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Overhead transmission lines are periodically inspected using both on-ground and helicopter-aided visual inspection. Factors including sun glare, cloud cover, close proximity to power lines and the rapidly changing visual circumstances make airborne inspection of power lines a particularly hazardous task. In this research, a finite element model is developed that can be used to create the theoretical dispersion curves of an overhead transmission line. The complex geometry of the overhead transmission line is the primary reason for absence of a theoretical solution to get the analytical dispersion curves. The numerical results are then verified with experimental tests using a non-contact and broadband laser detection technique. The methodology developed in this study can be further extended to a continuous monitoring system and be applied to other cable monitoring applications, such as bridge cable monitoring, which would otherwise put human inspectors at risk.

Coupling beams are structural elements used to connect two or more shear walls. The most common material used in the construction of coupling beam is reinforced concrete. The use of coupling beams along with shear walls require them to resist large shear forces, while possessing sufficient ductility to dissipate the energy produced due to the lateral loads. This study has been undertaken to produce a computational model to replicate the behavior of conventionally reinforced coupling beams subjected to cyclic loading. The model is developed in the finite element analysis software ABAQUS. The concrete damaged plasticity model was used to simulate the behavior of concrete. A calibration model using a cantilever beam was produced to generate key parameters in the model that are later adapted into modeling of two coupling beams with aspect ratios: 1.5 and 3.6. The geometrical, material, and loading values are adapted from experimental specimens reported in the literature, and the experimental results are then used to validate the computational models. The results like evolution of damage parameter and crack propagation from this study are intended to provide guidance on finite element modeling of conventionally reinforced concrete coupling beams under cyclic lateral loading.

Detta examensarbete beskriver undersökningen av kärnmaterial i en sandwichpanel under belastning. Arbetet har utförts tillsammans med CCG i Laholm, Sverige. Kärnmaterialen lämpar sig vid design av sandwichpaneler på grund av sin låga vikt och sin förmåga att klara av högt tryck. Då materialet uppvisar ett ickelinjärt beteende skapar det problem vid design av sandwichpaneler och leder till att materialsammansättningarna tillverkas konservativa mot verkligheten. Projektet har gått ut på reducera designprocessen genom att bygga upp och simulera materialmodeller i programvaran ABAQUS för att kunna analysera och förutse materialets beteende. Resultaten har presenterats i kraft- och förskjutningsdiagram samt visualiseringar och har försvarats med hjälp av teorier för kontaktmekanik samt matematik. Projektet har utförts på ett vetenskapligt sätt där hypotes verifieras mot teori för att sedan verifieras i experiment, allt för att säkerställa resultatet. / This thesis describes a study of the core materials used in composite panels under static indentation. The work was conducted together with CCG in Laholm, Sweden. These materials work well when designing sandwich panels due to their low weight and high compression strength. As the cores show a non-linear behavior problems can arise when constructing panels and oftentimes lead to choosing very conservative solutions that are not optimized.The main focus of this thesis has been the modelling and simulation of materials in the software ABAQUS to analyze and predict the materials behavior and reduce the time needed for the design of new panels. The result is presented in force- displacement plots as well as von Mises visualization plots and is sustained by theories of both contact mechanics and mathematics. The group endeavored to work in a scientific manner by verifying the hypotheses through theory and experiments in order to accomplish accurate results.

As the development of shale resources continue to accelerate in the United States, improving the effectiveness and the cost efficiency of hydraulic fracturing completion is becoming increasingly important. For such improvement, it is necessary to investigate the effects of various design parameters and in-situ conditions on the resulting fracture dimensions and propagation patterns. In this thesis, a 3D geomechanical model was built using ABAQUS Standard to simulate the propagation of multiple competing fractures in a single fracture stage of a horizontal well. The reservoir was modeled as a porous elastic medium using C3D8RP pore pressure & stress elements. In addition, a vertical plane of COH3D8P pore pressure cohesive elements was inserted at each perforation cluster to model fracture propagation. Also, the flow distribution among perforation clusters was simulated using a parallel resistors model. The results suggested that the fracture spacing has the dominant impact on the number of propagated fractures. Even when all other conditions were favorable to fracture propagation, small fracture spacing reduced the number of propagated fractures. Similarly, in a given fracture stage, decreasing the number of perforation clusters abated inter-fracture stress interference, and increased the number of propagated fractures. Higher injection fluid viscosity significantly increased the fracture widths and slightly decreased the fracture lengths, but did not have any impact on the number of propagated fractures. Also, higher injection rates led to longer and wider fractures, and increased the number of propagated fractures. Therefore, a high injection fluid viscosity and a high injection rate should be used to promote fracture propagation. Lastly, higher Young's modulus of the target formation led to increased stress interference, and the resulting fractures were shorter and narrower. Therefore, if the Young’s modulus of a target formation is high, a wider fracture spacing should be considered. Through this study, a 3D geomechanical model was successfully formulated to simulate the propagation of multiple competing fractures. In addition, the effects of various hydraulic fracturing design parameters and in-situ conditions on the resulting fracture dimensions and propagation patterns were demonstrated. / text

