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Stress evaluation on the head of seismic wave
Petroš, V. ; Holub, Karel
Paper is intended to investigation of ground velocites of the seismic waves propagation in the rock mass during rockbursts and other anomalous geomechanical events. These data will be used for experiments performed with the aim of comparison the behavior of rock in-situ and under laboratory loading.
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Vysokocyklová únava ložiskové oceli
Kunz, Ludvík ; Činčala, M.
S-N curve of 14109 bearing steel was experimentally determined in symmetrical tension-compression in the interval of 10 to 5 to 10 to 8 cycles to fracture. Continuous increase of the number of cycles to fracture with decreasing stress amplitude was observed. Large scatter of experimental data is related to the initiation of fatigue cracks on internal defects of Al2O3 and TiN type.
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Lomové chování kompozitů s křehkou matricí vyztuženou vlákny
Chlup, Zdeněk ; Dlouhý, Ivo ; Boccaccini, A. R. ; Chawla, K. K.
A number of examples exist that indicate the potential for increasing the fracture resistance of brittle matrix by dispersing brittle fibres. For applications development the real composite constituents response during mechanical loading under presence of flaws appears to be important. Theoretical and experimental knowledge sampled on glass matrix composites reinforced by fibres is shortly summarised in the paper. Borosilicate glass with continuous Nicalon fibres and the same matrix containing the chopped carbon fibres as well as the ZrO2 particles (hybrid composite) have been in focus of interests. Chevron notch technique was mainly used for the fracture toughness evaluation. High fracture toughness level of both composites has been proved when testing the as received state. Damage introduced by thermal ageing and/or thermal cycling has been discussed based on fracture toughness values and fracture behaviour analyses
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Přenositelnost lomové houževnatosti z malých těles na tělesa standardních rozměrů
Dlouhý, Ivo ; Chlup, Zdeněk ; Kozák, Vladislav
The capability of pre-cracked Charpy type specimens for prediction of fracture toughness characteristics for standard (1T) bend specimens has been analysed. The toughness scaling model and the master curve methodology have been combined for these purposes. Cast low-carbon manganese steel cut from midthickness of thick plate was used as an experimental material being tested as a candidate material for container casks of spent nuclear fuel. The Dodds-Anderson toughness scaling model was applied for toughness data correction from small scale pre-cracked Charpy specimens. This approach was combined with master curve methodology for the fracture toughness - temperature diagram and loading rate effects predictions supplying good correlation of predicted data with real behaviour
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