Master of Science, The Ohio State University, 2018, Mechanical Engineering

In this study, a two-dimensional model is proposed for determining theoretical contact lines, tooth separation, and approximated loaded transmission error with frequency spectra thereof, as well as various other output variables such as instantaneous center distance, operating pressure angle, and instantaneous contact ratio when circular runout error is applied to either or both gears in a spur or helical gear pair. As an addendum, a method for calculating off-line of action tooth separation using this model is described for spur gears. Additionally, a three-dimensional model is proposed for determining theoretical contact lines and tooth separation when any combination of circular runout or wobble error are applied to either or both gears in a spur or helical gear pair. Sample analyses are shown for spur and helical gear pairs with runout error applied using the two-dimensional model, and a helical gear pair with various combinations of runout and wobble error applied using the three-dimensional model. The results are discussed qualitatively with respect to the expected effects the applied errors would have on the tooth separation and related variables.

Committee: David Talbot (Advisor); Ahmet Kahraman (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2008, Mechanical Engineering

This study examines the salient effects of sliding friction on spur and helical gear dynamics and associated vibro-acoustic sources. First, new dynamic formulations are developed for spur and helical gear pairs based on a periodic description of the contact point and realistic mesh stiffness. Difficulty encountered in existing discontinuous models is overcome by characterizing a smoother transition during the contact. Frictional forces and moments now appear as either excitations or periodically-varying parameters, since the frictional force changes direction at the pitch point/line. These result in a class of periodic ordinary differential equations with multiple and interacting coefficients. Predictions match well with a benchmark finite element/contact mechanics code and/or experiments. Second, new analytical solutions are constructed which provide an efficient evaluation of the frictional effect and a more plausible explanation of dynamic interactions in multiple directions. Both single- and multi-term harmonic balance methods are utilized to predict dynamic mesh loads, friction forces and pinion/gear displacements. Such semi-analytical solutions explain the presence of higher harmonics in gear noise and vibration due to exponential modulations of periodic parameters. This knowledge also analytically reveals the effect of the tooth profile modification in spur gears under the influence of sliding friction. Further, the Floquet theory is applied to obtain closed-form solutions of the dynamic response for a helical gear pair, where the frictional effect is quantified by an effective piecewise stiffness function. Analytical predictions are validated using numerical simulations. Third, an improved source-path-receiver vibro-acoustic model is developed to quantify the effect of sliding friction on structure-borne noise. Interfacial bearing forces are predicted for the spur gear source sub-system given two whine excitations (static transmission error and sliding frict (open full item for complete abstract)

Committee: Rajendra Singh (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy, The Ohio State University, 2007, Mechanical Engineering

Planetary gear sets are widely used in many diverse automotive, aerospace and industrial drive train applications. Several unique system-level influences must be incorporated in the design of planetary gear sets. In this dissertation, the impact of the several important system-level factors on gear stresses and gear bending fatigue lives are investigated both experimentally and theoretically. First, results of an experimental study are presented to describe the impact of certain types of manufacturing errors on gear stresses and the individual planet loads of an n-planet planetary gear set (n=3 to 6). The experimental set-up includes a specialized test apparatus to operate a planetary gear set under typical speed and load conditions and gear sets having tightly controlled intentional manufacturing errors. A method for computing the planet load sharing factors from root strain time histories is proposed. The results clearly indicate that manufacturing errors influence gear stresses and planet load sharing significantly. Gear sets having larger number of planets are more sensitive to manufacturing errors in terms of planet load sharing behavior. A finite element based computational model and a discrete planet load-sharing model are also developed and validated. A set of closed-form planet load sharing formulae is derived assuming all planets carry a certain amount of load and they are equally spaced. A statistical analysis that uses these planet load-sharing formulae is also presented to predict the distribution of planet loads, given statistical distributions of manufacturing errors. Secondly, the impact of gear body deflections and gear spline conditions on gear strains are investigated using the same computational models and the experimental set up by considering the ring gear rim thickness as a variable. The results indicate that gear stresses are impacted by gear deflections and spline conditions significantly. At the end, a stress-life based gear tooth bending f (open full item for complete abstract)

Committee: Ahmet Kahraman (Advisor) Subjects:

PhD, University of Cincinnati, 2010, Engineering and Applied Science: Mechanical Engineering

