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

Lung cancer is leading cause of cancer-related deaths in the United States with 5-year survival rate of 18.6%. This is due to late detection of lung cancer and problems in screening for lung cancer. Indeterminate pulmonary nodules (IPNs) are pulmonary nodules size between 7-20mm diameter solid nodules. 90% of IPNs are incidentally found and they are hard to diagnosis due to their small size and current diagnosis methods such as CT, PET scans and biopsy involve high exposure to radiation or invasive and could lead to complications. The majority of lung cancer patients have non-small cell lung cancer (NSCLC) and 64% of these patients exhibit driver mutations such as epithelial growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK) and Ras mutations. These patients have shown to have improved survival rate if they are treated with targeted therapies directed against the driver mutations. Although these patients initially show strong response to targeted therapies, most patients develop resistance to these targeted treatments through secondary point mutation and epithelial to mesenchymal transition (EMT). The lung is a dynamic organ where alveolar epithelial cells are normally exposed to significant mechanical forces (i.e. ~8% cyclic strain, transmural pressure and shear stress) while primary lung tumor cells experience a 40-fold decrease in these mechanical forces/strain. Although biomechanical factors in the tumor microenvironment have been shown to be a significant driver of cancer progression, there is limited information about how biophysical forces alters drug sensitivity in lung adenocarcinoma cells. Based on the known importance of mechanical forces/strain on lung injury and repair and the significant difference in cyclic strain applied to normal and cancer cells in the lung, we hypothesized that cyclic mechanical strain would activate important oncogenic pathways and alter drug sensitivity. Although local mechanical properties of the lung tumor may (open full item for complete abstract)

Committee: Ghadiali Samir Dr. (Advisor); Joshua Englert Dr. (Committee Member); Arunark Kolipaka Dr. (Committee Member) Subjects: Biomedical Engineering

Master of Science in Engineering, Youngstown State University, 2023, Department of Mechanical, Industrial and Manufacturing Engineering

The field of metal additive manufacturing has experienced significant growth in recent years, and Laser Hot Wire Directed Energy Deposition (LHW-DED) has emerged as a popular technology due to its ease of use and ability to produce high-quality metal parts. In this study, we used a nonlinear transient thermo-mechanical coupled finite element model (FEM) in ANSYS APDL to conduct a detailed thermal and structural analysis of the laser hot wire DED metal additive manufacturing process. This analysis aimed to characterize the distortion caused by thermal effects and investigate the transient thermal process. In this study H13 iron chromium alloy material was deposited on an A36 low carbon steel substrate using a bidirectional laser toolpath. To record the temperature profile during printing, we employed a FLIR Infrared (IR) camera, while thermocouples mounted to the base plate measured heat transfer for validation purposes. Post-processing analysis was conducted using the CREAFORM laser 3D scan and Geomagic-X software to measure deformation from the nominal printed geometry. Overall, this study provides a significant contribution to our understanding of laser hot wire DED metal additive manufacturing, which will undoubtedly lead to further advancements in the field. This research has the potential to improve the productivity and quality of the additive manufacture of metals.

Committee: Kyosung Choo PhD (Advisor); Jae Joong Ryu PhD (Committee Member); Alexander H. Pesch PhD (Committee Member) Subjects: Aerospace Materials; Engineering; Materials Science; Mechanical Engineering

Master of Science, Miami University, 2021, Mechanical and Manufacturing Engineering

The design of structures requires an accurate characterization of their material properties. Recent fabrication technologies such as Fused Deposition Modeling (FDM) 3D printing allows for low-cost exploration of the design of structural components. The 3D printing process enables the fabrication of structures with spatially distributed multiple materials to achieve optimal performance. This research investigates the vibrational and aeroelastic response characteristics of axially graded 3D-printed structures with spatially distributed multiple viscoelastic polymeric materials. Viscoelastic polymers exhibit inherent material nonlinearities that depend on temperature, frequency, and strain rate. The vibration and aeroelastic performance of structures that are axially graded with such materials are investigated here through systematic material testing protocols and the development of a finite element model. Accuracy of the model is validated against available analytical solutions and some experimental results. It is shown how the grading patterns and distributed material properties affect the vibration (mode shape, frequency, damping, etc.) and aeroelastic performance (flutter) of such structures. Temperature and frequency-dependent properties of these materials are also shown to influence the structural performance. The model and solution strategies developed here may explore material nonlinearities and their relation to structural response such that cost-effective and safe design for next-generation structures can be developed.

