Browsing by Author "Ekwaro, Stephen Osire"
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Item Experimental studies on galling onset in OCTG connections: A review(Asme, 2008-03) Ekwaro, Stephen Osire; Karpat, Fatih; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 000-0001-8474-7328; A-5259-2018; 24366799400With today's high prices for natural gas and oil, the demand for oil and country tubular goods (OCTGs) with superior performance properties is very high. Failures in OCTG can be attributed to numerous sources, for example, makeup torque, corrosion, and galling. Thread galling is the most common mode of failure. This failure often leads to leakage, corrosion of the material, and loss of mechanical integrity. The failure of OCTG eventually amounts to excessive operational costs for the gas and oil industry. Numerous approaches have been taken to improve the galling resistance of OCTG connections. The advocacy of these approaches is often achieved through experimental studies using galling testers. There is a need to design and use effective galling testers to understand and improve the performance of OCTG connections. Thus, the objective of this paper is to present a concise review of literature related to the galling testers that may have applications to OCTG.Item An improved numerical method for the mesh stiffness calculation of spur gears with asymmetric teeth on dynamic load analysis(Sage Puplications, 2017-06-23) Ekwaro, Stephen Osire; Karpat, Fatih; Doğan, Oğuz; Yüce, Celalettin; Uludağ Üniversitesi/Mühendislik Mimarlık Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8474-7328; 0000-0003-4203-8237; 0000-0003-1387-907X; A-5259-2018; AAV-7897-2020; GXH-1702-2022; R-3733-2017; 24366799400; 7006415878; 56237466100Gears are one of the most crucial parts of power transmission systems in various industrial applications. Recently, there emerged a need to design gear drivers due to the rising performance requirements of various power transmission applications, such as higher load-carrying capacity, higher strength, longer working life, lower cost, and higher velocity. Due to their excellent properties, gears with asymmetric teeth have been designed to obtain better performance in applications. As the rotation speed of the gear transmission increases, the dynamic behavior of the gears has become a subject of growing interest. The most important contributing factor of dynamic behavior is the stiffness of the teeth, which changes constantly throughout the operation. The calculation of gear stiffness is important for determining the load distribution between the gear teeth when two sets of teeth are in contact. The primary objective of this article is to develop a new approach to calculate gear mesh stiffness for asymmetric gears. With this aim in mind, single tooth stiffness was calculated in the first stage of the study using a finite element method. This study presents crucial results to gear researchers for understanding spur gears with involute asymmetric teeth, and the results will provide researchers with input data for dynamic analysis.Item Influence of tip relief modification on the wear of spur gears with asymmetric teeth(Soc Tribologists & Lubrication Engineers, 2010-06) Ekwaro, Stephen Osire; Karpat, Fatih; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8474-7328; A-5259-2018; 24366799400Recently, spur gears with asymmetric teeth have been considered a way of increasing performance while maintaining the gearbox dimensions. Asymmetric teeth have different pressure angles on drive and coast sides. They provide, among other advantages, a high bending strength and low vibration. In spur gears with asymmetric teeth, wear has been observed to be a major failure mode. In this study, the impact of tip relief modification and pressure angle on the wear of spur gears with asymmetric teeth is numerically investigated. Here, the focus is on sliding wear A wear model based on Archard's equation is employed to predict wear depth. The pressure angle and the tip relief are parameterized. In the analysis, instantaneous contact loads and Hertz pressures are used in wear depth calculations. It is shown that as the amount of the tip relief increases, the wear depth, particularly at the beginning and end of the mesh, decreases. As the number of wear cycles increases, the effect of the tip relief modification on wear depths decreases slightly It was also shown that with an increase in tip relief, the dynamic load decreases. However if the amount of tip relief modification increases excessively the maximum dynamic load also increases. Therefore, an excessive increase in tip relief modification should be avoided, whereby the level of excessive increase depends on the tip relief configuration.