No description available.

Plastic hypodermic needles are a potential solution to the problem of disease spread through needle reuse. Plastics could be used to potentially reduce needle reuse as they are easier to destroy than steel. A key issue in their acceptance is the force required to penetrate a patient; a smaller force is associated with less pain. The effect that needle parameters have on the penetration force is studied in an effort to better understand how to reduce penetration forces and increase the success of penetrations for plastic needles. These parameters - geometry, tip radius, diameter, material, and lubricant - are studied through penetration, buckling, and coefficient of friction testing. The tests are conducted on steel needles, which serve as a control group, as well as two varieties of plastic needles. The outcome is a quantitative understanding of the effect that the various parameters have on penetration force, which is used to inform plastic needle design.

Wear of railroad rolling stock and rails costs millions of dollars annually in all rail systems throughout the world. The rail industry has attempted to address flange wear using rail curve lubricants and presently use a variety of lubricants and lubricant applicators. The choice of lubricant and applicator is currently based on considerations that do not address the wear problem directly. This research quantified rail curve lubricant performance through laboratory simulation. The effects of lubricants in the wheel/rail contact were investigated. Rail curve lubricant performance was measured with a laboratory rail/wheel simulator for the purpose of optimising the choice of lubricant. New methods for measurement of rail curve lubricant performance have been presented. These performance measurements are total absorbed energy, the energy absorbed in the lubricant film instead of being utilised for wear processes; total distance slid, the sliding distance or accumulated strain achieved prior to development of a set tractive force limit; half life of lubricant, the time taken for a lubricant to lose half of its sliding performance; and apparent viscosity, a measure of the lubricity presented with respect to accumulated strain. The rail/wheel simulator used in this research consists of two dissimilar wheels (disks) rotating in contact with one another simulating a conformal gauge corner contact. The first wheel, a simulated rail, is driven by an electric motor which then drives the second wheel, a simulated railroad wheel, through the contact. Hydraulic braking on the railroad wheel is used to simulate the rolling/sliding conditions. The variables of the simulated contact that are controlled with this equipment are normal force, input wheel speed, slip ratio between samples, sample geometries and material properties, and lubricant types. Rail curve lubricants were laboratory tested to define their properties using the ASTM and other appropriate standards. The performance differences measured using ASTM standards based tests were susceptible to repeatability problems and did not represent the contact as accurately as the rail/wheel simulator. This laboratory simulator was used to gather data in lubricated and unlubricated conditions for the purpose of providing lubricant performance measurements. These measurements were presented and the tested lubricants were ranked conclusively using three industrially relevant performance criteria. Total sliding distance and total absorbed energy measurements of the rail curve lubricants displayed clear differences in lubricant performance for both of these criteria. Total sliding distance is equivalent to the number of axles in the field situation, while total absorbed energy is the energy unavailable for wear processes of rails and wheels. Lubricants designed using these measurements will increase lubricant performance with respect to these performance criteria which in turn will reduce wear to both rails and wheels. Measurement of the apparent viscosity of rail curve lubricants, using the rail/wheel simulator, displayed changes in rheological characteristics with respect to accumulated strain. Apparent viscosity is a measure of the shear stress transmitted from the wheels to the rails. Designing a rail curve lubricant after analysing measurements taken from the rail/wheel simulator will assist in identifying lubricant properties to reduce the wear producing shear stresses generated in a rail wheel contact. Decay of lubricant performance was measured for three different rail curve lubricants under simulated conditions. The research found appreciable and quantifiable differences between lubricants. Industrial application of the findings will improve positioning of lubrication systems, improve choice of lubricants and predict effective lubrication distance from the lubricant application point. Using the new methods of lubricant performance measurement developed in this thesis, the objective of this research, to quantify rail curve lubricant performance through laboratory simulation, has been achieved.