Hypoid and bevel gears that are widely used in both on and off-highway vehicles have the potential of producing excessive vibrations and noise. The goal of this dissertation research is to establish more effective mathematical model and analytical techniques to characterize the mesh and dynamic behavior, predict vibratory response, and reveal the underlying physics of the hypoid and bevel geared rotor system. The multi-body and multiple-degree-of-freedom (MDOF) dynamic modeling scheme is adopted and the key issues addressed in this dissertation are discussed below. Firstly, since gear mesh and dynamic characteristics are highly dependent on the torque load, a series of comparative studies and parametric analysis under different nominal torque levels are performed. The purpose is to identify critical factors and applicability of different assumptions for the MDOF hypoid and bevel geared rotor system model. In addition, a dynamic load dependent mesh model is proposed to characterize the potential interaction between dynamics and gear tooth contact. Secondly, in order to simulate the interaction between the small-displacement gear vibration and the large-angular-displacement driveline torsional dynamics, a coupled multi-body dynamic and vibration model is proposed primarily for nonlinear or transient simulation. This modeling technique possesses the capability of obtaining more realistic response and simulating a wide variety of operating conditions as well as the potential to be applied in the multi-body dynamic analysis of more complete driveline system. Thirdly, a series of important dynamic and geometric (primarily due to manufacturing error) effects are modeled and analyzed respectively to quantify and/or qualify their influence. For gyroscopic effect as a critical rotor dynamic factor, the study emphasizes their influence on hypoid gear pair vibration as well as the role of rotor inertia distribution on this issue. For assembly errors i.e. misalignments, their (open full item for complete abstract)

Committee: Teik Lim PhD (Committee Chair); Ronald Huston PhD (Committee Member); David Thompson PhD (Committee Member); J. Kim PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2012, Mechanical Engineering

Planetary gear vibration causes undesirable noise. It may also excite structural resonances or shorten the life of bearings and other drivetrain components. Extensive theoretical research highlights the interest in this topic, but limited experimental data is available to direct and improve these analytical tools or provide practical design guidance to engineers who face increased pressure to reduce transmission noise. This research provides experimental data that has already confirmed, improved, and suggested new directions for analytical modeling. It is hoped that this intentionally broad effort will continue to show its usefulness in the literature. Experimental methods--including stationary modal analysis and spinning vibration tests--are applied to characterize the planar dynamic behavior of two spur planetary gears. Rotational and translational vibrations of the sun gear, carrier, and planet gears are measured. Natural frequencies, mode shapes, and dynamic response obtained by modal vibration testing are compared to the results from lumped-parameter and finite element models. Both models accurately predict the natural frequencies and modal properties established by experimentation. Rotational, translational, and planet mode types presented in published mathematical studies are confirmed experimentally. Two qualitatively different classes of mode shapes in distinct frequency ranges are observed in the experiments and confirmed by the lumped-parameter model, which considers the accessory shafts and fixtures to capture all of the natural frequencies and modes. The natural frequencies in the high-frequency range tend to gather into clusters (or groups). This behavior is first observed in the experiments and studied in further detail with numerical analysis. There are three natural frequency clusters. Each cluster contains one rotational, one translational, and one planet mode type. The clustering phenomenon is robust, continuing through parameter variations of sev (open full item for complete abstract)

Committee: Robert G. Parker (Advisor); Robert A. Siston (Committee Member); Daniel A. Mendelsohn (Committee Member); Mark E. Walter (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2011, Mechanical Engineering

Wind energy has received a great deal of attention in recent years in part due to its minimal environmental impact and improving efficiency. Increasingly complex wind turbine gear train designs, well-known rolling element bearing failures, and the constant push to manufacture more reliable, longer lasting gear trains generate the need for more advanced analysis techniques. The objectives of this thesis are to examine the mechanical design of Orbital2 flexible pin, multi-stage planetary wind turbine gear trains using three dimensional finite element/contact mechanics models. These models are constructed and analyzed using software that specializes in elastic gear tooth contact. Computational results, such as gear tooth root strain, are compared to full system experiments. Root strain is calculated at multiple locations across the facewidth of ring gears from the computational models and compared to experimental data. Computational results for tooth load distribution and planet load sharing factor are compared to experiments. The computational models consider gear misalignment and carrier eccentricity and permit design recommendations for improving tooth load distribution and planet load sharing.

