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LOW CYCLE FATIGUE BEHAVIOR AND FATIGUE CRACK INITIATION IN MAR-M247 AT 700 °C
Šulák, Ivo ; Obrtlík, Karel ; Hrbáček, K.
The second generation nickel-based superalloy MAR-M247 offers a satisfying combination of fatigue and creep properties and oxidation and corrosion resistance that are required for application at elevated temperatures in hostile environments. The microstructure consists mainly of the face centred cubic γ matrix and ordered γ´ strengthening precipitates (L12 crystal structure). The present work focuses on low cycle fatigue (LCF) behaviour of polycrystalline nickel-based superalloy MAR-M247 at high temperature. LCF tests were conducted on cylindrical specimens in a symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 700 °C in ambient air. Cyclic stress-strain curves and fatigue life curves in the representation of plastic strain amplitude vs. stress amplitude and stress amplitude vs. the number of cycles to failure, respectively, were plotted and compared with data obtained on Inconel 713LC. Special attention was paid to the investigation of crack initiation in MAR-M247 during low cycle fatigue. Crack initiation sites were studied by means of scanning electron microscopy (SEM) in dual beam microscope TESCAN LYRA 3 XMU FESEM equipped with focus ion beam (FIB). Specimens’ surface observations revealed the formation of pronounced surface relief indicating localisation of plastic deformation. Observations in transmission electron microscope (TEM) confirmed localisation of cyclic plastic deformation in persistent slip bands along {111} slip planes. Fractographic analysis revealed fatigue crack initiation sites. Fatigue crack propagation in stage I was typical of smooth facets up to 500 μm long.
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Influence of residual stress on pressure vessel part fatigue life
Boleloucký, Václav ; Vincour, Dušan (referee) ; Létal, Tomáš (advisor)
This bachelor’s thesis deals with the impact of a residual stress, caused by an applied cyclic pressure, on fatigue life of a pressure vessel part (flat end–cylinder connection). Bachelor’s thesis includes the design of the pressure vessel according to CSN EN 13 445 regulations, analytical solution in Maple software, from which stresses and deformations are determined. Then the results of the analytical approach are firstly verified by a FEM modelling in ANSYS Workbench software and secondly compared to each other in graphs and discussed. From the values of stresses in FEM, analysis fatigue life expectations are calculated with the respect to CSN EN 13 445 regulations, for two cases. First one, where a pressure test is applied and second one, where the pressure test is not applied before the pressure vessel is put into service. In the conlusion the obtained results are discussed.
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The High Pressure Fuel System Application for CI-engine
Ševčík, Ondřej ; Prokop, Aleš (referee) ; Dundálek, Radim (advisor)
This thesis focuses on the design of new high pressure injection system application on diesel engine. The design came from company Zetor’s demands. For this application was chosen system Common Rail supplied by company Bosch. Assignment was separated into several tasks. Research of suitable components for low pressure section, design of waste system and high pressure injection tubes design including injector clamping. Due to injectors used in this system was necessary to redesign cover for valves and even new system to lead wires from outside of the engine to injectors. Injector is attached by screw connection, which is composed from screw and clamping jaw. These parts are subjected to an analytic calculations. Clamping jaw of injector is even subjected to a FEM analysis, which focuses on fatigue life. Finally, the drawings were documented.
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Hydraulic part of plunger pump adjustment for higher pressures
Dvořák, Petr ; Klas, Roman (referee) ; Habán, Vladimír (advisor)
First part of the master thesis is about displacement pump. Second part is about power plunger pumps. In the third part are equations for power plunger pumps. In the last part the strength calculation of the proposed hydraulic part of the plunger pump was performed using the finite element method in ANSYS. The screw fatigue life is also calculated here. At the end of this section, ANSYS Fluent flow calculation is performed in the suction valve area.
