Conference Proceedings

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Analysis of electrochemical machining-textured surfaces under point contacts in rolling tribo-test.
(Springer, Cham., 2021) Gyimah, G. K.; Oman, E. K.; Nyanor, P.; Acakpovi, A.; Jiang, S.; Guo, Z.; Barber, G. C.
Purpose: The need for the right textured surface and selecting the right material in tribology is critical to friction reduction and energy savings in machine elements under full film lubrication rolling point contacts. This study provides a guide to proper material selection and the right surface texturing technique to enable machine elements to carry heavy loads at different speeds under the fully-flooded EHL regime. Design/Methodology/Approach: A lapped GCr15 ball bearing, cast iron (HT 500) plates, GCr15 tempered plates and GCr15 plates without tempering were used. The electrochemical machining (ECM) technique was used to manufacture Micro-texture surfaces on the plates. The ECM micro-textured surfaces and lapped plain surfaces of the same material were subjected to friction and wear behaviour between a ball and a plate test in a fully-flooded EHL point contact rolling condition. The tribological test was conducted under different rolling speeds and pressure. The topographical characteristics of the lapped plain surfaces and the Electrochemical Machining (ECM) textures surfaces were analysed by both optical and scanning electron microscopy. Findings: The outcome of the study showed that the geometry characteristics (micro-textured and lapped untextured) and the densities of the micro-texture impact was critical to the film formation in the tribological behaviour test against the lapped GCr 15 steel bearing balls. Significantly, low friction and wear were observed for the micro-textured surfaces as compared to the lapped untextured surfaces. Research Limitation/Implications: The research was on rolling point contact in fully-flooded EHL tribo-test using lapped untextured and micro-textured surfaces in contact with ball bearing. The study did not consider line contact and sliding force. The rolling point contact is the predominant phenomenon in gears, cams, tractions and balls in energy transmission. Practical Implication: The outcome of this research increase the knowledge base of this area, it informs technologies and tribologies to select and design machine elements with energy-saving criteria in mind. In addition, this work has opened other opportunities for research to harness the full potentials of the micro-texturing. Social Implication: This paper also guides to industrial and manufacturing sectors using machine elements as moving systems to generate and transmit energy in adopting energy-saving systems and policies that is based on the outcome of such studies. Originality/Value: The innovation of this research is centered on the tribological performance of GCr15 undergoing Micro-texturing by Electrochemical Machining which demonstrates better film thickness formation within EHL regime over HT 500 counterpart material. This outcome is a good starting point for further research and development.
Assessing the Performance of Liquid Waste Disposal Systems in West Africa: A Case Study in Ghana and Nigeria
(MDPI, 2022-09-28) Omani, J., & Acakpovi, A
This research is an assessment of existing liquid waste disposal systems in West Africa and their performances over the years, using systems in Ghana and Nigeria as a case study. The main purpose of the study was to improve upon the sustainability of the systems, which according to earlier research activities, have been failing and resulting in health hazards. Ghana and Nigeria were selected because, from occurrences, especially in the West African sub-region, the two countries dictate the pace in contributions to the body of knowledge. Many portable liquid waste disposal systems were identified as part of the research process, as earlier researchers called for a paradigm shift from the practice of Europeanized systems that had not been successful in the entire sub-region. Many reasons have been attributed to the failures, and more worryingly, the systems continue to be operational despite their states of malfunctioning. Frequent power cuts and ineffective revenue generation contribute to numerous problems. West Africans have been enduring these occurrences for a long time with no solution in place. In a few instances, raw sewage is piped into a central biogas system for the future generation of electrical power; this system was found to be right on point because it was determined from the initial stages of development that by-products could be used to mitigate the high costs of maintenance. Another system that combines a biofil digester with its treated wastewater being channeled into a saturation pond was found to be a success because the outflow from the biofil was not meant to be channeled into main drains, as it did not wholly meet EPA approvals. The centralized sewage treatment systems have been functioning well in advanced countries; however, they are found to be ineffective in developing countries. The reasons included lack of availability for spare parts and coagulants, etc., which were normally imported. Additionally, when a larger community is targeted, revenue generation becomes a problem, thereby affecting return on investments (ROI) and operating and maintenance (O&M). None of the available central sewerage systems harvest by-products, making revenue generation a difficult task. The portable systems have been discussed in this research study, with examples and a record of performance over the years that could contribute to the body of knowledge in the field of sustainability for sewage treatment processes suitable for West Africa and for the whole of sub-Saharan Africa.
Depreciation determination of a D9 earth moving mechanical plant.
(IEOM Society International, 2018) Deku, A.; Akinlabi, E.