Committee: Robert Parker PhD (Advisor); Sandeep Vijayakar PhD (Committee Member) Subjects: Design; Energy; Engineering; Mechanical Engineering; Mechanics

Master of Science, The Ohio State University, 2010, Mechanical Engineering

Planetary gears are used commonly in many power transmission systems in automotive, rotorcraft, industrial, and energy applications. Powertrain efficiency concerns in these industries create the need to understand the mechanisms of power losses within planetary gear systems. Most of the published work in this field, however, has been limited to fixed-center spur and helical gear pairs. An extensive set of experiments is conducted in this research study to investigate the mechanisms of spin power loss caused by planetary gear sets, in an attempt to help fill the void in the literature. A test set-up was designed and developed to spin a single-stage, unloaded planetary gear set in various hardware configurations within a wide range of carrier speeds. The measurement system included a high-resolution torque sensor to measure torque loss of the gear set used to determine the corresponding spin power loss. Repeatability of the test set-up as well as the test procedure was demonstrated within wide ranges of speed and oil temperature. A test matrix was defined and executed specifically to measure total spin loss as well as the contributions of its main components, namely drag loss of the sun gear, drag loss of the carrier assembly, pocketing losses at the sun-planet meshes, pocketing losses at the ring-planet meshes, viscous planet bearing losses, and planet bearing losses due to centrifugal forces. Multiple novel schemes to estimate the contributions of these components of power losses were developed by using the data from tests defined by the test matrix. Fidelity of these schemes was tested by comparing them to each other. Based on these calculations, major components of power losses were identified and rank ordered. Impact of the rotational speed and oil temperature on each component was also quantified.

Committee: Ahmet Kahraman PhD (Advisor); Gary Kinzel PhD (Committee Member) Subjects: Automotive Materials; Energy; Engineering; Experiments; Mechanical Engineering; Transportation

Doctor of Philosophy, The Ohio State University, 2022, Mechanical Engineering

Vibro-impacts of gears are common in various automotive geared drivetrains used in engines and transmissions, causing excessive rattle noise. External torque fluctuations lead to contact loss at gear mesh interfaces of such systems to result in sequences of impacts. Further, gear root and contact stresses might be elevated due to these impact events bringing durability concerns upfront. An experimental methodology is developed in this study to investigate such gear rattle problems observed in various powertrain applications formed by a single gear pair as well as multimesh gear trains. This test methodology allows one to simulate real-life gear rattle problems in a lab environment by imposing the external torque fluctuations at desired shapes and amplitudes within a wide range of operating speed through its servo motors. The rattle set-up is used to develop a new rattle severity index defined by gear impact velocities. Rattle severity index predicted using a torsional model within wide ranges of system parameters is compared to measured sound pressure level to demonstrate its effectiveness in predicting noise outcome solely from torsional dynamics of the drivetrain. A discrete torsional dynamic model of a single gear pair along with a computationally efficient piecewise-linear solution methodology is developed to conduct extensive parametric studies. Predictions of this model are compared to actual measurements from the rattle test machine for its complete validation. A no-rattle criterion that defines a boundary between no-impact and impacting motions is defined. A wide array of nonlinear behavior is demonstrated through presentation of periodic and chaotic responses in the forms of phase plots, Poincare maps, and bifurcation diagrams. The overall nonlinear response is characterized through parameter maps that showed bands of periodic responses with n and n +1 coast-side impacts per excitation period separated by bands of chaotic motions, with ty (open full item for complete abstract)

Committee: Ahmet Kahraman (Advisor) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2020, Mechanical Engineering

In this study, an experimental investigation on the influence of tensile mean stress on gear tooth bending fatigue life is performed. A newly developed single-tooth bending test machine is utilized to perform gear tooth bending fatigue experiments under various loading conditions. A new single-tooth bending test fixture is developed for a chosen test gear. A detailed experimental methodology is presented on dynamic and static strain measurements of the chosen test gear root fillet profile in order to (i) quantify any dynamic loading effects at high loading frequencies, and (ii) validate maximum root stress predictions. Two sets of fatigue tests are performed at load levels of R = 0.05 and R = 0.5 whose results are analyzed statistically to generate L50 and L10 curves for each loading case. Utilizing the L50 stress-life curves, a map of constant life is obtained, showing a straight-line relationships between mean stress and alternating stress. It is shown that an increase in the tensile mean stress reduces the fatigue lives of gear teeth.

