Search Results (1 - 25 of 33 Results)

Sort By  
Sort Dir
 
Results per page  

Anichowski, BrianAn Experimental Investigation of the Effect of Spacing Errors on the Loaded Transmission Error of Spur Gear Pairs
Master of Science, The Ohio State University, 2017, Mechanical Engineering
This paper complements recent investigations [Handschuh et al. (2014), Talbot et al. (2016)] of the influences of tooth indexing errors on dynamic factors of spur gears by presenting data on changes to the dynamic transmission error. An experimental study is performed using an accelerometer-based dynamic transmission error measurement system incorporated into a high-speed gear tester to establish baseline dynamic behavior of gears having negligible indexing errors, and to characterize changes to this baseline due to application of tightly-controlled intentional indexing errors. Spur gears having different forms of indexing errors are paired with a gear having negligible indexing error. Dynamic transmission error of gear pairs under these error conditions is measured and examined in both time and frequency domains to quantify the transient effects induced by these indexing errors. These measurements are then compared against the baseline, no error condition, as a means to quantify the dynamic vibratory behavior induced due to the tooth indexing errors. These comparisons between measurements indicate clearly that the baseline dynamic response, dominated by well-defined resonance peaks and mesh harmonics, are complemented by non-mesh orders of transmission error due the transient behavior induced by indexing errors. In addition, the tooth (or teeth) having indexing error imparts transient effects which dominate the vibratory response of the system for significantly more mesh cycles than the teeth having errors are in contact. For this reason, along with the results presented in Talbot et al. (2016), it was concluded that spur gears containing indexing errors exhibit significant deviations from nominal behavior, at both a system and time-domain level.

Committee:

Ahmet Kahraman (Advisor); David Talbor (Committee Member)

Subjects:

Engineering; Mechanical Engineering

Keywords:

Gear, Gears, Spur Gears, Dynamics, Transmission Error, Indexing Error, Manufacturing Error, Vibrations, Noise, Accelerometer, GearLab

Hotait, Mohammad AdelA Theoretical and Experimental Investigation on Bending Strength and Fatigue Life of Spiral Bevel and Hypoid Gears
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 displacements. A skyline solver is used to compute the nodal displacements and the resultant stresses at the Gauss points. An extrapolation matrix based on the least-square error formulation is applied to compute the stresses at the root surfaces. Predicted gear root stresses are shown to compare well with the measurements, including not only the extreme stress values but also the stress time histories. Through the same comparisons, the model is also shown to capture the impact of misalignments on the root stress distributions reasonably well.

At the end, a multiaxial, crack nucleation fatigue model of tooth bending is proposed; the model accounts for the multiaxial and non-proportional nature of the stress states predicted. Fatigue lives predicted by the proposed model are compared to those estimated by using a conventional uniaxial failure criterion to show that the predicted multiaxial fatigue lives are significantly lower. The fatigue model is also used to quantify the influence of the misalignments as well as certain key cutting tool parameters on the bending fatigue life of the hypoid gear pair.

Committee:

Ahmet Kahraman, PhD (Advisor); Gary Kinzel, PhD (Committee Member); Dennis Guenther, PhD (Committee Member); Anthony Luscher, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Hypoid Gears; Spiral Bevel Gears; Tooth Bending Fatigue Failure; Gear Root Stresses; Gear Misalignments; Multiaxial Fatigue

Polly, Joseph HAn Experimental Investigation of Churning Power Losses of a Gearbox
Master of Science, The Ohio State University, 2013, Mechanical Engineering
In this study, load-independent (spin) power losses of a gearbox operating under dip-lubrication conditions are investigated experimentally. A family of final drive helical gear pairs from an automotive transmission is considered as the example for this investigation. A dedicated gearbox is designed and fabricated to operate a single gear or a gear pair under given speed conditions. The test gearbox is incorporated with a high-speed test bed with power loss measurement capability. A test matrix that consists of sets of tests with (i) single spur, helical gears, or disks with no teeth, and (ii) helical gear pairs of varying gear ratios is executed with three different transmission fluids at various temperatures and immersion depths. Power losses from single gear and gear pair tests at identical operating conditions are compared to break down the total spin loss to its main components, namely gear drag loss, gear mesh pocketing loss, and bearing/seal loss. In addition, the space around the gears within the gearbox will be altered to quantify any influences of enclosures and peripheral shrouds on the spin losses of a rotating gear.

Committee:

Ahmet Kahraman, Dr. (Advisor); Donald Houser, Dr. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

gear; churning; spin power loss; lubrication; gearbox; housing; windage; efficiency; helical gears; spur gears

Merugu, SatyanarayanaAnalysis of geared shaft configurations and thin-rimmed gears using finite element method
Master of Science, The Ohio State University, 2001, Mechanical Engineering

A transmission system is a complex structure consisting of a driver (motor), many shafts, gears, couplers and load. The shafts and gears may be held to the housing with the help of bearings. The primary objective of this work is to obtain the natural frequencies and mode shapes of this complex system and then, obtain the dynamic response of the system due to external excitations such as transmission error, friction force and shuttling moment.

