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Micromechanical aspects of constraint effect at brittle fracture initiation
Chlup, Zdeněk ; Dlouhý, Ivo
Cast manganese steel predetermined for container casks of spent nuclear fuel has been tested extensively from the point of view of resistance against brittle fracture. For the fracture toughness evaluation the three-point bend specimens with different crack length (varying a/W ratio > 0,5; 0,2; 0,1) and with the same ligament below the crack tip have been used. Stress distributions below crack tip have been calculated by finite elements method (ABAQUS code) for each specimen geometry separately. Modification has been introduced into calculation taking into account specific material behaviour.
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Recent concepts of evaluation of brittle fracture properties
Dlouhý, Ivo ; Holzmann, Miloslav ; Chlup, Zdeněk ; Kozák, Vladislav
Rough overview of present state in brittle fracture characteristics of steels and critical analysis of recent solutions for crack tip stress field has been introduced applying approaches of one parameter linear elastic and elastic plastic fracture mechanics. Two parameter fracture mechanics as further development stage of fracture mechanics; effect of knowledge on fracture toughness determination. Master curve used for fracture toughness description in transition region. Local approach as additional methodology of fracture mechanics enabling brittle fracture characteristics to predict and to transfer data from one specimen geometry to another one by means of by means of micromechanical crack tip failure models.
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The effect of surface hardening on fracture behaviour of steels for gear wheels
Dlouhý, Ivo ; Holzmann, Miloslav
Three procedures of surface hardening (carburising, nitriding and surface quenching) combined with six structural steels have been followed. The properties evaluation is based on assessment and interpretation of load - deflection traces, obtained by means of instrumented impact tester and/or at static testing of notched bend specimens. Knowledge obtained has been formulated into generalised schematics of fracture behaviour.
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