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Basic Mechanism of Fatigue and Combined Fatigue/Creep Damage of Ni-based Superalloys MAR-M 247 and IN 713LC
Horník, Vít ; Kohout, Jan (referee) ; Pantělejev, Libor (referee) ; Kunz, Ludvík (advisor)
The thesis is focused on clarifying fatigue damage mechanisms and fatigue-creep damage mechanisms of MAR-M 247 and IN 713LC polycrystalline Ni-based superalloys. This thesis begins with basic information about nickel-based superalloys and their microstructure, followed by a description of fatigue and creep mechanisms and their mutual interaction. The next part contains experimentally obtained results describing the behavior of MAR-M 247 and IN 713LC superalloys under various sets of conditions. Three testing temperatures - 800, 900 and 950 °C were used for the measurement of fatigue properties under symmetrical loading cycle, because in the temperature range 800 – 950 °C, the mechanism of fatigue crack propagation of both superalloys should change from the originally crystallographic at "lower" temperatures (800 °C) to non-crystallographic at "higher" temperatures (950 °C). In addition the effect of processing technology on fatigue properties was studied on the superalloy IN 713LC. High-frequency cyclic loading (about 120 Hz) with high mean stress at elevated temperatures was applied to induce fatigue-creep interaction. The combined fatigue-creep loading was performed on the IN 713LC superalloy at 800 °C and on the MAR-M 247 superalloy at 900 °C.
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Safety factor evaluation for an out-of-plane frame under static loading
Málek, Michal ; Profant, Tomáš (referee) ; Burša, Jiří (advisor)
This bachelor thesis deals with evaluation of safety factor of a space frame when being statically loaded. This examination was demonstrated on a particular example. In order to solve the above mentioned, we exploit the frame symmetry. Unknown parameters were identified from deformation conditions in the point of intersection of the symmetry plane and the frame centreline, where the shift and two turning angles equal zero, and further by means of Maxwell- Mohr variant of Castigliano's theorem for determination of the frame deformation. The basis for calculations of stresses was represented by the theory of combined bar loading, particularly combination of bending and torsion. When examining the frame safety we took into consideration mainly dangerous points possibly occuring through cranks and fixed supports, where stress concentration occurs. The results of analytical solution were verified by numerical calculation in program ANSYS 10.0.
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Basic Mechanism of Fatigue and Combined Fatigue/Creep Damage of Ni-based Superalloys MAR-M 247 and IN 713LC
Horník, Vít ; Kohout, Jan (referee) ; Pantělejev, Libor (referee) ; Kunz, Ludvík (advisor)
The thesis is focused on clarifying fatigue damage mechanisms and fatigue-creep damage mechanisms of MAR-M 247 and IN 713LC polycrystalline Ni-based superalloys. This thesis begins with basic information about nickel-based superalloys and their microstructure, followed by a description of fatigue and creep mechanisms and their mutual interaction. The next part contains experimentally obtained results describing the behavior of MAR-M 247 and IN 713LC superalloys under various sets of conditions. Three testing temperatures - 800, 900 and 950 °C were used for the measurement of fatigue properties under symmetrical loading cycle, because in the temperature range 800 – 950 °C, the mechanism of fatigue crack propagation of both superalloys should change from the originally crystallographic at "lower" temperatures (800 °C) to non-crystallographic at "higher" temperatures (950 °C). In addition the effect of processing technology on fatigue properties was studied on the superalloy IN 713LC. High-frequency cyclic loading (about 120 Hz) with high mean stress at elevated temperatures was applied to induce fatigue-creep interaction. The combined fatigue-creep loading was performed on the IN 713LC superalloy at 800 °C and on the MAR-M 247 superalloy at 900 °C.
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Safety factor evaluation for an out-of-plane frame under static loading
Málek, Michal ; Profant, Tomáš (referee) ; Burša, Jiří (advisor)
This bachelor thesis deals with evaluation of safety factor of a space frame when being statically loaded. This examination was demonstrated on a particular example. In order to solve the above mentioned, we exploit the frame symmetry. Unknown parameters were identified from deformation conditions in the point of intersection of the symmetry plane and the frame centreline, where the shift and two turning angles equal zero, and further by means of Maxwell- Mohr variant of Castigliano's theorem for determination of the frame deformation. The basis for calculations of stresses was represented by the theory of combined bar loading, particularly combination of bending and torsion. When examining the frame safety we took into consideration mainly dangerous points possibly occuring through cranks and fixed supports, where stress concentration occurs. The results of analytical solution were verified by numerical calculation in program ANSYS 10.0.
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A study of bi-material notches under a combined loading mode
Kopp, Dalibor ; Klusák, Jan
In the range of linear elastic fracture mechanics, the conditions for critical loading assessment of structures made of two dissimilar materials are usually based on the assumptions of a prevailing normal mode of loading. The same assumption is usually applied to the stability criterion of bi-material notches. However, in engineering practice there are cases of loading and failure close to the shear mode. The aim of the work is the study of the stress distribution in the vicinity of a bi-material notch subjected to a combination of normal and shear modes of loading. Further, the assessment of crack initiation from the stress concentrator is shown.
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Loading processes with various spectral properties for fatigue tests
Balda, Miroslav
The paper describes mothods used for generating of Gaussian proceses with prescribed spectral densities and their implementation on electro-hydraulic testing machines for combined loading. Tube speciments were loaded by random forces and in torgue by diferent proceses. Since the machine does not interpret input proceses precisely, the actual proceses were measured, iterated and procesed into a complex damaging stres and its spectral properties.
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An influence of prestress by combined random loading
Svoboda, Jaroslav ; Balda, Miroslav ; Fröhlich, Vladislav
The contribution deals with findings concerning an influence of static load in combination with random dynamic torgue on fatigue life of tube specimens made out of the steel ČSN 411523.1. A generalized formula has been found for fatigue life expressed in a number of loading blocks of torgue process as a function of its standard deviation. It joins both components of the combined loading in one expression. The formula yields very precise estimates of fatigue lives.
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An influence of normal static prestress on fatigue life construction by torsional random loading
Fröhlich, Vladislav ; Balda, Miroslav ; Svoboda, Jaroslav
Definition influence static prestress on fatigue life for case that uniaxial harmonic loading is in literature enough noted and isn't problem influence those components to the calculation of life constructional whole include. Complicated is it in the event of multiaxial loading of different character and especially in cases, when has this loading random character. In the workplace CDM in Pilsen we are already on basis results for Skoda Power Inc . implementation few experiments on piped figure with opening, loading combination normal and torsional load, during which time one of the applied load was election constant and second are harmonic with zero mean value dynamically impact. Along competitive examinations we watcht place of rice cracks.
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