A finite element formulation is chosen for the above purpose and it can be used to transmissions using parallel axis shafts with spur and/or helical gears. In the program developed, shafts are modeled as beam elements with six degrees of freedom per node. The effect of bearings modeled by the use of 6x6 bearing stiffness matrix. The driver and load are modeled as discrete inertias, couplers as discrete inertias with a diagonal coupler stiffness matrix. The nodes between meshing gears are appropriately coupled together using the corresponding mesh stiffness. The complete system, involving many simultaneous equations, is formulated as an eigenvalue problem and first few natural frequencies and corresponding mode shapes are determined and then external excitations are applied and the frequency response of various degrees of freedom is obtained and later, this solution is used to calculate the dynamic transmission error, mesh force and bearing forces at various excitation frequencies. Using the program developed, a single stage reduction system, and an idler gear system are analyzed and the results are compared with already in-use programs like GearVib, developed at OSU Gearlab.

A secondary objective of this thesis is to develop a user-friendly analytical computer program for thin-rimmed spur or helical gears. A windows based front end is added to the thin rim program developed at OSU Gearlab and boundary conditions such as adjacent teeth effects are modified and parameters such as the number of sectors to be modeled in the program are studied for spur and helical gears.

Committee:

Donald Houser (Advisor)

Keywords:

GEARS; SHAFT; transmission error; force and bearing; helical gears; pinion

Hilty, Devin R.An Experimental Investigation of Spin Power Losses of Planetary Gear Sets
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

Keywords:

planetary gears; efficiency; power loss; transmission efficiency; gears; gear design; planetary gear efficiency; planetary gear power loss

Sanders, Aaron AnthonyAn Experimental Investigation of the Influence of Elliptical Root Shapes and Asymmetric Teeth on Root Stresses and Bending Fatigue Lives
Master of Science, The Ohio State University, 2010, Mechanical Engineering

In this study, effects of the root fillet geometry and the tooth asymmetry on the tooth bending stresses and the fatigue lives of spur gears are investigated. For this purpose, an existing gear analysis model, Load Distribution Program (LDP), is employed to define four basic tooth geometry variations. These four variations are (i) symmetric tooth profiles (i.e. identical loaded and unloaded flanks) with full circular root geometry (at the maximum radius possible), (ii) symmetric tooth profiles with an elliptical root geometry, (iii) asymmetric tooth profiles (i.e. loaded and unloaded flanks at different pressure angles) with full circular root geometries, and (iv) asymmetric tooth profiles with an elliptical root geometry on the right (loaded) flank and a circular root geometry on the left flank. Under these conditions, variations (ii), (iii), and (iv) are predicted to have maximum root stresses that are 7.6%, 22.4%, and 24.3% less than that of the baseline case (i).

Actual test articles representing these four variations are procured and qualified through dimensional measurements of the profiles as well as the root fillet regions. Certain teeth of each test variation are instrumented by using multiple strain-gauges placed at different root fillet locations. The strain measurements under various tooth load levels are compared to predictions to verify their accuracy for all four variations considered.

Single tooth bending fatigue tests are also performed to obtain fatigue data for each variation of the test gears. The resultant tooth bending fatigue performance of each gear variation is shown to correlate with the level of root stress reduction achieved. Experiments indicate that the most significant life increases compared to the baseline conditions are achieved with the last variation (asymmetric toot profiles and an elliptical root shape), where the mean life is increased by more than 30 times. It is also shown through examination of the broken teeth that the critical locations where the cracks initiated agree well with the predicted locations of the maximum root stresses.

Committee:

Ahmet Kahraman, PhD (Advisor); Donald Houser, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

gears; tooth profiles; root stresses; S20-S20; test gears; root geometry

Lewicki, David G.Crack propagation studies to determine benign or catastrophic failure modes for aerospace thin-rim gears
Doctor of Philosophy, Case Western Reserve University, 1995, Mechanical Engineering
Analytical and experimental studies were performed to investigate the effect of rim thickness on gear tooth crack propagation. The goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. Gear tooth crack propagation was simulated using a finite element based computer program. Principles of linear elastic fracture mechanics were used. Quarter-point, triangular elements were used at the crack tip to represent the stress singularity. Crack tip stress intensity factors were estimated and used to determine crack propagation direction and fatigue crack growth rate. The computer program used had an automated crack propagation option in which cracks were grown numerically using an automated re-meshing scheme. In addition, experimental studies were performed in the NASA Lewis Spur Gear Fatigue Rig. Gears with various backup ratios were tested to validate crack path predictions. Also, specialized crack propagation gages were installed on the test gears to measure gear tooth crack growth rate. From both predictions and tests, gears with backup ratios (rim thickness divided by tooth height) of 3.3 and 1.0 produced tooth fractures while a backup ratio of 0.3 produced rim fractures. For a backup ratio of 0.5 , the experiments produced rim fractures and the predictions produced both rim and tooth fractures, depending on the initial crack conditions. Good correlation between the predicted number of crack propagation cycles and measured number of cycles was achieved using both the Paris fatigue crack growth method and the Collipriest crack growth equation when fatigue crack closure was considered

Committee:

