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Influence of vertical compresive force on level of constraint in cubical specimen for wedge splitting test
Seitl, Stanislav ; Klusák, Jan ; Dymáček, Petr ; Řoutil, L. ; Veselý, V.
The subject of the contribution is to gain new aspects of knowledge about the fracture behaviour of cementitious building materials by the wedge splitting test (WST). The particularly, the paper investigates the influence of the vertical compressive force Pv, that represents a reaction of the bottom support of the specimen, on the fracture parameters via tools of the two-parameter fracture mechanics. The effects of the vertical compressive force, Pv, on the plastic and fracture process zones are examined.
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MKP studie protlačovacích zkoušek na miniaturních discích při podmínkách konstantního zatížení
Dymáček, Petr
Comparison of results of creep small punch tests (SPT) on miniaturized discs with results of their modeling by means of finite element method (FEM) is presented. Advanced heat resistant chromium steel P91 was selected for the investigations. In the numerical model, the Norton power-law and the exponential relationships were applied. Parameters of both relationships were derived from stress dependences of minimum creep rate obtained from conventional creep tests at 873 K. The FE model included contact elements taking in account the surface friction between all contact surfaces of the test setup. Various material models from elastic&creep to elastic-plastic&creep were applied in the FE model. Obtained results of the numerical analyses were compared with the experimental results. These computational results allow us to better understand the behavior of the specimen at accelerated creep rates and comprehend some of the principally important conditions of the SPT.
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Vývoj poškození u protlačovacích zkoušek na miniaturních discích při konstantní rychlosti deformace
Dymáček, Petr ; Milička, Karel ; Hrubý, V.
In this contribution a set of three steels of various ductility has been selected and tested using small punch technique. The set of specimens was loaded in incremental way, in order to determine at which load level the crack initiates. The location of crack initiation was evaluated and compared with the equivalent plastic strain distributions in the FEM model of the specimen. The findings should help for better comprehension of the fracture mechanisms that can occur in SP testing and recognizing the main differences between the conventional and SP testing.
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Parametrická studie protlačovacích zkoušek na miniaturních discích při podmínkách konstantní rychlosti zatěžování
Dymáček, Petr
The mechanical testing and numerical modeling of the small punch test on miniature disks from heat resistant steel type ČSN 41 5313 were performed. Current intensive methodical and application analysis of the possibilities of these tests is aimed mainly on relation between their results and conventional test results on massive specimens. One of the ways is empirical deduction of these relations another one is the numerical modeling. Finite element method offers good tool for creation of parametric model capable to simulate the process during the test and study the influence of geometrical and material characteristics on the test results. The experimental and calculated results mentioned in the paper are for punch testing at constant deflection rate at room temperature as well as operational temperature of the material.
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