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Využití kevlarových vláken v asfaltových směsích
Mazáč, Jan ; Hegr, Zdeněk (oponent) ; Hýzl, Petr (vedoucí práce)
Diplomová práce se zabývá tématem využití aramidových (kevlarových) vláken v silničním stavitelství v asfaltových směsích. V teoretické části práce jsou popsány obecné vlastnosti aramidových vláken a jejich technické využití. Práce se také zabývá výzkumem a použitím aramidových vláken v zahraniční a také v České republice. V praktické části je zkoumán vliv aramidových vláken, konkrétně FORTA FI vláken ve směsi s modifikovaným pojivem do obrusné vrstvy. Součástí práce je také popis všech zkušebních metod, které byly použity během zpracování praktické části. V závěru práce jsou zhodnoceny poznatky o problematice přidávání aramidových vláken do asfaltových směsí.
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STOCHASTIC CRACK PROPAGATION MODELLING USING THE EXTENDED FINITE ELEMENT METHOD
Nešpůrek, Lukáš ; Novák, Drahomír (oponent) ; Hutař, Pavel (oponent) ; Anthony Nouy, PhD., HDR (oponent) ; Knésl, Zdeněk (vedoucí práce)
This thesis is based on the work carried out in a doctoral research program under joint French- Czech tutorship at the French Institute of Advance Mechanics in Clermont-Ferrand and the Institute of Physics of Materials in Brno. An initial research project conducted in Brno investigated trough finite element analysis the stress field around the crack front of a through-thickness crack in thin metallic foils, focussing on the effect of the special type of singularity at the intersection of the crack front with the free surface. The main focus of the thesis was numerical modelling and stochastic analysis of complex-geometry crack propagation problems in two dimensions. The use of numerical mechanical models for such analysis had been scarce because of prohibitively high computational effort. This thesis shows that through application of advanced computational mechanics and suitable reliability analysis techniques, the task is tractable even on a personal computer. The First Order Reliability Method was employed in the reliability analysis. It was assumed that the crack growth rate obeys the Paris-Erdogan equation. A bi-variate statistical model for the parameters of the equation was found appropriate to capture the extreme sensitivity to their correlation. The mechanical response was obtained through the Extended Finite Element Method, which eliminates the computational effort and the numerical noise originating from remeshing in classical finite element analysis. Several direct differentiation formulae were developed to compute the derivatives of the response function, improving numerical stability and convergence of the reliability analysis and dramatically reducing computational time. The PREFFAS load transformation method was used to treat variable-amplitude loading. The use of distributed computing offered a further acceleration of the analysis.
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Využití kevlarových vláken v asfaltových směsích
Mazáč, Jan ; Hegr, Zdeněk (oponent) ; Hýzl, Petr (vedoucí práce)
Diplomová práce se zabývá tématem využití aramidových (kevlarových) vláken v silničním stavitelství v asfaltových směsích. V teoretické části práce jsou popsány obecné vlastnosti aramidových vláken a jejich technické využití. Práce se také zabývá výzkumem a použitím aramidových vláken v zahraniční a také v České republice. V praktické části je zkoumán vliv aramidových vláken, konkrétně FORTA FI vláken ve směsi s modifikovaným pojivem do obrusné vrstvy. Součástí práce je také popis všech zkušebních metod, které byly použity během zpracování praktické části. V závěru práce jsou zhodnoceny poznatky o problematice přidávání aramidových vláken do asfaltových směsí.
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STOCHASTICKÉ MODELOVÁNÍ ŠÍŘENÍ TRHLIN S VYUŽITÍM ROZŠÍŘENÉ METODY KONEČNÝCH PRVKŮ
Nešpůrek, Lukáš ; Knésl, Zdeněk (vedoucí práce)
This thesis is based on the work carried out in a doctoral research program under joint French- Czech tutorship at the French Institute of Advance Mechanics in Clermont-Ferrand and the Institute of Physics of Materials in Brno. An initial research project conducted in Brno investigated trough finite element analysis the stress field around the crack front of a through-thickness crack in thin metallic foils, focussing on the effect of the special type of singularity at the intersection of the crack front with the free surface. The main focus of the thesis was numerical modelling and stochastic analysis of complex-geometry crack propagation problems in two dimensions. The use of numerical mechanical models for such analysis had been scarce because of prohibitively high computational effort. This thesis shows that through application of advanced computational mechanics and suitable reliability analysis techniques, the task is tractable even on a personal computer. The First Order Reliability Method was employed in the reliability analysis. It was assumed that the crack growth rate obeys the Paris-Erdogan equation. A bi-variate statistical model for the parameters of the equation was found appropriate to capture the extreme sensitivity to their correlation. The mechanical response was obtained through the Extended Finite Element Method, which eliminates the computational effort and the numerical noise originating from remeshing in classical finite element analysis. Several direct differentiation formulae were developed to compute the derivatives of the response function, improving numerical stability and convergence of the reliability analysis and dramatically reducing computational time. The PREFFAS load transformation method was used to treat variable-amplitude loading. The use of distributed computing offered a further acceleration of the analysis.
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STOCHASTIC CRACK PROPAGATION MODELLING USING THE EXTENDED FINITE ELEMENT METHOD
Nešpůrek, Lukáš ; Novák, Drahomír (oponent) ; Hutař, Pavel (oponent) ; Anthony Nouy, PhD., HDR (oponent) ; Knésl, Zdeněk (vedoucí práce)
This thesis is based on the work carried out in a doctoral research program under joint French- Czech tutorship at the French Institute of Advance Mechanics in Clermont-Ferrand and the Institute of Physics of Materials in Brno. An initial research project conducted in Brno investigated trough finite element analysis the stress field around the crack front of a through-thickness crack in thin metallic foils, focussing on the effect of the special type of singularity at the intersection of the crack front with the free surface. The main focus of the thesis was numerical modelling and stochastic analysis of complex-geometry crack propagation problems in two dimensions. The use of numerical mechanical models for such analysis had been scarce because of prohibitively high computational effort. This thesis shows that through application of advanced computational mechanics and suitable reliability analysis techniques, the task is tractable even on a personal computer. The First Order Reliability Method was employed in the reliability analysis. It was assumed that the crack growth rate obeys the Paris-Erdogan equation. A bi-variate statistical model for the parameters of the equation was found appropriate to capture the extreme sensitivity to their correlation. The mechanical response was obtained through the Extended Finite Element Method, which eliminates the computational effort and the numerical noise originating from remeshing in classical finite element analysis. Several direct differentiation formulae were developed to compute the derivatives of the response function, improving numerical stability and convergence of the reliability analysis and dramatically reducing computational time. The PREFFAS load transformation method was used to treat variable-amplitude loading. The use of distributed computing offered a further acceleration of the analysis.
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