Konstrukcija uređaja za in-situ mehanička ispitivanja u μ-CT skeneru

master's thesis

• Title (english): Design solution of a loading device for in-situ mechanical tests inside μ-CT scanner
• Author: Gabrijel Mađerić
• Mentor: Zvonimir Tomičević (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2020-12-04, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; General Mechanical Engineering (Construction)

Abstract

Kompoziti ojačani vlaknima (eng. Fiber reinforced composites – FRC) ističu se kao adekvatna zamjena za konvencionalne inženjerske materijale te svoju primjenu najviše nalaze u zrakoplovstvu, automobilskoj industriji i brodogradnji. S obzirom na njihovu heterogenu strukturu potrebna je primjena naprednijih ispitivanja koja vrlo precizno mogu procijeniti odziv materijala uslijed mehaničkog opterećenja. Jedna od najčešće korištenih suvremenih metoda za nerazorna ispitivanja kompozitnih materijala, kojom je moguće odrediti lokalnu interkaciju između vlakana i matrice unutar materijala, kao i adhezijska svojstva spojeva između konstituenata, je računalna tomografija (CT). Navedenom metodom moguće je provođenje ex-situ ili in-situ mehaničkih ispitivanja unutar CT skenera. Kod ex-situ ispitivanja, uzorak se opterećuje izvan CT uređaja te se nakon toga provodi skeniranje odabrane zone intersa mjernog objekta. S druge strane, kod in-situ ispitivanja, uzorak se istovremeno opterećuje i skenira. Iako su se in-situ ispitivanja pokazala kao sveobuhvatnija u usporedbi s ex-situ, ona su mnogo složenija te zahtijevaju primjenu specifičnih uređaja za opterećivanje ispitnih uzoraka koji dimenzijski odgovaraju unutrašnjosti pojedinog CT uređaja, a da pri tome ne ometaju proces skeniranja uzorka.
U ovom radu konstruirana je kvazi-statička kidalica koja će omogućiti in-situ ispitivanja uzoraka izrađenih od kompozita ojačanih staklenim vlaknima. Uređaj je prilagođen za tri tomografa različitih proizvođača: NIKON XT H 225, Werth S i NortStar X50+. Na temelju funkcijske dekompozicije, morfološke matrice te konstrukcijskih zahtjeva i ograničenja predloženo je nekoliko temeljnih koncepata čijom je nadogradnjom i poboljšavanjem odabran konačan koncept, koji je u ovom radu konstrukcijski u potpunosti razrađen. Analitičkim i numeričkim proračunima provjerene su sve kritične komponente ispitnog uređaja. Novorazvijena kidalica za mehanička in-situ ispitivanja ima kapacitet od 5 kN te omogućava cikličko jednosmjerno i naizmjenično vlačno i tlačno ispitivanje ispitnih uzoraka različitih debljina.

Abstract (english)

Fiber reinforced composites (FRC) are an adequate substitute for conventional materials. They are mainly used in aviation, the automotive industry and shipbuilding. In view of their heterogeneous structure, it is necessary to establish advanced experimental methods that allow a reliable estimation of the material response induced by the imposed mechanical loading history. Computed tomography (CT) is one of the most commonly used modern methods for non-destructive testing of composite materials. The proposed method allows the identification of localized fiber-matrix interactions in the bulk of the investigated test sample, as well as the adhesion properties of the connection between the constituents. With this full-field acquisition method it is possible to perform ex-situ and in-situ mechanical tests inside the CT scanner. Considering the ex-situ test protocol, the test sample is loaded outside the CT device and then scanned in the unloaded stage. However, the in-situ investigation of the material behavior, comprises the simultaneous scanning and loading of the test sample. Although in-situ tests have proven to be more comprehensive than ex-situ, they are more complex and require the use of specific loading devices that fit dimensionally inside a particular CT scanner without interfering with the scanning process of the specimen.
In this thesis a quasi-static loading device is designed. The latter will allow an in-situ investigation of glass fiber reinforced composites. The device is adapted for three types of tomographs from different manufacturers: NIKON XT H 225, Werth S and NorthStar X50+. Based on the functional decomposition, morphological matrix and design requirements and constraints, several concepts have been proposed. By upgrading and improving all the aforementioned concepts, the final design of the in-situ loading machine was created. Furthermore, the adopted design was fully elaborated. All critical components of the loading machine were analysed via analytical calculations and numerical simulations. The developed device has a capacity of 5 kN, with the possibility to impose unidirectional and fully reversed cyclic tensile and compression loading histories. In addition, the modular design of the proposed device allows the investigation of test specimens of different thickness.

• Keywords: vlaknima ojačani kompoziti; nerazorna ispitivanja; računalna tomografija X-zrakama (X-CT); in-situ mehanička ispitivanja; kvazi-statička in-situ kidalica.
• Keywords (english): fiber reinforced composites; non-destructive testing; X-ray computed tomography (X-CT); in-situ mecanical tests; quasi-static in-situ tensile and compression loading device.
• Language: croatian
• URN:NBN: urn:nbn:hr:235:452512
• 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: 2022-12-01
• Created on: 2020-11-26 15:16:41