Committee: Kumar Singh Dr. (Advisor); Fazeel Khan Dr. (Committee Member); Giancarlo Corti Dr. (Committee Member); Raymond Kolonay Dr. (Committee Member) Subjects: Aerospace Engineering; Aerospace Materials; Applied Mathematics; Design; Engineering; Mechanical Engineering; Mechanics; Plastics; Polymers; Solid State Physics; Technology

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

Magnetically geared machines perform gearing operations by utilizing magnetic force interactions between the rotors as opposed to mechanical force interactions. Many benefits of magnetic gears derive from the fact that there is no contact between the rotors. Contactless gearing allows for quieter operation, eliminates the need for lubrication outside the bearings, decreases the need for maintenance, and provides inherent overload protection. Another benefit is that the magnetic gear design lends itself to direct implementation in motors as opposed to having a separate mechanical gearbox. A magnetic gear has three fundamental components: a high speed rotor, a low speed rotor, and a flux modulator. These components work in tandem to generate magnetic field harmonics which scale the torque and speed of the input shaft. There are many magnetic gear designs that accomplish this task, but this thesis focuses on coaxial magnetic gears (CMGs) that utilize Halbach array magnet rotors and no back iron. In this design, the flux modulator is radially nested within the low and high speed rotors with the high speed rotor typically positioned at the inner most layer. Inherent to magnetic gear behavior is a 3D inefficiency known as end-effect loss. This loss causes flux to leak over the axial ends of the gear and back to its source. This flux never makes it to the flux modulator and never contributes to torque. End-effect losses can cause a significant decrease in output torque (10% to 40% depending on the design) and can only be modeled with large 3D simulations. The first aspect of this research involves the development of a reduced length modeling method which accounts for the axial variation of end-effect losses within the gear to shorten the computation time of magnetic gearing models. It has been shown for the models in this thesis that computation time can be cut in half while the torque results stay within 5% of their true value. Several magnetic gear design variable (open full item for complete abstract)

Committee: Marcelo Dapino (Advisor); Rebecca Dupaix (Committee Member) Subjects: Mechanical Engineering

Master of Science (M.S.), University of Dayton, 2017, Mechanical Engineering

In this work, a model framework for the simulation of Fused Deposition Modeling (FDM) of thermoplastic and thermosetting polymers and Polymer Matrix Composites (PMCs) was developed. A Python script was constructed to automatically generate a 3D finite element heat transfer and stress model of individual roads within a 3D printed part. The script creates the road activation sequence based on the print path specified in the part G-code and associated boundary conditions which are continuously updated throughout the analysis with minimal input from the user. Thermosetting polymers and polymer matrix composites (PMCs) are modeled by implementing a material sub-model from Convergent Manufacturing Technologies called COMPRO that captures the curing kinetics of the material during the printing and post-cure cycle. The modeling approach is formulated for both material systems through tailorable conditions such as build plate temperature, ambient conditions, print temperature, etc. To the author's knowledge, no 3D finite element model of the FDM process exists for the thermal history and residual stress prediction of thermosetting polymers and PMCs. Although the objective of this work is to create a model for the prediction of thermosetting polymers and PMCs, the characterization and subsequent printing of these materials is still in the development stages. Therefore, in order to validate that the proposed model is capturing the correct physics for the FDM process, model predictions for Acrylonitrile Butadiene Styrene (ABS) coupons were compared with experimentally printed specimens. A series of sensitivity studies were then performed for this model to investigate significant effects as well as trends in the predictions from assumptions in the boundary conditions. The model is then extended to thermosetting PMCs to demonstrate the linkage between COMPRO and the modeling framework.

