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CYCLIC PLASTICITY AND DISLOCATION SUBSTRUCTURE OF ferritic STAINLESS STEEL
Petrenec, Martin ; Polák, Jaroslav
The cyclic plastic response of polycrystalline ferritic stainless steel with b.c.c. structure is analysed in terms of the general statistical theory of the hysteresis loop and cycled in the magnetic field. Simultaneously, the internal dislocation substructure developed in the material during cyclic straining is studied using transmission electron microscopy and Kikuchi lines. The inhomogeneous distribution of dislocations into the persistent slip bands can be correlated with the localization of the cyclic plastic strain. The analysis of the loop shape by plotting the first and the second derivative of the half-loop allows determining the effective stress and the probability density function of the critical internal stresses. Extra peak of the second derivative of the half-loop was explained by the inverse magneto-elastic effect.
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Criterion of minimal value of strain energy density in case of loading of V-notched body
Klusák, Jan
Presented paper deals with suggestion of stability criterion of V-notched solids under simple loading mode I or II or under combined loading mode I + II. The methods used to propose the stability criterion are based on an analogy of behaviour of cracked and notched bodies. The paper shows strain energy density distribution in the V-notch tip vicinity. Further, direction of assumed crack propagation is determined and an approach of criterion suggestion is presented in the paper.
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Comparison of fracture behaviour of cracks and sharp notches
Klusák, Jan ; Knésl, Zdeněk
The theoretical background of linear elastic fracture mechanics of V-notches is presented. A crack is considered as a special case of the V-notch with zero open angle. Conditions for stability of a general singular stress concentrator are formulated. Based on results obtained a fracture behaviour of notches and cracks is compared.
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Sborník semináře KŘEHKÝ LOM
Dlouhý, Ivo ; Chlup, Zdeněk
Contribution presented on one-day workshop paid to problems of mechanisms and mechanics of brittle fracture. Quantitative description of toughness transition behaviour. Problems of constraint indexing parameter and J-integral calculation at elastic plastic behaviour of material. Fracture mikromechanisms and their modelling.
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Master curve evaluation at static and dynamic conditions of loading (for cast ferritic steel and pressure vessel steels)
Dlouhý, Ivo ; Chlup, Zdeněk ; Holzmann, Miloslav
Various aspects of the master curve methodology have been investigated experimentally based on data obtained with different pressure vessel and container steel. A manganese cast steel has been utilised being considered for storage containers of spent nuclear fuel. Two locations of a segment of container cask, surface and midthickness, have been followed. Some results obtained with the RPV steel of VVER 1000 type and CrMo pressure vessel steel used in petrochemical applications have also been exploited. The applied mechanical testing procedures included: Standard fracture toughness tests at different temperatures using 1T bend specimen in order to determine fracture toughness - temperature diagrams, dynamic fracture toughness has been tested by using hydraulic test machine and drop weight tower. Pre-cracked Charpy specimens have also been tested. For each test technique larger sets of data have been generated in order to follow the statistical aspects. The investigations included procedures of reference temperature determination, both by the one and multitemperature methods, and the evaluation of the scale and constraint effects and the effect of loading rate. For static loading the multi- and single temperature methods of reference temperature determination have been tested with the same family of data. The transferability of results received on the small pre-cracked Charpy specimens was analysed and applied with good results.
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