A Novel Multiscale Modelling Approach for Evaluation of the ASR in Concrete Structures

This paper presents a new multiscale approach for evaluation of the volume change in concrete structures due to the alkali-silica reaction (ASR). A practical step by step approach that can be applied to the real structures is developed based on combined experimental and numerical assessment by considering the most influential ASR parameters at different scales. In the first step, the ASR expansion is measured using accelerated concrete cylinder test (ACCT) for different concrete mixtures covering different variables of important factors such as mix design (e.g., w/cm, fly ash type and replacement percentages), aggregate reactivity, alkali loadings, temperature, and relative humidity etc. All measured expansion data are then modelled using artificial neural network (ANN) modeling approach in the second step. In the third step, finite element (FE) model is utilized at different scales to analyze the real structures and representative volume element (RVE) taking into account the ASR gel expansion and structural boundary conditions. Finally, the effects of the structural constraints are taken into account by introducing correction factors to the predicted free expansion (i.e. no constraints) of the RVE by ANN model. It was found that a combined effect of both internal gel pressure and structural constraints determines the net volume expansion in a concrete structure. In order to show the applicability of the proposed approach, the model is employed for evaluation of the ASR-induced net volume expansion at different locations of a dam structure under realistic in-service conditions. The microstructural study was also done by using X-ray CT that can be used to estimate the ASR progress in concrete structure and validate / support the FEM based predictions

Study of Characteristic Equation of the Elastic Stress Field near Bimaterial Notche

Fracture occurs at interface corners due to stress singularity which generates as a result of material discontinuity and geometrical configuration. In elastic stress field near a bimaterial notch tip, eigenvalues extracted from Airy’s stress function approach determine the order of singularity. In this paper, the characteristic equation of elastic stress field near bimaterial notches is investigated. The study is done on singular eigenvalues as well as the first non-singular eigenvalue which has not been well studied before. First, different combination of materials and geometrical configurations for two of the most applicable paths in the Bogy diagram (β = 0, β = α/4) were studied and the results were comprehensively discussed. It was shown that the geometrical and materials configurations near a bimaterial notch tip can significantly affect on the stress singularity near these corners. Finally, the areas between two lines β = 0 and β = α/4 in the Bogy diagram with high stress singularities were determined and discussed for both the first and second singular eigenvalue.Исследуется характеристическое уравнение для упругого поля напряжений у вершины надреза на стыке двух материалов. Установлено, что разрушение происходит в угловых точках их стыка из-за возникновения сингулярных напряжений вследствие разрыва сплошности материала и особенностей геометрической конфигурации. В поле упругих напряжений у вершины надреза на стыке двух материалов порядок такой сингулярности определяют собственные значения функции напряжений Эри. Выполнен анализ сингулярных собственных значений и малоизученного первого несингулярного собственного значения. Рассмотрены различные комбинации материалов и геометрических конфигураций для двух наиболее используемых траекторий на диаграмме Боги (β = 0, β = α/4) и детально проанализированы полученные результаты. Показано, что геометрические конфигурации и комбинации материалов у вершины надреза существенно влияют на сингулярность напряжений вблизи угловых точек надреза. Области с высокой сингулярностью напряжений были выделены между линиями β = 0 и β = α/4 на диаграмме Боги и проанализированы как для первого, так и второго сингулярного собственного значения.Досліджується характеристичне рівняння для пружного поля напружень у вістрі надрізу на стику двох матеріалів. Установлено, що руйнування відбувається в кутових точках їх стику через виникнення сингулярних напружень внаслідок розриву суцільності матеріалу й особливостей геометричної конфігурації. У полі пружних напружень у вістрі надрізу на стику двох матеріалів порядок такої сингулярності визначають власні значення функції напружень Ері. Проаналізовано сингулярні власні значення і маловивчене перше несингулярне власне значення. Розглянуто різні комбінації матеріалів і геометричних конфігурацій для двох найбільш використовуваних траєкторій на діаграмі Богі (β = 0, β = α/4) та детально проаналізовано отримані результати. Показано, що геометричні конфігурації і комбінації матеріалів у вістрі надрізу суттєво впливають на сингулярність напружень поблизу кутових точок надрізу. Області з високою сингулярністю напружень виділено між лініями β = 0 і β = α/4 на діаграмі Богі і проаналізовано як для першого, так і другого сингулярного власного значення

Something about the Balancing of Thermal Motors

Internal combustion engines in line (regardless of whether the work in four-stroke engines and two-stroke engines Otto cycle engines, diesel and Lenoir) are, in general, the most used. Their problem of balancing is extremely important for their operation is correct. There are two possible types of balancing: Static and dynamic balance. The total static to make sure that the sum of the forces of inertia of a mechanism to be zero. There are also a static balance partial. Dynamic balance means to cancel all the moments (load) inertia of the mechanism. A way of the design of an engine in a straight line is that the difference between the crank 180 [°] or 120 [°]. A different type of construction of the engine is the engine with the cylinders in the opposite line, called "cylinder sportsmen". In this type of engine (regardless of their position, which is most often vertical) for engines with two cylinders, one has a static balance total and an imbalance in the dynamic. Similar to the model of the earth concentrated in rotation movement are resolved and load balancing shafts rotating parts. An important way to reduce losses of heat engines is how to achieve a better balance. The methods may be used in equal measure and on engines with external combustion, type Stirling or Watt

