Comparison of material properties of SCC concrete with steel fibres related to ingress of chlorides

The paper focuses on the evaluation of chloride ion diffusion coefficient of self-compacting concrete with steel fibre reinforcement. The reference concrete from Ordinary Portland Cement (OPC) and Self-Compacting Concrete (SCC) with several values of added steel fibres-0%, 1% and 2% of weight-were cast in order to investigate the effect of fibres. The three procedures of diffusion coefficient calculation are presented-rapid chloride penetration test, accelerated penetration tests with chloride as well as the surface measurement of electrical resistivity using Wenner probe. The resulting diffusion coefficients obtained by all methods are compared and evaluated regarding the basic mechanical properties of concrete mixtures.Web of Science103art. no. 22

Probabilistic modeling of chloride penetration with respect to concrete heterogeneity and epoxy-coating on the reinforcement

The presented article demonstrates the probabilistic method based modeling of the 2D chloride ingress into reinforced concrete structures with respect to concrete heterogeneity and epoxy-coated steel reinforcement. Spatial change of concrete diffusion is assessed through the investigation of random variation of the ability of concrete to resist chloride ingress. Time-dependent chloride concentration at the reinforcement level in both homogeneous and heterogeneous models is comparatively considered taking into account of the influence of reinforcement protection as well as the defects and holidays of the coating. Expansion optimal linear estimation method is exploited to generate a random field for the structure at the mesoscale and correlation length is employed to simplify the modeling process. Preliminary analyses of the built model are conducted in both deterministic and probabilistic solutions under the scheme of the finite element method. Thus, possibility of such analyses is exploited.Web of Science1224art. no. 406

Tools for CNC milling centres

Tato Bakalářská práce je zaměřena na frézovací nástroje pro CNC frézovací cent-ra. První kapitola této práce se zabývá krátkou teorií frézování a charakteristikou CNC frézo-vacího centra. V následující kapitole jsou rozděleny a popsány vlastní frézovací nástroje z hlediska užití a konstrukce. V této kapitole jsou dále popsány nástrojové materiály, upínání, povlakování a označování těchto nástrojů. Praktická část práce je věnována výrobnímu sorti-mentu fréz od významných producentů. Jedná se o rozbor, popis a zhodnocení sortimentů těchto firem. Za tímto účelem byly vybrány firmy Sandvik Coromant a Pramet Tools.This thesis is focused on milling tools for CNC milling centers. The first chapter of this thesis deals with a short theory of milling and the characteristics of CNC milling center. In next chapter are divided and described milling tools in terms of use and construction. This chapter also describes tool materials, clamping, coating and marking of these tools. The practical part is devoted to production assortment of mills from major producers. It is an analysis, description and evaluation of assortments of these producers. For this purpose were selected companies Sandvik Coromant and Pramet Tools.

Effect of cracking and randomness of inputs on corrosion initiation of reinforced concrete bridge decks exposed to chlorides

The paper is aimed at the indicative evaluation of the effect of random scatter of input parameters in case of durability of reinforced concrete bridge deck. The time to onset of corrosion of steel reinforcement of concrete bridge deck exposed to chloride is evaluated. The effect of cracking in concrete onto chloride ingress is considered. The selected steel reinforcement protection strategies are: unprotected steel reinforcement, epoxy-coated steel reinforcement and water-proof barrier bellow asphalt overlay. The preliminary model for damage effect on chloride ion ingress through water proof membrane under penetrable asphalt overlay is used. 2-D finite element chloride ingress model is combined with Monte Carlo simulation technique. The innovative crack effect modeling via highly penetrable elements is applied. Deterministic and probabilistic calculations are compared.Web of Science39372

Durability Analysis of Concrete Bridge Deck Exposed to the Chloride Ions Using Direct Optimized Probabilistic Calculation

Durability of reinforced concrete structures is a deeply discussed problem recently. Concrete structures in the external environment are very often affected by chloride ions from de-icing salt or sea water. Chloride ions penetrate through the concrete cover layer of the reinforcement and can cause eventually the corrosion of the steel. However, when estimating the durability of the structure, it is not sometimes possible to express the parameters by constant values; therefore, the probabilistic methods come in handy. Then, the variability of inputs and outputs can be expressed by histograms. Two probabilistic approaches were applied in this task – Monte Carlo simulation with Simulation-Based Reliability Assessment method, which is widely used for such type of problems, and the Direct Optimized Probabilistic Calculation, which is still relatively new type of approach. The result is a comparison of mentioned methods in terms of accuracy on the model of one-dimensional chloride penetration with time independent diffusion coefficient by using the Fick’s Second Law of Diffusion