Committee: Robert Brockman PhD (Committee Chair); Brent Volk PhD (Committee Member); Thomas Whitney PhD (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2017, Engineering and Applied Science: Civil Engineering

Computer modeling has become the conventional method of analyzing and designing structures of all complexities. A number of modeling software packages are currently in use for this purpose. Software with various specific abilities are available to engineers. While engineers have multiple options to consider for modeling, there are no guidelines to allow engineers and owners to agree upon extent of detailing needed during modelling. This study evaluates various benchmark problems at different Degrees of Detail and Level of Analysis to provide a basis for research and eventual development of guidelines for high-resolution modeling of steel structures. Observations from analysis of six benchmark problems provide information to define terms that necessary to develop the guidelines in the future. Four of the six examples are used to define Degree of Detail and the remaining two examples to define Level of Analysis (Definitions of Degree of Detail are discussed in detail and the concept of Level of Analysis is introduced in this document) Initial benchmark example problems mentioned above were analyzed using SAP2000 using various details such as frames, shells etc. Evaluation of further examples was using various known methods of static nonlinear analysis as recommended by AISC 360. To corroborate terms defined in the document, inferences from the results of the benchmark examples. While every problem could be evaluated using extreme detailing of models and complex analysis methods, the Degree of Detail and the Level of Analysis must be restricted based on necessity.

Committee: James Swanson Ph.D. (Committee Chair); Thomas M. Burns Ph.D. (Committee Member); Gian Rassati Ph.D. (Committee Member) Subjects: Civil Engineering

Master of Science, The Ohio State University, 2017, Civil Engineering

Probability risk assessment (PRA) of nuclear power plants (NPP) has been used since the mid-1970s to evaluate the associated risks or perform a risk-informed design of NPPs. Since its inception, PRA has considered both internal and external events to evaluate the risks to a NPP site. However, external event PRA has historically been recognized as having considerable safety margin until recent events have emphasized the need for a reevaluation. This research is part of a larger project with the goal of incorporating internal and external event PRA in a common platform using state-of-the-art methods. Specifically, the focus of the research in this thesis was to develop and evaluate structural models with different levels of complexity for several structures that are vital for seismic probabilistic risk assessment (SPRA) of NPPs. For SPRA, critical structures, systems, and components (SSCs) are investigated to evaluate their risk during seismic events. To evaluate the risk of critical SSCs, structural models are needed to predict their dynamic behavior. However, due to the large number of analyses required during SPRA, simple yet sufficient models are desired to increase the computational efficiency and reduce the run-time of models. As such, the focus of this research was to develop simple yet sufficiently accurate structural models for SSCs and to evaluate the uncertainty related to those models. Three critical NPP structures are investigated in this research to illustrate the capabilities and limitations of models with varying levels of complexity. The structures included a condensate storage tank (CST), auxiliary building, and containment structure. Realistic geometric and material properties for each structure are introduced, and both detailed three-dimensional (3D) and simplified two-dimensional (2D) models are created. Detailed 3D finite element (FE) models incorporated complex mechanical behavior such as fluid- iii structure interaction and slab flexibility (open full item for complete abstract)

Committee: Halil Sezen (Advisor); Abdollah Shafieezadeh (Committee Member); Jieun Hur (Committee Member) Subjects: Civil Engineering

