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The Influence of the Isothermal Transformation Dwell on the Structure and Mechanical Properties of ADI
Falta, Petr ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
The thesis ,,The Influence of Transformation dwell on the Structure and Mechanical Properties of ADI´´ deals with problems of optimal properties of the unalloyed nodular cast iron, which are obtained by the heat treatment. The heat treatment consists of austenitization and then rapidly quenching to the transformation temperature, isothermal transformation and water cooling in the end. The aim of the thesis is focused on estimating the influence of isothermal transformation on the content of stabilized austenite, static mechanical properties and on the fatigue properties in high-cycle fatigue region for selected samples. The theoretical part of this work analyses the production of the nodular cast iron and its possibilities of the heat treatment, final technological and mechanical properties. Furthermore, it examines the conditions of austempering (temperature and time of isothermal dwell), which has a fundamental influence on mechanical properties of ADI. Problems of fatigue properties are described at the end of this part. The experimental part contains a chemical composition of studied samples and their metallographic analysis. Among others the basic mechanical static properties were determined as well as the Wöhler curves including values of fatigue limits for ten on seventh cycles. Wöhler curves were obtained by a mathematical processing using data reached by fatigue tests.
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Low Cycle and High Cycle Fatigue Properties of Austempered Ductile Iron
Zapletal, Josef ; Bokůvka, Otakar (referee) ; Kunz, Ludvík (referee) ; Věchet, Stanislav (advisor)
The thesis is focused on assessment of fatigue behaviour of austempered ductile iron with nodular graphite. Optimal period of transformation was determined based on the best combination of stress and strain characteristics established by tensile test. Cyclic response and low-cycle fatigue life were studied under both stress-control and longitudinal strain-control mode at room temperature. For both modes, shapes of cyclic hardening curves are dependent on stress amplitude. Cyclic deformation curves (CDC) were fitted by power regression function. Results were compared with CDC established by multiple step test in both modes with verification of the influence of cyclic creep (high stress levels, stress-control mode). Experimental data of S-N curves are in agreement with the Manson-Coffin and the Basquin law. Fatigue and cyclic parameters were compared. Fatigue life time in high-cycle fatigue region was determined. Experimental data were fitted by suitable regression functions. Regression parameters and fatigue limit were established by means of each regression function. Experimental data in low- and high-cycle fatigue regions were used to construct S-N curve and to determine relevant parameters. Discontinuity of experimental data was not observed. Low-cycle fatigue behaviour was predicted. Approximation of tolerance bands was realized in high-cycle and both high and low cycle fatigue regions.
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Color metallography of foundry alloys
Nekuda, Pavel ; Záděra, Antonín (referee) ; Kaňa, Václav (advisor)
The theoretical part of the diploma thesis deals with the preparation and application of the most common color etchants and in the practical part, the applicability of selected reagents is tested. The obtained results are compared with the findings obtained from previous research works. Attention was mainly focused on etching samples of alloyed cast irons with Beraha's I, Beraha-Martensite and Beraha's CdS reagents in order to find the optimal method of color etching of austempered ductile iron. These samples differed in their chemical composition and wall thickness of the initial Y-block. Image analysis was also performed, where the sizes of the individual color areas, obtained by the Beraha's I reagent, were determined on the microstructures. The practical part of the thesis also deals with the application of Weck's reagent on two samples of AlSi7Mg silumin, while only one of them was heat treated.
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Rich Internet Application in PLC PFC200
Michalík, David ; Kaczmarczyk, Václav (referee) ; Arm, Jakub (advisor)
This bachelor’s thesis is mainly focused on implementation of our own means of controlling a PLC PFC200, made by Wago company, through a dynamic website application. This thesis includes basic information about PLC, known means of controlling it, a list of available web servers for Linux operating systems and a description of how to create our own real-time control. Result of this thesis is a web application running on a webserver inside the PLC using our own runtime system in a form of daemon programs.
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Structural and Mechanical Characteristics of Nickel-Alloyed Ductile Cast Iron
Tesařová, Hana ; Kohout, Jan (referee) ; Kruml, Tomáš (referee) ; Konečná,, Radka (referee) ; Pacal, Bohumil (advisor)
The aim of this dissertation work is the evaluation of the influence of nickel alloying on the structure and mechanical properties, both monotonic and dynamic, of nodular cast iron with ferritic and bainitic matrix. Two chock melts with 0.5 and 2.7 % Ni were used to study the nickel influence. The quantitative evaluation of structure of these melts using image analysis was done and basic tensile mechanical properties were determined. Subsequently, the time optimization of two-stage ferritic annealing and isothermal austempered heat treatment at 375 °C was performed with the aim to obtain optimal ferritic and bainitic structures with best static and dynamic mechanical properties. After ferritic annealing the nickel alloying contributes to substitution hardening of ferritic matrix which positively affects its strength and other mechanical properties. The higher nickel content in the bainitic structure causes the shift of phase transformation times to longer times which results in restricted production of small carbides and in bigger volume of retained austenite. These features were confirmed by observation in transmission electron microscope. Precise tensile and low cycle fatigue tests at temperatures 23 and – 45 °C were performed on the optimized structures of both nodular cast irons. As a result of the notch effect of graphite nodules, microplastic deformation of both nodular cast irons was observed at stresses which were lower than the yield stress. The Hollomon's equation very well describes the individual parts of tensile curves for both nodular cast irons including their mutual comparison. From the low cycle fatigue tests, the cyclic hardening/softening curves, the evolution of elastic modulus and hysteresis loop shape parameters, cyclic stress-strain curves and fatigue life curves were obtained for both temperatures and materials. Moreover, the decrease of retained austenite volume was measured by neutron diffraction and the evolution of surface relief was characterized during cyclic straining for both austempered nodular cast irons at both temperatures. On the basis of these results both cyclic plasticity and fatigue degradation mechanisms in relation to the cyclic strain localization were described for both nodular cast irons.
