The objective of the investigation is to analyze effect of surface layer on mechanical properties of metal.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xxi, 282 p.; also includes graphics (some col.). Includes bibliographical references (p. 262-282).

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 191-198.

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Released for public view from 10 November 2008. Includes bibliographical references: leaf 136-146.

Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on July 8, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Materials Engineering, Department of Chemical and Materials Engineering, University of Alberta. Includes bibliographical references.

Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2003 / Systematic laser cladding experiments were performed using a mixture of a Nickel base alloy powder mixed with tungsten carbide powder (percentage contents of tungsten carbide from 10% to 40%) on EN8 steel substrate with pre-placed powder method. Laser cladding of the Nickel base alloy powder + 50% tungsten carbide powder on EN9 steel substrate was performed with powder injection method as well. A Finite Element Method for calculating the surface temperature distribution was used to help prediction of temperature distribution laser cladding results. Composition of cladding materials was designed; a sticking agent was chosen for the pre-placed powder method. Clad coatings were obtained for different process parameters for laser cladding, and a detailed study of the affects of these parameters has been carried out. The characteristic microstructure and properties of the clad layers and interface were investigated by using an optical microscope, a micro hardness tester and a makeshift wear test. A comprehensive review is presented on the dilution of the coating and the typical problems experienced with the coating substrate interface. The results show that microstructure of clad layers comprise three zones: the cladding layer, bonding zone and heat-affected zone. The results showed that tungsten carbide particles increased the hardness and wear resistance as expected. Wear resistance of laser cladding coating is 3.5 times than that of substrate. The micro hardness range of the cladding layer is from RV 981.5 to RV 1187, which is 2-3 times than that of substrate. The micro hardness varies from cladding coating to transition layer then to heat affected zone and substrate along a gradient.

Over the past decade, fiber optic strain sensors have begun to transition from use in laboratory research to commercial sector applications. This transition is somewhat hindered due to the high cost associated with many optical components required for fiber optic-based sensing systems. Multiplexing systems for fiber optic sensors are one approach to reducing the per-channel cost of fiber optic sensor implementation, however, in many applications, on-line monitoring of sensor elements is not required and the periodical addressing of sensor elements is acceptable. Commercially available fiber optic strain sensor systems are now available which support periodical sensor addressing by providing absolute information about the strain state of the sensor. A post-damage inspection fiber optic sensor design which employs a thick metal coating to retain information regarding the strain history of a sensor is demonstrated. Additionally demonstrated is a corrosion sensing technique which exploits the residual strain retention of the post-damage inspection sensor. Finally, the temperature sensing properties of the metal-coated sensor is investigated. / Master of Science

Today, drilling can be considered the most common of all metal cutting operations. Drilling can be accomplished on nearly all machines that can produce a relative rotation of the spindle, and/or the workpiece. These machines can include drill presses, lathes, milling machines and machining centers. Of the more than 1.70 million machine tools in the United States, that are located in plants employing more than twenty workers, more than half of these machines can, and probably are performing drilling functions. Drilling has been studied in numerous investigations with the objective of increasing drill performance. Severely lacking in this research has been the use of statistically designed experiments. Traditional experimental techniques in tooling have been conducted under a one variable at a time methodology. The twist drill, however, is one of the most complex metal cutting tools in existence today. Changing one variable at a time can lead to unwanted changes in other variables. With today's statistical techniques and computers, variables and variable interactions should be able to be adjusted and controlled. Because drilling is one of the leading metal cutting operations, an ever so slight increase in the level of drill performance could yield important benefits to manufacturing. Investigation into drill geometry and variable interaction may also lead to significant increases in drill performance. A quantitative analysis was performed to determine the effect of different independent variables on tool life for Titanium Nitride Coated tools. This was accomplished in two stages. In Stage 1, the variables lip height, helix angle, and margin width were tested one at a time for their effect on tool life. In Stage 2, the variable lip height from Stage 1 and the independent variables, speed and feed, were tested for their effect on tool life in a three variable, two level factorial treatment design. Secondary measurements were also taken in Stage 2 on acceleration, torque and face wear. Stage 1 showed that tighter tolerances on lip height could improve tool life. The 39 degree helix angle was more of a detriment than an aid, to increase tool life. The lowest level of margin width had lower tool life than either of the other two levels. In stage 2 feed and lip height had a significant effect on tool life at the 90% confidence level. Speed did not have an effect on tool life. No variable in Stage 2 had an significant effect on acceleration at either the 95% or 90% confidence level. At the low level of the feed, acceleration readings seemed applicable in determining pending tool failure. The largest values of crater width on the face were associated with the low values of feed. No true distinction can be made with torque, between any of the combinations of levels tested. This research has attempted to further quantify some of the variables and variable interactions associated with drilling for Titanium Nitride Coated tools. / M.S.

