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Fatigue properties of materials prepared by SLM method
Hanáček, Josef ; Pantělejev, Libor (referee) ; Štěpánek, Roman (advisor)
This work deals with description of SLM (Selective Laser Melting) method, which is one of ALM (Additive Layer Manufacturing) method. In first part the general laws of fatigue and SLM method are described. The second part deals with the influence of processing parameters to final properties of material. The main goal of work is to determine dependence between processing parameters and mechanical properties of SLM processed components. Special attention is dedicated to fatigue properties.
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Mechanical properties of magnesium alloy AZ91E prepared by ECAP method
Darida, Jiří ; Válka, Libor (referee) ; Pantělejev, Libor (advisor)
This thesis deals with mechanical and fatigue properties of magnesium alloy AZ91 processed by EX-ECAP method. This method involves the application of extrusion followed by equal-channel angular pressing. To obtain basic mechanical characteristics, the tensile test were carried out at room and elevated temperatures. Further the fatigue tests were performed and obtained data were used to compile S-N curve. The work also includes metallographics analysis of microstructure and fractographic analysis of fracture surfaces of tensile and fatigue test specimens.
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Kinetics of Short - crack Growth in Superduplex Steel
Bártová, Lenka ; Pantělejev, Libor (referee) ; Polák, Jaroslav (advisor)
The fatigue life and the kinetics of short crack growth in specimen of austenitic-ferritic duplex steel cycled with constant stress amplitude and different mean stresses is studied. Fatigue life was determined on smooth cylindrical specimens. Strain amplitude and mean strain were recorded. Short crack growth was studied in cylindrical specimens with a shallow notch. Cyclic straining was interrupted and crack length was measured using an optical microscope mounted on the testing machine. Crack length and crack growth rates were evaluated. The effect of the mean stress on the rate of short cracks and fatigue life were discussed.
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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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Propeller fan damage analysis
Vašáková, Kristýna ; Štěpánek, Roman (referee) ; Pantělejev, Libor (advisor)
This bachelor’s thesis deals with propeller fan damage analysis, which is used for air blasting of recycled glass wool. In the frame of experimental work the fractographic analysis for evaluation of damage mechanisms was performed. Further, material analysis for assessment of the material grade (chemical and metallographic analyses) was conducted. Measurement of Vickers hardness with low load was performed for determination of mechanical properties of used materials.
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Microstructural stability of materials prepared by aditive manufacturing methods
Hyspecký, Michal ; Pantělejev, Libor (referee) ; Štěpánek, Roman (advisor)
This work deals with the microstructural thermal stability of material 2618 produced by the Selective Laser Melting metho - SLM. Microstructural stability is compared with the stability of material produced by conventional methods. Stability itself is evaluated by changes of microstructure and microhardness. The main finding is that the sample produced by SLM method reached a microhardness of 125 HV 0.3 and after sixteen hours of annealing at 200 °C a decrease of only a few units to 120 HV 0.3 was recorded. Based on the data obtained, it was concluded that the sample produced by SLM method is structurally stable, as it did not occur any significant changes in the microstructure or in the observed mechanical properties. As a result, components produced by SLM method become usable in operation in places with an elevated temperature up to 200 °C (with a given choice of criteria).
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Mechanical-structural characteristics of multi-materials prepared by additive technologies
Hyspecký, Michal ; Válka, Libor (referee) ; Pantělejev, Libor (advisor)
The diploma thesis deals with the mechanical-structural characteristics of the multimaterial interface prepared by the additive cold-spray (CS) technology. In the experimental part of the work, the titanium alloy Grade 23 was applied to the surface of aluminum alloy EN AW 2618, after heat treatment T6. Furthermore, a separate bulky block made of Grade 23 alloys for the production of tensile bodies was created using the CS method. The sprays were evaluated in two planes perpendicular to each other, respectively in longitudinal and transverse section. The average porosity of the coatings was evaluated at 2,6 ± 0,6%. The hardness value at low load did not change significantly with increasing distance from the interface and the mean value was 347 ± 51 HV 0,3. The tensile test did not show a significant effect of the sample orientation on the resulting value of the yield strength, which had the diameter of 345 ± 12 MPa. Successful deposition takes place at the temperature of 1010 ° C and the pressure of 5 MPa. The achieved results of the mechanical properties of the coating determined on the basis of tensile tests are at a relatively good level. Therefore, it is possible to consider the use of coating by this method, under given conditions, for rotating components operating at elevated temperatures, and increase their efficiency or service life.
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