|
|
Prediction of the fracture toughness temperature dependence
Václavík, Martin ; Pantělejev, Libor (referee) ; Válka, Libor (advisor)
The thesis is focused on the prediction of the fracture toughness temperature dependence through a universal curve of fracture toughness (also known as the master curve). To determine the parameters of the universal curve of fracture toughness, values acquired from the measurement results of fracture toughness and tensile tests of structural steel P91 are used. The theoretical part is based on a summary of the relevant information from the field of fracture mechanics and brittle-ductile fracture behavior of steels that are important for the understanding of fracture-strain response of materials depending on load conditions. The experimental part of the thesis contains the results from practical measurements and analyses, which were used for determining the parameters of a universal curve of fracture toughness as well as for the evaluation of fracture behavior and description of the impact of structural parameters on this behavior in case of steel P91.
|
|
|
Prediction of the fracture toughness temperature dependence
Václavík, Martin ; Pantělejev, Libor (referee) ; Válka, Libor (advisor)
The thesis is focused on the prediction of the fracture toughness temperature dependence through a universal curve of fracture toughness (also known as the master curve). To determine the parameters of the universal curve of fracture toughness, values acquired from the measurement results of fracture toughness and tensile tests of structural steel P91 are used. The theoretical part is based on a summary of the relevant information from the field of fracture mechanics and brittle-ductile fracture behavior of steels that are important for the understanding of fracture-strain response of materials depending on load conditions. The experimental part of the thesis contains the results from practical measurements and analyses, which were used for determining the parameters of a universal curve of fracture toughness as well as for the evaluation of fracture behavior and description of the impact of structural parameters on this behavior in case of steel P91.
|
|
|
Transgranular and intergranular failure competition as a manifestation of steel degradation
Dlouhý, Ivo ; Hadraba, Hynek ; Strnadel, B.
Main purpose of the work was to quantify causes and characteristics that control the intergranular fracture initiation and occurrence of this fracture micromechanism in competition with cleavage one. A CrNi steel of commercial quality and the same steel with increased content of impurity elements, Sn and Sb, was used. Step cooling treatment was applied in order to induce intergranular embrittlement and brittle fracture initiation in both steel melts. For fracture toughness determination standard bend specimen and pre-cracked Charpy type specimens both tested in three point bending were applied. Relation of cleavage fracture stress and critical stress for intergranular failure has been followed showing capability of this parameter for quantification of the transgranular/intergranular fracture. In order to characterise the quantitative morphological differences in fracture surfaces fractal analysis was applied.
|
|
|
Micromechanical aspects of transgranular and intergranular failure competition
Dlouhý, Ivo ; Němec, Ondřej
Main purpose of the work was to quantify causes and characteristics governing the intergranular fracture initiation and occurrence of this fracture micromechanism in competition with cleavage one. A CrNi steel of commercial quality and the same steel with increased content of impurity elements have been used for investigation. Step cooling treatment has been applied in order to induce intergranular embrittlement and brittle fracture initiation in both steel melts. Except for standard specimen geometry for three-point bending the pre-cracked Charpy type specimens were applied for determination of fracture mechanical properties. Fractal analysis was applied in order to characterise the quantitative morphological differences in fracture surfaces. Relation of cleavage fracture stress and critical stress for intergranular failure has been followed.
|
guest ::