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Development of loading spectra and fatigue life analysis of small two-seat composite aircraft
Daňko, Matúš ; Juračka, Jaroslav (referee) ; Augustin, Petr (advisor)
Primary goal of this thesis is to present proposed method for fatigue life evaluation applicable to light composite aircraft. The first chapter of this thesis is focused on certification specifications and requirements for fatigue life proof of structure. Significant part of this thesis is dedicated to fatigue life evaluation and guideline how to proceed in evaluation of fatigue data. Thesis also points out on possible methods of statistical fatigue data analysis and critical parts of structure in means of fatigue life. The last part of thesis is focused on design of experimental evaluation of structure including test rig and load sequence. This chapter also provides inside into possible means of introducing artificial defects into the structure.
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High cycle fatigue life of Ti6Al4V alloy produced by direct metal laser sintering
Konečná, R. ; Nicoletto, G. ; Bača, A. ; Kunz, Ludvík
High cycle fatigue life of Ti6Al4V alloy specimens manufactured by Direct Metal Laser Sintering (DMLS) was experimentally determined. The DMLS fabrication process was characterized by a 400 W laser power and 50 micrometer layer melted thickness. Post-fabrication heat treatment consisted in stress relieving for 3 h at 720 °C in vacuum with subsequent cooling in argon atmosphere. Fatigue testing of specimens oriented in three different directions with respect to the material build direction was performed with the aim to examine the influence of the layered microstructure on the fatigue behavior. Results of measurement of surface roughness, metallographic examinations of the layered material and fractographic investigation of the fatigue fracture surfaces were employed in the discussion of fatigue crack initiation in DMLS fabricated Ti6Al4V alloy.
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The fatigue life of steel specimens under axial, torsional and combined axial-torsional loading
Mička, Jan ; Horníková, Jana (referee) ; Slámečka, Karel (advisor)
The master’s thesis deals with the fatigue life prediction under multiaxial cyclic loading. First, the fatigue process is discussed and the methods for fatigue life prediction under uniaxial and multiaxial loading are described. In the practical part, the accuracy of selected criteria is assessed based on experimental data obtained on cylindrical samples made of 1.2210 steel that were tested under synchronous symmetric axial-torsion loading. Application of criteria requires to determine the fatigue strength under pure axial and torsional loading.
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Strength control of bicycle crank assembly
Kolenčík, Richard ; Skalka, Petr (referee) ; Burša, Jiří (advisor)
This bachelor thesis is intent on strength-deformation check of bicycle crank assembly. The first part is devoted to check safety of fatigue failure of crank bicycle, which is loaded with combination loading. The second part is devoted on safety analysis of fatigue failure in the case of pedal. Because of low safety´s coefficient is made calculation of high cyclic life of pedal. The last section is devoted to the calculation of maximum deformation of the crank assembly. The analytical calculation was performed by the software Matlab R2012b.
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Fatigue Life Evaluation of Composites Structures
Mihalides, Dušan ; Kopřiva, Tomáš (referee) ; Juračka, Jaroslav (referee) ; Klement, Josef (advisor)
The doctoral thesis deals with fatigue life evaluation of composites structures. The thesis pro-vides complex review of problematic and it is based on recent situation assessment. The main ob-jective of the thesis is to design the methodology of fatigue life evaluation of composites struc-tures. The designed methodology is applied to fatigue life evaluation of sailplane wing and propel-ler blades. One part of the thesis deals with laboratory fatigue tests of composite specimens which are intended for comparison of the effect of manufacturing technology and environment condition.
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Fatigue damage mechanism of MAR-M 247 superalloy
Jíša, Jakub ; Štěpánek, Roman (referee) ; Pantělejev, Libor (advisor)
The thesis deals with the fatigue resistance of material MAR-M 247 at temperatures of 650 °C, 800 °C and 900 °C. Based on the results obtained, curves of durability ("S/N curves") were drawn and the effect of temperature on the fatigue behaviour of nickel-based superalloys MAR-M 247 and IN713 LC was evaluated. Fractographic analysis was used to examine the failure mechanism and the effect of casting defects on the fatigue crack initiation.
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