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Mechanical properties of Nodular Cast Iron prepared by method Tundish and process Initek
Vítek, Radovan ; Hotový, Ivan (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis deals with a properties and production of nodular cast iron. The first section describes the classification, distribution and structure of nodular cast iron. The second part is focuses on the description of nodular cast iron, modification, inoculation and production. A strong effort is made on the production of nodular cast iron using the Tundish Cover method and the Initek process. In conclusion, the structure of the material is evaluated on samples that were delivered for metallographic analysis. The final evaluation of the structure of the material is used to compare the mechanical properties of a nodular cast iron produced by Tundish Cover method and Initek process.
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Color metallography of foundry alloys
Nekuda, Pavel ; Záděra, Antonín (referee) ; Kaňa, Václav (advisor)
The theoretical part of the diploma thesis deals with the preparation and application of the most common color etchants and in the practical part, the applicability of selected reagents is tested. The obtained results are compared with the findings obtained from previous research works. Attention was mainly focused on etching samples of alloyed cast irons with Beraha's I, Beraha-Martensite and Beraha's CdS reagents in order to find the optimal method of color etching of austempered ductile iron. These samples differed in their chemical composition and wall thickness of the initial Y-block. Image analysis was also performed, where the sizes of the individual color areas, obtained by the Beraha's I reagent, were determined on the microstructures. The practical part of the thesis also deals with the application of Weck's reagent on two samples of AlSi7Mg silumin, while only one of them was heat treated.
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Interaction between a teacher and a student in the group-form method of teaching skiing
Jedličková, Eva ; Matošková, Petra (advisor) ; Süss, Vladimír (referee)
Title: Interaction between a teacher and a student in the group-form method of teaching skiing Objectives: The aim of this thesis is to compare the interaction between the teacher and the student in the process of teachig skiing in the foreign ski schools. Methods: In our thesis we used the method of observation with utilization of categorial system according to the standardized method MADI (modificated analysis of didactic interaction). This method involves seven categories describing forms of behaviour of a teacher, didactic content of training, didactic situation and the postural activity. Results: The teachers' profiles were proved to be different, which was caused primarily by the amount of experience and partially by the gained education. The results showed that the main differences were manifested at the teacher number three who gained the shortest practices. This teacher diametrically differs in all examined categories from other teachers. Between the other two teachers there were found differences as well, but not essential. The teacher number three commited many didactitc faults. Some of his forms of behaviour, demonstration and action were not coherent with the process of learning so that they were not able to be analysed. Keywords: ADI, MADI, ski school, ski education
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Analysis of Didactic Interaction in Group Skiing Lessons for Adults
Říha, Jakub ; Matošková, Petra (advisor) ; Süss, Vladimír (referee)
Title: Analysis of Didactic Interaction in Group Skiing Lessons for Adults Objectives: The aim of this thesis is to perform detailed analysis and comparison of the didactic teacher - student interaction during adult skiing lessons between two instructors with the same level of experience but different educational background. Methods: In our research we have employed a participant observation method using classification into a category system based on a standardised MADI (Modified Analysis of Didactic Interaction) technique. This includes 7 categories describing the forms of the teacher's behaviour, the didactic content of the lessons, didactic situations, and attitudinal characteristics. Results: The results of the study confirmed, among others, a higher incidence of the two most effective forms of teacher behaviour (correction and feedback information provision) in the instructor with pedagogical education, which was associated with a higher quality of the teaching process. Keywords: teaching, skiing, instructor, didactic interaction, analysis, ADI, MADI
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Interaction between a teacher and student in comparasion group and individual skiing lessons.
Punčochář, Michal ; Jindra, Matouš (advisor) ; Gnad, Tomáš (referee)
Title of the thesis: Interaction between a teacher and a student compared group and individual teaching skiing. Objectives: The aim of this work was to find, which and how big differences are in the didactic interaction in comparison of group and individual ski lessons. Methods: In this work we used the method of observation, data collection was realized using a video camera and the subsequent recording was evaluated using the MADI method (modified analysis of didactic interaction). Results: From the results we found that the greatest difference was in the expression factual purportwhich in individual lessons grow avarage by 20%. Furthermore, in the individual lesson form grow education activity above organizational by on avarage10% and in the type of attitude activity integration has increased on avrage 7%. The results also showed that in the individual form of teaching did not appear activity without direct control. Conclusion: The biggest difference between individual and group teaching was the increase in individual teaching in the expression of the subject matter, integration attitude activities above the dominant, the teaching activity increased over the organizational and the performance of the pupil's activity was constantly under direct control. Key words: Individual and group skiing...
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