Committee: Ahmet Kahraman Dr. (Advisor); Talbot David Dr. (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering; Statistics

Master of Science, The Ohio State University, 2019, Mechanical Engineering

Noise and vibration performance of a gear system is critical in any industry. Vibrations caused by the excitations at the gear meshes propagate to the transmission housing to cause noise, while also increasing gear tooth stresses to degrade durability. As such, gear engineers must seek gear designs that are nominally quiet with low vibration amplitudes. They must also ensure that this nominal performance is robust in the presence of various manufacturing errors. This thesis research aims at an experimental investigation of the influence of one type of manufacturing error, namely random tooth spacing errors, on the vibratory responses of spur and helical gear pairs. For this purpose, families of spur and helical gear test specimens having intentionally induced, tightly controlled random spacing error sequences are fabricated. These specimens are paired and assembled in various ways to achieve different sequences of composite spacing errors. Static and dynamic motion transmission error measurements from these tests are compared to the baseline case of “no error” gear to quantify the impact of random spacing errors on the dynamic response. These comparisons show that there is a significant, quantifiable impact of random spacing errors on both spur and helical gear dynamics. In general, vibration amplitudes of gear pairs having random spacing errors are higher than those of the corresponding no-error gear pairs. In the frequency domain, gears having random spacing errors exhibit broad-band spectra with significant non-mesh harmonics, pointing to potential noise quality issues.

Committee: Ahmet Kahraman (Advisor); David Talbot (Committee Member) Subjects: Engineering; Mechanical Engineering

PhD, University of Cincinnati, 2017, Engineering and Applied Science: Mechanical Engineering

Hypoid and bevel gears are widely used in the rear axle systems for transmitting torque at right angle. They are often subjected to harmful dynamic responses which cause gear whine noise and structural fatigue problems. In the past, researchers have focused on gear noise reduction through reducing the transmission error, which is considered as the primary excitation of the geared system. Effort on the dynamic modeling of the gear-shaft-bearing-housing system is still limited. Also, the noise generation mechanism through the vibration propagation in the geared system is not quite clear. Therefore, the primary goal of this thesis is to develop a system-level model to evaluate the vibratory and acoustic response of hypoid and bevel geared systems, with an emphasis on the application of practical vehicle powertrain system. The proposed modeling approach can be employed to assist engineers in quiet driveline system design and gear whine troubleshooting. Firstly, a series of comparative studies on hypoid geared rotor system dynamics applying different mesh formulations are performed. The purpose is to compare various hypoid gear mesh models based on pitch-cone method, unloaded and loaded tooth contact analysis. Consequently, some guidelines are given for choosing the most suitable mesh representation. Secondly, an integrated approach is proposed for the vibro-acoustic analysis of axle systems with right-angle geared drive. The approach consists of tooth contact analysis, lumped parameter gear dynamic model, finite element model and boundary element model. Then, a calculation method for tapered roller bearing stiffness matrix is introduced, which is based on the Finite Element/Contact Mechanics model of axle system with right-angle geared system. The effect of rigid bearing support and flexible bearing support is studied by comparing the flexible axle system model with rigid supported gear pair model. Other important system dynamic factors are also investigated, such as (open full item for complete abstract)

Committee: Teik Lim Ph.D. (Committee Chair); Michael Alexander-Ramos Ph.D. (Committee Member); Jay Kim Ph.D. (Committee Member); Manish Kumar Ph.D. (Committee Member) Subjects: Mechanical Engineering; Mechanics

Master of Science, The Ohio State University, 2015, Mechanical Engineering

While there are numerous theoretical and experimental investigations of dynamic behavior of gear pairs of higher quality grades, very little is known about the same when certain classes of manufacturing errors are present. This study aims at investigating the effects of tooth index errors, one of the most common types of manufacturing errors. Using the changes in stresses along the tooth root regions as the metric, an experimental study is executed here to (i) establish a baseline dynamic behavior under no tangible index error and (ii) characterize the changes caused by tightly-controlled intentional index errors to this baseline dynamic behavior. For this, various gears having different forms of index errors are paired with an instrumented gear having no such errors. For each gear pair, tests are performed within wide ranges of torque and speed. A data processing scheme is proposed to normalize the measured stress signals to multiplication factor. It is shown that the baseline dynamic response represented solely by the dynamic stress factor is altered significantly by transient vibrations induced by the indexing errors, in some cases fully altering the baseline dynamic behavior and increasing the stress multiplication factors significantly. The experimental database formed in this study is expected to guide much needed theoretical studies on this topic.