There is an increasing awareness in clinical dentistry of the need to better understand the aetiology and management of tooth wear, as increasing numbers of elderly patients are retaining their natural teeth to a stage when they present with extensive wear. In addition, more younger patients are presenting with wear of both primary and permanent teeth. In order to comply with the philosophy of minimal intervention dentistry, clinical management of tooth wear should focus on early detection and prevention before a restorative approach is considered. Fluoride is a commonly used agent in the management of tooth wear, with previous studies showing that it can protect teeth against erosion (at around pH 2.0 and 3.0) and toothbrush abrasion in an acidic environment (at around pH 3.0). However, it does not reduce attritional wear between opposing tooth specimens. Nightguards are commonly used to prevent attritional wear but there is still a need to improve preventive strategies to manage the risk of erosive tooth wear. Previous in vitro studies have shown that a remineralizing agent in the form of CPP-ACP (casein phosphopeptide – amorphous calcium phosphate) can reduce erosion of both enamel and dentine by white wine. A recent study has also highlighted the potential lubricating and remineralizing properties of a CPP-ACP containing paste (Tooth Mousse®, G C Asia Pty Ltd) in reducing dentine wear in both an acidic environment (pH 3.0) and a near neutral environment (pH 6.1). In this context, it is desirable to investigate the effect of CPP-ACP on enamel wear under conditions simulating various clinical situations and to better understand the nature of third-body components at the wear interface. The aims of the present study were: (i) to determine the effect of CPP-ACP on enamel wear under conditions simulating three clinical situations: heavy attrition with gastric regurgitation (at pH 1.2); toothbrush abrasion after an erosive episode (at pH 3.2); and erosion from gastric regurgitation (at pH 1.2), and (ii) to clarify its mode of action by characterizing the enamel surface treated with CPP-ACP. Electro-mechanical tooth wear machines were used to simulate attrition and toothbrush abrasion in combination with erosion, but no machine was used in experiments investigation erosion alone. The effect of paste containing CPP-ACP in reducing erosive tooth wear was also compared with that without CPP-ACP. Enamel surfaces with and without treatment with CPP-ACP were then characterized by using Time of Flight – Secondary Ion Mass Spectrometry (ToF-SIMS). CPP-ACP was found to reduce enamel wear under conditions simulating heavy attrition combined with gastric regurgitation, and toothbrush abrasion after an erosive episode. However, it did not protect enamel from erosion under conditions simulating gastric regurgitation alone, indicating that its lubricating effect was more pronounced than its remineralizing effect. Silicone and ethyl siloxane were present in trace amounts on the enamel surface treated with Tooth Mousse®, thus they were found to be included in its formulation. These findings imply that CPP-ACP nanocomplexes and silicon can act as third body components to lubricate the wear interface. The findings presented in this thesis have implications for clinical management of tooth wear and may lead to new strategies of tooth wear prevention. Although some caution is needed in extrapolating these findings to the in vivo situation, it should be noted that in vitro studies provide valuable insights into separate components of the tooth wear process that are often difficult to distinguish in clinical situations. Overall, this thesis provides new information about the role of CPP-ACP in reducing erosive enamel wear and provides a basis for future experimental and clinical studies focussing on tooth wear prevention. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1379897 / Thesis (Ph.D.) -- University of Adelaide, School of Dentistry, 2009

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 254-262).

Thesis (Ph.D)--Geosystems, Georgia Institute of Technology, 2010. / Committee Chair: Frost, J. David; Committee Member: Burns, Susan E.; Committee Member: Gokhale, Arun; Committee Member: Mayne, Paul W.; Committee Member: Rix, Glenn J. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Efficiency of internal combustion engines (ICEs) is far from optimal. Due to the continuously increasing demands on CO2 regulations, automobile industries are forced to improve such efficiency. A crankshaft roller bearing (CSRB) can lead to significant improvements in engine efficiency. However, before this can be implemented into an actual engine, several challenges have to be addressed. One such challenge is the satisfactory performance of CSRB. The current crankshaft limits the service life since it must act as a roller bearing raceway. Therefore, better material properties are required for the use of CSRB in crankshaft applications. In order to select suitable material for the CSRB, development of several characterization methods is required. These methods are based on failure modes that are expected to occur in the actual application. Surface initiated fatigue was shown to be the main failure mode that could lead to complete failure of such a component. The following three characterizations needs are identified: material characterization, lubricant characterization and surface roughness characterization. Two of these methods are partially part of this thesis. Material characterization is required to select the optimal steel candidate for the CSRB component. A method was developed to assess the damage modes on a reference 100Cr6 steel pair under conditions prevalent to CSRB application. However, fully formulated oil was excluded from this investigation and only low-additive oil was employed. Micro-pitting and wear damage modes were identified and were later assessed. Different surface roughness combinations were tested, from where micro-pitting regions were identified. In addition, the effects of surface hardness and sliding on micro-pitting and wear were investigated. It was found that hard steel contacts are more prone to micro-pitting damage compared to soft ones, but less susceptible to mild wear. In addition, higher sliding increases the degree of micro-pitting and wear. Lubricant characterization was performed to optimize the engine oil formulation for rolling contacts. A method to assess different engine oils in terms of micro-pitting and wear damages of rolling contacts was employed. The effect of viscosity, additive chemistry and different mixtures of base oils on aforementioned performance were presented and discussed. In addition, lubricant characterization will provide in-depth knowledge for engine oils’ manufacturers to improve engine oil formulations for satisfactory performances of CSRB design.

