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Reliability assessment of bodies with general singular stress concentrator
Klusák, Jan
The paper presents a method leading to reliability assessment of bodies with general singular stress concentrator. The method uses combination of analytical and numerical procedures to determine fracture-mechanics parameters. The approach is based on comparison of fracture behaviour of body with a crack and a body with a general singular stress concentrator. The goal of the paper is to determine value of applied stress that leads to initiation of failure of construction.
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Kritérium stability bi-materiálového vrubu se dvěma singularitami
Klusák, Jan
Interfaces with a step change of material properties occur often in technical constructions. In combination with a sharp notch it usually leads to singular stress distribution in a vicinity of such a wedge. The existence of two singularities seems to be the main problem within study of this stress concentrator. The other problem is that each singularity does not correspond to particular mode of loading. The presented contribution studies stress distribution in a bi-material wedge vicinity and shows a method of solution of the problems in case of existence of multiple stress singularity
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Influence of the T-stress on Plastic zone shape and size for different form of specimens
Seitl, Stanislav
In framework of two-parameter fracture mechanics the shape and size of the plastic zone at the tip of a crack were studied. Analytical estimate of the size and shape of the plastic zone was made by substituting Mises yield criterion. For three different specimens (namely CCT-center cracked plate tension specimen, CT-compact tension specimen and 3PB-single edge cracked three point bending specimen) the numerical solution is calculated by using ANSYS. Numerical results are presented to show the influences of the T-stress on the plastic zone. Both solutions are compared and the effect of constraint on the plastic zone was discussed
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Multiscale design of advanced materials
Král, L. ; Million, Bořivoj
In this paper, the results of measurements of chemical diffusion of Mn in steel weldments are reported. Chemical concetnration of Mn an interval 0-15 wt.% Mn was varied. Alloys were casted in induction furnace under protective Ar atmosphere. Diffusion couples were annealed at 800-1100°C for 96-1.5 hours respectively. Measurement of Mn redistribution was done in a normal direction to welding interface using scanning electron microscope Philips SEM-505WDS equipped with Microspec WDX-2A. Diffusion coefficients of Mn were obtained by fitting experimental curves to the known analytical solution.
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The structural and the fundamental mechanical properties of intermatallics on the base of TiAl
Krahula, Karel ; Dlouhý, Ivo
Gamma TiAl alloys are emerging as a pervasive structural material. Remarkable progresses have been made through refining lamellar microstructure and grains, microalloying, chemistry modification, process development and/or their combination. The main thrust was to enhance resistance to creep deformation, oxidation and high cycle fatigue deformation/failure. Less or even no knowledge have been obtained in the field of the intermetalics fracture at uniaxial or bending loading, there are missing data about their behaviour at the presence of cracks and other defects. The reason is simply in the other properties that are key from application point of view. Due to their brittleness at temperature close to room temperature the investigation of the intermetalics fracture is complicated but promissible provided it bring ideas for the further development of the alloying and microstructure. The paper is focused on the first steps in this field.
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Multiscale design of advanced materials
The proceedings of the 1st conference of PhD students Multiscale design of advanced materials organised in the frame and with financial support of doctoral project of Czech Science Foundation No. 106/05/H008.
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Instrumentovaný indentační test v nano- a mikroměřítku
Buršíková, V. ; Buršík, Jiří ; Bláhová, O. ; Dušek, J. ; Navrátil, V.
Several materials were chosen to span a wide range of hardness and structure,including pure copper,nickel,titanium,cadmium,zinc and silver.Nanoindentation hardness and microhardness values in wide interval of loads,measured by DSI method and classical Vickers microhardness method were compared in view of indentation Size Effect.
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