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

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

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

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

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 Electron Dimension

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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

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