain for passive vibration damping of lightweight structures and machines using particle dampers. Thereby, using simulations that are verified by experiments, also a deeper understanding of the micro-mechanical processes in the dampers are obtained. This is crucial in the systematic design of particle dampers using numerical methods. Using the developed toolchain single particle damper units with predefined characteristics are developed which do not rely on a specific application. Hereby, hybrid approaches are used to increase the efficiency of the individual particle dampers. Hence, it is possible to extend particle dampers to a variety of very different applications.Publicationtype: Book part90 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Structure-preserving model reduction for dissipative mechanical systemsSuppressing vibrations in mechanical systems, usually described by second-order dynamical models, is a challenging task in mechanical engineering in terms of computational resources even nowadays. One remedy is structure-preserving model order reduction to construct easy-to-evaluate surrogates for the original dynamical system having the same structure. In our work, we present an overview of recently developed structure-preserving model reduction methods for second-order systems. These methods are based on modal and balanced truncation in different variants, as well as on rational interpolation. Numerical examples are used to illustrate the effectiveness of all described methods.Publicationtype: Book part30 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Adaptive Quadrature and Remeshing Strategies for the Finite Cell Method at Large DeformationsNumerical methods based on a fictitious domain approach, such as the finite cell method, simplify the meshing process significantly as the mesh does not need to conform to the geometry of the underlying problem. However, such methods result in elements/cells which are intersected by the domain boundary. Consequently, special integration methods have to be applied for the broken elements/cells to achieve accurate results. One of the methods that is commonly used in the finite cell method is an adaptive scheme based on a spacetree decomposition. Unfortunately, it results in a large number of integration points which makes the method quite expensive. In the first part of this contribution, we try to overcome this problem by introducing an adaptive scheme for the moment fitting to be able to integrate broken cells efficiently and robustly for nonlinear problems. Furthermore, a remeshing strategy for the finite cell method will be introduced to improve the solution quality and overcome the large distortion of the mesh during the simulation which can cause the analysis to fail. To this end, a new mesh with a good quality is created whenever the old mesh is no longer capable of taking any further deformations. Afterwards, a data transfer between the old and the new meshes is performed with the help of a local radial basis function interpolation. Different numerical examples are presented to study the performance of the proposed methods.Publicationtype: Journal Article50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Experimental data for JBC resistance, sinkage, trim, self-propulsion factors, longitudinal wave cut and detailed flow with and without an energy saving circular duct(Springer, 2021); ; ; ; In this Chapter, measured data of resistance, sinkage, trim, self-propulsion factors, longitudinal wave cut and detailed flow are summarized for Japan Bulk Carrier (JBC) with and without an energy saving circular duct. JBC is a newly designed ship for CFD validation of a ship with an energy saving device (ESD). Resistance and self-propulsion tests are conducted in towing tanks of National Maritime Research Institute (NMRI) and Osaka University (OU) using model ships of different sizes. Detailed local flow data are acquired using SPIV (Stereo Particle Image Velocimetry) for several cross sections at towing tanks of NMRI and OU. The local flow data are also measured by SPIV in a wind tunnel at Hamburg University of Technology (TUHH).Publicationtype: Book Part301 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Multiscale experimental and computational investigation of nature’s design principle of hierarchies in dental enamel(Springer, 2018); ; ; ; Dental enamel possesses extraordinary mechanical properties due to a complex hierarchical and graded microstructure. In this study, multiscale experimental and computational approaches are employed and combined to study nature’s design principle of the hierarchical structure of bovine enamel for developing bioinspired advanced ceramics with hierarchical microstructure. Micro-cantilever beam tests are carried out to characterize the mechanical properties from nano-to mesoscale experimentally. In order to understand the relationship between the hierarchical structure and the flaw-tolerance behavior of enamel, a 3D representative volume element (RVE) is used in a numerical analysis to study the deformation and damage process at two hierarchical levels. A continuum damage mechanics model coupled to hyperelasticity is developed for modeling the initiation and evolution of damage in the mineral fibers as well as protein matrix. Moreover, debonding of the interface between mineral fiber and protein is captured by a cohesive zone model. The effect of an initial flaw on the overall mechanical properties is analyzed at different hierarchical levels to understand the superior damage tolerance of dental enamel. Based on the experimental and computational investigation, the role of hierarchical levels on the multiscale design of structure in dental enamel is revealed for optimizing bio-inspired composites.Publicationtype: Book Part190