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

Researchers have long studied the mechanical response of skin and underlying tissue. In particular, understanding the mechanical response of finger pads has been an area of interest due to the number and variety of interactions finger pads undergo every day. However, modern testing systems are expensive, non-portable, and pose a safety risk to the test subject when performing in vivo tests since they are machine-driven. This research explores a portable, subject-driven push-button fixture as a means of measuring the mechanical response of in vivo finger pad tissue. Simulation techniques will be utilized to determine if such a device is viable and what the requirements of this device are in order to attain data accurate enough to determine material parameters. This research has three major stages. In the first stage, a urethane material that mimics human finger pad tissue hardness is chosen as a surrogate to human tissue (hereinafter referred to as mimic material). Durometer testing is performed on male and female subjects with a wide age range in order to determine the target hardness of the urethane mimic material. Preliminary simulations are made on a simplified finger geometry and compared to the theoretical solution in order to determine the optimal general boundary conditions. In the second stage, the mimic material undergoes traditional material testing to determine a nonlinear constitutive material model. Circular compression samples are then tested using the proprietary push-button fixture to determine output force and displacement. A finite element (FE) model of the fixture that utilizes the determined material model is then used to establish the specific boundary conditions of the fixture, first in an axisymmetric configuration followed by a full 3D model. In the third stage, a mold of a female index finger is taken and used to cast a mimic material finger. The finger is scanned and its geometry is used in the 3D fixture FE mode (open full item for complete abstract)

Committee: Kumar Vemaganti Ph.D. (Committee Chair); Gary Gross M.S (Committee Member); Yijun Liu Ph.D. (Committee Member); Ala Tabiei Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Science (MS), Ohio University, 2014, Civil Engineering (Engineering and Technology)

Adjacent box beam bridges have been widely used in the United States for decades due to the ease and speed of construction. Despite the current design requirements, this type of bridge often experiences longitudinal cracking along joints. This is often the result of a deficient load transfer mechanism between beams. In addition, reflective cracking can occur in asphalt overlays or a cast-in-place concrete deck. This can cause chemical agents to leak between the beams, causing corrosion in the reinforcement, which affects the lifetime of the structure. A parametric study on the load transfer mechanism between adjacent prestressed concrete box-beams was developed using ABAQUS. Several finite element models consisting of two adjacent beams connected through a shear key and transverse ties were created for the analysis. The effects of filled and non-filled transverse post-tensioning ducts were included in the models. This was to show the contribution of the dowel action in the load transfer mechanism of adjacent prestressed concrete box-beams. In addition, effects of temperature gradients were considered with the aim of simulating a behavior resembling the reality of bridges in the field. Additional parameters, including grout compressive strength-to-concrete compressive strength ratio, amount of transverse post-tensioning (TPT), span-to-depth ratio (L/D), and number of internal diaphragms (N), were included in the models. This study was divided into two main parts. The first part consisted of analyzing the behavior of a pair of beams with fixed length and number of internal diaphragms, while increasing the amount of TPT force. The second part consisted of analyzing the behavior of a pair of beams with zero transverse post-tensioning, while varying beam span length and number of internal diaphragms. The significance of the results from all finite element models was statistically analyzed using Analysis of Variance (ANOVA). Results indicated that differential def (open full item for complete abstract)

Committee: Eric Steinberg (Advisor) Subjects: Engineering

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

Magnetostrictive materials deform in response to applied magnetic fields and change their magnetic state when stressed. Because these processes are due to moment realignments, magnetostrictive materials are ideally suited for sensing and actuation mechanisms with a bandwidth of a few kHz. Significant research effort has been focused on two magnetostrictive alloys: Terfenol-D (an alloy of terbium, iron and dysprosium) and Galfenol (an iron gallium alloy), for their ability to produce giant magnetostrictive strains at moderate fields. Terfenol-D has higher energy density and magnetomechanical coupling factor than Galfenol but it is brittle and suffers from poor machinability. Galfenol on the other hand has excellent structural properties. It can be machined, welded, extruded into complex shapes for use in transducers with 3D functionality. Advanced modeling tools are necessary for analyzing magnetostrictive transducers because these materials exhibit nonlinear coupling between the magnetic and mechanical domains. Also, system level electromagnetic coupling is present through Maxwell's equations. This work addresses the development of a unified modeling framework to serve as a design tool for 3D, dynamic magnetostrictive transducers. Maxwell's equations for electromagnetics and Navier's equations for mechanical systems are formulated in weak form and coupled using a generic constitutive law. The overall system is approximated hierarchically; first, piecewise linearization is used to describe quasistatic responses and perform magnetic bias calculations. A linear dynamic solution with piezomagnetic coefficients computed at the bias point describes the system dynamics for moderate inputs. Dynamic responses at large inputs are obtained through an implicit time integration algorithm. The framework simultaneously describes the effect of magneto-structural dynamics, flux leakages, eddy currents, and transducer geometry. Being a fully coupled formulation, it yields system lev (open full item for complete abstract)

