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Computational analysis of the dynamic behavior of the thrust bearings
Žatko, Miroslav ; Kos, Pavel (referee) ; Malenovský, Eduard (advisor)
This master´s thesis solves the problem of stationary viscous flow of incompressible fluids in thin layers of fluid film lubrication in fixed pad thrust bearings. The parametric computational model of oil domain was created for investigation the distribution of pressure, velocity and thermal fields together with the determination of the basic parameters as axial force, heating up and friction loss. Subsequently this model was applied for investigation influence of uneven bearing clearance. The problem task was solved by final volume method in Ansys CFX 12.0 software.
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The properties of welding joint after hot-dip galvanizing
Vítek, Pavel ; Suchánková, Ivana (referee) ; Kubíček, Jaroslav (advisor)
The project elaborated in frame of Master's studies branch 2303T002 presents a study of welded joints for hot-dip galvanizing. On the basis of literature study it is assumed that zinc influences the properties of welded joints. Samples were made of high strength steels DOMEX and wear-resistant steels HARDOX which were welded using MAG. Subsequently, half of the samples treated with zinc. The evaluation is used tear test and test Vickers hardness. Finally, the project is the comparison of the measured values of galvanized steel and steel without zinc.
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Vliv tepelného namáhání na mechanické vlastnosti FeNiB amorfní slitiny
Zábranský, Karel ; Jirásková, Yvonna
An influence of thermal treatment in the temperature range of 150 - 350 °C on the structural and mechanical properties of an amorphous FeNiB alloy is investigated. The high tensile strength of 2200 MPa in the as-prepared amorphous state slightly decreases with increasing temperature of annealing up to approximately 200 °C in opposite to microhardness where an increase is observed. Above 200 °C a pronounced deterioration of both characteristics reflect the embrittlement of amorphous structure without any indications of crystallization.
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Fatigue properties of AZ61 magnesium alloy
Provazníková, Andrea ; Juliš, Martin (referee) ; Pantělejev, Libor (advisor)
This master’s thesis is dealing with low-fatigue behavior of magnesium alloy AZ61, prepared via squeeze casting method. The main aim of this work was to obtain the basic mechanical properties as well as the low cycle fatigue data. Additional metallographical evaluation of microstructure and fractographical analysis after fatigue tests was made.
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Creep Behaviour of Aluminium after Severe Plastic Deformation (ECAP)
Král, Petr ; Dvořák, Jiří ; Svoboda, Milan ; Sklenička, Václav
In this work the behaviour of ECAP aluminium with different number of passes at the creep tests was studied. The data indicated that an increase fraction of high angle boundaries has a strong effect on the creep properties of ECAP aluminium which can be explained by extensive grain boundary sliding contributing to the total creep deformation. However, the samples of ECAP aluminium with the identical number of ECAP passes showed significant differences of creep properties. The observed scatter in the creep behaviour is probably a direct consequence of different microstructures in the as-pressed state after ECAP.
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Influence of Microstructure Changes on the Mechanical Behaviour of Aluminium Processed by ECAP Method
Král, Petr ; Dvořák, Jiří ; Svoboda, Milan ; Sklenička, Václav
Extremely coarse – grained aluminium (99.99 %) was subjected to severe plastic deformation (Equal-Channel Angular Pressing) at room temperature. The properties of the ECAP material may considerably differ from properties of material with a standard coarse grain size. The largest changes of microstructure take place during the first four ECAP passes. Thus, the microstructure after twelve passes consists of roughly equiaxed grains (~m) with high fraction of high angle boundaries (~70%). In this work the behaviour of ECAP material with different number of passes at the tensile and creep tests has been studied. It is shown that ECAP aluminum provides a significant increase of the ultimate strength, however, there is low strain hardening during tensile deformation. The creep resistance of aluminum increased considerably already after one ECAP pass. However, repetitive ECAP pressing lead to a noticeable degrease in the creep properties. ECAP microstructure was examined in terms of the inhomogeneity. The results indicate that an inhomogeneity of the ECAP microstructure may influence the creep behaviour of the ECAP material.
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Propagation of inclined cracks to the interface of ceramic laminates
Novotná, Lenka ; Trunec, Martin (referee) ; Chlup, Zdeněk (advisor)
Composite materials with laminated structure provide advantages which are utilised during component design. Low density, temperature and chemical stability are the profitable properties predetermining application of ceramic laminates. The main obstacle for wide spread of ceramic materials is their inherent brittleness. Therefore, in this thesis, the crack propagation in ceramics laminates has been extensively studied. Laminated structures with various volume fractions of components (alumina and zirconia) were prepared by electrophoretic deposition. Evaluation of crack propagation through the interface and determination of basic mechanical properties was conducted on the basis of extensive literature search. Crack deflection originated in both presence of internal stresses and differences in elastic modulus during the crack interface passing was monitored. A special type of specimen geometry was employed with the aim to set arbitrary angle between crack and interface. It was experimentally found that the degree of crack deflection is dependent on entering angle and volume fraction of components. Higher crack deflection was already found in the bulk of the test piece comparing to the test piece surface. The 3D fracture surface reconstruction generated using laser confocal microscopy was used in this detailed crack propagation study. Further basic elastic and strength characteristics of laminates were determined and compared to those obtained from monolithic materials. The validity of the mix rule for elastic characteristics was confirmed by comparing of elastics modulus. The most reliable method for elastic modulus determination was marked the dynamic resonance method due to low scatter and consistency in measurement. The flexural strength of all laminates tends to be close to the flexural strength of the weakest component. Therefore the mix rule is not applicable for flexural strength estimation on the contrary of elastic characteristics. The change of component volume fraction leads only to change of flexural strength scatter. Thanks to gained knowledge about crack propagation and basic characteristic determination will be possible to design ceramic laminates more efficiently for given needs of application.
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