Dinamička analiza cikličke in-situ kidalice za ispitivanje materijala unutar CT skenera

master's thesis

• Title (english): Dynamic analysis of fatigue in-situ loading device for material testing inside a CT scanner
• Author: Luka Stanić
• Mentor: Zvonimir Tomičević (mentor)
• Mentor: Damjan Čakmak (komentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2021-05-14, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Kompoziti ojačani vlaknima, zbog mogućnosti modifikacije mehaničkih svojstava, preuzimaju ulogu konvencionalnih materijala te svoju primjenu pronalaze ponajprije u zrakoplovstvu i automobilskoj industriji. Mehanička svojstva kompozita ovise ponajviše o heterogenoj strukturi, raspodjeli i udjelu konstituenata, između kojih se mogu pojaviti različiti mehanizmi oštećenja. Za određivanje mehaničkih svojstava navedenih materijala potrebno je koristiti napredne metode ispitivanja koje pružaju uvid u fenomene koji se javljaju unutar ispitnog uzorka tijekom opterećivanja. Računalna tomografija (eng. Computed Tomography-CT) omogućuje trodimenzijski prikaz vanjskog i unutarnjeg stanja skeniranog objekta bez da ga ošteti. Mehanička ispitivanja mogu se provoditi ex-situ ili in-situ unutar CT skenera. Prilikom ex-situ ispitivanja opterećivanje uzorka provodi se izvan CT skenera te se potom uzorak skenira u rasterećenom stanju. Međutim, kod in-situ ispitivanja, uzorak se istovremeno opterećuje i skenira. Iako in-situ ispitivanja daju potpuni uvid u promjene unutar uzorka u odnosu na ex-situ ispitivanja, njihovo provođenje je kompleksnije i zahtjeva uporabu specifičnih ispitnih uređaja koji stanu unutar CT skenera.
Iz tog je razloga razvijena in-situ ciklička kidalica za potrebe projekta FULLINSPECT, koji se bavi promatranjem inicijacije i propagacije pukotina te identifikacijom mehanizama loma unutar kompozita ojačanim vlaknima uslijed cikličkih opterećenja. Prilikom rada takve kidalice javljaju se vibracije koje mogu oštetiti rotacijski stol CT skener ili utjecati na kvalitetu zabilježenih 3D slika. Stoga je u ovom radu izrađen pojednostavljeni model kidalice te je proučavan najkonzervativniji slučaj opterećivanja pri maksimalnoj amplitudi pomaka ispitnog uzorka od 1 mm. Primjenom metode konačnih elemenata određene su glavne forme vibriranja kidalice i izračunate su sile koje djeluju na rotacijski stol tomografa u frekvencijskom rasponu od 0 do 100 Hz.

Abstract (english)

Fiber-reinforced composites, due to possibility of modifying the mechanical properties, take on the role of conventional materials and find their application primarily in the aviation and automotive industries. The mechanical properties of composites depend mainly on the heterogeneous structure, distribution and fraction of constituents, between which various damages can occur. To determine the mechanical properties, it is necessary to use advanced test methods that provide insight into the phenomena that occur within the test specimen during loading. Computed Tomography (CT) allows a three-dimensional view of the external and internal state of a scanned object without damaging it. Mechanical tests can be performed ex-situ or in-situ inside the CT scanner. In ex-situ testing, the sample is loaded outside the CT scanner and then the sample is scanned in the unloaded state. However, in in-situ testing, the sample is loaded and scanned at the same time. Although in-situ tests provide a more complete insight into changes within the sample compared to ex-situ tests, their implementation is more complex and requires the use of specific test devices that fit inside the CT scanner.
For this reason, developed in-situ cyclic fatigue machine for the project FULLINSPECT, which deals with the observation of the initiation and propagation of cracks, and identification of mechanisms of fracture within the fiber-reinforced composites during cyclic loading. During the operation of such a fatigue machine, vibrations occur which can damage the rotary table of CT scanner or affect the quality of recorded 3D images. Hence, in this thesis, a simplified model of the fatigue machine was developed and the most conservative case of loading at the maximum displacement amplitude of the test specimen of 1 mm was studied. Using the finite element method, the main vibration shapes were determined and the forces acting on the rotary table of the tomograph in the frequency range from 0 to 100 Hz were calculated.

• Keywords: vlaknima ojačani kompoziti; oštećenja kompozitnih materijala; računalna tomografija; in-situ ciklička kidalica; metoda konačnih elemenata; modalna analiza; Rayleigh-evo prigušenje; dinamička analiza
• Keywords (english): fiber reinforced composites; damage of composite materials; computed tomography; in-situ fatigue machine; finite element method; modal analysis; Rayleigh damping; dynamic analysis
• Language: croatian
• URN:NBN: urn:nbn:hr:235:488504
• Project: Number: UIP-2019-04-5460; Title: Promatranje, identifikacija i kvantifikacija mehanizama mehaničkog oštećenja na kompozitima ojačanim staklenim vlaknima primjenom različitih metoda nerazornog ispitivanja; Title: Observation, identification and quantification of the mechanical damage mechanisms of glass fibre reinforced composites via multiple non-destructive testing methods; Acronym: FULLINSPECT; Leader: Zvonimir Tomičević; Jurisdiction: Croatia; Funder: HRZZ; Funding stream: UIP
• 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; Embargo expiration date: 2023-05-14
• Created on: 2021-05-10 11:31:09