Roberto Ballarini (Advisor)

Subjects:

Engineering, Mechanical

Keywords:

Crack propagation; Failure mode, benign/catastrophic; Gears

Jaiswal, PreetishInfluence of Various Surface Treatments on Power Losses of Spur Gear Pairs
Master of Science, The Ohio State University, 2017, Mechanical Engineering
In this study, an experimental investigation of the effects of tooth surface roughnesses on gearbox power losses is performed. Spur gears with five different surface roughness pairings are considered as specimens. They include (i) gears having hard ground surfaces to serve as the baseline condition, (ii) chemically polished surfaces with isotropic lay, (iii) ground-polished surfaces at roughness amplitudes that are comparable to chemically polished surfaces, (iv) ground-polished surfaces that are rougher than smooth ground-polished surfaces, and (v) a ground surface mating with a ground-polished surface. An efficiency test set-up is used to measure gearbox power losses under these surface conditions within the ranges of transmitted torque, speed and oil inlet temperature. Tests under unloaded conditions were performed to isolate the load-independent power losses and remove them from the loaded tests to determine load-dependent power losses. Several roughness parameters including those defined in relation to the bearing-area curve are quantified for each test to investigate which correlated to power loss. Results indicate that the load-independent losses are not influenced by surface treatments while load-dependent losses increase with increased surface roughness amplitudes. An increase in oil temperature, or decrease in viscosity, is seen to increase the gear mesh friction power loss while reducing rolling power losses of bearings, which appears to neutralize changes to gear mesh power losses.

Committee:

Ahmet Kahraman, PhD (Advisor); David Talbot, PhD (Committee Member)

Subjects:

Automotive Engineering; Mechanical Engineering

Keywords:

Spur gears; Surface Treatments;

Inalpolat, MuratA THEORETICAL AND EXPERIMENTAL INVESTIGATION OF MODULATION SIDEBANDS OF PLANETARY GEAR SETS
Doctor of Philosophy, The Ohio State University, 2009, Mechanical Engineering
A pair of mathematical models is proposed in this study to investigate the modulation sidebands that routinely exist in measured vibration spectra from planetary transmissions. As the first of these models, a simplified semi-analytical model is proposed to describe the mechanisms leading to modulation sidebands of planetary gear sets due to rotation of the planet carrier. The model includes key system parameters such as number of planets, planet position angles, and planet phasing relationships defined by the position angles and the number of teeth of the gears. The model is used to simulate a wide range of gear sets to show that they can be classified in five distinct groups based on their sideband behavior in terms of their frequencies and amplitudes. A special experimental planetary gear set-up is developed and planetary gear sets from of three of these five groups are procured. A methodology is developed to demonstrate modulation sidebands from the ring (internal) gear radial acceleration measurements. For each case, sets of ring gear acceleration measurements at various speed and torque conditions are presented to demonstrate rich sideband activity that agrees well with the model predictions. The second model proposed in this study is a non-linear time-varying dynamic model that includes periodically varying gear mesh stiffnesses and non-linearities due to tooth separations. This model employed an excitation formulation that captures the impact of various gear manufacturing errors such that the predicted dynamic gear mesh force spectra contain separate sets of sidebands at unique frequencies to correspond to these errors. This model is further combined with the first model to incorporate the effects of carrier rotation as well. Comparison to the measured spectra are used to demonstrate the capability of the model in predicting the sidebands of a planetary gear set with both gear manufacturing errors and a rotating carrier. At the end, based on results of the parametric studies and experiments, general rules on modulation sidebands of planetary gear sets are proposed.

Committee:

Ahmet Kahraman, Prof. (Advisor); Rajendra Singh, Prof. (Committee Member); Chia-Hsiang Menq, Prof. (Committee Member); Dennis Guenther, Prof. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

planetary gears;modulations;sidebands;vibrations;noise

Kolivand, MohsenDEVELOPMENT OF TOOTH CONTACT AND MECHANICAL EFFICIENCY MODELS FOR FACE-MILLED AND FACE-HOBBED HYPOID AND SPIRAL BEVEL GEARS
Doctor of Philosophy, The Ohio State University, 2009, Mechanical Engineering
A computationally efficient load distribution model is proposed for both face-milled and face-hobbed hypoid gears produced by Formate and generate processes. Tooth surfaces are defined directly from the cutter parameters and machine settings. A novel methodology based on the ease-off topography is used to determine the unloaded contact patterns. The proposed ease-off methodology finds the instantaneous contact curves through a surface of roll angles, allowing an accurate unloaded tooth contact analysis in a robust and accurate manner. Rayleigh-Ritz based shell models of teeth of the gear and pinion are developed to define the tooth compliances due to bending and shear effects efficiently in a semi-analytical manner. Base rotation and contact deformation effects are also included in the compliance formulations. With this, loaded contact patterns and transmission error of both face-milled and face-hobbed spiral bevel and hypoid gears are computed by enforcing the compatibility and equilibrium conditions of the gear mesh. The proposed model requires significantly less computational effort than finite elements (FE) based models, making its use possible for extensive parameter sensitivity and design optimization studies. Comparisons to the predictions of a FE hypoid gear contact model are also provided to demonstrate the accuracy of the model under various load and misalignment conditions. The proposed ease-off formulation is generalized next to include various types of tooth surface deviations in the tooth contact analysis. These deviations are grouped in two categories. The proposed ease-off based method is shown to be capable of modeling both global deviations due to common manufacturing errors and heat treat distortions and local deviations due to surface wear. The proposed loaded contact model is combined at the end with a friction model based on a mixed elastohydrodynamic lubrication model to predict the load dependent (mechanical) power losses and efficiency of the hypoid gear pairs. The velocity, radius of curvature and load information predicted by the contact model is input to the friction model to determine the distribution of the friction coefficient along the contact surfaces. At the end, the variations of predicted mechanical efficiency with geometry, surface and lubricant parameters are quantified.