In this study, various methods used in equipment depreciation were used to determine the depreciation of a D9 earth moving mechanical plant to determine the best method possible to achieve an effective result. For the study, total depreciation, annual depreciation, weekly, daily and hourly depreciation were considered and the best method recommended. These methods were used to compute the various depreciation of the plant and the results compared, analyzed in order to select the best method for determining depreciation. From the study, the capital outlay method was chosen to be the best method.
Improvers of pressure-viscosity coefficients of two-phase liquid-solid lubricants.
(2016) Gyimah, G. K.; Guo, Z. N.; Huang, P.; Jiang, S. Z.; Barber, G. C.; Liu, G. X.; Liu, J. W.
The prediction of the pressure-viscosity coefficient, α, is one of the most important properties for Elastohydrodynamic lubrication (EHL) condition; thereby, the need for improvers to aid its measurement and performance is necessitated. This article presented two phase liquid – solid lubricants of PTFE and MoS2 solution in SAE 30 oil at varying compositions. The lubricants tested are SAE #30, SAE #30 plus PTFE and SAE #30 plus MoS2. High-pressure viscosity measurement was done at pressure up to 1.5 GPa and temperature range at 20°C to 100°C. Viscosity indices are calculated from the measured viscosity at 40 and 100 ºC using ASTM D 2270. However, an attempt to predict α for the blended lubricants using the relationship between pressure-viscosity coefficient and Walther’s logarithm of kinematic viscosity at atmospheric pressure was used. The pressure-viscosity coefficient of two phase liquid – solid lubricants were successfully predicted and the influence of solid lubricant concentration, and temperature on the lubricants viscosity were determined, and compared with SAE #30 oil. The properties and viscosity of mixtures obtained are optimal lubricant factors which optimze the measurement and performance of the highest EHL pressure-viscosity coefficient of the mixtures, and also enhance the better chance to improve the lubrication of machine element than the SAE #30 conventional engine oil.
Oil film characterization of PTFE during EHL point contact and pure rolling tribology tests.
(IEEE, 2021) Gyimah, G. K.; Jiang, S.; Acakpovi, A.; Oman, E. K.; Nyanor, P.; Barber, G. C.
A polymer additive blended with commercial engine oil to have enhanced film-forming ability has been developed and studied using optical interferometry. An experimental study was carried out on the impact of polymer additives (Polytetrafluoroethylene – PTFE) in an oil film between a steel ball and a flat glass surface in non-conformal contact. The contact region was studied by means of optical interferometry using monochromatic two-beam interferometry, a microscope and a high-speed video recording device. A new method of determining the interference grade of the central film thickness was developed and used in this study. The interference intensities of the central point of contact at various speeds were captured by the high-speed video recording device and the central interference gray values were determined. These values were then used in new method to obtain the film thickness of the modeled lubricants, and compared with the rectangular SLIM fit and the LINE fit methods film thickness determination. Hamrock and Dawson calculations for EHL film thickness formation was also used for comparative analysis. The film thickness stability was simulated under both steady state and rolling state conditions. The lubricant film thickness stability obtained confirmed the beneficial effect of PTFE on film thickness behavior under pure rolling conditions. The regime observed by the profile of the film thickness suggest the transition between the hydrodynamics and elastohydrodynamic lubrication.
PTFE and MoS2 Additives for Mineral Oil Film Formation in EHL Point Contacts.
(ASME, 2016) Gyimah, G. K.; Guo, Z.; Huang, P.; Jiang, S.; Barber, G. C.
Lubricant film-forming viscosity index improvers blended with commercial engine oil have been developed and studied by using optical interferometry. The influence of the viscosity index improvers (PTFE and MoS2) mixed with oil were experimentally studied and compared with engine oil without the index improvers as the baseline. The effect of the viscosity index improvers on lubricant film thickness, contact pressure and rolling speed for the case of a steel ball loaded on a flat glass surface in point contact condition was investigated. An optical interferometry technique which utilized a monochromatic two-beam interferometry light source, a microscope and a high-speed video recording device was used for the investigation. Hamrock and Dawson calculations for EHL film thickness were also used for comparative analysis. The lubricants used were commercial SAE #30 engine oil and PTFE and MoS2 mixed with commercial SAE #30 engine oil. The oil viscosities ranged from 0.0109 Pa.s to 0.255 Pa.s. The rolling speed and the loads were varied between 0.189 m/s to 0.641 m/s and 1 N to 2.6 N respectively. The lubricant film thickness stability at the point of contact between the steel ball and the glass disc was investigated for both steady and rolling state conditions. The viscosity index improvers were found to have a significant effect on the film thickness behavior under pure rolling point contact conditions.

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