Razvoj postupka korištenja Neo-Hooke materijalnog modela za opis ponašanja krvnih žila

master's thesis

• Title (english): Mechanical characterization of arterial behaviour using Neo-Hooke material model
• Author: Mirta Džida
• Mentor: Igor Karšaj (mentor)
• Mentor: Lana Virag (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2021-07-16, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; General Mechanical Engineering (Construction)

Abstract

Razvojem medicine pojavljuje se sve veća potreba za znanjima iz područja biomehanike i inženjerstva, kako bi se liječnicima pomoglo pri liječenju, te povećala preciznost, a smanjio rizik pogreške pri operacijskim zahvatima. Veliku ulogu ima tehnologija aditivne proizvodnje koja omogućuje brzu izradu modela složenih geometrija. Kardiovaskularne bolesti su velik problem današnjice, a upravo 3D ispis prototipova modela za eksperimentalno ispitivanje doprinosi napretku u istraživanju. S obzirom da je materijal 3D ispisa polimer drugačijeg mehaničkog ponašanja od stijenke krvne žila, cilj rada je provjeriti hoće li 3D ispisana žila moći imati realno ponašanje na fiziološkom području opterećenja.
U radu korištena je numerička metoda konačnih elemenata i računalne simulacije pokusa istezanje-tlak kako bi se dobili materijalni parametri potrebni za opisivanje modela arterije. U programskom paketu Abaqus je napravljen pokus za nestlačivi model arterije koji je opterećen krvnim tlakom. Dva hiperelastična materijalna modela su korištena u simulaciji: Mooney-Rivlin i Holzapfel-Gasser-Ogden. Model koji opisuje anizotropno ponašanje te je razvijen za opisivanje ponašanja mekih tkiva naziva se Holzapfel-Gasser-Ogden, dok se model uz pomoć kojeg se definira izotropno ponašanje naziva Mooney-Rivlin. Te simulacije daju mjerenja pomaka unutarnje stijenke aorte tijekom srčanog ciklusa. Podaci prikupljeni iz simulacije su promjene vanjskog te unutarnjeg radijusa stijenke arterije za zadani raspon tlaka. Pomoću Octave programskog paketa je obavljeno određivanje materijalnih parametara. Podaci dobiveni iz simulacije približno su opisani Neo-Hooke materijalnim modelom koji dobro opisuje mehaničko ponašanje 3D ispisanih polimernih materijala. Rezultati numeričke simulacije Neo-Hooke modela uspoređeni su s rezultatima početnih modela, te je izračunata greška. Postupak simulacije opisan je detaljno u radu. Također, s obzirom da je stvarno meko tkivo vrlo heterogeno, ispitan je utjecaj heterogenosti na grešku između dobivenih i ciljanih pomaka.

Abstract (english)

With the development of medical science, there is a growing need for knowledge in the field of biomechanics and engineering, in order to assist doctors decide the optimal treatment and increase accuracy while reducing the risk of error in surgical procedures. The technology of additive manufacturing plays an important role, which enables the fast creation of models with complex geometries. Cardiovascular diseases are a leading cause of mortality, and it is the 3D printing of prototype models for experimental testing that contributes to research progress. Since the 3D printed material is a polymer with different mechanical behavior from the blood vessel wall, the aim of this work is to check whether the 3D printed vessel will be able to have a realistic behavior in the physiological pressure range.
This work uses the numerical finite element method and computer simulation of the extension-pressure experiment to obtain the material parameters needed to describe the artery model. The experiment was performed for an incompressible artery model loaded with blood pressure in the Abaqus software package. Two hyperelastic material models were used in the simulation: Mooney-Rivlin and Holzapfel-Gasser-Ogden. The model that describes anisotropic behavior and was developed to describe soft tissue behavior is Holzapfel-Gasser-Ogden, while the model used to define isotropic behavior is Mooney-Rivlin. These simulations give measurements of the displacement of the inner wall of the aorta during the cardiac cycle. The data from the change in the inner radii and outer radii of the artery wall for a given pressure range were collected from these simulations. The Octave software package was used to determine the material parameters. The data from the simulations are approximately described by a Neo-Hooke material model that describes the mechanical behavior of 3D printed polymeric materials very well. The results of the numerical simulation of the Neo-Hooke model were compared with the results of the initial models, and an error was calculated. The simulation procedure is described in detail in the work. Also, since the real soft tissue is very heterogeneous, the influence of heterogeneity on the error between the obtained and target displacements was examined.

• Keywords: arterije; aditivna proizvodnja; hiperelastičnost; mehanika kontinuuma; Neo-Hooke; Mooney-Rivlin; metoda konačnih elemenata; Holzapfel-Gasser-Ogden; određivanje materijalnih parametara
• Keywords (english): arteries; additive production; hyperelasticity; continuum mechanics; Neo-Hooke; Mooney-Rivlin; finite element method; Holzapfel-Gasser-Ogden; material parameter fitting
• Language: croatian
• URN:NBN: urn:nbn:hr:235:403661
• 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: 2021-07-08 15:32:50