Leon Kellner

Leon Kellner
Hamburg Unversity of Technology · Ship Structural Design and Analysis

Doctor of Engineering

About

16
Publications
31,278
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98
Citations

Publications

Publications (16)
Conference Paper
The environment in cold regions undergoes significant changes that manifest in rising temperatures and melting ice caps. These processes allow access to new areas for shipping and the installation of structures. However, the occurring changes are not solely a reduction of ice, but also waves increasingly occur in cold regions contributing to ice br...
Article
Full-text available
The size of the fully developed process zone (FDPZ) is needed for the arrangement of displacement sensors in fracture experiments and choosing element size in numerical models using the cohesive element method (CEM). However, the FDPZ size is generally not known beforehand. Analytical solutions for the exact FDPZ size only exist for highly idealise...
Thesis
Full-text available
Seasonally or partially ice-covered sea areas are attractive to many stakeholders. Ships and structures operating in these areas must be designed to withstand ice-induced loads. This is done with empirical methods and model-scale ice tests, but these have various drawbacks. Numerical simulations are a desirable remedy, but their accuracy is limited...
Method
Full-text available
Brief, step by step explanation on how to implement your own user material model in LS-Dyna. The focus is on software and implementation of material models, not material model theory.
Article
Building and using ice-related models is challenging due to the complexity of the material. A common issue, shared by both material models and (semi-)empirical approaches, is estimating unknown input parameters such as compressive strength. This is often done with additional empirical formulas which have drawbacks, e.g., they are based on a limited...
Article
Full-text available
Butt-welded joints are common in many industries. The fatigue behavior of such joints depends on numerous factors, e.g. load level, local weld geometry, or parent material strength. To make things worse, these factors often interact, yet mutual influence can hardly be quantified by multivariate studies, i.e. varying one factor at a time out of many...
Preprint
Full-text available
Prioritizing effects for material modeling of natural materials such as ice and rock is mostly done based on a subjective mix of knowledge, model purpose, and experimental studies limited to that purpose. This risks overlooking effects or interaction of effects, and limits transferability of material models to other scenarios. We compiled a large i...
Preprint
The size of the Fully Developed Process Zone (FDPZ) is needed for the arrangement of displacement sensors in fracture experiments and choosing element size in numerical models using the cohesive element method (CEM). However, the FDPZ size is generally not known beforehand. Analytical solutions for the exact FDPZ size only exist for highly idealise...
Conference Paper
Full-text available
Several Arctic waters are no longer ice-covered all year round. As a result, the northern sea routes are getting into the focus of the maritime industry. In addition less ice coverage in other sea areas such as the Baltic Sea leads to increased shipping traffic in the winter season. This repeatedly leads to damages to ships when sailing in ice-cove...
Conference Paper
Full-text available
The retreat of sea ice increases the economic interest in the arctic regions. The consequence is an increasing number of ship operations and offshore activities in ice-covered waters. Thus, ice-loads are significant for the design of maritime structures operating in these waters. Brittle ice structure interaction (ISI) is dominated by fracture in f...
Article
As aqueous model ice is used extensively in ice tanks tests on the performance of ship hulls in sheet ice, it is imperative that such model ice replicate the main flexural strength behavior of sheets of sea ice and freshwater ice. Ice tanks use various types of aqueous model ice types, each of which contain brine dopants to scale-reduce ice-sheet s...
Article
Ice material models often limit the accuracy of ice related simulations. The reasons for this are manifold, e.g. complex ice properties. One issue is linking experimental data to ice material modeling, where the aim is to identify patterns in the data that can be used by the models. However, numerous parameters that influence ice behavior lead to l...
Preprint
As aqueous model ice is used extensively in ice tanks tests on the performance of ship hulls in sheet ice, it is imperative that such model ice replicate the main flexural strength behavior of sheets of sea ice and freshwater ice. Ice tanks use various types of aqueous model ice types, each of which contain brine dopants to scale-reduce ice-sheet s...
Preprint
Full-text available
Preprint can be found on arxiv.org under following ID: arXiv:1812.03994 Machine learning and statistical tools are applied to identify how parameters, such as temperature, influence peak stress and ice behavior. To enable the analysis, a common and small scale experimental data base is established.
Conference Paper
Full-text available
Simulations of ice interaction scenarios are not as reliable as desired. The reason for this shortcoming is often the limitation of the ice model. Whereas steel models for the ship or the structure are well established, there is no model available for ice that can capture the complete interaction process. This is due to many reasons, such as comple...
Conference Paper
Sea ice can interact with offshore structures in regions with at least seasonal ice coverage. Therefore the prediction of ice loads on offshore structures is required by many standards or classification rules and guidelines. In order to do this, empirical formulas are often prescribed. These are based on assumptions in combination with model or ful...

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Projects

Projects (3)
Project
The motivation stems from ice-structure interaction, hence the focus is on modeling the dominant features of such scenarios. These are: elastic brittle behavior of ice, including fracture, under high loading rates and triaxial stress states along with a stochastic distribution of material properties.
Project
The project is focused on the analysis of the impact of sea ice loads on the global dynamics of offshore wind turbines
Archived project
Simulation of ice crushing against the foundation of an offshore wind turbine. Work packages: - Development of a representative volume element for ice (RVE) - Small and big scale ice crushing experiments - Coupling between a solver for the structure, the water and the ice