Committee: Marcelo Dapino PhD (Advisor); Ahet Kahraman PhD (Committee Member); Junmin Wang PhD (Committee Member); Rajendra Singh PhD (Committee Member) Subjects: Electromagnetics; Electromagnetism; Mechanical Engineering; Mechanics

Doctor of Philosophy, The Ohio State University, 2009, Mechanical Engineering

Ductile fracture in heterogeneous materials is strongly dependant on size, shape and distribution of heterogeneities in microstructure. Modeling mechanical response of such materials with explicit representation of microstructure morphology is computationally expensive and hence constrains the size of model. But analysis of a small microstructural model is not sufficient for prediction of fracture in a heterogeneous material. This demands the necessity of multi-scale analysis that can capture the material response over a large microstructural domain with explicit micro-mechanical analysis only in regions of dominant fracture. Addressing various pre-requisites to multi-scale modeling, a three step Morphology based Domain Partitioning (MDP) is introduced. The first step in MDP is generating high resolution microstructure images of the entire computational domain. Subsequently, morphology based metrics are identified to relate microstructural features to mechanical response of material. In the third step, entire computational domain is partitioned to identify statistically homogeneous and inhomogeneous regions. This delineation forms the basis for macroscopic and microscopic length scales respectively, for a coupled multi-scale analysis. The multiscale finite element model for ductile fracture developed in this work performs coupled analysis of macroscopic (level-0), and microscopic (level-2) length scales along with an intermediate swing region (level-1). The constitutive relations for macroscopic length scale are obtained by homogenization of microscopic representative volume element. Microscopic regions are analyzed with explicit representation of microstructure, using locally enhanced Voronoi Cell Finite Element Model (VCFEM) for ductile fracture. During the analysis, a macroscopic level-0 element adaptively evolves into level-1 and level-2, based on accumulation of damage. Macroscopic discretization error is minimized with h-adaptivity and modeling error is minimi (open full item for complete abstract)

Committee: Somnath Ghosh Professor (Advisor); June K Lee Professor (Committee Member); Stephen Bechtel Professor (Committee Member); Carol Smidts Professor (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2011, Mechanical Engineering

As the use of composite materials in aerospace structures continues to increase, the need to properly characterize these materials, especially in terms of damage tolerance, takes on additional importance. The world wide failure exercises (WWFE) are an example of the international interest in this issue. But though there has been a great deal of progress in understanding the initiation of damage and modeling damage propagation along known interfaces, methods that can capture the effects of interactions among various failure modes accurately remain elusive. A method of modeling coupled matrix cracks and delamination in laminated composite materials based on the finite element method has been developed and experimentally validated. Damage initiation is determined using the LARC03 failure criterion. Delamination along ply interfaces is modeled using cohesive zones. Matrix cracks are incorporated into the discretization of the problem domain through a robust Mesh-Independent Cracking (MIC) technique. The matrix cracking technique, termed the Regularized Extended Finite Element Method (Rx-FEM), uses regularized forms of the Heaviside and Dirac Delta generalized functions to transform the crack surface into a volumetric crack zone. The Regularized Extended Finite Element method is compared to benchmark cases. The sensitivity of the solution to mesh size and parameters within the cohesive zone model is studied. Finally, the full method with delamination is employed to study a set of experimental tests performed on open-hole quasi-isotropic laminates. The trends of hole-size and ply thickness are well predicted for the laminates. Rx-FEM is also able to simulate the pattern of damage, as demonstrated by comparisons to x-ray images. From the results of this series of analyses it can be concluded that failures occur when delamination originating at the hole links up with delamination originating at the edge along the path of matrix cracks.