Lightweight SFRC benefitting from a pre-soaking and internal curing process

The presented research program is focused on the design of a structural lightweight fiber-reinforced concrete harnessing an internal curing process. Pre-soaked waste red ceramic fine aggregate and pre-soaked artificial clay expanded coarse aggregate were utilized for the creation of the mix. Copper-coated steel fiber was added to the mix by volume in amounts of 0.0%, 0.5%, 1.0%, and 1.5%. Test specimens in forms of cubes, cylinders, and beams were tested to specify the concrete characteristics. Such properties as consistency, compressive strength, splitting tensile strength, static and dynamic modulus of elasticity, flexural characteristics, and shear strength were of special interest. The achieved concrete can be classified as LC12/13. A strength class, according to fib Model Code, was also assigned to the concretes in question. The proposed method of preparation of concrete mix using only pre-soaked aggregate (with no extra water) proved to be feasible.Web of Science1224art. no. 415

Scan matching by cross-correlation and differential evolution

Scan matching is an important task, solved in the context of many high-level problems including pose estimation, indoor localization, simultaneous localization and mapping and others. Methods that are accurate and adaptive and at the same time computationally efficient are required to enable location-based services in autonomous mobile devices. Such devices usually have a wide range of high-resolution sensors but only a limited processing power and constrained energy supply. This work introduces a novel high-level scan matching strategy that uses a combination of two advanced algorithms recently used in this field: cross-correlation and differential evolution. The cross-correlation between two laser range scans is used as an efficient measure of scan alignment and the differential evolution algorithm is used to search for the parameters of a transformation that aligns the scans. The proposed method was experimentally validated and showed good ability to match laser range scans taken shortly after each other and an excellent ability to match laser range scans taken with longer time intervals between them.Web of Science88art. no. 85

Reinforced Concrete Bridge Deck Model Considering Delayed Exposure to Chlorides

The paper is focused on the model of the effect of delayed chloride exposure on the chloride induced corrosion initiation on ideal reinforced concrete bridge. The Finite Element-based numerical model is applied. The effect of concrete quality is expressed in the form of time dependent diffusion coefficient in order to evaluate the effect of concrete type as well as the effect of aging. The influence of extended chloride exposure on the corrosion initiation is introduced

Rationalisation of production technology

Diplomová práce se zabývá racionalizací technologie výroby vybrané součásti. Úvodní část práce obsahuje krátké seznámení s firmou NTS Prometal Machining s.r.o. a stručný popis daného výrobku. V následující kapitole je proveden rozbor stávající výrobní technologie. Praktická část práce je věnována návrhu variant racionalizace výrobního procesu. Po vyhodnocení všech případných možností racionalizace byl vypracován nový technologický postup s ohledem na časové a finanční úspory. V závěru práce bylo provedeno ekonomické vyhodnocení a doporučení pro další výrobu součásti.This thesis deals with the rationalization of production technology of selected component. The first part contains a brief introduction of the company NTS Prometal Machining s.r.o. and brief description of the product. The following section is an analysis of existing manufacturing technology. The practical part is focusing on the proposal of rationalization versions of the production process. After evaluation of all possible options of rationalization there has been developed a new technological process with a respect to time and cost savings. Finally there was carried out economical evaluation and recommendation for further production of this component.

The Diagnostic System of Ladle Furnace Exhaustion Fan Condition

Import 29/09/2010Diplomová práce se zabývá technickou diagnostikou ventilátoru odprašovacího zařízení na zařízení pro plynulé odlévání. Nejprve je vysvětlen princip odprašovacího zařízení, jehož součástí je ventilátor. Následuje popis součástí a eventuálních poruch ventilátoru vedoucích ke zhoršení jeho technického stavu s návrhem možných metod technické diagnostiky. Vzhledem k různorodosti zařízení se nejlépe jeví metoda multiparametrické diagnostiky (vibrodiagnostika a termodiagnostika). Jako hlavní diagnostické metody je využito vibrodiagnostiky, kdy měřením absolutních vibrací zařízení a jejich analýzou (trendová analýza, frekvenční analýza, obálková metoda) získáme dostačující údaje o technickém stavu ventilátoru. S termodiagnostikou je uvažováno jako s doplňkovou metodou aplikovanou při zvýšených vibracích, mající původ v elektromotoru.The Master Thesis focuses on technical diagnosis of dust-collecting appliance fan of constant steel casting. First of all, the principle of dust-collecting appliance including the fan is explained. Secondly, there is description of components and possible errors of the fan with negative influence on its technical condition and suggestion of possible methods of technical diagnosis. Due to variability of the device, the best method is supposed to be multiparametric diagnosis (vibrodiagnostics and thermodiagnostic). Vibrodiagnostics is the main diagnosis method during which absolute vibration of the device is measured and analyzed (trend analysis, frequency analysis and envelope method) and brings sufficient information about technical condition of the fan. Thermodiagnostic is considered to be used as additional method applied during stronger vibrations resulting from electromotor.340 - Katedra výrobních strojů a konstruovánívýborn