Committee: Ahmet Kahraman (Advisor); Vishnu Sundaresan (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2014, Mechanical Engineering

Lubrication systems used in gear trains are intended to serve two distinct purposes: (i) provide the quantities of oil to gear mesh contact interfaces to allow formation of a healthy elastohydrodynamic fluid film and (ii) help remove heat generated at gear mesh contact interfaces. Failure of the lubrication system in either of these tasks often results in a temperature induced contact failure, called scuffing. This study investigates the effectiveness of various lubrication methods in preventing scuffing. A new high-speed gear test set-up is developed specifically for investigating the scuffing performance of high-speed, high-load helical gears operating at realistic oil temperature conditions. The objective of this study is to experimentally characterize the scuffing performance of the helical gears as a function of various lubrication methods and parameters defining each method. Sets of scuffing experiments are performed using the test methodology developed and lubrication methods that successfully prevented scuffing of the gears are identified. The test matrix includes two different automotive drivetrain lubricants and different lubrication methods of forced (jet) lubrication, dip lubrication and mist lubrication. The test specimens consist of gears having three surface finishes, (i) ground–honed gears which were identified as the baseline, (ii) super-finished gears and (iii) phosphate coated gears. The effects of parameters such as jet flow rate, jet velocity and impingement depth on scuffing are investigated and tabulated using the results from the jet lubricated tests. The impact of gear micro-geometry and edge-loading effects on scuffing initiation are also investigated.

Committee: Ahmet Kahraman Ph.D (Advisor); George Staab Ph.D (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2013, Engineering and Applied Science: Mechanical Engineering

Hypoid and bevel gears are widely used in the rear axles of both on and off-highway vehicles, and are often subjected to harmful dynamic responses which cause gear whine noise and structural fatigue problems. The primary goal of this thesis is therefore to develop a more realistic mesh and dynamic model to predict the vibratory response of hypoid and bevel geared systems, and study the effect of different working conditions, e.g. operating speed, torque load, on the dynamic responses of those systems. First, a multi-point hypoid gear mesh model based on 3-dimensional loaded tooth contact analysis is incorporated into a coupled multi-body dynamic and vibration hypoid gear model to predict more detailed dynamic behavior of each tooth pair. To validate the accuracy of the proposed model, the time-averaged mesh parameters are applied to linear time-invariant (LTI) analysis to calculate the dynamic responses, such as dynamic mesh force and dynamic transmission error, which demonstrates good agreement with those predicted by using single-point mesh model. Furthermore, a nonlinear time-varying (NLTV) dynamic analysis is performed considering the effect of backlash nonlinearity and time-varying mesh parameters, such as time-varying mesh stiffness, transmission error, mesh point and line-of-action. One of the advantages of the multi-point mesh model is that it allows the calculation of dynamic responses for each engaging tooth pair, and simulation results for an example case are given to show the time history of the mesh parameters and dynamic mesh force for each pair of teeth within a full engagement cycle. This capability enables the analysis of durability of the gear tooth pair and more accurate prediction of the system response. Secondly, to have more insights on the load dependent mesh parameters and dynamic responses of the hypoid and spiral bevel geared systems, a load dependent mesh model is developed by using 3-dimensional loaded tooth contact analysis (LTCA). T (open full item for complete abstract)

Committee: Teik Lim Ph.D. (Committee Chair); J. Kim Ph.D. (Committee Member); David Thompson Ph.D. (Committee Member) Subjects: Mechanics

PhD, University of Cincinnati, 2012, Engineering and Applied Science: Mechanical Engineering

