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Mechanical properties of 3D printed PLA plastic parts
Novosád, Ivan ; Dočkal, Kryštof (referee) ; Paloušek, David (advisor)
3D printing is being widely used by public and also in industry. The main advantage of 3D printing is rapid making prototypes. That is the reason why it is needed to know what the mechanical properties of the material that is being used are. This thesis is about making research of knowledge about 3D printing and mechanical properties of printed parts. Main task was comparing materials used in 3D printers and find out which producer makes materials with the best tensile strength. 5 producers were selected to be compared in this test. From each producer was bought PLA filament in natural colour, this material was then used to print testing specimens. All specimens were tested on maximum tensile strength and Young's elastic modulus and then was calculated the confidence interval for each producer.
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Influence of Homogenizing on Mechanical Properties of AZ91 Alloy
Provazníková, Andrea ; Liškutín, Petr (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis includes photos and graphic representations of the influence of heat treatment on the mechanical properties of magnesium alloy AZ91. The structures of the alloy are recorded on the light microscopy pictures as well as photographs taken using a scanning microscope of fracture areas in the material. Results of a Tensile Test determining the strength and plastic properties and measuring of hardness and microhardness of the material are also included.
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Possibilities of the description of stress-strain curves for computational simulations
Košťál, Josef ; Halabuk, Dávid (referee) ; Šebek, František (advisor)
Tato bakalářská práce se zabývala problematikou určování křivky zpevnění (taktéž „flow curve“) z experimentálně změřených výstupů tahové zkoušky a regresí této zjištěné křivky nelineárními vztahy. Byl prezentován teoretický základ zkoušky tahem a jejího výstupu a také byly popsány rozdíly mezi smluvním a skutečným napětím a přetvořením. Dále byla zmíněna analytická korekční metoda (Mirone-La Rosa) pro odhadnutí trendu křivky zpevnění. Tato metoda využívá standardních výstupů tahové zkoušky. Dále byly vypsány elasto-plastické po částech spojité materiálové modely, a navíc byly vybrány a detailněji rozebrány 4 nelineární vztahy pro popis křivky – Hollomon, Ludwik, Swift a Voce. Následně byla použita metoda konečných prvků pro určení a zkalibrování křivky zpevnění oceli 18CrNiMo7-6, změřené tahovou zkouškou. Pouze standardní výstup tahové zkoušky byl potřeba pro kalibraci. Křivka zpevnění byla zkalibrována iterační výpočtovou metodou na základě srovnání reakční síly ze simulace se silou z experimentu. Nakonec bylo vytvořeno uživatelské prostředí pro nalezení nejlepší regrese ze čtyř vybraných nelineárních vztahů.
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Testing of parts produced by Bound Metal Deposition technology
Hradil, Antonín ; Vaverka, Ondřej (referee) ; Koutecký, Tomáš (advisor)
Bachelor thesis on the topic Testing of parts produced by Bound Metal Deposition technology. Aim of the work is to obtain mechanical properties of products made by Studio System. We have achieved this by performing tensile test and optical metallography. The results of this thesis are mechanical properties of the tensile test. Re, Rm, E, etc. Another results are microscopic images of microstructure of material. Thanks to this work, we are getting closer to the technology Bound Metal Deposition. We approximate scientifically its mechanical properties and the microstructure of the product surface.
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Testing of commercial rubber sealing components exposed to different ambient conditions
Jančaříková, Marie ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
Diploma thesis studies the effect of temperature (75 and 105 °C) and the effect of 3 kinds of liquids (silicone and hydraulic oil and coolant) at room temperature and at 105 °C on change of the structure of 3 species butadiene-acrylonitrile (NBR) seals (o-ring and two types of bolts). The seals are inspected by the thermogravimetric analysis, differential scanning calorimetry and infrared spectroscopy, the influence of 105 °C on the o-rings is also evaluated in terms of changes in tensile properties. The greatest changes in the composition and structure are observed on o-rings particularly due to temperature of 105 °C, there was a significant reduction in dilatability and an increase in stiffness and glass transition temperature. The root cause is the surface and centre additive decomposition and oxidation. The bolts have suffered from decomposition of the protective surface layer and the additives in the centre, structural change was minor. Exposure to 75 °C has resulted in a gradual loss of low molecular weight substances. Liquids at room temperature didn‘t affect the structure of the seals, at 105 °C it caused a loss of weight due to decomposition of the protective surface layer and release of additives and the products of their decomposition. Results showed that the common use of the NBR seals at 105 °C is unsuitable, at 75 °C it leads to gradual changes, loss in mechanical and sealing properties.
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Physical ageing of polypropylene
Weiss, Jiří ; Kučera, Jaroslav (referee) ; Tocháček, Jiří (advisor)
Physical aging of commercially produced polypropylene homopolymers Mosten was studied. The work is focused on monitoring the changes in physical properties of polymer in the time period 90 days from the date of preparation of the test specimen. The aging of polymers was realized at storage temperatures of 23 and 80 °C. The changes in crystallinity, yield strength, modulus, elongation and impact strength using DSC method, tensile tests and impact tests according to Charpy were monitored. Molecular weight distribution was determined by means of GPC at each polymer. Relationships between the changes in physical properties and polymer molecular weight were sought.
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Adhesion of (Hydro)gel Materials to the Surface – Physico-chemical Description and Biological Concequences
Žibeková, Lucia ; Mravec, Filip (referee) ; Kalina, Michal (advisor)
This Bachelor´s thesis deals with study of adhesion of hydrogels materials to the surface. Three biopolymers were selected for this purpose, one of which is psychically cross-linked (agarose) and two are chemically cross-linked (based on sodium alginate cross-linked with Ca2+ and polyvinyl alcohol cross-linked with borax). In the experimental part of the work, adhesion was first examined by a visual method on an inclined plane. The tilt was at different angles (30°, 45°, 90°) where it was observed whether the hydrogel was able to attach to a solid surface or slip down. The agarose was examined in different concentrations from 0.5 wt% to 4 wt% in both methods. Also, the alginate gel was examined at various concentrations with two different cross-linked agent. However, alginate was only used in the visual method because of its inhomogeneity. In contrast, the PVA gel was examined at 10:1 and 4:1 ratios for the both methods. The second method in the experimental part was the tensile test carried out on the Inova apparatus – hydraulic pulsator, and thus the methodology for the study of physical and chemically cross-linked hydrogels was optimized. With increasing concentration of agarose gels, adhesion strength and work increased as well. For PVA gels, the adhesion work was higher, but the adhesive strength remained approximately the same as for the agarose gels.
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Control system design for small test machine
Rasocha, David ; Králík, Jan (referee) ; Věchet, Stanislav (advisor)
This thesis focuses on design of small testing machine for measuring tensile strength of materials. Appropriate hardware for driving the motor with serial communication will be used. Main drive is a stepper motor with microstepping. Instructions for motor is provided by microcontroler which will be comunicating with aplication in computer. This aplication will have all user functions nessesary for using this device.
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Fiber reinforcements for polymer composites
Knob, Antonín ; Grégr, Jan (referee) ; Čech, Vladimír (advisor)
The bachelor thesis is concerned with an influence of surface modification of fibrous reinforcements on mechanical properties at the fiber-matrix interface in fiber-reinforced polymer composites. Polyester resin was used as a matrix, glass and carbon fibers were the reinforcements. The composite sample consisted of polymer matrix in a form of cylindrical body placed on a bundle of fibers. Untreated fibers and fibers with a commercial sizing were used for fabrication of composite samples. The tensile test using a materials testing machine (Zwick) was employed to evaluate adhesion at the fiber-matrix interface.
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