Reduction of Structural Damage from the Thermal Expansion of Concrete Using Multifunctional Materials

This study leveraged past successes in the analysis and design of shape memory alloy (SMA) components to address the issue of thermal expansion in concrete structures. Since the SMA used in the current work is relatively cheaper than other common SMAs (less than $50/lb compared to NiTi which is$200/lb due to difficulties in processing), it is anticipated that the findings of the study could be implemented in real infrastructures made of concrete, asphalt concrete, and other complex large infrastructure. Low-cost Fe-SMAs and other multifunctional materials can be considered as a replacement for components made of steel (e.g., in reinforced or plain jointed concrete pavements) to control distresses resulting from thermal expansion during seasonal/daily temperature change. This study conducted a series of finite element (FE) case studies of various configurations of concrete (blocks, slabs, and beams) with embedded, pre-strained SMA rods. This included developing new models to investigate temperature induced deflection in concrete slabs to analyze their curling behavior. It also included investigating the optimal position of the SMA rod and required rod radius. It is hoped that the results of this work could help to design smarter civil infrastructure incorporating multifunctional materials into established civil engineering materials

On the Use of Interfacial Fracture Mechanics Approaches for Evaluation of the End Movement in Concrete Slabs

This dissertation aims to study effects of different design factors on the end movements in Continuously Reinforced Concrete (CRC) pavements subjected to environmental loads. End movement in CRC pavements is an important distress leading to deterioration of in-service pavement structures. Different models, including closed form solutions and numerical approaches for prediction of the concrete slab displacements, are introduced and discussed. The effect bond strength between the concrete slab and the subbase layer on concrete slab end movement is investigated using interfacial fracture mechanics concepts. First, the theoretical criteria describing the mechanism of interfacial crack propagation are discussed in a general framework. A modified version of the maximum tangential stress criterion is developed for strong interfaces and it is shown that the proposed model provides more accurate prediction of the experimental data. A new fracture test specimen, which covers all mixed mode conditions, is proposed for evaluation of the bond strength between two dissimilar materials. The new test specimen is then employed for evaluation of the bond strength between the asphalt concrete and the Portland cement concrete. As the next step, a series of three dimensional finite element simulations are performed to investigate end movements in CRC pavements. The concrete slab/ subbase layer and concrete slab/ reinforcing steel bar interfaces were modelled using a zero thickness cohesive layer which follows traction-separation constitutive law. The results of the finite element simulations are compared with those measured from experiments by previous researchers. Finally, the effects of CRC dimensions, material properties, bond strength, and environmental loads on the end movements in CRC pavements are explored using three dimensional finite element simulations. The results obtained in the present work can help pavement engineers to better understand the mechanism of end movements in CRC pavements

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

The Computer Algorithm for Machine Equations of Classical Distribution

This paper presents an algorithm for setting the dynamic parameters of the classical distribution mechanism of the internal combustion engines. One presents the dynamic, original, machine motion equations. The equation of motion of the machine that generates the angular speed of the camshaft (which varies with position and rotation speed) is obtained by conservation kinetic energy of the machine. An additional variation of angular speed is added by multiplying by the coefficient dynamic D (generated by the forces out of mechanism and or by the forces generated by the elasticity of the system). Kinetic energy conservation shows angular speed variation (from the camshaft) with inertial masses, while the dynamic coefficient introduces the variation of w with forces acting in the mechanism. Deriving the first equation of motion of the machine we obtain the second equation of motion dynamic. From the second equation of motion of the machine, we determine the angular acceleration of the camshaft. It shows the distribution of the forces on the camshaft mechanism to the internal combustion heat engines. Dynamic, the velocities can be distributed in the same way as forces. Practically, in the dynamic regimes, the velocities have the same timing as the forces. Calculations should be made for an engine with a single cylinder

Inverse Kinematics to a Stewart Platform

Mechanical systems in motion type parallel structures are solid, fast and accurate. Between mobile systems parallel the best known and used system is that of a Stewart platforms, as being and the oldest system, quickly, solid and accurate. The paper presents a few main elements of the Stewart platforms. In the case where a motto element consists of a structure composed of two elements in a relative movement from the point of view of the train of propulsion and especially in the dynamic calculations, it is more convenient to represent the motto element as a single moving item. The paper presents an exact, original analytical geometry method for determining the kinematic and dynamic parameters of a parallel mobile structure. Compared with other methods already known, the presented method has the great advantage of being an exact analytical method of calculation and not one iterative-approximately

A Methodology to Determine the Effective Plastic Zone Size Around Blunt V-Notches under Mixed Mode I/II Loading and Plane-Stress Conditions

ABSTRACT:The determination of the ductile failure behavior in engineering components weakened by cracks and notches is greatly dependent on the estimation of the plastic zone size (PZS) and, particularly, the effective plastic zone size (EPZS). Usually, time-consuming complex elastic-plastic analyses are required for the determination of the EPZS. Such demanding procedures can be avoided by employing analytical methods and by taking advantage of linear elastic analyses. In this sense, this work proposed a methodology for determining the PZS around the tip of blunt V-notches subjected to mixed mode I/II loading and plane-stress conditions. With this aim, firstly, existing approximate mathematical expressions for the elastic stress field near round-tip V-notches reported in the literature are presented. Next, Irwin's approach (fundamentally proposed for sharp cracks) and a yield criterion (von Mises or Tresca) were applied and are presented. With the aim of verifying the proposed methodology, elastic-plastic finite element analyses were performed on virtual AISI 304 steel V-notched specimens. It was shown that the analytical formulations presented cannot estimate the complete shape of the plastic zone. However, the EPZS, which is crucial for predicting the type of ductile failure in notched members, can be successfully estimated

Inverse Kinematics to a Stewart Platform

Mechanical systems in motion type parallel structures are solid, fast and accurate. Between mobile systems parallel the best known and used system is that of a Stewart platforms, as being and the oldest system, quickly, solid and accurate. The paper presents a few main elements of the Stewart platforms. In the case where a motto element consists of a structure composed of two elements in a relative movement from the point of view of the train of propulsion and especially in the dynamic calculations, it is more convenient to represent the motto element as a single moving item. The paper presents an exact, original analytical geometry method for determining the kinematic and dynamic parameters of a parallel mobile structure. Compared with other methods already known, the presented method has the great advantage of being an exact analytical method of calculation and not one iterative-approximately

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

Control of Thermal Deflection in Concrete Structures Using Iron-Based Shape Memory Alloys

Mitigating the structural damage brought about by thermal expansion is a primary objective in the design of vital concrete infrastructures, such as bridges or buildings. Shape memory alloys (SMAs), through their ability to recover strains through thermal loading-induced phase transformations, offer a distinct advantage in achieving this design goal as such strain recovery in embedded components could be used to oppose thermal expansion in a surrounding matrix (e.g. concrete). This study seeks to characterize the thermal expansion of system, comprised of an SMA rod embedded in a concrete block undergoing a thermal loading cycle. Characterization is produced through a full factorial analysis, wherein evaluation is performed through the Abaqus unified finite element analysis suite. This preliminary analysis indicates that, while iron-based SMAs show promise in this field due to their low manufacturing costs, their large thermal hysteresis may lead to limited phase transformation in this application

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