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Elimination of degradation processes of metallic thin films
Danovič, Jakub ; Šubarda, Jiří (referee) ; Šimonová, Lucie (advisor)
This work deals with issues of thin films, their behaviour in different enviroments and protection of theese films against unwanted degradation processes. Metal thin films are made by special physical or chemical methods in the presence of vacuum. Deposition is performed on properly cleaned substrate made of different materials, for example glass, ceramics or another metal. Theese films degrades under the influence of moisture, heat and other. There are several types of films on different bases made to prevent thin films against degradation.
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Elimination of degradation processes of metallic thin films
Danovič, Jakub ; Šubarda, Jiří (referee) ; Šimonová, Lucie (advisor)
This work deals with issues of thin films, their behaviour in different enviroments and protection of theese films against unwanted degradation processes. Metal thin films are made by special physical or chemical methods in the presence of vacuum. Deposition is performed on properly cleaned substrate made of different materials, for example glass, ceramics or another metal. Theese films degrades under the influence of moisture, heat and other. There are several types of films on different bases made to prevent thin films against degradation.
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Numerical analysis of a surface crack propagation in protective layers
Majer, Zdeněk
The paper contains a numerical analysis of a surface crack propagation in an elastic surface layer. It was analysed an influence of elastic material parameters of both system components, initial length and orientation of crack on fatigue crack propagation direction. The typical behaviour of crack propagation in thin layers was described. The finite element method for determination of the direction of the farther crack propagation was used.
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Determination of threshold values of components with protective layers
Náhlík, Luboš ; Bareš, Pavel
The contribution is focused on the influence of existing fatigue cracks in protective layers on fatigue life of structures with protective layers. The problem is solved under conditions of linear elastic fracture mechanics with help of finite element method. Is shown, that in the case of the hard protective layer on the ductile substrate represents existing crack with its tip on the bi-material interface dangerous singular stress concentrator, because of decrease of threshold values of applied loading necessary for crack propagation. Knowledge of crack propagation in protective film is of paramount importance when studying potential failure of the substrate.
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Estimation of the Critical Stress for Failure of a Protective Layer
Náhlík, Luboš
This contribution describes a study of the behaviour of a crack growing in a protective layer and penetrating through an interface into a substrate. Special attention is devoted to a crack touching the interface. Conditions for the stability of a crack terminating at the interface between two materials are analyzed. The problem is studied under the assumptions of linear-elastic fracture mechanics. A new tentative criterion of stability based on application of the strain energy density concept is formulated and applied to the problem. The suggested criterion is used to estimate the critical applied stress for the failure of a substrate caused by a crack growing through the protective layer. It is shown that the critical stress may strongly depend on the fracture toughness of the substrate and on the bi-material parameters.
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Estimation of the Critical Stress for Failure of a Protective Layer
Náhlík, Luboš ; Knésl, Zdeněk
This contribution describes a study of the behaviour of a crack growing in a protective layer and penetrating through an interface into a substrate. Special attention is devoted to a crack touching the interface. Conditions for the stability of a crack terminating at the interface between two materials are analyzed. The problem is studied under the assumptions of linear-elastic fracture mechanics. A new tentative criterion of stability based on application of the strain energy density concept is formulated and applied to the problem. The suggested criterion is used to estimate the critical applied stress for the failure of a substrate caused by a crack growing through the protective layer. It is shown that the critical stress may strongly depend on the fracture toughness of the substrate and on the bi-material parameters.
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