Committee: Robert A. Brockman PhD (Committee Chair); Steven L. Donaldson PhD (Committee Member); Endel V. Iarve PhD (Committee Member); James M. Whitney PhD (Committee Member) Subjects: Mechanical Engineering; Mechanics

Doctor of Philosophy, Case Western Reserve University, 2011, Biomedical Engineering

Despite the use of exercise countermeasures, bone mineral density (BMD) and bone strength changes which have been shown to occur at a rate of ~ ‐1 to ‐3% per month are a potentially serious medical scenario that may lead to increased fracture risk. These decrements in bone are likely due to the decrease in mechanical loading experienced by the musculoskeletal system while living on‐orbit. The primary objective of this dissertation is to shed light on the effects of altered gravity environments on the mechanobiology of bone. This objective is explored through surrogate measures using the bedrest model of bone loss, direct measures onboard the International Space Station (ISS) and theoretical calculations using Finite Element (FE) and musculoskeletal modeling techniques. Through the enhancement of previous algorithms relating daily mechanical loading to bone homeostasis, we have developed the Enhanced Daily Load stimulus (EDLS) as a method of prescribing exercise in a “dose” based manner during bedrest. We were able, on average, to prevent bone loss in exercise subjects. To expand the 17 examination of the efficacy of exercise countermeasures beyond the limitations of BMD measures, we developed subject specific, voxel‐ and Computed Tomography (CT)‐based Finite Element (FE) models of the proximal femur. With these models, we were able to account for the 3D geometry of the bone and calculated bone strength and show that, on average, exercise subjects had lower decrements in bone strength than control subjects. The FE models used to examine strength changes during space flight use boundary conditions that are in the context of Earth gravity (1g), thus these models are likely not relevant when examining fracture risk in crewmembers living on other planets or in reduced gravity. Therefore, we combined FE and musculoskeletal modeling to develop a preliminary modeling framework that would allow the examination of tissue level stresses that may occur in the femur during a mor (open full item for complete abstract)

Committee: Peter Cavanagh PhD DSc (Advisor); Patrick Crago PhD (Advisor); Christopher Hernandez PhD (Committee Member); Robert Kirsch PhD (Committee Member); Antonie vna den Bogert PhD (Committee Member) Subjects: Biomechanics; Biomedical Engineering; Kinesiology

Master of Science in Engineering, University of Akron, 2010, Biomedical Engineering

Space travel has placed humans in an interesting physiological situation that makes it necessary to secure the health of the astronauts. In space, due to the lack of gravity, there is a fluid shift toward the upper body that results in a decrease in plasma volume. As a result, there is a significant drop in red blood cell mass over the flight period, which could result in space flight anemia. To monitor this change, ultrasound must be used, since it is the most trusted and only flight surgeon approved imaging/detecting modality for space flight. Continued research into the use of ultrasound for monitoring hematocrit levels can improve the lives of humans both in space and on Earth. A physical means to examine the viability of a cross-correlation detection method for ultrasound (originally demonstrated for optical light scattering) that minimizes multiple scattering effects [23] was demonstrated by conducting a Young's two-pinhole experiment. This was implemented using a pinhole mask on the receiving transducer to affect cross-correlation. The resulting interference pattern should have a period predicted by the pinhole size, spacing, and frequency of the ultrasound signal. Interference patterns were produced for a series of masks with different pinhole sizes and pinhole separations. The fringe patterns were analyzed, with the measured period compared to the predicted period, and the 300/700(pinhole diameter/separation) mask was determined as the most optimal. A two-dimensional computer model was developed using the Comsol Multiphysics software package (Comsol AB.). The model was created to analyze the physical cross correlation method and help explain the experimental results, accounting for some of the effects not captured by the analytical model. The simulations showed that the masks with smaller pinholes (~100μm) had periods that were not consistent with the analytic predictions, indicating the presence of effects that were not properly modeled analytically. One o (open full item for complete abstract)

Committee: Bruce Taylor Dr. (Advisor); Stanley Rittgers Dr. (Committee Member); Dale Mugler Dr. (Committee Member) Subjects: Biomedical Research

