National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Design of optimal parameters of multilayer ceramic protective coating for high temperature applications
Dohnalík, Petr ; Hrstka, Miroslav (referee) ; Ševeček, Oldřich (advisor)
The main objective of this work was to design a suitable composition of a protective coatings, made of several different layers of specific materials - with respect to residual stress, induced due to a mismatch in thermal expansion coefficients of each layer. Protective coating in this work means both the thermal and the environmental barrier. These coatings protect components against high temperatures and harsh environment. In this work, necessary theoretical background in the field of the thermal and environmental barrier coatings is introduced. There are mentioned some basic design approaches, commonly used materials and processing methods for the coating structure. The literature review gives an overview of modeling of such coated structures, in particular it is devoted to the thermal barrier coatings deposited by air plasma spray process. The next chapter closely describes classical laminate theory used for calculation of residual stresses in the coating. One of the assumptions of this theory is homogenous temperature field through the coating’s thickness. However, in this work was revealed a way to extend the classical lamination theory of such cases, in which the temperatures vary along the thickness of the coating. In the practical part, the analytical model was used for designing suitable properties of some coatings, which were consists of two, three and four layers. The calculations were performed both for constant temperature and for the temperature gradient. All results obtained from analytical approach were verified by numerical calculations.
Linear elastic fracture mechanics and its application on study of composed materials
Dohnalík, Petr ; Ševeček, Oldřich (referee) ; Máša, Bohuslav (advisor)
The main objective of this bachelor thesis is the introduction to computational methods of fracture parameters of the crack, which terminates at the bi-material interface. The preface of the work deals with composites, where possible crack can grow in materials with different elastic properties. In this part advantages of composite materials are closely described and usual structure arrangements of the components are presented. The next part of this work is focused on the linear elastic fracture mechanics and available concepts for assessment of the body with presence of the crack in the homogenous material are described. These concepts are based on analytical expressions and, also, on numerical methods. This problem is furthermore extended in the next chapter by case, when the crack terminates perpendicularly to the bi-material interface. Here are given procedures, which can provide information about the further crack behaviour. In practical part all presented procedures have been used in order to evaluate the crack parameters in the homogenous material and for the crack terminating at bi-material interface. Necessary calculations were performed using the finite element method implemented in the commercial system ANSYS. Calculated results were compared and closely discussed in the conclusion.

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2 Dohnalík, Pavel
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