Valve stem seal leakage is a major source of fugitive emissions, and controlling these emissions can result in added expense in leak detection and repair programs. Elastomeric O-rings can be used as valve stem seals, and O-ring manufacturers recommend lubrication of elastomeric seals to prevent damage and to assure proper sealing. In this research, a metallic coating was applied as a lubricant using a vacuum vapor deposition process to the surface of elastomeric valve stem seals. Valve stem leak measurements were taken to determine if the coated O-rings, alone or with the recommended lubrication, reduced valve stem seal leakage. This research determined that the metallic coating did not reduce valve stem leakage.

Thermal energy storage (TES) is one of the most attractive and cost effective solutions to the intermittent generation systems like solar, wind and other renewable sources, compared to alternatives. It creates a bridge between the power supply and demand during peak hours or at times of emergency to ensure the continuous supply of energy. Among all the TES systems, latent heat thermal energy storage (LHTES) draws lots of interests as it has high energy density and can store or retrieve energy isothermally. Two major technical challenges associated with the LHTES are low thermal conductivity of the phase change materials (PCMs), and corrosion tendency of the containment vessel with the PCMs. Macro-encapsulation of the PCM is one of the techniques to encounter the low thermal conductivity issue as it will maximize the heat transfer area for the given volume of the PCM and restrict the PCMs to get in contact with the containment vessel. However, finding a suitable encapsulation technique that can address the volumetric expansion problem and compatible shell material are significant barriers of this approach. In the present work, an innovative technique to encapsulate PCMs that melt in the 100-350 oC temperature range was developed for industrial and private applications. This technique did not require a sacrificial layer to accommodate the volumetric expansion of the PCMs on melting. The encapsulation consisted of coating a non-reactive polymer over the PCM pellet followed by deposition of a metal layer by a novel non-vacuum metal deposition technique. The fabricated spherical capsules were tested in different heat transfer fluid (HTF) environments like air, oil and molten salt (solar salt). Thermophysical properties of the PCMs were investigated by DSC/TGA, IR and weight change analysis before and after the thermal cycling. Also, the constrained melting and solidification of sodium nitrate PCM inside the spherical capsules of different sizes were compared to explore the charging and discharging time. To accomplish this, three thermocouples were installed vertically inside the capsule at three equidistant positions. Low-density graphene was dispersed in the PCM to increase its conductivity and compared with pure PCM capsules. A laboratory scale packed-bed LHTES system was designed and built to investigate the performance of the capsules. Sodium nitrate (m.p. 306oC) was used as the PCM and air was used as the heat transfer fluid (HTF). The storage system was operated between 286oC and 326oC and the volumetric flow rate of the HTF was varied from 110 m3/h to 151 m3/h. The temperature distribution along the bed (radially and axially) and inside the capsules was monitored continuously during charging and discharging of the system. The effect of the HTF mass flow rate on the charging and discharging time and on the pressure drop across the bed was evaluated. Also, the energy and exergy efficiencies were calculated for three different flow rates. Finally, a step-by-step trial manufacturing process was proposed to produce large number of spherical capsules.