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Complex assessment of fracture properties of cast ferritic steel
Dlouhý, Ivo ; Chlup, Zdeněk ; Kozák, Vladislav ; Holzmann, Miloslav
Complex analysis of fracture behaviour for low carbon manganese steel intended for fabrication of large containers of spent nuclear fuel (SKODA) has been carried out. Two locations, surface layer and central part, of the thick-walled plate have been followed in order to evaluate the material fracture resistance of full-scale cask segment. Fracture toughness data were determined for two different loading rates. Two specimen geometries, standard ones and subsized Charpy type specimens have been applied for the investigation. For dynamic loading two calculation procedures of dynamic fracture toughness determination have been applied, the first one arising from quasistatic approach and the other based on concept of dynamic key curve method. The transferability of results received on the small pre-cracked Charpy specimens was analysed and applied with good results.
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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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Properties of steel for thick wal castings normalised from intercritical region
Dlouhý, Ivo ; Chlup, Zdeněk
In the present work, the fracture resistance of ferritic C-Mn steel predetermined for the radwaste container cask is analysed. Because of necessity of the comparable microstructure obtaining throughout the wall thickness the steel was treated thermally by controlled cooling from intercritical temperature interval. The fracture behaviour assessment is based on standard fracture toughness determination; data obtained by instrumented impact tests of Charpy type specimens and static tests of pre-cracked Charpy type specimen have been also applied. For the last specimen geometry the problem of transferability of fracture mechanical data from small test specimens to full size specimens or components is solved.
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Vysokoteplotní tahové vlastnosti kvazikrystalické Al slitiny
Chlup, Zdeněk ; Dlouhý, Ivo
Low density, sufficient strength and high temperature resistance are the basic requirements for materials used for aerospace and automotive applications. The nanostructured aluminium alloy reinforced by quasi-crystals prepared by powder metallurgy supposes to be a good alternative to currently used alloys. The aim of this paper is to describe high temperature tensile properties of nanostructured quasi-crystalline aluminium alloy including the changes in fracture mechanism at different strain rates and temperatures. High temperature behaviour was assessed by tensile tests of cylindrical testpieces at temperatures ranging from 20C to 550C. Two strain rates 2.7x10 -4 and 1.1s -1 were applied over the whole temperature range of interest. Fractographic analysis was used to describe fracture mechanism and its changes with increasing temperature and loading rate. The material under investigation proved the potential for high temperature applications
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Fracture toughness and fracture micromechanisms in fibre reinforced brittle matrix composites
Dlouhý, Ivo ; Chlup, Zdeněk ; Boccaccini, A. R.
Fracture toughness and fracture micromechanisms in fibre reinforced brittle matrix composites. For monolithic ceramics, the fracture toughness determination using a specimen with straight and/or chevron notch in the three (four) point bend test for monolithic ceramic materials can be taken as standard techniques. In case of composite materials, mainly of brittle matrix reinforced by fibres the crack growth resistance increases as the crack propagates. In addition, the long fibres stimulate delaminations along their interfaces with the matrix perpendicularly to the major crack. Fracture toughness determination in cases when delaminations take place is difficult. The chevron notch technique appears to be the only technique that enable to obtain exact fracture toughness characteristics by its natural ability to "keep" the mode I major crack propagation. Based on fractographic analyses and comparisons of data from chevron and straight notch technique the corresponding evidences are supplied.
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