This dissertation research focuses on evaluating the nonlinear dynamics of driveline systems employed in motor vehicles with emphasis on characterizing the excitations and response of right-angle, precision hypoid-type geared rotor structure. The main work and contribution of this dissertation is divided into three sections. Firstly, the development of an asymmetric and nonlinear gear mesh coupling model will be discussed. Secondly, the enhancement of the multi-term harmonic balance method (HBM) is presented. Thirdly and as the final topic, the development of new dynamic models capable of evaluating the dynamic coupling characteristics between the gear mesh and other driveline structures will be addressed. A new asymmetric and nonlinear mesh model will be proposed that considers backlash, and the fact that the tooth surfaces of the convex and concave sides are different. The proposed mesh model will then be fed into a dynamic model of the right-angle gear pair to formulate the dimensionless equation of motion of the dynamic model. The multi-term HBM will be enhanced to simulate the right-angle gear dynamics by solving the resultant dimensionless equation of motion. The accuracy of the enhanced HBM solution will be verified by comparison of its results to the more computationally intensive direct numerical integration calculations. The stability of both the primary and sub-harmonic solutions predicted by applying multi-term HBM will be analyzed using the Floquent Theory. In addition, the stability analysis of the multi-term HBM solutions will be proposed as an approximate approach for locating the existence of sub-harmonic and chaotic motions. In this dissertation research, a new methodology to evaluate the dynamic interaction between the nonlinear hypoid gear mesh mechanism and the time-varying characteristics of the rolling element bearings will also be developed. The time-varying mesh parameters will be obtained by synthesizing a 3-dimensional loaded tooth conta (open full item for complete abstract)

Committee: Teik Lim PhD (Committee Chair); Sundaram Murali Meenakshi PhD (Committee Member); Dong Qian PhD (Committee Member); David Thompson PhD (Committee Member) Subjects: Mechanics

MS, University of Cincinnati, 2010, Engineering and Applied Science: Mechanical Engineering

Hypoid and spiral bevel gears, used in the rear axles of cars, trucks and off-highway equipment, are subjected to harmful dynamic response which can be substantially affected by the structural characteristics of the shafts and bearings. This thesis research, with a focus on gear-shaft-bearing structural analysis, is aimed to develop effective mathematical models and advanced analytical approaches to achieve more accurate prediction of gear dynamic response as well as to investigate the underlying physics affecting dynamic response generation and transmissibility. Two key parts in my thesis are discussed below. Firstly, existing lumped parameter dynamic model has been shown to be an effective tool for dynamic analysis of spiral bevel geared rotor system. This model is appropriate for fast computation and convenient analysis, but due to the limited degrees of freedom used, it may not fully take into consideration the shaft-bearing structural dynamic characteristics. Thus, a dynamic finite element model is proposed to fully account for the shaft-bearing dynamic characteristics. In addition, the existing equivalent lumped parameter synthesis approach used in the lumped parameter model, which is key to representing the shaft-bearing structural dynamic characteristics, has not been completely validated yet. The proposed finite element model is used to guide the validation and improvement of the current lumped parameter synthesis method using effective mass and inertia formulations, especially for modal response that is coupled to the pinion or gear bending response. Secondly, a new shaft-bearing model has been proposed for the effective supporting stiffness calculation applied in the lumped parameter dynamic analysis of the spiral bevel geared rotor system with 3-bearing straddle-mounted pinion configuration. Also, based on 14 degrees of freedom lumped parameter dynamic model and quasi-static three-dimensional finite element tooth contact analysis program, two typical s (open full item for complete abstract)

Committee: Teik Lim PhD (Committee Chair); Ronald Huston PhD (Committee Member); David Thompson PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2011, Mechanical Engineering

In this study, an experimental investigation is performed to investigate the impact of various gear errors on transmission error and root fillet stresses. A test set-up is devised to operate a pair of spur gears under loaded, low-speed conditions. Two measurement systems; one an optical encoder-based transmission error measurement system and the other a multi-channel strain measurement system, are developed and implemented with the test set-up. A set of test gears having various types and tightly-controlled magnitudes of manufacturing errors are designed and procured. These errors include indexing errors of different tooth sequences, pitch line run-out errors and lead wobble errors. An extensive test matrix is executed to quantify the impact of these errors on the loaded static transmission error and the root stresses of the spur gears. At the end, the same test conditions are simulated by using a recent feature of gear analysis model (LDP) to assess the accuracy of its predictions.

