Browsing by Author "Kennedy, John Maurice"

Now showing 1 - 5 of 5
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    The Abaqus/CAE Plug-in for Premium Threaded connection 3D parameter Finite Element Model
    Yan, Kaidi (Virginia Tech, 2017-06-22)
    Finite Element Analysis (FEA) is proposed to simulate the connection response of practical in-service conditions and test the performance of Oil Country Tubular Goods (OCTG) premium threaded connections. A plug-in is developed in Abaqus/CAE for creating the 360-degree full 3D parametric finite element model with helical threads as an effective design and analysis tool. All size, position and material data of the model are parameterized. The premium connection plug-in accepts input from the Graphical User Interface (GUI) for further modification. Each premium connection component is programed as a collection of single-purpose independent functions organized as an independent module in order to allow users to modify specific function behavior conveniently. A main program is designed as an Abaqus kernel plug-in to achieve all the functions by calling these independent functions, making the plug-in flexible. Each single script file is not too long to jeopardize readability. The GUI of the plug-in is designed with proper layout arrangement and illustrations to make the plug-in user-friendly and easy to use. The premium connection FE model is used in a virtual test to validate the model against the ISO 13679 test protocol and is used to develop the seal metrics for points on the ISO 13679 sealability envelope. The plug-in can be used to develop and evaluate the design envelope of the premium connection.
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    Design and Optimization of Carbon-Fiber Chassis Panels
    Anderson, Eric Carlton (Virginia Tech, 2014-06-05)
    Each year, the Virginia Tech (VT) Formula SAE (FSAE) team creates a high performance car to compete against 120 teams from around the world in a series of dynamic events evaluating acceleration, maneuverability, and handling. In an effort to improve upon the VT 2013 car, the torsional stiffness of the chassis was increased. Increasing the torsional stiffness of the chassis allows the suspension to be more precisely tuned, resulting in a better overall performance. An investigation was conducted into methods for improving the chassis stiffness, and it was determined that many state-of-the-art vehicles from go-karts to super cars incorporate strength-bearing, tailored advanced composite materials in their structure. Examples of components that use composites in vehicles include sandwich structures in load-bearing panels, layups in the skin of vehicles for aesthetic purposes and carbon-fiber frame tubes. The VT FSAE car already includes untailored carbon-fiber panels on the bottom and sides of the structure for packaging and aerodynamic purposes. By integrating and optimizing these carbon-fiber panels, the torsional stiffness and therefore overall performance of the structure may be increased. This thesis explores composite testing, optimization methods, experimental and computational analysis of the chassis, and results. The fiber orientation of the panels may be optimized because carbon-fiber composite materials are generally anisotropic. Therefore the composite materials can be tailored to maximize the stiffness, resulting in the optimum stiffness per added weight. A good measure for testing stiffness per added weight is through measuring natural frequencies because natural frequency is proportional to stiffness per unit mass. A computer program was developed in MATLAB to optimize the composite configuration, and uses an objective function involving the first three natural frequencies of the original steel space frame chassis and the first three natural frequencies of the steel chassis augmented with three composite panels. The composite material properties were determined using specimen tensile testing and checked with finite elements. The natural frequencies of the half-scale chassis were determined experimentally, compared to the simulated version, and varied by less than seven percent. The optimization of the full-scale model determined that eight layers of optimized, integrated carbon-fiber composite panels will increase the first, second, and third natural frequencies by sixteen, twenty-six, and six percent, respectively. Natural frequency increases of these amounts show that by using tailored, load-bearing composite panels in the structure, the torsional stiffness of the structure increases, resulting in easier suspension tuning and better performance at the VT FSAE competitions.
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    An Experimentally-Validated V-Belt Model for Axial Force and Efficiency in a Continuously Variable Transmission
    Messick, Matthew James (Virginia Tech, 2018-09-19)
    Rubber V-belt Continuously Variable Transmissions (CVT's) are commonplace in the Baja SAE collegiate design competition, and are also used widely in the power sports industry. These transmissions offer benefits of simplicity in mechanical design, consisting of only two pulleys, and are easy to use. While most teams in the competition use commercially available designs, custom designs are becoming more common, and the Baja team at Virginia Tech has used custom CVT's since the 2014 season. The design of these CVT's has relied heavily on trial and error, requiring significant adjustments to be made during the testing phase. In addition, only qualitative information is known for the relationship between efficiency and design parameters, such as sheave angle. The goal of this thesis is to create an improved V-belt model that may be used as a design tool. This model provides quantitative information about efficiency that can be used to make more informed design decisions. The belt model also provides insight into the magnitude and relationship between the axial forces in the pulleys. This can be used to create an initial design that is more accurate, and possibly reduce the time required for tuning. A CVT dynamometer was constructed to validate the analytical results for efficiency, and this will also serve as a tuning tool for future Baja teams at Virginia Tech. This thesis will advance the state of the custom CVT design and testing process at Virginia Tech, and hopefully lead to improved results at competition in the future.