Adaptive coatings are an important development in tribology. These coatings widen the range at which solid lubricants are useful in various environments. In this paper, coatings founded on molybdenum nitride are studied, with a focus on thermal cycling. These coatings were fabricated by unbalanced magnetron sputtering and characterized with techniques including x-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, energy dispersive x-ray spectroscopy (EDS), and pin-on-disk tribometer. The results of two sets of coatings are reported. The first set of coatings is a nanocomposite of Mo2N/MoS2/Me (Me = Ag, Au, Cu). The second is a complex multi-layer system of Mo2N/Ag and a diffusion barrier of TiN which has been etched, then filled and coated with a layer of MoS2. After heating, these compounds produced silver molybdates. The Mo2N/MoS2/Ag nanocomposite shows promise with a 0.02 coefficient of friction at room temperature, while the multi-layer system eventually equilibrated at approximately 0.6. At high temperatures, again the nanocomposite was better, producing a 0.25 frictional coefficient compared to a 0.3 from the multilayer system. These results provide insight into what is needed to achieve thermal cycling.

No description available.

A parametric study of oil-jet lubrication in gear wheels is conducted using Computational Fluid Dynamics (CFD) to study the effect of the different design parameters on the cooling performance in a gearbox. Flow in oil jet lubrication is found to be complex with the formation of oil ligaments and droplets. Various hole radii of 1.5, 2 and 2.5 mm along with five oil velocities is analyzed and it is found that at lower volumetric rates, velocity has more effect on the cooling and at higher volumetric rates, hole size has more effect on the cooling. At higher velocities, the heat transfer is much greater than the actual heat production in the gear wheel, hence these velocity ratios are considered less suitable for jet lubrication. At low velocity ratios of below 2, the oil doesn’t fully impinge the gear bottom land and the sides leading to low cooling. Based on the cooling, impingement length and amount of oil lost to the casing surface, 2 mm hole with a velocity ratio of 2.225 is selected for a successful oil jet lubrication. Varying the inlet position in X, Y and Z directions (horizontal, vertical and lateral respectively) is found to have no improvement on the cooling. Making the oil jet hit the gear wheel surface at an angle is found to increase the cooling. Analysis with the use of a pipe to supply oil was conducted with circular and square inlet and it was found that the heat transfer decreases in both cases due to the splitting of oil jet caused by the combination of the effects of high pressure from the pipe and vorticity in the air field. A method has been developed for two gear analysis using overset meshes which can be used for further studies of jet lubrication in multi-gear systems. Single inlet is found to be better for cooling two gear wheels as it would require a reduced volumetric flow rate compared to double inlets. Oil system requirements for jet lubrication was studied and it was concluded that larger pumps have to be used to provide the high volumetric rates and highly pressurized oil required. On comparing the experimental losses from dip lubrication and the analytical losses for jet lubrication, dip lubrication is found to have lesser loses and more suitable for this case. Good quality lubrication would reduce the fuel consumption and also increase the longevity of gearboxes and hence more research into analyzing alternate lubrication systems can be carried out using the results from this thesis.