Committee: Ahmet Kahraman PhD (Advisor); Donald Houser PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2011, Mechanical Engineering

The tooth bending strength characteristics of spiral bevel and hypoid gears are investigated in this study both experimentally and theoretically, focusing specifically on the impact of gear alignment errors. On the experimental side, a new experimental set-up is developed for operating a hypoid gear pair under typical load conditions in the presence of tightly-controlled magnitudes of gear misalignments. The test set-up allows application of all four types of misalignments, namely the shaft offset error (V), the horizontal pinion position error (H), the horizontal gear position error (G) and the shaft angle error (γ). An example face-hobbed hypoid gear pair from an automotive axle unit is instrumented with a set of strain gauges mounted at various root locations of multiple teeth and incorporated with digital signal acquisition and analysis system for collection and analysis of strain signals simultaneously. A number of tests covering typical ranges of misalignments and input torque under both drive and coast conditions are performed to quantify the influence of misalignments on the root stress distributions along the face width. On the theoretical side, the computational model developed in earlier by Kolivand and Kahraman [31] is expanded to generate the root surfaces of spiral bevel and hypoid gears cut by using either face-milling or face-hobbing processes. A new formulation is proposed to define the gear blank and a numerically efficient cutting simulation methodology is developed to compute the root surfaces from the machine settings, the cutter geometry and the basic design parameters, including both Formate and Generate motions. The generated surfaces are used to define customized finite element models of N-tooth segments of the pinion and the gears via an automated mesh generator. Toot contact loads predicted by a previous load distribution model of Ref. [31] is converted to nodal forces based on the same shape function used to interpolate for nodal displa (open full item for complete abstract)

Committee: Ahmet Kahraman PhD (Advisor); Gary Kinzel PhD (Committee Member); Dennis Guenther PhD (Committee Member); Anthony Luscher PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2010, Mechanical Engineering

This thesis presents a mobility analysis of a simplified helicopter gearbox system focusing on structure-borne noise, based on linear time-invariant system theory. The internal gear dynamic system, with a unity spur gear pair, shafts and bearings, is modeled as an 8 degree of freedom linear time-invariant system with static transmission error and sliding friction as the primary excitations with assumed magnitudes that are uniform throughout the entire frequency range (5-20000 Hz). Natural frequencies are obtained and eigenvalue derivatives are used to identify variations in each natural frequency with respect to small changes in each system parameter using a Taylor's series approximation. Analytical expressions are derived through the mobility synthesis technique for the linear and rotational motions of the gear and pinion, dynamic transmission error and dynamic bearing and mesh forces in terms of the effective shaft/bearing stiffnesses, mesh stiffness, masses and inertias of the gears and shafts. These results are compared with the direct matrix inversion methods. The asymptotic trends in the frequency responses are compared with static forces. The gear motions predicted by this model are used to predict sound radiation from the casing by means of experimental pressure/acceleration transfer functions. Measured individually for line of action and off-line of action paths, these transfer functions are considered to be made up of separate transfer functions corresponding to the gear system response, bearing transmissibility, casing transmissibility and sound radiation efficiency. The variation of the overall transfer function for changes in internal sub-system parameters (mesh stiffness, bearing/shaft stiffness) is formulated assuming that the bearing and casing characteristics remain unaffected. These modified transfer functions are then employed to predict the effect of assumed variation in the internal parameters and source excitations on the radiated sound. Furthe (open full item for complete abstract)

Committee: Rajendra Singh PhD (Advisor); Ahmet Kahraman PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2009, Mechanical Engineering

In this study, a test methodology for measuring load-dependent (mechanical) and load-independent power losses of helical gear pairs is developed. A high-speed four-square type test machine is adapted for this purpose. Several sets of helical gears having varying module, pressure angle and helix angle are procured, and their power losses under jet-lubricated conditions are measured at various speed and torque levels. The experimental results are compared to a helical gear mechanical power loss model from a companion study to assess the accuracy of the power loss predictions. The validated model is then used to perform parameter sensitivity studies to quantify the impact of various key gear design parameters on mechanical power losses and to demonstrate the trade off that must take place to arrive at a gear design that is balanced in all essential aspects including noise, durability (bending and contact) and power loss.

Committee: Ahmet Kahraman PhD (Advisor); Donald Houser PhD (Committee Member) Subjects: Mechanical Engineering