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

Ville-Pekka Lilja

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

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

Ville-Pekka Lilja

Energia- ja konetekniikan laitos

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Tässä opinnäytetyössä tutkittiin uudella kolmidimensionaalisella, yhdistetyllä diskreetti-elementtimenetelmällä (FE-DE) mallinnetun jäälautan elastisia ja vauriomekaanisia ominaisuuksia. Niin ikään työssä tutkittiin FE-DE-menetelmällä mallinnetun jäälautan ja kartiomaisen offshore-rakenteen välisen vuorovaikutuksen mekaniikkaa. Yhdistettyä FE-DE-menetelmää käytettäessä jäälautta diskretoidaan deformoitumattomin diskreetein elementein, joiden massakeskipisteet yhdistyvät tasomaisen palkkielementtiverkon välityksellä. Palkkielementtiverkon elementit ovat korotationaalisia, lineaarisviskoosisesti vaimennettuja ja kohesiivisia Timoshenko-palkkielementtejä. Työssä tutkitut jäälautat generoitiin keskeis-Voronoi-tessellointiin perustuvalla iteratiivisella menetelmällä. Palkkielementtiverkon topologiasta, palkkielementtien sisäisestä vaimennuksesta ja vaurioitumisen kuvaamisessa käytettävän konstitutiivisen mallin kohesiivisuudesta johtuen mallinnetun jäälautan efektiivinen vaste osoittautuu sekä venymänopeudesta että tutkittavan kappaleen koosta riippuvaksi. Opinnäytetyössä tutkittiin, tiivistetysti, onko uusi yhdistetty FE-DE-menetelmä soveltuva kuvaamaan merijäälauttojen elastisia ja vauriomekaanisia ominaisuuksia. Mallinnettavan jäälautan absoluuttisen ja suhteellisen koon vaikutuksen ymmärtämiseksi, kuten myös menetelmän yleisen toimivuuden osoittamiseksi jäämekaniikan alaan kuuluvien ilmiöiden numeerisessa mallintamisessa, joista keskeisin on jää-rakenne-vuorovaikutus, toteutettiin työssä useita verrattain yksinkertaisia numeerisia kokeita neliömäisillä jäälautoilla, joiden sivunpituutta, paksuutta ja käytettyä elementtikokoa varioitiin. Työn tuloksena yhdistetyllä FE-DE-menetelmällä mallinnettavan jäälautan mikromekaanisten materiaaliparametrien valitseminen siten, että lautan efektiivinen konstitutiivinen vaste, sekä elastinen että vauriomekaaninen, on toivotunlainen, helpottuu. Mallinnetun jäälautan mekaanisten ominaisuuksien keskinäisiä riippuvuussuhteita kuvaavia relaatioita löydettiin useita. Tehdyt elastiset taivutustestit osoittivat lisäksi, että menetelmä on kykenevä kuvaamaan vapaan Kirchhoff-Love-laatan taivutusta Winklerin alustalla hyvällä tarkkuudella. Työssä esiteltiin lopuksi uusi epäsuora menetelmä jääkuormien laskemiseksi kartiomaisella offshore-rakenteella. Menetelmä tarjoaa lisäksi keinon sen osoittamiseksi, että kehitetty numeerinen menetelmä on kykenevä kuvaamaan sekä radiaalisten että kehämäisten säröjen synnyn. Työn sisältö rajoittui jäämekaanisiin sovellutuksiin. Työn tulosten tulisi kuitenkin olla sovellettavissa myös muunlaisten kohesiivisina palkkiverkkorakenteina mallinnettavissa olevien materiaalien tutkimuksessa, esimerkiksi keraamikomposiittien tai betonin ab initio-tyyppisessä konstitutiivisessa mallinnuksessa.

