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Experimental determination of stress-strain dependence of non-standard materials
Vavřík, Daniel ; Drdácký, Miloš
The subject of this work is experimental determination of mechanical properties for different types of animal hairs. Mortars reinforced by thin fibres have promising properties for application in cultural heritage protection. Theoretical research is based on mathematical modeling of composite materials with inorganic (brittle) matrix and differential types of reinforcement fibres - natural as well as man made polymeric fibres. For these models, knowledge of mechanical properties of the fibres is needed. Optical method developed especially from this purpose will be introduced in this paper.
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TWO-PARAMETER DESCRIPTION OF CRACKS IN THE VICINITY OF INHOMOGENEITY
Seitl, Stanislav ; Knésl, Zdeněk
In case of two-parameter linear fracture mechanics a study of inhomogeneity influence on behaviour of short cracks is performed. The values of stress intensity factor (KI), T-stress and strain energy density (SED) are shown as a function of material constants of both components. The calculation of numerical values of mechanical parameters is accomplished by using finite element method ANSYS.
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Comparison of stability criteria of V-notched body under combined mode of loading
Klusák, Jan ; Knésl, Zdeněk
The stability criteria of V-notched bodies under combination of loading modes I and II are suggested and compared in the article. Methodology of stability criterion suggestion is based on analogy between behaviour of body with a crack and with a V-notch. Analytical approach to suggestion of stability criteria and methods of numerical estimation of magnitudes controlling stability of the concentrators are shown in the article. Corresponding evaluations are obtained from finite element method system ANSYS. Suggested criteria are mutually compared.
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Concrete as a two-phase material: statistical/sensitivity modelling of failure
Keršner, Z. ; Náhlík, Luboš ; Knésl, Zdeněk
Concrete is represented as a two-phase material. Behaviour of a crack with its tip on the interface between two different materials ů hardened cement paste (matrix) and aggregate(particle) ů is modelled. Input variables of the model are considered as random variables using LHS method/FREET software. Then results of statistical/sensitivity analyses of output variable ů the critical stress for the intersection of coarse aggregate particle ů are presented.
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Fracture behaviour of the short crack near the stress concentrator
Hutař, Pavel ; Knésl, Zdeněk
A two-parameter fracture mechanics method is applied to small cracks near a stress concentrator. The small crack in the present contribution is considered as crack influenced by the stress concentrator. The sharp V-noch or V-noch with radius $R$ are studieded here. The effect of V-notch geometry on the small crack fracture parameters is analysed. The necessary calculations are performed by using a finite element method (system Ansys). Obtained results are discussed from point of view of the small crack behavior. The small fatigue crack growth is especially influenced by the constraint level. The results improve the quality of fatigue life estimation of structure with concentrators.
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