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    Fatigue Crack Growth Analysis with Finite Element Methods and a Monte Carlo Simulation
    Melson, Joshua Hiatt (Virginia Tech, 2014-06-04)
    Fatigue crack growth in engineered structures reduces the structures load carrying capacity and will eventually lead to failure. Cycles required to grow a crack from an initial length to the critical length is called the fatigue fracture life. In this thesis, five different methods for analyzing the fatigue fracture life of a center cracked plate were compared to experimental data previously collected by C.M. Hudson in a 1969 NASA report studying the R-ratio effects on crack growth in 7075-T6 aluminum alloy. The Paris, Walker, and Forman fatigue crack growth models were fit the experimental data. The Walker equation best fit the data since it incorporated R-ratio effects and had a similar Root Mean Square Error (RMSE) compared to the other models. There was insufficient data in the unstable region of crack growth to adequately fit the Forman equation. Analytical models were used as a baseline for all fatigue fracture life comparisons. Life estimates from AFGROW and finite elements with mid-side nodes moved to their quarter point location compared very with the analytical model with errors less than 3%. The Virtual Crack Closure Technique (VCCT) was selected as a method for crack propagation along a predefined path. Stress intensity factors (SIFs) for shorter crack lengths were found to be low, resulting in an overestimated life of about 8%. The eXtended Finite Element Method with Phantom Nodes (XFEM-PN) was used, allowing crack propagation along a solution dependent path, independent of the mesh. Low SIFs throughout growth resulted in life estimates 20% too large. All finite element analyses were performed in Abaqus 6-13.3. An integrated polynomial method was developed for calculating life based on Abaqus' results, leading to coarser meshes with answers closer to the analytical estimate. None of the five methods for estimating life compared well with the experimental data, with analytical errors on life ranging from 10-20%. These errors were attributed to the limited number of crack growth experiments run at each R-ratio, and the large variability typically seen in growth rates. Monte Carlo simulations were run to estimate the distribution on life. It was shown that material constants in the Walker model must be selected based on their interrelation with a multivariate normal probability density function. Both analytical and XFEM-PN simulations had similar coefficients of variation on life of approximately 3% with similar normal distributions. It was concluded that Abaqus' XFEM-PN is a reasonable means of estimating fatigue fracture life and its variation, and this method could be extended to other geometries and three-dimensional analyses.
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    Quantitative Laser-based Assessment of Top of Rail Friction Modifiers for Railroad Application
    Hasan, Abdullah Mohammed (Virginia Tech, 2016-05-04)
    The primary purpose of this study is to assess the effectiveness and utility of laser-based sensors for measuring, quantitatively, the presence and extent of top-of-rail (TOR) friction modifiers that are commonly used in the railroad industry for reducing friction between railcar wheels and rail. Modifying the friction between the wheel and rail is not only important for significantly reducing rolling resistance, but it also contributes to reducing wheel and rail wear, lowering rolling contact fatigue, and potentially curving resistance. It is common to monitor rail lubrication empirically by manually observing the sheen of the rail and tactically sensing any residues that may be present on the rail. Often performed by experienced railroad engineers, such methods are highly subjective and do not provide a quantitative assessment of how lubricated or unlubricated the track may be. A new, quantitative measurement method for accurately assessing the state of lubrication of rail is developed and studied in depth. The method takes advantage of the light reflection and dispersion properties of laser-based optical sensors to provide a repeatable, verifiable, and accurate measure of the presence of TOR friction modifiers on the rail. The measurement system is assembled in a self-contained, portable rail cart that can be pushed on the rail at walking speeds. Various TOR states are assimilated in the lab for assessing the effectiveness of the laser system. Additionally, the laboratory results are repeated in the field on various tracks, including revenue service track. The results of the tests indicate that the developed system is able to accurately measure the presence of TOR friction modifiers from none to fully-saturated, but is not affected by environmental factors such as rain, sunlight, type of rail, and top-of-rail condition. The measurements provide the means for classifying the state of rail friction in an indexed manner. The results of the study will not only have a significant effect on more efficient use of TOR friction modifiers for promoting better fuel efficiency, but they can also have a major impact on braking practices in applications such as Positive Train Control (PTC).