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This study has investigated the severe corrosion of Biogas engines by the blowby gases. The formation of blowby its composition and flow rate have been measured and simulated. The nature of the piston ring sealing, lubrication and breakdown has been examined. A study of Biogas engines showed that Copper corrosion of the small end and camshaft bearings by HZS gas was the reason for engine failure. H2S is present in all Biogas at a concentration of usually less than 1%, but succeeds in chemical attack despite its good combustion properties, and the expected reaction with the bases present in the lubrication oil. The HZS was corroding in its gaseous state, but only those bearings with indirect lubrication. The solution to this problem is either to adopt force fed lubrication of the bearings, or to replace the alloy with Aluminium-Tin. The experimental work used four engines of differing wear. The constant speed work showed that the fuel content of blowby gas increases with load despite any increase in fuelling rate. This trend was consistent for all gaseous fuels present including H2S. A series of computer calculations of piston ring blowby were completed, using conventional and novel input data. The resultant blowby flow was within an order of magnitude, confirming that two blowby mechanisms, ring gap blowby and ring seal breakdown, are present on worn engines. The composition results showed that the fuel content of blowby is subject to the complex nature of the quenching process in the combustion chamber. A study of the oil present at the top ring showed that the oil is greatly modified when compared with the sump oil, as a result of thermal degradation and base depletion. The oil has a high acid TAN, which suggests it could encourage corrosive wear of the cylinder liner.

A process planning strategy was proposed to suppress the wear effect of tool in a polishing of axially symmetrical work. This strategy can keep machining rate of tool to be constant. In study, we need to design the proper dwelling time distribution for tool to remove error of axially symmetrical surface and use computer to simulate. Observe the residual error on surface of work. Analyze the outcome of experiment and estimate feasibility of the strategy. According to the way of motion of tool, it could cause two difficulties: 1.To design the dwelling time distribution of tool will be more difficult. 2.The load of tool will be unstable. In order to solve this first difficulty, in a new strategy of working, the dwelling time distribution of tool must be a multiple of integral of the period of work rotation. And experiment to prove it, analyze and discuss the outcome of experiment. Second problem cause the load of tool to be unstable in experiment. To improve the load of tool, a new strategy was proposed to control load and to verify effectiveness for the strategy. Finally, analysis and discuss the outcome of experiment, and estimate the practicability of the strategy.

Friction, wear, and lubrication have direct influence on performance, reliability, and service life of mechanical systems with moving components. The useful life of these systems and their efficiency can be improved by improving the surface properties/ performance at sliding interfaces. Further, the usage of materials for sliding systems is limited in extreme environments, such as high temperature, and space, etc., due to their limited surface properties. This thesis focuses on the development of a new class of composites with superior surface properties, i.e., low friction and high wear resistance for extreme environmental conditions. Alumina, a well understood material for its tribological performance, is a merit choice for applications where high wear resistance is required, such as pump bearings, seal rings, valve seats, piston components, gears, cutting tool inserts and artificial joints. We propose to develop a novel alumina based ceramic composite to enhance its surface and tribological properties using a powder compaction technique. The newly developed composites will be characterized by X-ray Diffraction (XRD), Fourier Transform Infrared spectroscope (FTIR), Optical microscope, Environmental Scanning Electron Microscope (E-SEM), Goniometer and Surface profilometer. In-situ formation of high temperature stable phases, effect of sintering temperature, and percentage of reinforcement on phase formation will be studied. Investigation of effect of sintering temperature and percentage of reinforcement on density, porosity, and grain size will be conducted. The composites will be characterized for their tribological properties (friction and wear). The mechanisms for modified friction and wear will be proposed. The process parameters and compositions will be optimized. XRD results confirmed the formation of Al18B4O33, and AlB2 and FTIR confirmed the presence of B2O3. Increase in sintering temperature and wt % of boron affected the porosity, grain size, and hardness of the composites. The coefficient of friction was lower for the composites compared to pure alumina ceramic. The coefficient of friction decreased with increase in sintering temperature. The wear mechanism was found to be micro-fracture using ESEM and SEM studies.

Use-wear studies were undertaken to determine if the Clovis bifaces discovered at the Gault site in Central Texas were utilized implements or rather products of lithic raw material procurement. Those bifaces bearing microscopic traces indicative of use were studied in detail to determine the use-history of the tools. This thesis describes an experimental program aimed to build analogues for probable biface functions. A series of projectile impact studies, butchering experiments, and expedient-like tool useactivities were conducted to document the traces acquired on the tool surface from use. The experimental results are used to identify the utilized tools, demonstrate their functional purpose, and suggest the extent of tool use of the prehistoric biface assemblage.

As alumina plays ever more important roles in advanced technologies, such as substrates for in vivo biological sensors, catalysts for water purification and components of novel fuel devices, it is exposed to various environments. These environments lead to wear and degradation due to chemical and mechanical forces. Macroscale tribological tests including the scratch test and indentation are unable to analyze nanoscale properties due to their limited sensitivity. Today, nanotribologists incorporate three main tools to analyze nanoscale tribological properties: atomic force microscopy (AFM), the nanoindentor and surface force apparatus. Of these, AFM is the instrument of choice due to the sensitivity to and diversity of surface properties analyzed in a single setting. Through adhesion measurements and scratch testing under known loads the AFM was used to analyze the effect of OH- on the degradation of the alumina surface. Fourier transform infrared spectroscopy (FTIR) and AFM were also used to analyze the stability of self-assembled monolayers (SAMs) on the alumina surface. Through scanning a region of the surface with a defined force in an aqueous environment, the tribochemical surface properties were found. The pressure required to induce degradation of the first O-Al layer (~2 �) ranged from 3.10 GPa at a pH 3 to 1.58 GPa at pH 10. Further analysis of adhesion across the surface and within a defect region exposed significant changes in the forces of adhesion as the alumina surface experienced wear. At pH 3, 5, 7, and 10 the adhesion was approximately double that of the defect free surface. Two well known molecules were examined for their ability to protect the surface from bond rupture due to the catalytic effect of OH-. SAMs of octadyclephosphonic acid (OPA) and Octadycletrichlorosilane (OTS) were assembled on the alumina surface. FTIR spectra indicated well ordered monolayers formed from each molecule. The exposure of OPA to aqueous environments of pH >7 lead to the degradation of the SAM. OTS, on the other hand, demonstrated significantly more resilience to degradation as indicated through FTIR and AFM analysis.

The adhesive effects between abrasive particle and work on tool wear of the polishing process were considered in the study. Adhesive strength of the interfaces may affect wear rates of tool on the different adhesive way. Several sets of experiments were designed to reveal some phenomena about the wear rates of tool and work. There are variations in the adhesive of the interface causing different degree of tool wear for distinct kind of abrasive particle¡Bwork and tool¡¦s material. The experimental study demonstrated that the wear rate of tool was related to the adhesive strength between abrasive particle and work. Any change of the adhesive strength may significantly alter the wear rate of tool. An analytical study was done to examine the role played by the adhesive strength at the interfaces of abrasive particle on the wear rates of tool and work. It was derived from the law of force equilibrium and the principle of minimum potential energy. Tool wear was affected for polishing process by altering adhesive strength. The computer simulations indicated that an enhancement of adhesion between abrasive particle and work would always increase the wear rate at tool while the wear rate of work could be increased or decreased. To prove analytical study was reasonable by experimental study. Finally,the possible causes of observed phenomena and the limitations of the study were discussed.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 122-126).

Thesis--M. Sc., University of Hong Kong, 1982.