Finite-discrete element modelling of sea ice sheet elasticity, sea ice sheet fracture, and ice-structure interaction - A three-dimensional, lattice-based approach

• Published in: Marine Structures
• Main Author: Lilja, Ville-Pekka
• Other Authors: Tuhkuri, Jukka, Prof., Aalto University, Finland, Insinööritieteiden korkeakoulu, School of Engineering, Konetekniikan laitos, Department of Mechanical Engineering, Polojärvi, Arttu, Asst. Prof., Aalto University, Department of Mechanical Engineering, Finland, Solid Mechanics, Aalto-yliopisto, Aalto University
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Aalto University 2020
• Subjects: Mechanical engineering; ice; ice-structure interaction; plates; beam lattice networks; fracture mechanics; size effect; numerical algorithms; centroidal Voronoi tessellation; jää; jää-rakenne-vuorovaikutus; laatat; palkkiverkkorakenteet; murtumismekaniikka; kokoefekti; yhdistetty diskreetti-elementtimenetelmä; numeeriset algoritmit; Ice Sheet; Sea ice
• Online Access: https://aaltodoc.aalto.fi/handle/123456789/55391

A doctoral dissertation completed for the degree of Doctor of Science (Technology) to be defended, with the permission of the Aalto University School of Engineering, via a remote connection link: https://aalto.zoom.us/j/63875924913 on 9.12.2020 at 12 o'clock. In this thesis, the elastic and inelastic properties of an ice sheet modelled by a new hybrid, three-dimensional finite-discrete element (FE-DE) method were examined. Ice-structure interaction between an ice sheet and a conical offshore structure was studied as well. By this new method, an ice sheet is modelled with undeformable, i.e. rigid, discrete elements. The mass centroids of the discrete elements connect then via an in-plane beam lattice of co-rotational, viscously damped, de-cohesive Timoshenko beam finite elements. A centroidal-Voronoi-tessellation-based iterative scheme (CVT) was applied in creating the studied FE-DE meshes, i.e. the modelled ice sheets. Due to the internally damped, de-cohesive, lattice-based construction, the mechanical response of a modelled ice sheet turns out to be both strain rate- and size-dependent (dependent on both the absolute and relative sizes), the investigation of which formed an integral part of the present study. A general objective of this thesis was to study the applicability of the new, hybrid FE-DE method in modelling the elasticity and fracture of sea ice sheets. In order to understand the effects of scale and to demonstrate the feasibility of the approach in studying ice mechanics applications in general, i.e. the ice-structure interaction, several conceptually simple constitutive tests with square FE-DE sheet samples of varying side lengths, thicknesses, and discrete element sizes were performed. The results presented gave a partial guideline for choosing the microscale material parameters of a CVT-tessellated, lattice-based FE-DE model of an ice sheet in order to achieve a desired macroscale response, both elastic and inelastic. Furthermore, the results provided substantial insight into the functional ...