Committee:

Ahmet Kahraman, Prof. (Advisor); Donald R. Houser, Prof. (Committee Member); Gary L. Kinzel, Prof. (Committee Member); Henry H. Busby, Prof. (Committee Member)

Subjects:

Design; Engineering; Mechanical Engineering; Mechanics

Keywords:

Hypoid Gears; Tooth Contact Analysis; Ease-off topography; Efficiency; Surface deviation

Hwang, Jenq-FongAdvanced computer-aided design method on the stress analysis of internal spur gears
Master of Science, The Ohio State University, 1986, Mechanical Engineering

Committee:

Dennis Guenther (Advisor)

Keywords:

GEARS; FILLET; RIM THICKNESS; INTERNAL GEAR; RIM; ROOT FILLET; TOOTH

Brenneman, James WAn Experimental Study on the Scuffing Performance of High-Power Spur Gears at Elevated Oil Temperatures
Master of Science, The Ohio State University, 2013, Mechanical Engineering
In this study, a number of spur gear tests were performed under high-power and high-temperature conditions representative of certain aerospace gearing applications. As the first type of tests, long cycle tests of 100 million cycles were performed at set operating speed, load, and temperature conditions. The second type of tests, load-staged scuffing tests, implemented an incrementally increased torque schedule under constant speed and oil temperature conditions. Two different gear tooth surfaces were considered in these tests: hard ground surfaces representative of rough, as machined gear surfaces and chemically polished gear surfaces that were an order of magnitude smoother than the ground surfaces. The primary failure mode of concern was scuffing of the contact surfaces due to temperature build up. The impact of surface roughness amplitudes, contact stress, and oil inlet temperature on scuffing failures were investigated. Effects of ramp up procedures for the speed and torque, as well as the introduction of a break-in test stage were also investigated to show that they are critical to the scuffing performance of gears.

Committee:

Ahmet Kahraman (Advisor); Brian Harper (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

gears; scuffing; high temperature;contact fatigue

Boguski, Brian C.An Experimental Investigation of the System-Level Behavior of Planetary Gear Sets
Master of Science, The Ohio State University, 2010, Mechanical Engineering

An experimental study consisting of three separate investigations is conducted on the system-level behaviors of a planetary gear set. A test rig is designed and procured for the purpose of measuring (i) transmission error, (ii) planet-to-planet load sharing and (iii) sun gear radial orbits under quasi-static conditions within a range of input torque. Several test matrices are implemented and are designed to quantify the effects of gear manufacturing errors and modifications as well as kinematic configurations under which the planetary gear set operates in a repeatable and accurate manner.

The test matrix for the planetary gear set transmission error study includes three distinct phasing conditions (in phase, sequentially phased and counter-phased) of a four-planet gear set as well as two planet tooth profile modifications and two sun gear run-out error values. Two distinct power flow conditions with a fixed planet carrier and a fixed ring gear are also included in addition to an array of five carriers with different pin hole position errors. The transmission error results indicate that the phasing condition of the gear set is the most critical factor resulting in varying levels and numbers of modulation sidebands around the gear mesh orders. A novel method of measuring planet load sharing is developed to investigate the effects of mesh phasing and carrier pin hole position errors on individual planet loads. Strain gauges mounted directly on the planet pins are used to record the loads carried by the planets assembled in a fixed carrier continuously. The results of the tests indicate that the planet mesh phasing has no influence on the planet load sharing while the tangential pin hole position errors dictate the amount of load each planet carries. A single effective planet error parameter is shown to dictate the planet load sharing of four-planet gear sets. Finally, the orbital patterns of the planetary sun gear are recorded using a proximity probe measurement system designed for this study. These measurements show that a floating sun gear moves along a well-defined trajectory consisting of an integer number of trochoidal loops in an attempt to self-center the gear set. The exact number of these loops is shown to be dictated by the overall period of the gear set.

By analyzing the collected data, various conclusions are made at the end of the study in regards to the three system-level effects under investigation. It is shown that several of the test variables have design consequences and affect the behavior of the gear set. A list of recommendations for future work is also proposed to guide further investigations on this topic.

