Browsing by Author "Ekwaro-Osire, Stephen"
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Item Dynamic analysis of involute spur gears with asymmetric teeth(Pergamon-Elsevier, 2008-12) Ekwaro-Osire, Stephen; Karpat, Fatih; Çavdar, Kadir; Babalık, Fatih Cengiz; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8474-7328; 0000-0001-9126-0315; A-5259-2018; A-4627-2018; 24366799400; 56242537600; 6508276205New gear designs are needed because of the increasing performance requirements, such as high load capacity, high endurance, low cost, long life, and high speed. In some applications, such as in wind turbines, the gears experience only uni-directional loading. In these instances, the geometry of the drive side does not have to be symmetric to the coast side. This allows for the designing of gears with asymmetric teeth. In previous studies related to bending stress and load capacity, high performance has been achieved for gears with asymmetric teeth. These gears provide flexibility to designers due to their non-standard design. If they are correctly designed, they can make important contributions to the improvement of designs in aerospace industry, automobile industry, and wind turbine industry. At high operation speeds, there is always a concern of dynamic loads and vibrations of equipment. Therefore, there is a need to fully understand the dynamic behavior of gears with asymmetric teeth. Thus, the primary objective of this paper is to use dynamic analysis to compare conventional spur gears with symmetric teeth and spur gears with asymmetric teeth. The secondary objective is to optimize the asymmetric tooth design in order to minimize dynamic loads. This study offers preliminary results to designers for understanding dynamic behavior of spur gears with asymmetric teeth. For this study, a dynamic model was developed, using MATLAB. and used for the prediction of the instantaneous dynamic loads of spur gears with symmetric and asymmetric teeth. Furthermore, a 2-D three-tooth model was developed for finite element analysis. Fast Fourier transform was used for the frequency analysis of the static transmission errors. It is shown that generally, the dynamic factor, for spur gears with asymmetric teeth, increases with increasing pressure angles on the drive side. For asymmetric teeth, increasing the addendum leads to a significant decrease in the dynamic factor. The static transmission error, at the center of the single tooth contact zone, decreases with increasing pressure angle. The first two harmonics slightly increase with increasing pressure angle. It is further shown that the amplitudes of harmonics of the static transmission errors are significantly reduced when asymmetric teeth with long addendum providing high gear contact ratio close to 2.0 are used.Item Efficiency of the high contact ratio involute spur gears with asymmetric teeth(Amer Soc Mechanical Engineers, 2012) Ekwaro-Osire, Stephen; Karpat, Fatih; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8474-7328; A-5259-2018; 24366799400Gears with asymmetric teeth have unique potential for application in gearboxes, particularly when uni-directional loading is applied. Most recently, gears with asymmetric teeth have received much attention for use in applications that require high performance due to increased load capacity. Such applications include aircraft and wind turbine. These gears offer flexibility to designers due to their non-standard design. In asymmetric teeth, the geometry of the drive side is not to be symmetric to the coast side. In other words, the pressure angle on the drive side is greater or smaller than that on the coast side. Asymmetry between tooth sides provide vital in obtaining key properties, such as high load carrying capacity, low weight, low wear or low vibration. In order to effectively design asymmetric teeth, it is necessary to perform analyses on the efficiency of these gears under various loading. In this study, the results obtained on high contact ratio involute spur gears with asymmetric teeth are presented and discussed. The impact of a few design parameters, such as pressure angle or tooth height, on sliding velocities and friction is investigated and illustrated with numerical examples.Item Influence of tip relief modification on the wear of spur gears with asymmetric teeth(Taylor & Francis, 2008) Ekwaro-Osire, Stephen; Karpat, Fatih; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8474-7328; 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.Item Influences of gear design parameters on dynamic tooth loads and time-varying mesh stiffness of involute spur gears(Springer, 2020-07-13) Ekwaro-Osire, Stephen; Doğan, Oğuz; Karpat, Fatih; Kopmaz, Osman; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makina Mühendisliği Bölümü.; 0000-0001-8474-7328; 0000-0003-4203-8237; GXH-1702-2022; A-5259-2018; DAF-9103-2022; AAV-7897-2020; 7006415878; 24366799400; 6603311475Gears are one of the most significant machine elements in power transmission due to the many advantages such as high load capacity, long life, and reliability. Due to the increasing power and speed values, the characteristics expected from the transmission elements are also increasing. Significant changes occur in the dynamic behavior of the gears at high speed due to the resonance. For this reason, determining the resonance frequencies is becoming an important issue for designers. This paper presents a method for determining the resonance regions of the gear system under different design parameters. The main purpose of this study is to examine the effects of different gear design parameters on spur gear dynamics. For this aim, the effects of these parameters on the mesh stiffness and contact ratio are examined, and the interaction of mesh stiffness, contact ratio, and dynamic response is presented. Different mesh stiffness calculation methods used to calculate time-varying mesh stiffness and a parametric gear dynamic model are proposed. To solve the equations of motions, a computer program is developed in MATLAB software. Five different design parameters, which are teeth number, pressure angle, reduction ratio, profile shifting factor, addendum factor, and damping ratio, are taken into consideration. The dynamic factor variation is calculated for 1600 rpm a constant pinion speed for each parameter for a single mesh period. Furthermore, the dynamic factor is calculated for the pinion speed between 400-30000 rpm and the frequency response and the resonance regions of the gear system are defined. As a result of the study, the profile shifting and the addendum factor are the most effective two