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Použití lokálního přístupu při řešení transferability lomově mechanických parametrů
Dlouhý, Ivo ; Hadraba, Hynek ; Jurášek, L.
In some applications the pre-cracked Charpy specimens (PC) can be, after meeting the validity conditions applied for specification of fracture toughness characteristics corresponding to standard specimens. Typically this is the case of pearlitic steel R7T (used for railway wheelset production) with Lüders’ flow and higher strength properties. It has been found that there is a gap in fracture toughness data of PC specimens between the 60 and 90 MPam1/2 due to plastic hinge in net section of PC specimens. The distribution of maximum principal stress ahead of the crack tip in PC specimen loaded into fully plastic regime was found to be identical with that of reference stress-strain field in plane-strain SSY condition. 3D FEM simulations also shown that there is no constraint loss in PC specimens.
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Transferability of Fracture Mechnaical Characteristics
Dlouhý, Ivo ; Lenkey, G. B. ; Pluvinage, G.
Comprehensive review of proved recent methods for transfer of fracture mechanical characteristics from smaller to standard specimen geometry is supplied thinking at the same time on transferability of these characteristics from laboratory experiments to real components. Application procedures for local approach, master curve methodology, toughness scaling models, dynamic fracture properties and notch sensitivity are workout and discussed.
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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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