Committee:

Ahmet Kahraman (Advisor); Gary Kinzel (Committee Member)

Subjects:

Automotive Engineering; Engineering; Mechanical Engineering

Keywords:

planetary gears; transmission error; planet load sharing; sun gear orbit; automatic transmission;

Janakiraman, VenkatakrishnaModelling of Steady-State and Transient Power Losses in Planetary Gear Trains
Doctor of Philosophy, The Ohio State University, 2017, Mechanical Engineering
Planetary gear trains are the preferred gear configuration in automatic transmission applications for their advantages such as coaxial input and output shafts, higher power density, favorable noise characteristics, kinematic flexibility, and reduced radial support structure requirements. Their power losses might be high due to multiple sets of external and internal gear meshes, planet bearings, and rotating gear components and connecting structures. The main objective of this study is to develop a physics-based model to quantify power losses of multi-stage planetary gear trains. The intended application of this model is automotive automatic transmission gear sets. Power losses in planetary gear trains can be divided into load-dependent (mechanical) and load-independent (spin) losses. The load-dependent power losses are the result of friction in the loaded rolling-sliding contacts of gear meshes and bearings. The load independent losses are primarily due to fluid interactions with rotating components. The power transmitted by each component is altered by the power losses along the gear train while the power losses are dictated by the power transmitted. As the first step, an iterative power flow model is developed for multi-stage planetary gear trains consisting of single-planet and double-planet gear sets, including component loss torques in the formulation. The two-way interactions between the power flow and power losses in the gear train are captured through this computationally efficient algorithm. In the second step, mechanical power loss models for the gear meshes and planet bearings are included in the overall power flow formulation. These models utilize closed-form rolling and sliding friction formulae regressed from many elastohydrodynamic lubrication simulations, thus including the effect of operating conditions, and lubricant and design parameters implicitly. An example system is introduced to demonstrate the capability of the model. Spin power loss models for drag of rotating components such as gears, carrier assemblies, connecting drums and wet clutches are included in the power flow formulation next to obtain total losses in the gear train including both load-dependent and load-independent ones. Parametric studies on the example system show that mechanical loss dominates the total loss in the lower gear ranges while spin losses are prominent in the higher gear ranges. EPA driving cycles are simulated to evaluate total losses and efficiency under typical driving scenarios. As the final step, the steady-state power loss model developed thus far is extended to include transient effects particularly that imposed by gear shifts. With gear shift power losses included, simulations of different EPA driving cycles show that power loss is increased significantly especially in city driving cycles where gear shifts occur frequently.

Committee:

Ahmet Kahraman (Advisor); Marcello Canova (Committee Member); Levent Guvenc (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Planetary Gears, Automatic Transmissions, Gear Trains, Power Loss, Efficiency

Wang, YawenVibration and Sound Radiation Analysis of Vehicle Powertrain Systems with Right-Angle Geared Drive
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 the gear-shaft interaction, rotordynamics effect and housing flexibility. Finally, some conclusions and recommendations for future studies are given.

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

Keywords:

Gear noise;Powertrain systems;Hypoid Bevel gears;Vibro acoustic analysis;Gear dynamics

Del Donno, Andrew MarkExperimental Study of Multi-Mesh Gear Dynamics
Master of Science, The Ohio State University, 2009, Mechanical Engineering

This thesis presents a multi-faceted investigation into the dynamics of a three-gear idler gear train. Previous work and motivation for current research is discussed. Modifications to the physical test stand, new experimental procedures, and data acquisition software developments are detailed. Results for multiple phases of testing are given. Impact testing and shaker testing results on the complete system and isolated test gearbox are shown. Results from spinning system tests following bearing modifications are given along with a comparison to previous assemblies. Modal testing on the gearbox housing is shown as is the discovery of significant unexpected shaft bending behavior in the test gearbox shafts. Development of analytical models to incorporate additional degrees of freedom outside the gearbox is undertaken and correlation for the most recent test gearbox assembly is presented along with accepted system parameters.

Following characterization of the new assembly, conclusions and recommendations for future work are made.

Committee:

Robert Parker, PhD (Advisor); Ahmet Kahraman, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Dynamics; gears; idler; analytical modeling; modal testing, vibrations

Benatar, Michael AAn Experimental Investigation of the Load Distribution of Splined Joints under Gear Loading Conditions
Master of Science, The Ohio State University, 2016, Mechanical Engineering
Splined joints are commonly used to transmit rotary motion from a shaft to machine elements such as gears. While computationally efficient spline load distribution models have recently been proposed, there is no validated model of a spline due to lack of high-fidelity experimental data. Accordingly, this study aims to (i) establish an extensive experimental database on load distributions of splined joints subject to gear loading conditions and (ii) assess the accuracy of the spline load distribution model of Hong et al. (2014) through direct comparisons of its predictions to experimental measurements. On the experimental side, a quasi-static, spline-specific test setup is designed, fabricated, and instrumented. A test matrix covering various loading conditions is executed in order to compile an extensive spline load distribution database. The modeling effort centers around expanding the model of Hong et al. (2014) by adding a new root stress prediction module. The experimental data illustrates the cyclic nature of loads and resultant stresses on spline teeth caused by rotation of the spline teeth in relation to the gear mesh that loads the splined joint. A nonlinear relationship between torque applied and resultant stress is revealed, as well as the relationship between the location of maximum stress along the face width and the amount of lead crown modification applied. Through correlations to the experimental results, the model is shown to be accurate; it captures several unique effects of spur and helical gear loading conditions.