parameters on the gear dynamics. Also, the contact ratio and mesh stiffness have a great effect on the dynamic response of the system. The methods decreasing dynamic load factors are also discussed at the end of the study.Item A novel method for calculation gear tooth stiffness for dynamic analysis of spur gears with asymmetric teeth(American Society of Mechanical Engineers, 2015-03-13) Ekwaro-Osire, Stephen; Karpat, Fatih; Doğan, Oğuz; Celalettin, Yüce; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8474-7328; 0000-0003-1387-907X; 0000-0003-4203-8237; A-5259-2018; A-6896-2015; R-3733-2017; 24366799400; 7006415878; 56237466100Recently, there have been a number of research activities on spur gears with asymmetric teeth. The benefits of asymmetric gears are: higher load capacity, reduced bending and contact stress, lower weight, lower dynamic loads, reduced wear depths on tooth flank, higher reliability, and higher efficiency. Each of the benefits can be obtained through asymmetric teeth designed correctly. Gears operate in several conditions, such as inappropriate lubrication, excessive loads and installation problems. In working conditions, damage can occur in tooth surfaces due to excessive loads and unsuitable operating conditions. One of the important parameters of the tooth is stiffness, which is found to be reduced proportionally to the severity of the defect by asymmetric tooth design as described in this paper. The estimation of gear stiffness is an important parameter for determining loads between the gear teeth when two sets of teeth are in contact. In this paper, a 2-D tooth model is developed for finite elements analysis. A novel formula is derived from finite element results in order to estimate tooth stiffness depending on the tooth number and pressure angle on the drive side. Tooth stiffness for spur gears with asymmetric teeth is calculated and the results were compared with well known equations in literature.Item Probabilistic analysis of MEMS asymmetric gear tooth(Asme, 2008-04) Ekwaro-Osire, Stephen; Khandaker, Morshed P.H.; Karpat, Fatih; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; 0000-0001-8474-7328; A-5259-2018; 24366799400Currently, there is an increased interest in the application of microelectromechanical system (MEMS) gear drives. Additionally, requirements for transmitted power and related reliability issues have increased. Reliability issues often occur due to uncertainties of material, geometry, and loading conditions of the MEMS gears. Asymmetric gear teeth are used to improve the performance of gears by increasing the load capacity or by reducing vibrations. In this paper, asymmetric gear teeth are proposed for MEMS applications. The objective of this research is to investigate the feasibility of applying asymmetric gears for MEMS devices while accounting for uncertainty. The Weibull failure theory was applied to four different MEMS gear configurations. The following analyses were carried out in this research: (i) for the calculation of root stress, four different asymmetric gears were used; (ii) for the calculation of the probability of failure, the Weibull failure theory formulization was used, and (iii) the efficacy of the various asymmetric tooth configurations was discussed. Specifically, the probability of failure of the asymmetric gear was extracted for various parameters. The parameters considered included pressure angle, tooth height, and contact ratio. The efficacy of using asymmetric gear teeth was shown in this study.Publication Stress analysis of additive manufactured lightweight spur gears(Amer Soc Mechanical Engineers, 2021-01-01) Ekwaro-Osire, Stephen; Yılmaz, Tufan Gürkan; YILMAZ, TUFAN GÜRKAN; Kalay, Onur Can; Karpat, Fatih; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi.; 0000-0003-3772-7871; 0000-0001-8643-6910; 0000-0001-8474-7328; 0000-0002-9548-8648; V-6153-2017; A-5259-2018Additive manufacturing processes (AMP) have grown and spread in the last twenty years. Additive manufacturing methods, which were first used for plastic materials, are now increasingly finding a place in metals. With these methods, more lightweight component designs which cannot be generated with traditional methods can be manufactured. With the spreading of electric drive vehicles, weight reduction is becoming more important since weight is primarily responsible for energy consumption. There is a one-stage gear system in electric vehicles in general. For this reason, the subject of reducing the mass of gears is gaining importance. The weight reduction can be achieved with holes and slots on the gear body for involute spur gears or reducing gear web thickness. Several optimization methods can be used for this aim. Another way is to use light materials for the gear body, while steel material is used in the tooth-rim region. Carbon fiber composites are preferred for this purpose. However, using adhesives to join steel and carbon fiber reinforced plastics may cause problems in different environmental conditions. On the other side, parts are generated with single material with AMP methods. In this study, involute spur gears with different designs convenient for generation by AMP are created in a 3D CAD program. The involute tooth region is defined as design space. The effects of different designs on root stress and tooth stiffness are investigated by finite element analyses. For this purpose, the mathematical modeling of involute spur gear is set to get points of a tooth based on Litvin's approach in MATLAB. A point cloud code is obtained and imported to the 3D CAD program. After that, three teeth 3D finite element spur gear models are generated. Static analyses are conducted in ANSYS. Meshing force is implemented on the highest point single tooth contact line. Root stress value is the most important reason for tooth root fatigue, one of the most common failure modes of involute spur gears. Tooth deflection and stiffness are significant parameters for the dynamic behavior of involute spur gears. The tooth stiffness affects mesh stiffness and transmission error which are the primary source of gear whine. For these reasons, tooth root stress and tooth deflection values should be determined for different gear designs.In this study, stress analyses of additive manufactured gears are conducted with the finite element method. The effect of shell thickness, infill radius, and infill stiffener on tooth root stress and deformation is recorded. According to the results, shell thickness is the most effective parameter on the root stress and deformation. It is followed by infill orientation angle and infill radius, respectively.