The goal of this thesis is to improve the understanding of the stitch bonding process in microelectronic wire bonding. In particular, it focuses on investigating the effect of the process parameters bonding force, scrub amplitude, and skid on experimental bond quality responses, including qualitative (non-sticking, sticking, and tail-lifting) and quantitative (stitch pull force, tail pull force). In addition to the experimental work, a finite element (FE) model is developed for the stitch bonding process using ABAQUS software, and compared with the experimental observations. For the first set of experiments, the stitch bonding is performed with a 18 ??m diameter Pd coated Cu (PCC) wire on a ???low bondability??? Au/Ni/Pd plated quad-flat non-lead (QFN) substrate. Results showed that a high bonding force, a high scrub amplitude, and a positive skid provoke the sticking of the stitch bond and reducing the chance of non-sticking observation. However, such parameters also increase the chance of tail-lifting. As a trade-off for a low bondability substrate, a process parameter combination containing a high bonding force and a high scrub amplitude and a negative skid could ensure a strong enough stitch bonding process with low chance of tail-lifting. For the second set of experiments, the stitch bonding is performed with a 18 ??m diameter uncoated Cu wire on a ???high bondability??? Ag plated QFN substrate. Statistical analysis of stitch and tail pull force showed that the skid and scrub parameters have a more significant influence than bonding force. A positive skid can degrade the stitch pull force, while enhancing the tail pull force. A high scrub amplitude is found to degrade both the stitch and the tail pull forces. The bonding force is shown to improve the stitch and tail pull forces slightly. Performing an optimization, process parameters of 70 gf (687 mN) bonding force, 3 ??m scrub amplitude, and zero skid result in acceptable stitch and tail pull forces, along with a reliable stitch bond appearance (low peeling and shallow capillary tool impression). The influence of the process parameters is significantly different depending on if bonding on low or high bondability substrates. For example, a positive skid increases the chances of sticking and tail-lifting on low bondability substrate, but it decreases the tail pull force and increases the tail pull force for high bondability substrate. This indicates that finding a general experimental rule for understanding the effect of process parameters on the stitch bond quality is difficult if not impossible. In other words, instead of general rule, it is more likely to find individual rules for specific individual applications. To improve the understanding of stitch bonding a three dimensional (3D) dynamic explicit FE model is developed in ABAQUS. The model components and boundary conditions are constructed and applied to reflect the experimental conditions. The bonding force, scrub, and skid are successfully implemented into the model. Mass scaling is applied carefully to save calculation time while ensuring there are no artificial effects of inertia. The model is able to render the conventional responses reported in the past including stress and strain distributions. However, these conventional outputs were not sufficient to provide a correlation between model and experiment. Therefore, new candidate responses were developed and extracted from the numerical results. The new responses are based on accepted welding mechanisms. One of the mechanisms is interfacial cleaning by frictional energy which is beneficial for bonding. Thus the friction energy accumulated during the simulated bond duration is extracted as a candidate response. For classical cold welding processes, the interfacial surface expansion is a key mechanism, as it opens up cracks in the surface contamination and oxide layers and thereby generates paths to bring the fresh metals together under pressure. Therefore, candidate responses related to surface expansion at the contact interface are extracted from the model. The complete set of new responses extracted from the numerical model includes contact areas, surface expansion per areas, frictional energy, and combination of frictional energy combined with surface expansions per areas. In addition the bond interface is divided into ???wedge??? and ???tail??? regions. The model is run for the same DOE cells as used in the first set of experiments and candidate responses are extracted and compared with the experimental observations. By ranking the correlation coefficients of each individual candidate responses, for the first time correlations that are relatively strong are found between a numerical response and experimental observations of stitch bonding. Responses that have correlation coefficients of 0.79 and 0.85 were found for wedge sticking and tail-lifting, respectively. Such relatively strong correlation indicates that the friction enhanced cleaning and the surface expansion mechanisms are proper theories for the current stitch bonding system. These theories can be used for developing similar models for other types of the solid-state bonding processes. Based on the best candidate responses, a procedure to determine numerical process windows is demonstrated for a specific application. Such a window defines the parameter ranges which result in an acceptable stitch bonding process and is an excellent indication of how suitable a process is for mass production. Depending on the application, materials, geometries, and tools, the FE model and process window procedure allow a variety of numerical process windows to be produced and compared.