Committee:

Ahmet Kahraman (Advisor)

Subjects:

Mechanical Engineering

Keywords:

Splines; Splined Joint; Load Distribution; Gears

Klein, Mark AndrewAn Experimental Investigation of Materials and Surface Treatments on Gear contact Fatigue Life
Master of Science, The Ohio State University, 2009, Mechanical Engineering

This study consists of experimental studies involving two modes of gear contact fatigue failure: gear pitting (spalling) and gear scuffing. For pitting studies, several materials and surface treatments were investigated at various stress levels. These surface treatments included (i) hobbed and shaved (baseline), (ii) chemically polished, (iii) shot peened and plastic honed, and (iv) ground gears. Pitting fatigue lives of chemically polished gears were greater than those of baseline specimens. Both shot peened and plastic honed gears and ground gears were shown to have greater pitting fatigue lives than baseline gears. The improved pitting fatigue life of ground gears over baseline gears appears related to the improved involute profile shapes of the specimens.

For gear scuffing experiments, the standard ISO 14635-1 FZG Scuffing Test was performed on AISI 8620 type A spur gears. These experiments included four uncoated gear pairs and one gear pair coated with an experimental PVD coating. Uncoated gears encountered scuffing during Stages 11 and 12. A high correlation between temperature and scuffing results was detected for both coated and uncoated specimens.

Committee:

Ahmet Kahraman, PhD (Advisor); Donald Houser, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

gear; scuffing; spalling; pitting; fatigue contact; spur gears; FZG;

Olson, Garrett WestonExperiments on the High-Power and High-Temperature Performance of Gear Contacts
Master of Science, The Ohio State University, 2012, Mechanical Engineering
In this study, gear contact tests were performed using a recently developed test methodology capable of both high-power (pitch-line velocities up to 50 m/s and pinion torques up to 450 N-m) and high-temperature (oil inlet temperatures up to 150C) operating conditions. Test specimens and operating conditions were chosen in order to simulate high-power automotive and aerospace applications. Automotive test specimens were made from a typical automotive transmission gear steel, SAE 4118M, at surface roughnesses typical of hard ground gears. Aerospace test specimens were made out of a high performance (high-temperature) proprietary gear steel. These aerospace specimens were either chemically polished or super-finished following grinding to achieve roughness amplitudes more than 10 times smoother than typical ground surfaces. Throughout each test interim inspections were used to identify and monitor failure modes. Experimental testing for automotive applications is shown to consistently produce contact fatigue failures in the form of micro-pitting and macro-pitting. Tests were suspended when macro-pits exceeded the test methodologies pre-determined failure criteria. Experimental testing for aerospace applications is shown to be absent of any contact fatigue failures due to the extremely smooth contact surfaces. The primary mode of contact failure in aerospace tests is observed to be scuffing.

Committee:

Ahmet Kahraman (Advisor); Gary Kinzel (Committee Member)

Subjects:

Aerospace Engineering; Aerospace Materials; Automotive Engineering; Automotive Materials; Engineering; Mechanical Engineering

Keywords:

gears; gear contacts; high-power; high-temperature; contact fatigue; pitting; scuffing

Madhavan, SriramA Study of Geometry and Deformable-body Characteristics of Non-right Angle Worm Gear Pairs
Master of Science, The Ohio State University, 2012, Mechanical Engineering
In this study, a formulation to define the three-dimensional geometry of worm gear drives having non-right angle shafts is developed. The geometry of the worm is determined by defining the geometry of the cutter and solving the corresponding equation of meshing between the worm and the cutter. The geometry of the worm gear is then defined by using a cutter which has the exact shape of the worm and solving the corresponding equation of meshing between the worm and the worm gear. Both right- and left-hand, single enveloping worm drives of ZK type with any number of worm threads are included in this formulation. With the tooth surface geometries defined, a commercial finite element gear analysis package with specific worm mesh generators is used to develop a deformable-body model of a non-right angle worm gear pair A parametric design sensitivity study is performed by using this deformable-body model to quantify the effects of basic geometric parameters including the shaft cross angle, lead angle, pressure angle, and addendum and dedendum coefficients on the maximum contact stress and mechanical efficiency of the gear pairs. In addition, variations to shaft center distance and cross angle are introduced to investigate their influence on gear pair performance.

