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Analysis of degradation processes of the shock absorber rod
Sýkorová, Jitka ; Juliš, Martin (referee) ; Klakurková, Lenka (advisor)
The bachelor thesis deals with the analysis of degradation processes of the rods of the synchronizer generator. The theoretical part deals with the description of the generator, the analysis of the material, the properties of the brass for the production of the absorber rod and the possible parameters influencing its degradation. The experimental part of the thesis analyzes damaged bars of the shock absorber using destructive and non-destructive techniques, suggests non-destructive testing in-field and determines the dependence of electrical properties on the structure.
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Thermomechanical and Isothermical Fatigue of Surface Treated Nickel Superalloys
Šulák, Ivo ; Pantělejev, Libor (referee) ; Polák, Jaroslav (referee) ; Obrtlík, Karel (advisor)
Yttria-stabilized zirconia-based thermal barrier coating systems are the most widely used commercial coatings in the industry, with practical applications in aircraft engines and land-based power turbines. The purpose of thermal barriers is primarily to protect the substrate from high temperatures and also to increase its oxidation resistance. Currently, concerning the relatively frequent volcanic eruptions and increasing air traffic intensity in desert areas, increased attention is being paid to the development of new thermal and environmental coatings that will withstand the so-called CMAS attack and still successfully meeting the strictest requirements of the aerospace industry. Two newly developed experimental coatings consisting of three successive layers have been developed for this work. The upper two layers are thermal insulating ceramic coatings, where two different uppermost coatings were deposited. The first uppermost layer of the coating is a mixture of mullite and hexacelsian in a ratio of 70/30 wt. %. The second upper most type of coating consists of Al6Si2O13 + MgAl2O4 + BaCO3 in a ratio of 6:3:1 wt. %. The interlayer is made of the commercially utilized yttria-stabilized zirconia. The metallic CoNiCrAlY coating, which is directly deposited on the nickel-based superalloy MAR-M247, fulfils a compensatory function between the mechanical properties of the nickel superalloy and the ceramic coating. The thermal and environmental barrier system was deposited using air plasma spraying (APS) technology. The main objective of this work was to evaluate the effect of the newly developed thermal and environmental barrier coating, which has a high potential for the protection of component surfaces in an aggressive environment, on isothermical and thermomechanical fatigue behaviour of nickel-based superalloy MAR-M247. Low cycle fatigue tests were performed in strain control mode with constant strain amplitude on both uncoated and TEBC coated superalloy. Fatigue hardening/softening curves, cyclic stress-strain curves and fatigue life curves in the representation of total strain amplitude, plastic strain amplitude and stress amplitude on the number of cycles to failure were obtained. Microstructural analysis of MAR-M247 superalloy and a newly developed experimental coating was performed in a scanning electron microscope. The fatigue crack initiation sites were identified and the process of fatigue crack propagation was described. The dislocation arrangement after fatigue loading of MAR-M247 was investigated in a transmission electron microscope. The findings of isothermical and thermomechanical low cycle fatigue behaviour of uncoated and TEBC coated MAR-M247 superalloy and identification of damage mechanisms presented in this dissertation will improve the estimation of safe-life that is particularly relevant to aircraft engines components.