Master of Science, University of Akron, 2025, Mechanical Engineering

This study investigates the effect of cohesive properties on the impact behavior of hybrid sandwich composites through finite element analysis (FEA) validated with experimental data. Two hybrid configurations, GC (GFRP outer layers) and CG (CFRP outer layers), were analyzed under varying cohesive strength, stiffness, and fracture energy, using Hashin and Strain-Based (SB) failure criteria. The results demonstrate that SB provides better agreement with experiments, particularly in capturing progressive failure and post-impact deformation, while Hashin overpredicts peak force and delays failure initiation. The findings reveal that cohesive strength primarily governs peak force and permanent deformation, while fracture energy significantly influences energy dissipation. Additionally, stacking sequence plays a crucial role, with CFRP-dominant configurations (CG) absorbing more energy, whereas alternating hybrid layups (GCGC, CGCG) improve load distribution and reduce residual damage. These insights provide guidelines for optimizing cohesive properties and stacking sequences to enhance the impact resistance of hybrid composites for aerospace, naval, and industrial applications.

Committee: Dr. Kwek Tze Tan (Advisor); Dr. Hyeonu Heo (Committee Member); Dr. Tanmay Tiwari (Committee Member) Subjects: Materials Science; Mechanical Engineering

Doctor of Philosophy, Case Western Reserve University, 2025, EMC - Mechanical Engineering

Soft robots and other devices benefit from a wide range of material properties increasingly available from modern polymers. Sometimes, the passive adaptivity of the soft material mitigates the need for precise design and control. In other cases, modeling deformations precisely enables designs to fully exploit and optimize the material properties with minimal physical iteration. For example, while many soft robots have replicated adaptable locomotion of worms and other soft animals, in applications with additional constraints such as the use of novel soft actuation and in confined underground burrows, I show that modeling provides valuable design insights. This work begins by demonstrating and comparing prominent viscoelastic models applied to a simple polymeric system, an elastic/viscoelastic bilayer, where it is shown that a Generalized Maxwell model, composed of a superposition of multiple relaxation time constants, best captures the dynamic response of the bilayers. Building on these insights, material-based models are used to guide the design, analysis, and performance predictions of a polymer-bilayer-based compliant worm-like robot. The resulting robot included much less metal than previous robots and is capable of directional locomotion on various surfaces and squeezing itself through constrictions that are 45% smaller than its height in the resting state. Next, I present simulation and analysis of several worm-like actuator systems with compliant components for future use in a practical application, specifically the installation of underground electrical conduits for power and telecommunications industries. Each system was preliminary evaluated for its geotechnical capabilities, focusing on their abilities to radially expand into soil while supporting the forces necessary for advancement of a drilling head. Although each actuator system has its merits, a fluidic powered peristaltic actuator is shown to require the least amount of total unactuated length, ≈100 (open full item for complete abstract)

Committee: Gary Wnek (Committee Member); Kathryn Daltorio (Advisor); Ozan Akkus (Committee Member); Roger Quinn (Committee Member) Subjects: Materials Science; Mechanical Engineering; Robotics

Doctor of Philosophy, The Ohio State University, 2024, Mechanical Engineering

The mechanical properties of materials are fundamentally governed by their microstructural characteristics, delineating a profound relationship between structure and behavior. Whether manifesting as polycrystalline arrangements composed of grains, particulate dispersion within composites, or the intricacies of Selective Laser Melting (SLM)-induced melt pools, microstructural heterogeneity profoundly influences material response to external loads. Moreover, the presence of defects such as voids, precipitates, and cracks introduces additional complexities, underscoring the critical role of microstructural analysis in elucidating material performance. As such, comprehending and manipulating these microstructural features hold paramount importance in the design and optimization of materials tailored to specific engineering requirements. This introductory exploration sets the stage for a comprehensive investigation into the interplay between microstructure and mechanical behavior in diverse material systems. The first component of this dissertation focuses on modeling Polycrystalline materials from imaging data. As mentioned earlier, polycrystalline microstructures are composed of grains and hence, it is important to accurately capture the grain boundaries when modeling them from microstructure images. Moreover, it is also possible for defects to be present in microstructures such as precipitates, voids, and cracks, which can impact mechanical behavior. Therefore, we also present an example modeling the presence of precipitates in a polycrystalline microstructure, which shows that the developed framework can handle them. To do this, we introduce a set of integrated image processing algorithms for processing low-resolution images of a polycrystalline microstructure and convert the grain boundaries into a Non-Uniform Rational B-Splines (NURBS) representation. Next, the NURBS representation of the material microstructures is used as an input to a non-iterative mesh (open full item for complete abstract)

