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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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Application of Homogenization Annealing to Suppress Silicon and Nickel Segregation in Ductile Iron
Pavloušková, Zina ; Zemčík, Ladislav (referee) ; Vřešťál, Jan (referee) ; Švejcar, Jiří (advisor)
This doctoral thesis deals with the comparison of different methods of alloying elements’ concentration measurement based on energy dispersive spectroscopy and also with the suitability of particular methods of quantitative assessment of heterogeneity of the spheroidal graphite cast iron matrix. The segregation curves construction, distribution coefficient and heterogeneity index formulation is also discussed. The notion “normalized distribution coefficient” is introduced newly. The goal of the thesis, which is to be achieved by means of evaluation of large experimental data sets, is the evaluation of applicability of homogenization annealing of spheroidal graphite cast iron with the aim to eliminate segregation of silicon, and mainly nickel, as pearlite- and carbide-forming agent at the border of an eutectic cell. The result is an optimized homogenization annealing schedule maximizing the suppression of silicon and nickel segregation while taking into account the minimization of financial expenses and risk of grain coarsening.
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PROGRESSIVE PRODUCTION PROCESSES AND SIMULATION OF STRUCTURES AND PROPERTIES OF SPHEROIDAL GRAPHITE CAST IRON
Musilová, Iveta ; Mores, Antonín (referee) ; Pacal, Bohumil (referee) ; Šenberger, Jaroslav (advisor)
The thesis is concerned with relationships between progressive technological processes of spheroidal graphite cast iron’s production and their structural properties. The aim of the work is to explain causal relationship between parameters of the proposed manufacturing technology of the iron type given (involving selected variants of modification and inoculation of melt and the parameters of melt crystallization, solidification and cooling down in a mould), their structure and even chemical heterogeneity of elements in this structure. For close specification of presented relationships three-dimensional model of spheroidal graphite growth was used, which was developed at the Brno University of Technology, Faculty of Mechanical Engineering. Its usability in praxis has been verified on the basisis of the application of this model on experimentally acquired data. The U GRAFIT 20 model of the authors Stránský and Million counting segregation in the frame of eutectic cell has not still been used for prediction of segregation in real condition in greater extent. On the basis of the above mentioned model microsegregation within “on average” of the cell has been discovered during experimental melts. Microsegregation has been described by segregation and heterogeneity indexes. Calculated values of segregation and heterogeneity indexes have been compared with experimentally verified values. On the basis of comparison of calculated and measured values the possibility of further usage of the mentioned model in praxis has been explored.
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Heat treatment processes optimalization of ADI with graded Ni content
Klimentová, Jiřina ; Stránský, Karel (referee) ; Pavloušková, Zina (advisor)
This work is focused on segregation processes in the matrix of spheroidal graphite cast iron with different silicon and nickel content during heat treatment. The aim of this work is to trace the redistribution of the elements of interest during homogenization annealing with different dwell time by comparison of the effective distribution coefficients. Comparison of some specific properties and description of structure development of spheroidal graphite cast iron matrix from initial state to the state after ferritization and homogenization annealing is included in this work.
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Influence of cement moulds on the structure of nodular iron castings
Stachovec, Ivo ; Šenberger, Jaroslav (referee) ; Rusín, Karel (advisor)
The object of the diploma thesis was to solve and to describe the influence of cement sands moulds on the structure of castings with cast iron LKG. The work was intent on watching the tendency of cement sands to the metal penetration of castings, rising of the compounds on the metal mould interface and liquid metal and accompanies elements on the shape of the graphite in the surface of casting. The study of this processes has a big theoretical and a practical meaning, for prevent and prediction of rising of the defects that are attached with unsuitable choice of sand.
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Mechanical Properties of the Casting from Ductile Iron
Semrád, Lukáš ; Andres, Jan (referee) ; Věchet, Stanislav (advisor)
Graduation theses consist of two parts. The first one, theoretical is focused on piece of knowledge regarding nodular iron history, its mechanical properties, chemistry, production and heat treatment. Theoretical part also includes information relating to graphite and white irons that relate closely with nodular iron. Important chapter is description of isothermal refining which is the subject of these theses. The second, experimental part is focused on isothermal refining of nodular iron casting. Description of the casting introduces this section, material specification, production and application. Following chapters describe preliminary conditions for isothermal refining that is applied on every single specimen made of the casting. These specimens have been tested mechanically. Optimal procedure of isothermal refining is applied on whole the casting and characterized final mechanicals. Final mechanical properties after casting isothermal refining has been analyzed and confronted with literature.
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The study of increase in efficiency of manufacturing preparation of technology
Šudoma, Michal ; Lána, Ivo (referee) ; Jurová, Marie (advisor)
This paper discusses different alternatives of more efficient preparation of spheroided graphite cast iron production. Secondary metallurgy and chemical heating technology are used to recast cast iron fused in copula furnace. The work applies the known physical-chemical rules used in the production of quality spheroided graphite cast iron in regular production conditions. Based on the previous developments, the aim was to prepare implementation of verified secondary metallurgy processes in adjusted casting ladle. The casting ladle was adjusted in order to allow execution of all processes required in order for the relevant standards and material lists requirements to be met in respect to spheroided graphite cast iron quality. Comments regarding the trends in ferroalloy metallurgy and related marketing approach of the company. The work is concluded by a summary of advantages brought in by the new approaches compared to the traditional ones from the economical as well as environmental perspective.
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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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Production of Ductile Iron with Feritic Matrix
Blaha, Marek ; Šupálek, Milan (referee) ; Molliková, Eva (advisor)
This bachelor thesis deals with the properties and production of ductile cast iron with ferritic matrix. Theoretical part is focused on basic information about ductile iron, its chemistry, structure and mechanical properties. The production of ductile iron with ferritic matrix in JMA Hodonín Ltd is described in the next chapter of this thesis. In the experimental part the real cast is described together with its production technology and material. The practical part is concentrated on comparison of chemical composition, structure and mechanical properties of material of cast and keel blocks made of the same melt. Finally the results of experiments are summarized and the arrangements for improving conformity between material of cast and of keel block are suggested.
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