Julkaisun otsikon käännös	Finite-discrete element modelling of sea ice sheet elasticity, sea ice sheet fracture, and ice-structure interaction - A three-dimensional, lattice-based approach
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Polojärvi, Arttu, Vastuuprofessori Tuhkuri, Jukka, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-64-0139-3
Sähköinen ISBN	978-952-64-0140-9
Tila	Julkaistu - 2020
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

jää
jää-rakenne-vuorovaikutus
laatat
palkkiverkkorakenteet
murtumismekaniikka
kokoefekti
yhdistetty diskreetti-elementtimenetelmä
numeeriset algoritmit

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-64-0140-9

Sormenjälki

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Siteeraa tätä

@phdthesis{9aebfcd156e24b2a973e3130fea50bad,

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

abstract = "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 dependencies each studied physical quantity has. In addition, the elastic bending tests showed that the model is able to emulate a free Kirchhoff-Love plate in bending on a Winkler-type foundation with a good accuracy. Finally, a new in-direct approach to compute ice-breaking loads on a conical offshore structure was proposed. The novelty of the approach lies in its simplicity. It provides a device not only to compute cone ice loads but also to investigate the ability of a numerical method to produce both radial and circumferential cracking. While the contents of this thesis were strictly restricted to applications that are closely related to ice mechanics, i.e. the modelling of intact sea ice sheets, their fracture, and ice-structure interaction, the results presented should apply to other cohesive, lattice-based models on other application areas as well, in the ab initio-type constitutive modelling of ceramic matrix composites or concrete for instance.",

keywords = "ice, ice-structure interaction, plates, beam lattice networks, fracture mechanics, size effect, numerical algorithms, centroidal Voronoi tessellation, j{\"a}{\"a}, j{\"a}{\"a}-rakenne-vuorovaikutus, laatat, palkkiverkkorakenteet, murtumismekaniikka, kokoefekti, yhdistetty diskreetti-elementtimenetelm{\"a}, numeeriset algoritmit, ice, ice-structure interaction, plates, beam lattice networks, fracture mechanics, size effect, numerical algorithms, centroidal Voronoi tessellation",

author = "Ville-Pekka Lilja",

year = "2020",

language = "English",

isbn = "978-952-64-0139-3",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "188",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Finite-discrete element modelling of sea ice sheet elasticity, sea ice sheet fracture, and ice-structure interaction

T2 - A three-dimensional, lattice-based approach

AU - Lilja, Ville-Pekka

PY - 2020

Y1 - 2020

N2 - 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 dependencies each studied physical quantity has. In addition, the elastic bending tests showed that the model is able to emulate a free Kirchhoff-Love plate in bending on a Winkler-type foundation with a good accuracy. Finally, a new in-direct approach to compute ice-breaking loads on a conical offshore structure was proposed. The novelty of the approach lies in its simplicity. It provides a device not only to compute cone ice loads but also to investigate the ability of a numerical method to produce both radial and circumferential cracking. While the contents of this thesis were strictly restricted to applications that are closely related to ice mechanics, i.e. the modelling of intact sea ice sheets, their fracture, and ice-structure interaction, the results presented should apply to other cohesive, lattice-based models on other application areas as well, in the ab initio-type constitutive modelling of ceramic matrix composites or concrete for instance.

AB - 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 dependencies each studied physical quantity has. In addition, the elastic bending tests showed that the model is able to emulate a free Kirchhoff-Love plate in bending on a Winkler-type foundation with a good accuracy. Finally, a new in-direct approach to compute ice-breaking loads on a conical offshore structure was proposed. The novelty of the approach lies in its simplicity. It provides a device not only to compute cone ice loads but also to investigate the ability of a numerical method to produce both radial and circumferential cracking. While the contents of this thesis were strictly restricted to applications that are closely related to ice mechanics, i.e. the modelling of intact sea ice sheets, their fracture, and ice-structure interaction, the results presented should apply to other cohesive, lattice-based models on other application areas as well, in the ab initio-type constitutive modelling of ceramic matrix composites or concrete for instance.

KW - ice

KW - ice-structure interaction

KW - plates

KW - beam lattice networks

KW - fracture mechanics

KW - size effect

KW - numerical algorithms

KW - centroidal Voronoi tessellation

KW - jää

KW - jää-rakenne-vuorovaikutus

KW - laatat

KW - palkkiverkkorakenteet

KW - murtumismekaniikka

KW - kokoefekti

KW - yhdistetty diskreetti-elementtimenetelmä

KW - numeeriset algoritmit

KW - ice

KW - ice-structure interaction

KW - plates

KW - beam lattice networks

KW - fracture mechanics

KW - size effect

KW - numerical algorithms

KW - centroidal Voronoi tessellation

M3 - Doctoral Thesis

SN - 978-952-64-0139-3

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -