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

This dissertation research focuses on developing and experimentally validating a three-dimensional load distribution model for helical gear pairs that is suitable for both quasi-static and dynamic conditions. As one phase of this research, the modeling work is carried out in two main steps. The first step focuses on quasi-static conditions by (i) developing a generalized procedure to define instantaneous contact lines along the gear mesh interface, (ii) formulating the flexibility introduced by the support structures such as bearings and shafts in a systematic way, and (iii) including gear blank related manufacturing errors such as eccentricity and wobble. The contact problem under these conditions, governed by compatibility and equilibrium equations, are solved by using an iterative elastic contact algorithm. In the second step, dynamic effects are included in the model of the first step to develop a dynamic load distribution model of a helical gear pair having the same novel features of the quasi-static model. For this, the compatibility equations of the quasi-static model are coupled to the equations of motion in the state-space representation and solved by using a backward Euler method. The other phase of this research is focused on validation of the quasi-static and dynamic load distribution models. As very little experimental helical gear data is available in the literature, an experimental study is conducted to generate an extensive database for validation of the models of this study as well as for guiding future helical gear modeling efforts. The experimental study considers a family of unity-ratio helical gear pairs having varying amounts of micro-geometry modifications as well as several spur gears having certain manufacturing errors. An encoder-based measurement system is devised to quantify the static transmission error at various transmitted torque levels to form Harris charts and define the design load values. An accelerometer-based measurement syst (open full item for complete abstract)

Committee: Ahmet Kahraman (Advisor); Kiran D'Souza (Committee Member); David Talbot (Advisor) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2021, Mechanical Engineering

Planetary gearsets are indispensable power transfer components in several mechanical systems and are preferred over counter-shaft gears due to their coaxial arrangement, high power density, minimal radial loads, and multiple possible kinematic combinations. In spite of their several benefits and widespread use, the complex arrangement of components in a planetary gear system makes them susceptible to noise and vibration issues. Analysis and design tools specific to planetary gear sets are sparse, accurate models that are available for detailed analyses of planetary gear sets require significant computational effort and expert users. In contrast, the computationally efficient lumped parameter models available in the literature are not very effective for root cause analysis because of the simplifications made in modeling the gear meshes. These challenges become multifold with the advent of electric drive units, not only due to their high operating loads and speeds but also due to the fact that there is no broadband noise from the engine to mask the transmission noise. Considering the aforementioned challenges with planetary gear design and lack of accurate and computationally efficient analysis tools, this dissertation presents a three-dimensional dynamic load distribution model for planetary gearsets. The proposed formulation uses a numerical integration scheme in conjunction with an iterative elastic contact algorithm to solve the multibody contact problem, and unlike previous models, can implicitly capture the influence of probable assembly and manufacturing errors in a planetary gear set. The developed dynamic load distribution model for planetary gears builds upon the quasi-static model of Hu et al. as its basis. Therefore to build trust in the fundamental framework, tightly controlled quasi-static planetary gear experiments were conducted to thoroughly validate the quasi-static model before developing the dynamic model. A unique experimental methodology, tha (open full item for complete abstract)

Committee: David Talbot (Advisor); Ahmet Kahraman (Committee Member); Carlos Castro (Committee Member); Manoj Srinivasan (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

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

In this study, an asymmetric tapered plate model is used to study the deflections of an asymmetric involute gear tooth. The bending and shear compliance of the plate was solved using the semi-analytical Rayleigh-Ritz energy method. The transverse deflection from the shear plate model were shown to be in excellent agreement with Finite Element Method (FEM) results, with acceptable normalized errors for different load cases. Computational efficiency of this semi-analytical model over FEM allows it to be used in Load Distribution Program (LDP), an existing gear analysis program, for predicting the load distribution, loaded transmission error, root stress, contact stress, mesh stiffness, tooth forces and other design evaluation parameters. A profile generation method for asymmetric gears from arbitrary rack profiles is used to predict root stresses using Boundary Element Method (BEM) in LDP. Root stress predictions are made for pressure angles. Two cases of pressure angle variation for asymmetric gears with drive pressure angle greater than coast pressure angle are explored, (i) Increasing drive pressure angle while keeping coast pressure angle constant, (ii) Decreasing coast pressure angle while increasing drive pressure angle. Results indicate that bending stress reduces considerably in case (i) as the drive pressure angle is increased. In case (ii), root stresses remain unaffected on increasing asymmetry.

