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Influence of notches under cyclic high-frequency fatigue loading
Kozáková, Kamila ; Ševeček, Oldřich (referee) ; Klusák, Jan (advisor)
The diploma thesis deals with the evaluation of the lifetimes of smooth and notched specimens. The comparison of their lifetimes is focused on the case of high-frequency cyclic loading in the area of high-cycle and gigacycle fatigue of materials. The theory of critical distances is used to evaluate and recalculate the life curves of the notched specimens. The effect of the notch is quantified using the Line method. The critical length parameter is determined so that the life curve of the notched specimens corresponds to the curve measured on smooth specimens. The result is the dependence of the critical length parameter on the number of cycles to fracture. Knowledge of critical length parameters can be used to determine the lifetime of notched specimens as well as real notched components using the results of fatigue tests of smooth specimens.
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Determination of Fatigue Characteristics of Concrete Using Fracture-Mechanics Parameteres
Šimonová, Hana ; Králik,, Juraj (referee) ; Terzijski, Ivailo (referee) ; Bílek,, Vlastimil (referee) ; Keršner, Zbyněk (advisor)
The topic of this PhD. thesis is the issue of determining fatigue characteristics of selected cement-based composites. First, the history of fatigue of metal is mentioned, and some basic notions related to fatigue are clarified. The thesis also summarizes current research in the field of cement-based composites fatigue, and failure mechanisms of plain concrete during static and dynamic tests are described. Furthermore, the thesis deals with the evaluation of static and dynamic experiments’ results with extensive series of C30/37 and C45/55 class concrete specimens. In order to achieve relevant fatigue test evaluation which takes into account the age of the specimens, a new correction procedure of the data measured based on the approximation of the basic fracture-mechanics parameters of tested materials over time was suggested and verified. The annexes of this thesis present complete data obtained during static and dynamic experiments.
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Fatigue properties of EN-AW 7020 aluminium alloy
Kuběna, Martin ; Němec, Karel (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis focuses on the fatigue properties of wrought aluminum alloy EN-AW 7020. The theoretical part deals with the properties and use of aluminum alloys and metal response to cyclic loading. The experimental section is concerned with the structure of alloy EN-AW 7020 and its mechanical properties, especially fatigue characteristics. The goal is to construct S-N curves in the high- and low-cycle region and determine the fatigue endurance limit at 10^8 cycles.
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Fatigue properties of structural steel 11 523
Kudelka, Martin ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis studies the mechanical properties of steel 11 523 in the state after normalization annealing. Its purpose is an assessment of the structure in material and determination of static and fatigue characteristics. In the theoretical part of thesis, there is explained, how to divide and mark kinds of steel. There is also a mention about basic parameters of material and the main attention is paid to fatigue and its laws. The metallographic analysis, tensile test and the fatigue test were realized in the experimental part of thesis. Experimentally determined values were compared with data in the literature.
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Influence of notches under cyclic high-frequency fatigue loading
Kozáková, Kamila ; Ševeček, Oldřich (referee) ; Klusák, Jan (advisor)
The diploma thesis deals with the evaluation of the lifetimes of smooth and notched specimens. The comparison of their lifetimes is focused on the case of high-frequency cyclic loading in the area of high-cycle and gigacycle fatigue of materials. The theory of critical distances is used to evaluate and recalculate the life curves of the notched specimens. The effect of the notch is quantified using the Line method. The critical length parameter is determined so that the life curve of the notched specimens corresponds to the curve measured on smooth specimens. The result is the dependence of the critical length parameter on the number of cycles to fracture. Knowledge of critical length parameters can be used to determine the lifetime of notched specimens as well as real notched components using the results of fatigue tests of smooth specimens.
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|
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Determination of Fatigue Characteristics of Concrete Using Fracture-Mechanics Parameteres
Šimonová, Hana ; Králik,, Juraj (referee) ; Terzijski, Ivailo (referee) ; Bílek,, Vlastimil (referee) ; Keršner, Zbyněk (advisor)
The topic of this PhD. thesis is the issue of determining fatigue characteristics of selected cement-based composites. First, the history of fatigue of metal is mentioned, and some basic notions related to fatigue are clarified. The thesis also summarizes current research in the field of cement-based composites fatigue, and failure mechanisms of plain concrete during static and dynamic tests are described. Furthermore, the thesis deals with the evaluation of static and dynamic experiments’ results with extensive series of C30/37 and C45/55 class concrete specimens. In order to achieve relevant fatigue test evaluation which takes into account the age of the specimens, a new correction procedure of the data measured based on the approximation of the basic fracture-mechanics parameters of tested materials over time was suggested and verified. The annexes of this thesis present complete data obtained during static and dynamic experiments.
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Fatigue properties of structural steel 11 523
Kudelka, Martin ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis studies the mechanical properties of steel 11 523 in the state after normalization annealing. Its purpose is an assessment of the structure in material and determination of static and fatigue characteristics. In the theoretical part of thesis, there is explained, how to divide and mark kinds of steel. There is also a mention about basic parameters of material and the main attention is paid to fatigue and its laws. The metallographic analysis, tensile test and the fatigue test were realized in the experimental part of thesis. Experimentally determined values were compared with data in the literature.
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Fatigue properties of EN-AW 7020 aluminium alloy
Kuběna, Martin ; Němec, Karel (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis focuses on the fatigue properties of wrought aluminum alloy EN-AW 7020. The theoretical part deals with the properties and use of aluminum alloys and metal response to cyclic loading. The experimental section is concerned with the structure of alloy EN-AW 7020 and its mechanical properties, especially fatigue characteristics. The goal is to construct S-N curves in the high- and low-cycle region and determine the fatigue endurance limit at 10^8 cycles.
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Fatigue parameters of cement based composited: measuring and modeling
Keršner, Z. ; Seitl, Stanislav ; Pukl, R.
This paper introduces the basic fracture mechanics parameters of advanced building materials –selected glass fibers reinforced cement based composites and their fracture and fatigue behavior is investigated. Specimens tested were prepared as high performance concrete/mortar developed by ZPSV, a.s. company for production of thin-walled panels/elements. The dosage of cement CEM I 42.5R Mokra was 1000 kg per m3 of fresh mixture, water to cement ratio was 0.28, superplasticizer Spolostan; sand aggregates of 4 mm maximum size were used. . Alkali-resistant glass fibers (glass with high content of zirconium oxide) are applied with a dosage of 5 kg per m3. The introductory study was introduced by the authors, the study is performing in matter of the project Basic fatigue characteristic and fracture of advanced building materials.
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