Global ETD Search

1	Effects of Storage on the Linear Viscoelastic Response of Polymer-Modified Asphalt at Intermediate to High Temperatures Reubush, Stacey Diane 09 January 2000 (has links) The design and construction of roads with longer service lives is a priority of civil engineers. The selection of appropriate highway materials with respect to climatic and loading conditions may significantly increase the lifespan of pavements. One material receiving interest in the area of improved roadway performance is polymer-modified binder. The complex behavior of polymer-modified binders, particularly over time, is not yet well-understood by engineers. Therefore, an experimental study was performed to determine the effects of four years of storage at room temperatures (23°C) on the dynamic mechanical properties of polymer-modified binders at intermediate and high temperatures. A typical paving grade (AC-20) and three elastomeric modifiers, each at three concentrations were used. Initial tests were performed in 1995 to evaluate the effects of short-term aging as simulated by the Rolling Thin Film Oven Test (RTFOT) procedure. This study encompasses a second phase of testing occurring after the modified binders were stored at ambient room temperature (23°C) for four years. The study found that significant changes affecting the dynamic response of binders occur during long term storage at a temperature of 23°C. These changes are dependent on the type and concentration of modifier and may be beneficial. Additionally, four mathematical models describing the dynamic response of binders were evaluated and found to be variable in their ability to accurately predict response of modified binders. Most of these models are not well suited for prediction of the response of stored binders. / Master of Science storage complex shear modulus Aging dynamic mechanical testing polymer-modified asphalt
2	An investigation into the velocity-dependence of the coefficient of friction between concrete and maraging steel Duncan, Trace A 09 August 2022 (has links) This work investigates the velocity-dependent coefficient of friction between concrete and 300 Maraging steel over short displacements. A modified torsional Hopkinson bar is utilized for rotating thin-walled steel rings in contact with a concrete disk under static precompression. Rotational velocity is varied between tests to determine the velocity dependence of the friction coefficient. Normal force is varied between certain tests to determine the pressure dependence of the friction coefficient between the concrete and steel. Three different types of concrete are tested to deduce any composition effect on the friction coefficient. Dry and greased conditions’ impact on the friction coefficient are also evaluated. Lastly, the displacement dependence (fade) is considered for the concrete with regards to the steel. Discussion of the usefulness of this data in modeling and experimentation of impact between concrete and steel is disclosed. Coefficient of friction slip velocity Hopkinson Bar Maraging steel dynamic mechanical testing friction versus velocity Applied Mechanics Tribology
3	FROM THEORY TO APPLICATION: THE ADDITIVE MANUFACTURING AND COMBUSTION PERFORMANCE OF HIGH ENERGY COMPOSITE GUN PROPELLANTS AND THEIR SOLVENTLESS ALTERNATIVES Aaron Afriat (10732359) 20 May 2024 (has links) <p dir="ltr">Additive manufacturing (AM) of gun propellants is an emerging and promising field which addresses the limitations of conventional manufacturing techniques. Overall, this thesis is a body of work which serves to bridge the gap between fundamental research and application of additively manufactured gun propellants.</p> Organic chemical synthesis Theoretical quantum chemistry Aerospace materials Powder and particle technology Composite and hybrid materials Polymers and plastics Solid mechanics additive manufacturing composite propellant gun propellant afriat method afriat isoconversional method solventless gun propellant vibration-assisted printing vibration assisted printing VAP 3DThermoDIC instrumented ram extruder low-vulnerability ammunition 3D internal geometries extrusion based additive manufacturing rheology of lova propellant lova propellant dynamic mechanical testing anisotropy gun propellant paste rheology clogging analysis high strain rate failure 3d digital image correlation thermal imaging powder gun gun firing ballistic performance

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