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

Master of Sciences, Case Western Reserve University, 2019, EECS - System and Control Engineering

This thesis describes the design and implementation of a finite state machine representation of a voltage regulation control system for a load tap-changing transformer. It also introduces a method for observing physical operating conditions based on sequences of state transitions within the control system. Simulation of a daily load pattern applied to a distribution network yields the probabilities of specific sequences occurring, which can be used to detect irregular behavior. State transition data correlated with an expected load pattern can be used to verify whether behavior is consistent with the sensor data observed by a system operator. Possible adverse scenarios include when either the operator or the control system is receiving falsified measurements, as would occur during a replay attack. The effectiveness of this technique is quantified by how quickly it can detect voltage anomalies as they occur.

Committee: Kenneth Loparo PhD (Advisor); Vira Chankong PhD (Committee Member); Marija Prica PhD (Committee Member) Subjects: Electrical Engineering; Energy; Systems Design

Doctor of Philosophy (PhD), Ohio University, 2018, Civil Engineering (Engineering and Technology)

Adjacent precast prestressed concrete box beam bridges have been used for short and medium spans for decades. This type of bridge is preferred due to its high torsional rigidity, vertical clearances, and overall aesthetics. However, one of the major issues with this type of bridges is cracking that can occur between adjacent beams, at the longitudinal connection, which could lead to reflective cracks in composite deck or overlay surfaces. These cracks can cause water to leak through the joints, which can accelerate the corrosion of steel reinforcement from salt water exposure, causing the load transfer, between adjacent beams, to be reduced or diminished significantly. Despite several studies, the root cause of the cracking has yet to be addressed, therefore, a grout material with superior mechanical properties, interface bond strength, and long term durability is needed for this type of bridge in order to reduce or eliminate longitudinal cracks. In this doctorate study, ultra-high performance concrete (UHPC), which is becoming a common grout material in bridge connections, was used in the longitudinal joints of prestressed concrete box beam bridge. The new longitudinal joint design consisted of UHPC as the grout, with threaded dowel bars spaced evenly along the shear key joint length. This new shear key connection led to the elimination of transverse post-tensioning, composite deck, and transverse tie rods. The performance of this type of connection was investigated in laboratory testing conducted by the Federal Highway Administration's (FHWA) Turner-Fairbank Highway Research Center for a pair of box beams under cyclic and temperature loads. However, the field performance can vary greatly from grout produced under ideal lab conditions. Further investigations of this type of connection are needed because most of the studies indicated that the longitudinal cracks were initiated by temperature effects, and propagate due to applied load. To test this, a bridg (open full item for complete abstract)

Committee: Eric Steinberg Ph.D. P.E. (Advisor) Subjects: Civil Engineering

Doctor of Philosophy, The Ohio State University, 2017, Mechanical Engineering

Planetary gear sets are used commonly in various automotive, aerospace and industrial applications. They are indispensable components of automotive automatic transmissions, aerospace engine turbofan gearboxes, rotorcraft gearboxes, as well as wind turbine speed increasers. In spite of their widespread use, analysis and design models of planetary gear sets present unique problems stemming from the fact that there are multiple gear meshes formed by multiple planet branches. Computational models that are available for detailed analyses of planetary gear sets require significant computational effort and expert users. As such, common practice of planetary gear set design often ignores various crucial system-level effects by assuming that gear meshes can be designed independently. This study proposes a multi-mesh load distribution analysis methodology that is applied to planetary gear sets. This methodology solves for the load distributions along all gear meshes simultaneously and in a computationally efficient manner for it to be considered as a design tool. It accounts for any kinematic configurations of a gear set while capturing both system-level and gear mesh-level design variations, manufacturing and assembly error sensitivities, as well as any interactions amongst gear meshes and gear set components. Intricacies induced by various support and piloting conditions of the components of these gear sets are also represented accurately in this methodology. The multi-mesh load distribution analysis methodology is applied to both simple (single-planet) and double-planet planetary gear sets having any reasonable number of planet branches. This methodology is complemented by a finite element based flexible ring gear model consisting of three-node curved beam elements so that the impact of ring gear rim deformations on the individual gear mesh load distributions as well as planet-to-planet load sharing behavior can be accounted for. The accuracy of the baseline formulations (open full item for complete abstract)

Committee: Ahmet Kahraman (Advisor); Rebecca Dupaix (Committee Member); Noriko Katsube (Committee Member); Robert Siston (Committee Member) Subjects: Mechanical Engineering

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

Doctor of Philosophy, The Ohio State University, 2015, Mechanical Engineering

While spline joints are commonly used in power transmission devices and drivetrains of most automotive, aerospace and industrial systems, the level of design knowledge of them is far lower than other components such as gears, shafts and bearings. This study proposes a family of semi-analytical models to predict load distribution of clearance-fit (side-fit), major diameter-fit and minor diameter-fit spline joints with the intention of enhancing spline design practices. These models include all major components of spline compliance stemming from deformations associated with bending, shear and base rotation of the teeth as well as contact and torsional deformations. For clearance-fit splines, only drive side tooth surfaces are allowed to contact while top and root lands of the external spline are also chosen as potential contact zones in case of major diameter-fit and minor diameter-fit splines, respectively. Any helix mismatch or interference conditions are also handled by allowing contacts on back side tooth surfaces as well. All of these models are formulated for any general loading condition consisting of torsion, radial forces and tilting moments, such that loading conditions of gear-shaft splines can be modeled conveniently. Since contacting spline tooth surfaces are conformal, the potential contact zone covers all of the tooth surfaces, whose direct load distribution solution might require significant computational time. A new multi-step discretization solution scheme is devised and implemented in the semi-analytical models to reduce the computational time significantly such that they can be used as convenient design tools. Meanwhile, accuracy of the predictions of the proposed modelsis demonstrated through comparisons to those from a detailed deformable-body contact model. As afforded by their computational efficiency, proposed models are used to perform extensive parameter studies to quantify influences of loading conditions, misalignments, tooth modi (open full item for complete abstract)

Committee: Ahmet Kahraman (Advisor); Robert Siston (Committee Member); Soheil Soghrati (Committee Member); Sandeep Vijayakar (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2014, Industrial and Systems Engineering

Rucksack, or backpack, design has been the subject of scientific study for over fifty years, yet improvements are still being implemented in both industry and the military. In particular, the need for female-specific equipment in the US military has become more evident since the combat exclusion rule was lifted allowing women to serve in combat roles. Female soldiers use exactly the same rucksack as the men in training and in the field. Women experience greater injury rates than men in the military; load carriage is a major cause of these injuries. Although load carriage affects patterns in gait, physiological effects, and health outcomes, the differences in male and female response to the current military rucksack under dynamic, field conditions are unknown. This investigation establishes a foundation for future design research to improve the military load carriage system. The objectives of this investigation are to examine past research on the effects of rucksack use and design, concentrating on military applications, and to analyze the current military rucksack suspension system design using finite element modeling in the context of creating a better adapted design in the future for female soldiers. A review of the literature was completed exploring biomechanical, physiological, and health effects of load carriage, specifically focusing on military applications and effects on female users. In addition, an analysis of military equipment was completed to gain a full understanding of the system and the interactions between the clothing, personal protective equipment, and load carriage devices. Individual and group interviews of experienced users provided information about equipment use in the field. Furthermore, a targeted analysis using finite element modeling was completed for the purpose of investigating the interaction between frame design and load carriage effects on female anthropometry for the current US military rucksack (MOLLE IV). The result (open full item for complete abstract)

Committee: Carolyn Sommerich PhD (Advisor); Blaine Lilly PhD (Advisor); Rebecca Dupaix PhD (Committee Member); Steve Lavender PhD (Committee Member) Subjects: Industrial Engineering; Mechanical Engineering

