Analiza učinkovitosti bionički nadahnutih karotidnih stentova izrađenih od polimera s memorijom oblika

master's thesis

• Title (english): Efficiency analysis of bionic-inspired shape memory polymer carotid stent
• Author: Magdalena Mijatović
• Mentor: Lana Virag (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2023-01-25, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; General Mechanical Engineering (Construction)

Abstract

Primarna svrha ovog diplomskog rada je razvoj numeričke procedure za modeliranje ugradnje stenta izrađenog od polimera s memorijom oblika u karotidnu arteriju te analiza učinkovitosti bionički nadahnutih modela stentova s osvrtom na zaostalu stenozu i naprezanja u stijenci arterije. Pri tome je potrebno modelirati stijenku arterije što realnije. Budući da stvarno ponašanje stijenke arterije karakterizira anizotropija, uzrokovana rasporedom kolagenih vlakana, stijenci je dodijeljen anizotropni hiperelastični materijal opisan Holzapfel-Gasser-Ogden (HGO) modelom, a aterosklerotskom plaku i stentu izotropni hiperelastični materijal opisan Neo-Hooke modelom. Pri tome je korištena korisnička rutina UMAT za implementaciju HGO modela s predistezanjem elastina i kolagena u programski paket Abaqus 6.14-4. U programskom paketu SOLIDWORKS Premium 2022 SP2.0. je izrađen model konvencionalnog modela stenta, kao i niz prijedloga bionički nadahnutih modela stentova. Simulacijom ugradnje stentova u stijenku s 50 % stenoze je analizirana njihova učinkovitost. Rezultati su uspoređeni za slučaj krutog, hipocelularnog aterosklerotskog plaka čiji sastav i mehanička svojstva uzrokuju najopasniji slučaj bolesti, najniži stupanj redukcije stenoze.
Evaluacijom rezultata je utvrđeno da predloženi Favus-O model nadahnut strukturom pčelinjeg saća osigurava povoljnije uvjete ugradnje stenta u odnosu na konvencionalni i druge predložene modele redukcijom stenoze s 50 % na 31 % uz očekivano povećanje naprezanja u stijenci uzrokovano većim radijalnim pomacima.

Abstract (english)

The primary purpose of this master’s thesis is the development of a numerical procedure for modelling of a shape memory polymer carotid stent implementation and efficiency analysis of bionic-inspired stent models. The stenting efficiency is defined by the residual stenosis and arterial wall stress. To achieve that, it is necessary to model the arterial wall as realistically as possible. Since the real arterial wall behaviour is characterized by anisotropy due to the arrangement of collagen fibres, the arterial wall was modelled as an anisotropic hyperelastic material described by the Holzapfel-Gasser-Ogden (HGO) model, while isotropic hyperelastic material described by the Neo-Hooke model was used for both atherosclerotic plaque and stent. User material subroutine (UMAT) was used for the implementation of HGO model that takes into account pre-stretches in elastin and collagen in Abaqus 6.14-4 software. A model of a conventional stent and various proposed bionic-inspired stents were created in SOLIDWORKS Premium 2022 SP2.0 software. Their efficiency was analysed by simulating the stent implantation into an artery with 50 % degree of stenosis. The obtained results were compared for the case of the stiff hypocellular atherosclerotic plaque, whose composition and mechanical properties generate the most threatening case of the disease, and result in the least reduction of stenosis.
The numerical results show that the suggested Favus-O model inspired by the honeycomb structure provides more favourable lumen expansion after stent implementation in comparison to the conventional, but also to the other proposed models, by reducing the stenosis from 50 % to 31 % with the expected increase in wall stress caused by larger radial displacements.

• Keywords: numerička analiza; hiperelastični materijal; stent; bionika; stenoza
• Keywords (english): numerical analysis; hyperelastic material; stent; bionics; stenosis
• Language: croatian
• URN:NBN: urn:nbn:hr:235:439984
• Study programme: Title: Mechanical Engineering; specializations in: Design, Process and Energy Engineering, Production Engineering, Engineering Modelling and Computer Simulation, Marine Engineering, Industrial Engineering and Management, Materials Engineering, Mechatronics and Robotics, Autonomous Systems; Course: Design; 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: 2023-01-19 10:42:01