Browsing by Author "Dr. John S. Strenkowski, Committee Chair"

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Development of a Practical Fatigue Analysis Methodology for Life Prediction of Rotary-Wing Aircraft Components.
(2006-08-28) Cowell, Jason Michael; Dr. Kara J. Peters, Committee Member; Dr. Jerome J. Cuomo, Committee Member; Dr. John S. Strenkowski, Committee Chair
A practical fatigue analysis methodology was developed for predicting the life of rotary-wing aircraft components. The focus of this fatigue capability was two-fold. First, to gain insight into the current life prediction methodologies and their use, and second, to be able to predict the service life of aircraft components and determine if reworked parts are suitable for continued service. Commercially available software, ANSYS and Fe-safe, were utilized as the finite element and fatigue life prediction solvers, respectively. It was demonstrated that the predicted fatigue life on aircraft components can be performed with reasonable accuracy and efficiency by utilizing commercially available software. This methodology was first demonstrated by investigating the predicted fatigue life of a flat plate with a centrally located hole under constant amplitude and variable amplitude loading. This approach was validated by comparing simulated life predictions using several stress-life and strain-life algorithms with previously published experimental data. In addition, an illustrative helicopter main gear drag beam was analyzed and the effect on fatigue life due to a reduction in the beam thickness was demonstrated. This research had demonstrated that a fatigue life methodology can be successfully utilized to predict the service life of aircraft components in a practical manner and to determine if reworked parts are suitable for continued service.
Integrated Modeling Analysis of Glass Furnace Forehearths as Applied to Production Planning Optimization
(2004-07-18) Belz, Robert Michael; Dr. Jerome J. Cuomo, Committee Member; Dr. James W. Leach, Committee Member; Dr. John S. Strenkowski, Committee Chair
A two-dimensional model was developed to investigate thermal variations within a glass furnace forehearth as used in the production of glass fibers. The goal of the simulations was to develop a production planning tool that can be used not only to help establish product changeover guidelines but also to identify undesirable processing conditions. Commercially available software, FLUENT and FIDAP, were utilized as the finite element computational fluid dynamic (CFD) solvers. The models incorporated sufficient detail to investigate primary production control parameters for various types, configurations, and geometries of forehearths as used throughout the industry. The models incorporated various throughput rates as represented by different fiber forming bushings and processing parameters. In addition, the height of the glass surface was computed and integrated into the molten glass flow and heat transfer equations. Steady-state and transient forehearth simulations were conducted and the results were compared with previously published forehearth experimental operating data. The simulations illustrated that a bushing changeover has a significant impact on the glass temperature and flow in the forehearth, whereas variations of glass height were shown to have a minimal effect. The models developed in this thesis are adaptable to other bushing configurations and the models should provide useful product changeover guidance for the purpose of optimizing production planning.
A Numerical and Experimental Investigation of the Machinability of Elastomers
(2003-08-29) Rodkwan, Supasit; Dr. John S. Strenkowski, Committee Chair
In this dissertation, a better understanding of the machinability of elastomers is established. The main objective of the research is to determine the machining conditions for which an elastomer can be machined with a smooth surface finish. Both machining experiments and numerical simulations were carried out to achieve this goal. For the experimental studies, a series of orthogonal machining tests were conducted to investigate the effects of various machining parameters on chip morphology, machined surface condition, and resulting machining forces. Feed speed and rake angle were found to have a significant effect on the type of chip generated during orthogonal machining. High feed speed conditions and large rake angle tools produced long and continuous ribbon-like chips and a corresponding smooth machined surface. The design of workpiece fixture in the cutting was also found to be very critical for machining smooth surfaces. In the numerical investigation, wedge indentation models were developed to simulate the incipient separation of elastomers. It was found that high tensile normal stress and maximum principal stresses, as well as a large concentrated strain energy density near the separation point lead to favorable conditions for formation of continuous chips and a good surface finish. The indentation simulation agrees well with the cutting tests in which tools with a large rake angle and large feed produced continuous chips and a smooth surface finish. The models offer potential for identifying these cutting conditions and tools that produce a smooth machined surface finish of elastomers.