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Quantitative Assessment of the T-stress in Short Fatigue Crack Propagation
Seitl, Stanislav ; Knésl, Zdeněk
Two parameter constrained based fracture mechanics is applied to quantitative assessment of microstructurally short fatigue cracks propagation. The different levels of a stress constraint are quantified by T-stress. Corresponding calculations are performed by finite element method (ANSYS system). The values of the T-stress are numerically estimated as a function of material properties, location and orientation of the short crack with respect to the grain boundary. The influence of constraint on small fatigue crack growth kinetic is discussed. It is shown that the level of constraint of the near-tip fields for microstructurally short fatigue cracks may influence the fatigue crack rate substantially.
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Problémy a modely v předpovídání záplav
Hokr, Milan ; Maryška, Jiří ; Šotner, O.
In the paper, we deal with the flood forecasting, in particular with determining the water flow as result of known precipitation. In the first part, we present several approaches how to express the water flow in the environment concluding underground flow, surface flow and channel flow in the ricer system (water runoff and flood routing). We discuss possibilities to simplify the shallow-water equations for slowly varying flow to either potential flow or advection-dispersion process. On the second part, we present results of two example models of 2D surface flow in the landscape, first based on the advection-dispersion representation of surface flow and the second mixed-hybrid FEM model based on potential flow approximation.
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