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Fraktální anisotropie a heterogenita lomových ploch oceli
Strnadel, B. ; Dlouhý, Ivo
The change in the fractal dimension of the fracture surface demonstrates a wavy character and dispersion depending on the microstructural state of the tested steel. The results of the fractal analysis in the crack growth direction and across the entire crack front were used as the basis for a reconstruction of the geometry of the fracture surface. The competing effects of transgranular and intergranular brittle fracture may lead to increased roughness of the fracture surface and its fractal dimension.
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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.
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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.
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