Master of Science, The Ohio State University, 2021, Mechanical Engineering

The design of a gearbox is subject to multiple performance requirements that must be met. One such requirement is power density, a metric defined as power transmitted per gear volume or per weight. In aerospace applications, one method of reducing gearbox weight to increase power density has been removing material from gear blanks through the use of thin webs. This study adapts a representative spur gear pair design to investigate the effects of using thin-web gears. A deformable-body model of the gear pair is developed to perform quasi-static and dynamic analyses of the gear pair variations with solid and thin webs, subjected to errors causing the load distribution to skew axially. Under quasi-static conditions, the flexible web deflections are shown to ease some of the adverse effects of gear errors. To determine the dynamic conditions where flexible rim modes could be a factor, impact tests are performed along with a modal analysis using the model. The contributions of these rim modes to the overall dynamic behavior are shown to be modest.

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

Master of Science, Miami University, 2024, Mechanical and Manufacturing Engineering

Lattice structures are celebrated for their lightweight characteristics and superior mechanical performance. In this research, a strut reinforcement technique was employed to enhance the energy absorption capacities of 3D re-entrant auxetic (Aux), hexagonal (Hex), and hybrid Auxetic-Hexagonal (AuxHex) lattice structures. The investigation involved finite element analysis to delve into the mechanical and energy absorption properties of these novel designs during quasi-static compression testing. The results from the uniaxial compression tests of the reinforced designs were then compared with those from traditional 3D hexagonal and re-entrant auxetic lattice structures. To accurately simulate the mechanical behavior of the 3D printed lattice structures, the mechanical properties of the PA2200 matrix material—manufactured via additive manufacturing—were utilized. The outcomes indicated by the stress-strain and energy absorption curves suggest that these newly proposed designs are optimal for applications requiring high energy absorption at large strains. Thus, these findings pave the way for developing novel designs in 3D hexagonal and re-entrant auxetic lattice structures, which are poised to offer enhanced mechanical strength and exceptional specific energy absorption properties. Expanding on these insights, future research could explore further variations in lattice geometry and reinforcement methods to optimize the performance of these structures under different loading conditions.

Committee: Muhammad Jahan (Advisor); Carter Hamilton (Committee Member); Jinjuan She (Committee Member); Jeff Ma (Advisor) Subjects: Biomechanics; Experiments; Materials Science; Mechanical Engineering; Mechanics

Master of Science, The Ohio State University, 2023, Biomedical Engineering

The shoulder girdle complex, through engagement with the seat belt, influences motor vehicle occupant upper body movement during frontal impacts, affecting the movement of the head, neck, and thorax. The recently developed LODC ATD was designed with flexible shoulder girdle structures that capture the unique kinematics in pediatric occupants. However, the LODC shoulder has not been evaluated for biofidelity due to the lack of biomechanical data available on pediatric shoulder responses. This study evaluated quasi-static pediatric shoulder girdle complex responses through non-invasive displacement measurements. These data were obtained to compare to the LODC ATD, to assess its biofidelity. Shoulder range of motion and anthropometric measurements were obtained from 25 pediatric volunteers, ages 8-12 years old. Loads were applied bilaterally exclusively to the shoulder complexes in increments of 25 N up to 150 N per shoulder at 90, 135, and 170 degrees of shoulder flexion. Still photos were used to determine shoulder displacement in the sagittal plane from images captured prior to and following the load applications. Data analysis consisted of motion tracking to evaluate the absolute and relative displacement of the right acromion and T1. The displacements for each volunteer were normalized based on the volunteer's shoulder width compared to the shoulder width of the LODC ATD. For the 90° load, the acromion moved relative to T1 an average of 28.1 mm forward and 3.1 mm downward at maximum displacement. For the 135° load, the acromion moved relative to T1 an average of 12.4 mm forward and 40.0 mm upward at maximum displacement. Similar displacements at higher loads indicated that the volunteers achieved their maximum range of motion. The same test procedure was completed for the LODC ATD, resulting in a biofidelity comparison in displacements using Biofidelity Ranking Score. Results from this analysis indicated that the LODC was found to have better biofidelity in the fo (open full item for complete abstract)

Committee: John Bolte IV (Committee Member); Julie Mansfield (Advisor) Subjects: Biomechanics; Biomedical Engineering; Engineering

