Primjena optičkih metoda za određivanje ponašanja bioloških mekih tkiva pri ravninskom dvoosnom opterećenju

master's thesis

• Title (english): Application of optical methods to asses the material response of soft tissues subjected under in-plane biaxial loading regime
• Author: Ivan Nemčić
• Mentor: Janoš Kodvanj (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2016-03-25, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Bolesti srca i krvnih žila predstavljaju jedan od najvećih medicinskih problema suvremenog svijeta i jedan su od vodećih uzroka smrtnosti u razvijenim zemljama. Kako bi se bolje razumijele posljedice bolesti krvnih žila postoji potreba za provedbom mehaničkih ispitivanja s ciljem određivanja pouzdanijih materijalnih svojstava krvožilnog tkiva.

U radu su analizirana četiri ravninska dvoosna eksperimenta na uzorcima pripremljenim od svinjske aorte. Na tri uzorka mjerenje deformacija provedeno je videoekstenzometrom i metodom korelacije digitalne slike (DIC). Videoekstenzometrom su praćeni pomaci dvaju markera na uzorku, po svakoj osi opterećenja. DIC metodom je analizirano cijelo polje pomaka površine uzoraka s umjetnom teksturom. Primjenom virtualnog/optičkog ekstenzometra uspoređeni su rezultati dobiveni videoekstenzometrom. Kod četvrtog uzorka RT3-DIC algoritmom određena su polja pomaka i deformacija na cijeloj površini uzorka kako bi se odredio utjecaj eksperimentalnog postava. Dobiveni rezultati pokazali su da DIC metoda rezultira manjom mjernom nesigurnošću zbog uzimanja u obzir kontinuiranosti polja pomaka. Eksperimentalno ispitivanje na predloženom biološki mekom tkivu zabilježilo je veću krutost u smjeru vlakana. Iz provedenih mjerenja za jedan ispitni uzorak određeni su parametari materijala za tri hiperelastična konstitutivna modela. Analizirani su materijalni modeli neo – Hooke, Mooney – Rivlin i Ogden. Usporedbom standardne greške između eksperimentalnih podataka i identificiranih krivulja te provjerom uvjeta Druckerovog kriterija stabilnosti može se zaključiti da konstitutivni zakon Ogden polinomske forme prvog reda najpouzdanije opisuje dvoosno ponašanje ispitivanog materijala.

Abstract (english)

Cardiovascular diseases are one of the biggest medical problems of the modern world and one of the leading causes of death in developed countries. In order to better understand the consequences of vascular diseases there is a need for the implementation of mechanical tests in order to determine reliable properties of cardiovascular tissues.

In this work four planar biaxial experiments have been analyzed on specimens prepared from porcine aorta. On three samples strain data was accessed using the videoekstenzometer and Digital Image Correlation Method (DIC). By means of videoextensometer displacements of two markers were tracked for each sample on each loading axis. As a full-field measurement technique, DIC method was applied to measure displacemen/strain fields on surface of the samples. A virtual/optical strain gauge was used to determine mean strain components. Latter were compared videoextensometer measurements. At fourth specimen the whole surface was taken into account to obtain the strain fields. From the performed test the influence of the experimental setup on the material response was evaluated. Obtained results showed that DIC method yields with lower measurement uncertainty since it takes into account the continuity of the displacement field. Experimental investigation on the proposed soft tissue reports higer stiffness in the fiber direction.

According to the obtained results for one measurement material parameters for three hiperelastic constitutive laws were determined. Neo-Hooke, Mooney-Rivlin and Ogden material models were taken into account. In order to find the most suitable model to describe the material behaviour two criterions were considered. First, the residuals between the experimental and identified data for the applied models was taken into account. The second point was to satisfy the Drucker stability criterion. Ogden's material model described as polynomial of the first order reports the best fit of the experimental data.

• Keywords: aorta; ravninski dvoosni eksperiment; videoekstenzometar; metoda korelacije digitalne slike; hiperelastični materijalni model
• Keywords (english): aorta; planar biaxial test; videoextensometer; digital image correlation; hyperelastic material model
• Language: croatian
• URN:NBN: urn:nbn:hr:235:605836
• 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: 2019-05-22 16:28:17