Committee:

Dr. Ahmet Kahraman, PhD (Advisor); Dr. Donald Houser, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

"Worm Gears;Non-right shaft angles;geometry of ZK type worm and worm gear;CALYX deformable body analysis"

Leque, NicholasDevelopment of Load Sharing Models for Double-Helical Epicyclic Gear Sets
Doctor of Philosophy, The Ohio State University, 2015, Mechanical Engineering
Epicyclic gear systems provide several advantages over their fixed-center, counter-shaft alternatives, including higher power-density, smaller tooth modules, reduced size and decreased radial bearing support requirements. Use of double-helical gears in an epicyclic configuration provides the advantage of further increasing the load-carrying capacity of the gearbox, while cancelling out nominal axial forces acting on the gears, simplifying their axial bearing support requirements considerably. A substantial challenge arises when planet branches or the two gear decks do not share load equally, due to the presence of various manufacturing errors and assembly variations. This research study aims at investigating quasi-static load sharing behavior of double-helical epicyclic gear sets theoretically. An axial-torsional discrete load sharing model is proposed first in order to describe the coupling between the axial motions and torsional rotations of gears that often self-compensates for stagger errors of double-helical gears in the set. This model includes the axial stiffness of the supporting structures and investigates its influence on both the axial motions and the resultant right-to-left deck load sharing. The model is generalized such that any N-planet double-helical gear sets can be analyzed. A complete three-dimensional load sharing model of a double-helical epicyclic gear set is proposed next with all six degrees of freedom of each component included. This model includes various types of manufacturing errors, both constant and time-varying with respect to gear rotation. Specific examples of constant errors are right-to-left stagger errors of double-helical gears, planet pin position errors on the carrier and average tooth thickness (size) errors of planets. Examples of time-varying errors are eccentricities and run-out errors of gears assembled in any arbitrary way with respect to each other. This model relies on a loaded gear contact analysis model to prescribe the appropriate load-dependent stiffness to each of the internal or external gear meshes. The flexibilities of structures supporting all the gears and the carrier are included to fully comprehend the effects of floating members radially as well as axially. The 3D model is verified through comparisons of its predictions to those from a deformable-body model for select example cases. Results indicate that the deck-to-deck load sharing is superimposed on the planet-to-planet load sharing in each deck. Statistical analyses of multi-error cases are performed using the 3D load sharing model as the predictor. For this, assembly variations are assumed to be uniformly distributed while the each error on each component is described by a normal distribution. The maximum load sharing distributions are predicted as functions of manufacturing tolerance band widths. These statistical maximum load distributions indicate that the worst-case configurations defined deterministically are significantly more conservative than those revealed by a statistically-likely load sharing distribution. As a final model refinement, influence of the variation of gear mesh stiffness caused by the fluctuations in the number of teeth in contact is investigated. A gear load distribution model is used to predict the instantaneous gear mesh stiffness values rather than time-averaged ones. With this, periodically time-varying mesh stiffnesses at their appropriate load level are used with proper planet mesh phasing relationships. It is shown that, while secondary to the effects of manufacturing errors, mesh stiffness fluctuations can still cause variations of planet-to-planet load sharing within each mesh cycle.

Committee:

Rebecca Dupaix (Committee Member); Noriko Katsube (Committee Member); Marcello Canova (Committee Member); Ahmet Kahraman (Advisor); Sabine Jeschonnek (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Gears, epicyclic, static; load sharing; helical; planetary

Snyder, Shane MichaelThe Mechanics of War: Procedural Rhetoric and the Masculine Subject in the Gears of War and Mass Effect Series
Master of Arts (MA), Bowling Green State University, 2015, English
This thesis attempts to illustrate how war video games deploy their rules and mechanics to rhetorically reinforce or reconfigure the male-gendered (hyper-)masculine player-subject. Because video games enable player-subjects to interactively take part in simulations of war, video games have rhetorical power that scholars, video game developers, and players must learn to critically harness in order to tell imaginative narratives that value peace over violence. Split into three chapters, this thesis critically examines what I believe constitutes a small representative sample of influential or potentially influential war video games. The first chapter argues that the Gears of War series of video games reinforces the traditional hyper-masculine subject of war with a xenophobic narrative that glorifies violence against a feminized and reified enemy threat. By contrast, the second chapter argues that the Mass Effect series of video games responds to this violence by more imaginatively reconfiguring the masculine subject of war through its encouragement of diplomacy instead of aggression. The third and final chapter argues that the independently-produced September 12 and This War of Mine both further reconfigure and ultimately redefine the masculine subject of war by enabling the player to embody the subject positions of multiple civilians adversely affected by war. The thesis comes to the conclusion that critical video game studies must seek to access larger portions of the video gaming population in order to shift the public’s demand toward narratives of peace that nonetheless entertain.

Committee:

Kimberly Coates, PhD (Advisor); Kristine Blair, PhD (Committee Member)

Subjects:

Gender Studies; Literature

Keywords:

Masculinity; Gender and Sexuality; Game Studies; War; Rhetoric; Procedural Rhetoric; Gears of War; Mass Effect; September 12; This War of Mine

Wright, Zachary HarrisonLoaded Transmission Error Measurement System for Spur and Helical Gears
Master of Science, The Ohio State University, 2009, Mechanical Engineering
The majority of loaded static transmission error test stands developed in the past had little success generating accurate results versus analytical predictions for parallel-axis gearing. Design flaws historically caused issues with speed and torque control, ultimately, leading to erroneous results. Fortunately, some of these issues were corrected through the years, most recently by Schmitkons [1], for loaded transmission error testing of bevel gears sets. The original goal of this thesis was to translate those successes into a test rig for parallel-axis gearing that can measure static transmission error and shaft deflections to take a look at transmission error, shuttling and friction force excitations. However, due to difficulties in achieving a good comparison between experimental results and analytical predictions, the goal was shifted towards simply assessing the performance of the new test stand. By using virtually the same control setup and measurement setup as the loaded bevel gear static transmission error test stand, the new test stand generated static transmission error results for both spur and helical gears at various torque levels. Those results were compared to analytical prediction software codes (WindowsLDP, RomaxDesigner and Helical3D), using optimal and measured micro-geometry topographies. The static transmission error results compared well at low torque values, but deviated from the predicted trends at higher torque values. Ultimately, lessons learned from this test setup will be reflected in future experimental work in order to better assess the accuracy of prediction tools.