Master of Science, The Ohio State University, 2014, Anatomy

Data are desired that accurately represent the pediatric population for anthropomorphic test devices (ATD). Current pediatric ATDs are designed from scaled-down adult data, but their biofidelity is questioned. Because the use of pediatric cadavers is an ethical issue, different methods of testing are required to obtain data. This study will ultimately aid in leading to a more appropriate pediatric model of the shoulder. The data from this study will allow for (1) a comparison between adult volunteer and post mortem human subject (PMHS) quasi-static data, (2) a comparison between PMHS quasi-static and dynamic data, and (3) a comparison between dynamic lateral and oblique loading conditions. Side impacts of the PMHS were conducted in both quasi-static and dynamic manners. The impact was delivered in both purely lateral and oblique loading conditions for each test. With the application of a light load to the impacting shoulder in quasi-static testing, translational data were acquired from sensors fixed to the acromion processes and manubrium. Force data were also acquired. In dynamic testing, the PMHS was instrumented with a triaxial accelerometer block on each acromion process, the manubrium, and T1, strain gages placed on ribs 2–5 and the clavicles, and a chest band in the axillae. A 4.5 m/s impact was delivered through a pneumonic ram to one shoulder in the lateral loading condition while the opposing shoulder was impacted next at the same speed in the oblique loading condition. For all tests, the full girdle (acromion-to-acromion) deflection was calculated to determine overall deflection. A force-displacement plot was generated and stiffness values were calculated and were compared to previous studies. Injuries resulting from dynamic testing were included to demonstrate differences between lateral and oblique impacts. To date, quasi-static stiffness in the oblique direction, X-component (KX) and Y-component (KY), is very similar to adult volunteer data (KY = 10.3 ± (open full item for complete abstract)

Committee: John Bolte (Advisor) Subjects: Anatomy and Physiology; Biomechanics; Biomedical Engineering

Master of Science, The Ohio State University, 2012, Mechanical Engineering

Face gears are cross-axis gear drives with much simpler geometries and manufacturing process in comparison to other cross-axis gearing such as spiral bevel and hypoid gears. Face gears can provide high power density solutions with high gear ratios. These advantages come with issues associated with rim and web deflections of the large face gear. In aerospace applications where weight of the gearbox is a major concern, web deflections become more challenging. This study explores the feasibility of incorporating a thrust bearing with a face gear drive to remedy rim deflection effects in a compact and light-weight manner. A baseline face gear pair is defined in this study where the face gear is supported by a conical web that is used to preload a rolling element thrust bearing axially to limit gear deflections under load. A state-of-the-art contact mechanics software package is used to analyze this baseline system to identify potential problems. A detailed parametric study covering basic bearing parameters, face gear geometry parameters, axial preload and gear tooth modifications is performed to determine conditions and design approaches that can remedy some of these problems. These results are compiled at the end into simplified guidelines for the face gear drive design.

Committee: Ahmet Kahraman (Advisor); Sandeep Vijayakar (Committee Member) Subjects: Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2011, Chemical and Biomolecular Engineering

For bulk production of high purity protein drugs to meet FDA standards, pharmaceutical industries typically process proteins by repeated precipitations and crystallizations. The solution conditions for protein phase separation are routinely determined by trial and error. A thermodynamic model of underlying weak protein-protein interactions will help in a rapid screening of solution conditions in obtaining protein crystals of desired quality and stability. The principal objective of the thesis is, therefore, to understand the fundamental molecular level interactions among different components of protein solutions: protein, water and co-solvents, in particular, the role of hydration and co-solvent preferential interactions on protein-protein interactions. Spatial heterogeneities in protein chemistry and surface topography results in uneven specific hydration of protein surface, which alters the protein-protein interactions by eliminating some complimentary configurations. The dynamics of water at such specific hydration sites was examined in terms of average water residence times and average vacancy times and found to have little impact on protein-protein interactions. The influence of local heterogeneities in surface charge and surface roughness on specific hydration and water dynamics have also been examined. A detailed investigation of the effect of surface curvature on hydration revealed that hydration of a concave surface is thermodynamically expensive than the hydration of a chemically equivalent convex surface. The concave surface is found to remain hydrated only when the interaction between the water and constituent surface atoms are attractive. Protein phase separation is typically induced by adding a precipitating agent or co-solvent, such as inorganic salts or organic compounds: alcohols, polyols, or polyethylene glycol (PEG). Addition of a cosolvent to protein solutions alter the preferential hydration of proteins depending upon its affinity to interact (open full item for complete abstract)

Committee: Michael E. Paulaitis PhD (Advisor); Aravind Asthagiri PhD (Committee Member); Dilip Asthagiri PhD (Committee Member); Sherwin J. Singer PhD (Committee Member) Subjects: Chemical Engineering