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Kritérium stability bi-materiálového vrubu se dvěma singularitami
Klusák, Jan
Interfaces with a step change of material properties occur often in technical constructions. In combination with a sharp notch it usually leads to singular stress distribution in a vicinity of such a wedge. The existence of two singularities seems to be the main problem within study of this stress concentrator. The other problem is that each singularity does not correspond to particular mode of loading. The presented contribution studies stress distribution in a bi-material wedge vicinity and shows a method of solution of the problems in case of existence of multiple stress singularity
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The structural and the fundamental mechanical properties of intermatallics on the base of TiAl
Krahula, Karel ; Dlouhý, Ivo
Gamma TiAl alloys are emerging as a pervasive structural material. Remarkable progresses have been made through refining lamellar microstructure and grains, microalloying, chemistry modification, process development and/or their combination. The main thrust was to enhance resistance to creep deformation, oxidation and high cycle fatigue deformation/failure. Less or even no knowledge have been obtained in the field of the intermetalics fracture at uniaxial or bending loading, there are missing data about their behaviour at the presence of cracks and other defects. The reason is simply in the other properties that are key from application point of view. Due to their brittleness at temperature close to room temperature the investigation of the intermetalics fracture is complicated but promissible provided it bring ideas for the further development of the alloying and microstructure. The paper is focused on the first steps in this field.
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Rheological properties of binders
Hotař, Petr ; Fišer,, Jiří (referee) ; Kudrna, Jan (advisor)
The comparison of rheological properties (complex shear modulus and phase angle and dynamic viscosity) of four paving bitumens and two polymer modified bitumens is performed in this diploma thesis. Furthermore, the empirical tests (needle penetration and softening point) were determined on these binders. Effect of asphalt binders aging was modeled using RTFOT test and modified RTFOT test (3 x RTFOT).
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Influence of a particullar heat on properties and structure of duplex steel welded joint
Němec, Karel ; Kubíček, Jaroslav (referee) ; Daněk, Ladislav (advisor)
The research project is focused on an influence of a particullar heat on properties and structure of duplex steel DIN 1.4462. Samples prepared by using different welding speeds 10, 15, 20, 25, 30 cm.min-1, were tested for tensile, metalographical analysis and hardness test. Experimental results proved the optimal welding speed for material with 2 mm thickness to be 15 cm.min-1. Usage of lower speed 10 cm.min-1 led to formation of hot cracks while higher speeds 20, 25, 30 cm.min-1 didn‘t cause material penetration.
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Analysis of Iron-Phosphorus Reaction Products Formation During Heat Treatment Processes
Skoumalová, Zuzana ; Jan, Vít (referee) ; Doležal, Pavel (advisor)
During high pressure pulsation tests repeated cracks of CP3. housings occur. High pressure pump CP3 is part of injection system Common Rail. Cracks can be caused by segregation of phosphorous from a washing medium on grain boundaries during subsequent heat treatment process. The present master´s thesis focuses on analysis of phosphorous compounds on specimen surface made from steel 20MnCr5, which were soaked in solutions with different concentration of phosphorous. Master’s thesis is also focused on potencial influence of phosphorous on structure and properties of this material. The first part of the thesis provides a summary of current knowledge in the studied field, experimental results can be found in the second part. The surface analysis XPS, the light microscopy, the scanning electron microscopy equipped by energy dispersive chemical analysis, the glow discharge optical emission spectroscopy, the methods of the phase analysis by means of the X-ray diffraction and impact test were used.
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