Something about the Balancing of Thermal Motors

n/

Tangential strain-based criteria for mixed-mode I/II fracture toughness of cement concrete

Experimental and theoretical works are performed on the mixed-mode I/II brittle fracture of cement concrete tested by edge cracked semicircular bend specimens. Theoretical background of the traditional fracture criteria including strain energy density, maximum tangential stress, and maximum tangential strain (MTSN) are introduced. The ability of each fracture criterion in prediction of the fracture test data is investigated. The comparison between the evaluations by the traditional criteria and the experimental data shows that none of them are capable of successfully estimating the fracture resistance of cement concrete. An enhanced version of the MTSN criterion is then employed to predict the test data. It is demonstrated that the extended MTSN criterion can successfully predict the test data in a higher accuracy than traditional criteria. © 2017 Wiley Publishing Ltd

EMTSN criterion for evaluating mixed mode I/II crack propagation in rock materials

This paper investigates the results of brittle fracture in rock materials subjected to the mixed mode I/II loading using different fracture criteria. Two sets of mixed mode fracture test data in the entire range of mode mixity, from pure mode I to pure mode II, reported in the literature for semi-circular and triangular shape specimens and subjected to three point bend loading (i.e. SCB and ECT specimens) are utilized to study the brittle fracture in two marble rocks. First, the onset of fracture initiation is examined by different conventional fracture criteria including Maximum Tangential Stress (MTS) and Maximum Tangential Strain (MTSN) criteria. It is shown that these two conventional fracture criteria, which only consider singular crack tip stress/strain terms, are not able to accurately predict the mixed mode fracture test data. The experimental mixed mode fracture toughness data are then predicted by an extended version of the maximum tangential strain (EMTSN) criterion which takes into account the effect of first nonsingular strain term as well as the singular strain components. It is found that both mixed mode fracture toughness results of the investigated rock materials and the crack propagation direction can be predicted successfully by the EMTSN criterion. (C) 2017 Elsevier Ltd. All rights reserved

Strain-based criteria for mixed-mode fracture of polycrystalline graphite

The mixed-mode brittle fracture of two types of commercial graphite is investigated focusing on strain-based fracture criteria. The previously published experiments using centrally-cracked Brazilian disk specimens subjected to mixed-mode loadings are simulated by two strain-based fracture criteria: the traditional maximum tangential strain (MTSN) criterion only considering the singular terms, and the extended maximum tangential strain (EMTSN) criterion, which considers the first nonsingular strain term as well as the singular terms. Numerical simulations on the centrally-cracked Brazilian disk specimen show that the first nonsingular tangential strain term significantly influences the tangential strain distribution around the crack tip. The comparison of the evaluations by the MTSN and EMTSN criteria with the experimental data shows that the EMTSN criterion is more capable of successfully estimating the fracture resistance of graphite materials rather than the traditional MTSN criterion. In addition, when the first nonsingular term is considered, the strain-based fracture criterion provides better predictions for near mode II loadings than the stress-based fracture criterion

Extended MTSN criterion for fracture analysis of soda lime glass

This paper investigates brittle fracture in soda lime glass subjected to mixed mode I/II loading using different fracture criteria. Different sets of mixed mode I/II fracture test data from literature, conducted by cracked Brazilian disk specimen, are utilized to study brittle fracture in soda lime glass. The fracture initiation conditions in soda lime glass is examined by different traditional fracture criteria including Strain Energy Density, Maximum Tangential Stress, and Maximum Tangential Strain criteria. It is shown that the traditional criteria, which only consider singular stress (strain) terms, are not able to properly predict the fracture test data. The test data are then predicted by an extended version of the maximum tangential strain (EMTSN) criterion which takes into account the effect of first nonsingular strain term as well as the singular strain terms. It is found that the mixed mode fracture toughness of the soda lime glass as well as the crack initiation direction can be predicted successfully by the EMTSN criterion

Something about Electron Dimension

In this study will be exposed the theoretical principles necessary for the determination of the exact size of an electron in motion, depending on its speed of travel. Equations, aimed to accurately determines the radius R of the electron in motion, relating the electron moving speed v and its rest mass m0 are discussed. Mechanical moment of inertia of a sphere around of one of its diameters shall be determined by the relationship relating the total kinetic energy of one electron in motion, as a sum of the two components (translational and rotational). Using the theory of Louis de Broglie, which shows the conservation of the pulse, the wavelength (particle associated) has been calculated. Wave frequency (associated with the electron in motion) has been determined and moving electron kinetic energy has been estimated by subtracting the total electron rest energy from total electron energy in movement