Concrete and asphalt are the most common materials used in permanent roadway pavements. Roadways are also constructed for temporary use in the resource industry, for remote site construction, and for disaster relief. Although temporary roads have been used for almost as long as permanent ones, little research has been done to optimize their design in view of their relatively short service lives or to investigate the advantages of constructing them with reusable materials or employing structural systems that require minimal subgrade preparation. With this in mind, the purpose of this study is to conduct research to determine the feasibility of a reusable, modular road plate system requiring minimal preparation of the subgrade. This thesis presents a literature review, summarizing the currently available products that perform a similar function and the methods currently available to design such products, including terramechanics and foundation design. Alternative concept designs for a modular road plate system are then introduced. Following this, a simple structural steel plate system is designed to resist vertical, traffic-induced loads using several methods. Specifically, an equivalent thickness method and finite element (FE) analysis are employed. Different loading conditions, soil conditions, and plate assemblies (i.e. boundary conditions) are compared. The different loading conditions include: single and multi-wheel loading, and centre versus edge loading of the plate. The different modelled plate assemblies include: single plates, four plates assembled with fixed connections, and four plates assembled with hinged connections. Structural steel plates are considered in the FE analysis study, in order to develop the design methodology, prior to applying it to the other materials or structural systems. Soil properties and panel thicknesses are studied covering a broad range of conditions under which temporary roadways may be built. Thirty scenarios are created from five soil types and six panel thicknesses. With the different loading and boundary conditions investigated, a total of 120 scenarios are analyzed in total, using several different FE models. The results from the FE analysis studies show that there is a significant difference between hinged and fixed connected panels, and that these different boundary conditions can be considered by modelling a single plate that is centre loaded (to represent a multi-plate system with fixed plate connections) or a single plate that is edge loaded (to represent a multi-plate system with hinged plate connections). The results of this research in general provide a practical framework for developing a modular road plate system constructed using any material or structural system under a range of soil and loading conditions.

Concrete and asphalt are the most common materials used in permanent roadway pavements. Roadways are also constructed for temporary use in the resource industry, for remote site construction, and for disaster relief. Although temporary roads have been used for almost as long as permanent ones, little research has been done to optimize their design in view of their relatively short service lives or to investigate the advantages of constructing them with reusable materials or employing structural systems that require minimal subgrade preparation. With this in mind, the purpose of this study is to conduct research to determine the feasibility of a reusable, modular road plate system requiring minimal preparation of the subgrade. This thesis presents a literature review, summarizing the currently available products that perform a similar function and the methods currently available to design such products, including terramechanics and foundation design. Alternative concept designs for a modular road plate system are then introduced. Following this, a simple structural steel plate system is designed to resist vertical, traffic-induced loads using several methods. Specifically, an equivalent thickness method and finite element (FE) analysis are employed. Different loading conditions, soil conditions, and plate assemblies (i.e. boundary conditions) are compared. The different loading conditions include: single and multi-wheel loading, and centre versus edge loading of the plate. The different modelled plate assemblies include: single plates, four plates assembled with fixed connections, and four plates assembled with hinged connections. Structural steel plates are considered in the FE analysis study, in order to develop the design methodology, prior to applying it to the other materials or structural systems. Soil properties and panel thicknesses are studied covering a broad range of conditions under which temporary roadways may be built. Thirty scenarios are created from five soil types and six panel thicknesses. With the different loading and boundary conditions investigated, a total of 120 scenarios are analyzed in total, using several different FE models. The results from the FE analysis studies show that there is a significant difference between hinged and fixed connected panels, and that these different boundary conditions can be considered by modelling a single plate that is centre loaded (to represent a multi-plate system with fixed plate connections) or a single plate that is edge loaded (to represent a multi-plate system with hinged plate connections). The results of this research in general provide a practical framework for developing a modular road plate system constructed using any material or structural system under a range of soil and loading conditions.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Includes bibliographic references (p.140-143).