Committee:

Donald Houser, PhD (Advisor); Ahmet Kahraman, PhD (Committee Member)

Subjects:

Engineering

Keywords:

transmission error; spur; helical; gears

Janakiraman, VenkatakrishnaAn Investigation of the Impact of Contact Parameters on the Wear Coefficient
Master of Science, The Ohio State University, 2013, Mechanical Engineering
Wear models developed for gears often employ Archard’s wear equation, which states that the change of wear depth with sliding distance is proportional to contact pressure. The constant of proportionality, the wear coefficient, represents all other contact parameters with potential impact on wear, ranging from lubricant parameters, surface conditions and operation conditions to material type and hardness. As such, application of the Archard’s equation to gear wear problems requires that the wear coefficient be defined empirically. This study aims at quantifying the influence of various contact parameters on the wear coefficient such that this dependence on empirical means can be minimized. For this purpose, a wear model of point contacts formed by surfaces in relative sliding is developed. The model combines a contact pressure formulation and the Archard’s wear equation to predict the accumulation of wear on contact surfaces. A family of two-disk roller contact experiments are simulated using this model and the wear coefficient value that results in a good match between the measured and predicted wear profiles is determined for each test. With simulations of tests performed at various speeds, normal forces (contact pressures), oil temperatures (i.e. viscosities), and surface roughnesses, impact of these contact parameters on the wear coefficient values is quantified. A regression analysis of the wear coefficient values as a function of dimensionless force, speed, viscosity and roughness parameters is carried out at the end to obtain an expression for the wear coefficient that includes these parameters.

Committee:

Ahmet Kahraman (Advisor); Gary Kinzel (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Wear Coefficient; Archard's Wear Model; Twin Disk Tests; Gears

Sondkar, Prashant B.Dynamic Modeling of Double-Helical Planetary Gear Sets
Doctor of Philosophy, The Ohio State University, 2012, Mechanical Engineering

This dissertation aims at investigating the dynamic response of double-helical planetary gear sets theoretically. A three-dimensional discrete dynamic model of a double-helical planetary gear set is proposed, including all gear mesh, bearing and support structure compliances. The model is presented in three levels of complexity: (i) a linear time-invariant (LTI) model, (ii) a LTI model with gyroscopic effects included, and (iii) a nonlinear time-varying (NTV) model with parametrically time-varying gear mesh stiffnesses and nonlinear tooth separation effects included.

As the first step, a generic linear (no tooth separations), time-invariant (constant gear mesh stiffnesses) dynamic model is formulated to analyze any N-planet double-helical planetary gear system. The model includes any planet phasing conditions dictated by the number of planets, number of gear teeth and planet position angles as well as any phase shifts due to the designed stagger between the right and left sides of the gear set. The forced response due to gear mesh transmission errors excitations is computed by using the modal summation technique with the natural modes found from the corresponding Eigen value problem for the undamped system. The strain energies of the mode shapes are computed to identify the modes excitable by these excitations. Parametric studies are presented to demonstrate sizable influences of planet phasing, stagger conditions, gear and carrier support conditions as well as the number of planets on the steady-state forced response.

In the second modeling step, the LTI model is modified to include a class of gyroscopic effects due to vibratory skew of spinning gears for the case of a stationary carrier. The complex Eigen solutions are examined to quantify the influence of rotational speed of the gear set through gyroscopic effects on the natural modes. A complex modal summation formulation is used to compute the forced response with gyroscopic effects. Results indicate that the influence of gyroscopic moments on natural frequencies is modest within typical speed ranges, with only a sub-set of modes exhibiting dominant tilting motions impacted by the gyroscopic effects. Effect of gyroscopic moments on forced response curves is found to be limited to slight changes in amplitudes and frequencies of certain resonance peaks.

As the final step, mesh stiffness fluctuations due to change in number of tooth pairs are introduced as internal parametric excitation along with the transmission error excitations at the same phasing relations. Tooth separation functions are also applied to obtain a set of NTV equations of motion, which are solved by using direct numerical integration. Differences observed between the forced response curves for time-varying and time-invariant systems are characterized by additional resonance peaks and overall increases in response amplitudes while no signs of nonlinear behavior are noted.

Committee:

Ahmet Kahraman, Dr. (Advisor); Daniel Mendelsohn, Dr. (Committee Member); Manoj Srinivasan, Dr. (Committee Member); Junmin Wang, Dr. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Gears; Dynamics; Planetary

Next Page