The increasing use of polymer-based materials (PBMs) across all types of industry has not been matched by sufficient improvements in understanding of polymer tribology: friction, wear, and lubrication. Further, viscoelasticity of PBMs complicates characterization of their behavior. Using data from micro-scratch testing, it was determined that viscoelastic recovery (healing) in sliding wear is independent of the indenter force within a defined range of load values. Strain hardening in sliding wear was observed for all materials-including polymers and composites with a wide variety of chemical structures-with the exception of polystyrene (PS). The healing in sliding wear was connected to free volume in polymers by using pressure-volume-temperature (P-V-T) results and the Hartmann equation of state. A linear relationship was found for all polymers studied with again the exception of PS. The exceptional behavior of PS has been attributed qualitatively to brittleness. In pursuit of a precise description of such, a quantitative definition of brittleness has been defined in terms of the elongation at break and storage modulus-a combination of parameters derived from both static and dynamic mechanical testing. Furthermore, a relationship between sliding wear recovery and brittleness for all PBMs including PS is demonstrated. The definition of brittleness may be used as a design criterion in selecting PBMs for specific applications, while the connection to free volume improves also predictability of wear behavior.

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A study has been undertaken to investigate the loss of ductility and modified work hardening characteristics of zinc single crystals coated with mercury. Important results of tensile tests performed under fixed experimental conditions are summarized to be: (1) increase in critical resolved shear stress, and increase of work hardening slope in stage A and stage B (2) decrease in transition strain from stage A to stage B (3) decrease in fracture stress and fracture strain. The results have been interpreted in the context of the present understanding of deformation theory of C.P.Hex. metals. In addition, relevant mechanisms for crack initiation have been studied with the aid- of microscopic observations of deformed crystals. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

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Thesis (M.S.)--West Virginia University, 1998. / Title from document title page. "December 1998." Document formatted into pages; contains viii, 92 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 73-78).

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [256]-267 ).

Master of Science / Department of Geology / Abdelmoneam Raef / Matthew W. Totten / The Woodford shale in west-central Oklahoma is an organic and silica rich shale that is a prolific resource play producing gas and liquid hydrocarbons (Gupta et al., 2013). Unconventional shale wells are only producible due to modern hydraulic fracturing techniques. Production surveys from unconventional reservoirs show significant variability between wells and even between fracking stages (Kennedy, 2012). The production potential of a particular shale appears to be related to its brittleness and kerogen content "sweetness". Thus, brittleness analysis becomes important when choosing which shales to produce. A rocks brittleness index can be related directly to elastic properties derived from P- and S-wave velocities, as well as, its specific mineral makeup. This project's main focus is to determine the elastic rock properties that affect or relate to Woodford shale brittleness and how they relate to the rock's specific mineral makeup and kerogen content. Measurements to determine elastic properties, based on ultrasonic laboratory testing, were conducted on available Woodford cores. The estimated elastic moduli were evaluated via cross-plotting and correlation with a variety of rock properties. Elastic properties are of essential relevance to forward seismic modeling in order to study seismic response. Mineral makeup, determined via XRD and XRF analyses done by Kale Janssen (2017), was used to calculate a mineral-based brittleness index for comparison with the elastic moduli. Evaluation of the elastic moduli assisted in determining which elastic properties directly relate to the brittleness of the shales and, in turn, to geomechanical aspects. These properties were correlated with data from previous studies including mineral percentages, total organic content (TOC), and thermal maturity. These correlations were used to determine which elastic properties best predict a rock's brittleness index. The calculated brittleness was used to develop a brittleness index map of the Woodford Formation.

M.Tech. (Civil Engineering) / The results of an investigation on the local buckling of cold-formed stainless steel compression sections arc presented in this dissertation. The stainless steel under consideration is AISI Type 304 Austenitic, manufactured by the South African based speciality steel producing company Middelburg Steel & Alloys. All sections were manufactured by press braking process. The purpose of this investigation was to study the critical buckling stress and buckling coefficient (k), of cold-formed, partially stiffened stainless steel compression elements in order to determine the applicability of the current design specification. The mechanical properties of the stainless steel under consideration as well as the results of 28 partially stiffened double hat sections are compared with theoretical predictions. It was concluded in this study that the experimental results of the critical buckling stress compare well when using the plasticity reduction factor Es/Eo in the theoretical predictions. However the theoretical buckling coefficient (k) shows to be not representative to the experimental results obtained in this investigation.