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Thermomechanical and Isothermical Fatigue of Surface Treated Nickel Superalloys
Šulák, Ivo ; Pantělejev, Libor (referee) ; Polák, Jaroslav (referee) ; Obrtlík, Karel (advisor)
Yttria-stabilized zirconia-based thermal barrier coating systems are the most widely used commercial coatings in the industry, with practical applications in aircraft engines and land-based power turbines. The purpose of thermal barriers is primarily to protect the substrate from high temperatures and also to increase its oxidation resistance. Currently, concerning the relatively frequent volcanic eruptions and increasing air traffic intensity in desert areas, increased attention is being paid to the development of new thermal and environmental coatings that will withstand the so-called CMAS attack and still successfully meeting the strictest requirements of the aerospace industry. Two newly developed experimental coatings consisting of three successive layers have been developed for this work. The upper two layers are thermal insulating ceramic coatings, where two different uppermost coatings were deposited. The first uppermost layer of the coating is a mixture of mullite and hexacelsian in a ratio of 70/30 wt. %. The second upper most type of coating consists of Al6Si2O13 + MgAl2O4 + BaCO3 in a ratio of 6:3:1 wt. %. The interlayer is made of the commercially utilized yttria-stabilized zirconia. The metallic CoNiCrAlY coating, which is directly deposited on the nickel-based superalloy MAR-M247, fulfils a compensatory function between the mechanical properties of the nickel superalloy and the ceramic coating. The thermal and environmental barrier system was deposited using air plasma spraying (APS) technology. The main objective of this work was to evaluate the effect of the newly developed thermal and environmental barrier coating, which has a high potential for the protection of component surfaces in an aggressive environment, on isothermical and thermomechanical fatigue behaviour of nickel-based superalloy MAR-M247. Low cycle fatigue tests were performed in strain control mode with constant strain amplitude on both uncoated and TEBC coated superalloy. Fatigue hardening/softening curves, cyclic stress-strain curves and fatigue life curves in the representation of total strain amplitude, plastic strain amplitude and stress amplitude on the number of cycles to failure were obtained. Microstructural analysis of MAR-M247 superalloy and a newly developed experimental coating was performed in a scanning electron microscope. The fatigue crack initiation sites were identified and the process of fatigue crack propagation was described. The dislocation arrangement after fatigue loading of MAR-M247 was investigated in a transmission electron microscope. The findings of isothermical and thermomechanical low cycle fatigue behaviour of uncoated and TEBC coated MAR-M247 superalloy and identification of damage mechanisms presented in this dissertation will improve the estimation of safe-life that is particularly relevant to aircraft engines components.
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Analysis of degradation processes of the shock absorber rod
Sýkorová, Jitka ; Juliš, Martin (referee) ; Klakurková, Lenka (advisor)
The bachelor thesis deals with the analysis of degradation processes of the rods of the synchronizer generator. The theoretical part deals with the description of the generator, the analysis of the material, the properties of the brass for the production of the absorber rod and the possible parameters influencing its degradation. The experimental part of the thesis analyzes damaged bars of the shock absorber using destructive and non-destructive techniques, suggests non-destructive testing in-field and determines the dependence of electrical properties on the structure.
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Nanoindentation methods of evaluation of mechanical properties and behaviour and complex application for evaluation of technology and degradation
Štěpánek, Ivo ; Mertová, Andrea ; Šimečková, Lucie ; Štěpánová, Lucie ; Ulrychová, Monika
Nanoindentation methods used for evaluation surface layers are static indentation and scratch indentation too. Static indentation methods are used namely for evaluation hardness characteristics and for evaluation elastic deformation and plastic deformation of surface layers too based on measurement indentation curves - dependence depth indentation and normal force during all indentation process during loading and unloading. Cyclic and step by step indentation modes give possibilities to evaluate much more information about resistivity of surface layers to the indentation stress. Scratch indentation methods are used for evaluation namely adhesive cohesive properties and behaviour of surface layers with very small thickness or/and thin films with very low resistivity of thin films and low hardness. The surface layering is created by technology process of creation of thin films and surface treatment process or by initiation and evolution of degradation process and\nageing process. The initiation of degradation and ageing are evaluated in the starting stadium and in the next with step by step sensitive analysis of changing properties and behaviour. From this point of view static nanoindentation and scratch nanoindentation are very useful for analysis step by step changing of mechanical properties and behaviour with high sensitivity and depth resolution too. The paper presented utilization of nanoindentation static and scratch nanoindentation too for very different application in surface treatment but for evaluation of degradation and ageing process too.
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