MS, University of Cincinnati, 2007, Engineering : Civil Engineering

Bridges B-0071 and B-0171 in Hamilton County, Ohio have been in service for about fifty years. They are short span bridges with prestressed concrete girders. Until late 2001, they had conventional reinforced concrete decks, which have been replaced with fiber reinforced polymer (FRP) decks. Two girders in bridge B-0171 were replaced with new prestressed girders. These bridges are significant as there are few instances of FRP decks on concrete girders. The Hamilton County Engineers Office contracted with the Civil Engineering Department at the University of Cincinnati to perform load testing on the bridges. Information gained from this research will seek to confirm the safety of the new technology, evaluate construction and design techniques with reference to the FRP deck, and determine overall performance of the bridge to provide understanding of the system. The two short span prestressed concrete bridges with fiber reinforced polymer decks were subjected to four sets of nondestructive truckload testing. Strain gauges were placed along the height of the girder cross-section, and longitudinally and transversely across the bottom of the deck. Displacement transducers were placed to measure overall girder displacement, relative deck displacement, deck panel separation, and deck-girder connection separation. A three-dimensional finite element analysis model was created to replicate the performance of each bridge. The two new prestressed girders in bridge B-0171 strengthened the bridge considerably and increased its load carrying capacity. But the old prestressed girders in bridge B-0071 and bridge B-0171 did not show any sign of deterioration. The four sets of test data collected over a two-year period show that the age effect on structural behavior is very small for both the bridges. The deck had very little influence on the distribution of loads in the structure for these bridges. Due to low deck stiffness and incomplete connectivity, the FRP deck did little to streng (open full item for complete abstract)

Committee: Dr. Michael Baseheart (Advisor) Subjects: Engineering, Civil

PhD, University of Cincinnati, 2002, Engineering : Engineering Mechanics

The posterior cruciate ligament (PCL) is the primary restraint to posterior translation and is a secondary restraint to varus, valgus and external rotation.[12, 32, 43, 60] PCL injuries increase posterior translation and impair a person's ability to perform daily activities.[59, 67, 100] If left untreated, degenerative changes will appear earlier in the injured knee than in the contralateral knee.[17, 79, 82] A variety of surgical procedures have been used in an attempt to restore normal posterior translation. Some procedures have been unable to restore posterior translation,[48, 77, 111, 127] while others have been unable to maintain normal posterior translation[65, 85, 90]. The failure to control posterior translation has been attributed to graft elongation.[48, 81, 85] In an attempt to prevent graft elongation, two-bundle reconstructions have been investigated[65, 81, 119] and have shown promising initial results. However, the resistance to posterior translation is unknown. The purpose of this research was to investigate the ability of one and two-bundle PCL reconstructions to resist posterior translation during cyclic fatigue testing. The femoral attachment of the one-bundle graft and one bundle (AL2) of all two-bundle grafts were located within the PCL's anterolateral band, which is named for its anterior femoral insertion and its lateral tibial insertion. The second bundle was placed posterior to the AL2 bundle in one of three locations that varied in their depth within the notch: shallow (S), intermediate (I), and deep (D). The specimens were cycled from near full extension to 120 degrees of flexion with 100 N applied posterior force. The knees were cycled until the tension in both bundles was 50 N or less. The two-bundle reconstructions did not provide better resistance to posterior translation than the one-bundle reconstruction for a 2.5-mm posterior translation increase. The AL2-I reconstruction resisted the return of posterior translation for significantl (open full item for complete abstract)

Committee: Dr. Edward S. Grood (Advisor) Subjects: Engineering, Biomedical

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, 2009, Mechanical Engineering

The thesis aims to develop a procedure for the creating of geometry and analysis of straight bevel gears. The gear geometry is generated from standard AGMA equations that use Tregold's approximation to create planar involute teeth. Contact lines are based on the rolling action of the pitch cones and a finite element model is used to compute the compliance of the straight bevel gear pair. The program analyzes the gear pair for the transmission error and the load distribution and may be used to evaluate the contact stresses. The effect of the microgeometry modifications on the model is studied to optimize the contact pattern and noise excitations. The program results are compared with the results from the finite element gear analysis software, CALYX.

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

Master of Science, The Ohio State University, 1989, Civil Engineering

Committee: Alfred Bishara (Advisor) Subjects: