Numerička analiza prihvata uzorka dvoosne kidalice

master's thesis

• Title (english): Numerical analysis of the clamps on a biaxial testing machine
• Author: Ana Andačić
• Mentor: Igor Karšaj (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2022-07-20, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; General Mechanical Engineering (Construction)

Abstract

Za procjenu mehaničkih svojstava anizotropnih materijala potrebno je koristiti dvoosno vlačno ispitivanje prilikom kojeg se mjere podaci o naprezanju i deformacijama u dva smjera. Dvoosno vlačno ispitivanje se provodi na uređajima koji se nazivaju kidalice. U praksi se ova vrsta ispitivanja najčešće koristi za ispitivanje svojstava biomaterijala, poput arterijskog tkiva, ili za ispitivanje različitih kompozitnih materijala. S obzirom da su uzorci biomaterijala jako malih dimezija, treba obratiti pozornost na odabir vrste prihvata uzorka s ciljem ostvarenja što veće homogenosti polja naprezanja i deformacije. Najčešće se koristi prihvat u obliku steznih čeljusti čiji se kontakt s uzorkom zasniva na faktoru trenja.
U ovom radu je eksperimentalno određeno pet faktora trenja na dodiru čeljusti i pet različitih vrsta uzoraka. Uz poznatu maksimalnu silu razvlačenja i faktor trenja, određena je vrijednost normalne sile koja se koristila kao ulazni podatak za numeričku simulaciju koja se provodila pomoću metode konačnih elemenata. Cilj ove simulacije je bio provjeriti čvrstoću i krutost stezne čeljusti prilikom maksimalnog opterećenja.
Također, prikazana je numeriča analiza pet različitih hiperelastičnih materijala u teorijskom i realnom slučaju. U teorijskom slučaju uzorak je opterećen samo vlačnim silama, dok je u realnom slučaju u obzir uzeto i djelovanje sile pritezanja stezne čeljusti te dodirna površina između uzorka i čeljusti. Cilj ove simulacije je bio analizirati utjecaj sile pritezanja na homogenost polja naprezanja te odrediti približno potreban moment pritezanja. Ako je moment pritezanja prevelik, uzorak se nepotrebno deformira pri postavljanju na uređaj i povećava se koncentracija naprezanja. S druge strane, ako je moment pritezanja premali, uzorak tijekom eksperimenta može iskliznuti i eksperiment je tad neuspješan.
Za izradu modela korišten je programski paket SolidWorks, dok su numeričke analize provedene u programskom paketu Abaqus.

Abstract (english)

To evaluate the mechanical properties of anisotropic materials it is necessary to use biaxial testing test during which data on stress and deformations are measured in two directions. Biaxial tensile testing is performed on devices called tensile testing machines. In practice, this type of testing is most often used to test the properties of biomaterials such as arterial tissue or to test different composite materials. Since the samples of biomaterials are small in size, we should pay attention to the choice of the type of sample acceptance with the aim of achieving greater homogeneity of the stress and deformation field. The most commonly used sample acceptance is in the form of clamping jaws whose contact with the specimen is based on the coefficient of friction.
In this paper, five coefficients of friction at contact between clamping jaws and five different types of samples were experimentally determined. With the known maximum stretching force and coefficient of friction, the value of normal force was determined which was used as input data for the numerical simulation, which was carried out using finite element method. The aim of this simulation was to verify the strength and stiffness of the clamping jaws during maximum load.
Also, a numerical analysis of five different hyperelastic materials in theoretical and real case is presented. In the theoretical case, the sample is loaded only by tensile forces, while in the real case, the action of force of tightening the clamping jaws is also taken into account. The aim of this simulation was to analyze the influence of the tightening force on the homogeneity of the stress field and to determine the approximately required tightening torque. If the tightening torque is too high, the sample is unnecessarily deformed when placed on the device and the stress concentration increases. On the other hand, if the tightening torque is too small, the sample may slip during the experiment and the experiment is then unsuccessful.
The SolidWorks software package was used to create the model, while numerical analyzes were performed in the Abaqus software package.

• Keywords: dvoosno vlačno ispitivanje; metoda konačnih elemenata; stezne čeljusti; hiperelastični materijal; moment pritezanja
• Keywords (english): biaxial tensile testing; finite element method; clamping jaws; hyperelastic material; tightening torque
• Language: croatian
• URN:NBN: urn:nbn:hr:235:654628
• 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: 2022-07-13 13:42:34