Određivanje materijalnih parametara polimernog materijala na osnovi jednoosnog vlačnog testa

master's thesis

• Title (english): Estimation of constitutive material parameters of polymers from uniaxial tensile test
• Author: Kristijan Kubik
• Mentor: Igor Karšaj (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2019-07-11, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Precision Mechanical Engineering

Abstract

Ovaj rad usko je povezan sa sve učestalijom bolesti krvnih žila u svijetu pod nazivom aneurizma intrakranijalnih arterija, što podrazumijeva lokalno proširenje krvnih žila koje se nalaze u području mozga. Kao posljedica širenja aneurizme može doći do pucanja (rupture) arterije i/ili krvarenja koje može imati smrtni ishod. Kako bi se bolje razumijeli uzroci i posljedice bolesti krvnih žila, postoji potreba za provedbom mehaničkih ispitivanja s ciljem određivanja pouzdanijih materijalnih svojstava arterija. Tema ovog diplomskog rada podijeljena je u dva dijela. U prvom dijelu provodi se eksperimentalno ispitivanje različitih polimernih materijala pomoću kojih se žele oponašati svojstva krvnih žila, odnosno arterija. Ispitni uzorci od polimernih materijala ispisuju se PolyJet tehnikom 3D ispisa te se podvrgavaju jednoosnom statičkom vlačnom testu na kidalici. Iz eksperimentalnih rezultata rješavanjem optimizacijskog problema fitanja određuju se vrijednosti materijalnih parametara različitih hiperelastičnih konstitutivnih modela kojima se opisuje ponašanje polimernih materijala u mehanici kontinuuma. U drugom dijelu provodi se implementacija odabranih hiperelastičnih konstitutivnih materijalnih modela putem korisničke rutine UMAT u programski paket Abaqus. Za to je potreban razvoj Fortran 77 računalnog koda koji u sebi prema odgovarajućim pravilima sadrži definirane sve varijable za dotični hiperelastični model koje su potrebne programskom paketu Abaqus prilikom provođenja nelinearne inrkementalno–iterativne analize pomoću metode konačnih elemenata.

Abstract (english)

This paper is closely related to one of the worlds most common cardiovascular diseases by the name intracranial aneurysm, which referes to a localized dilation or ballooning of the blood vessel in the brain. Aneurysms have a high risk of rupture. If an aneurysm ruptures, blood leaks into the space around the brain, which can lead to sudden death. In order to better understand the causes and consequences of cardiovascular diseases, there is a need for carrying out mechanical tests in order to determine reliable material properties of cardiovascular tissues. The subject matter of this paper is divided into two parts. In the first part, experimental testings are being conducted for a range of selected different polymer materials, with which strain–stiffening behavior of soft tissues (i.e. arteries) wants to be mimicked. The specimens, that were fabricated by the means of 3D printing technique called PolyJet, are subjected to a uniaxial tensile test. From the experimental data employing optimization fitting procedure, material parameters of different hyperelastic constitutive models are determined. Hyperelastic material models are used in continuum mechanics approaches for describing the typical behaviour of polymer materials. In the second part, implementation of selected hyperelastic material models into a finite element software Abaqus is being done throughout a user–defined subroutine called UMAT. In order to accomplish a successful implementation, development of Fortran 77 code is needed. Following a defined set of rules for this kind of material constitutive model implementation, the code should contain all the variables for a particular hyperelastic model which are necessary to run a nonlinear incremental and iterative finite element method analysis in Abaqus.

• Keywords: Intrakranijalna aneurzima; polimerni materijali; 3D ispis; jednoosni eksperiment; hiperelastični model; fitanje; materijalni parametri; UMAT; implementacija; metoda konačnih elemenata.
• Keywords (english): Intracranial aneurysm; polymer materials; 3D print; uniaxial test; hyperelastic model; fitting; material parameters; UMAT; implementation; finite element method.
• Language: croatian
• URN:NBN: urn:nbn:hr:235:374916
• Project: Number: IP-2018-01-3796; Title: Eksperimentalna platforma za simulaciju endovaskularnog liječenja intrakranijskih aneurizmi; Acronym: EIPlaSTICA; Leader: David Ozretić; Jurisdiction: Croatia; Funder: Hrvatska zaklada za znanost; Funding stream: Istraživački projekti
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-07-04 02:17:05