Committee: Soheil Soghrati (Advisor); David Talbot (Committee Member); Rebecca Dupaix (Committee Member) Subjects: Artificial Intelligence; Computer Science; Materials Science; Mechanical Engineering

Doctor of Philosophy (PhD), Wright State University, 2024, Engineering PhD

Implantable leads used in pacemakers, defibrillators, and cardiac resynchronization therapy are designed for in-vivo applications, yet their longevity is inevitably shaped by the conditions within the human body. The mechanical behavior of these leads can be affected over time, necessitating the evaluation of their residual properties. Two main insulators, silicone, and polyurethane are commonly used for the outer insulation of cardiac leads. Understanding the long-term performance of these insulators is crucial for ensuring the reliability and safety of cardiac implantable devices. The research aims to assess the long-term mechanical properties and performance of implantable leads utilized in cardiovascular implantable electronic devices (CIEDs), which are subjected to the in-vivo environment with finite lifespans. Utilizing more than 300 samples obtained from the Wright State University Anatomical Gift Program. Tests were conducted according to ASTM standard D 1708-02a and ASTM Standard D 412-06a using the Test Resources Q series system. Electromagnetic interference (EMI) from electric vehicles on CIEDs, particularly Subcutaneous Implantable Cardioverter-Defibrillators (S-ICDs) were quantified within a Tesla Model 3. SolidWorks and MIMICS 25.0 were used for three-dimensional heart modeling, and were developed with CIED leads inside the heart for finite element analysis. ANSYS Workbench 2022R1 was utilized for simulating cardiac leads behavior inside the heart with specific residual properties, and used computational simulations to predict lead performance. This research found silicone insulation to show some degradation in mechanical properties after 94 months of in-vivo environment, and polyurethane insulation demonstrated consistent performance without significant degradation after 108 months of in-vivo exposure. The proposed mechanical testing and FEM provide an insight into the durability and performance of different insulation materials, and how these materia (open full item for complete abstract)

Committee: Tarun Goswami D.Sc. (Advisor); Abdul Wase MBBS (Committee Member); Vic Middleton Ph.D. (Committee Member); Jaime E. Ramirez-Vick Ph.D. (Committee Member) Subjects: Biomedical Engineering

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Mechanical Engineering

The knee meniscus is an integral part of the human knee. It performs the function of joint shock absorption and stabilization. It is physiologically complex and designed in a manner to be able to perform such important functions. However, the meniscus tear is a common injury observed in elderly people and people who perform intense physical activity. The meniscus has limited self-repair capabilities. Thus surgery is an eventual option for serious conditions. These surgical procedures may lead to complications and risks such as infection, nerve damage, persistent pain, etc. Given the complex function performed by the meniscus, it shows a complex material behavior at low strain rates. It exhibits basically hyperelastic material behavior of low strain rates and visohyperelasticity and damage of high strain rates. Thus, understanding the viscohyperelastic material properties of the meniscus is a basic step toward preventing meniscus damage. There is a need for models that can not only accurately capture the mechanical behavior of the meniscus but also be able to predict the damage and fracture behavior. In this study, a combination of experimental and computational methods are applied to characterize the mechanical behavior of knee meniscus and to establish mechanical damage criteria. To this end, the following are the specific aims of this study: -Specific aim 1: Design experiments and develop a finite element model to quantify the variation in mechanical properties of the meniscus under quasi-static deformation. -Specific aim 2: Develop novel constitutive models for high-strain rate behavior of the meniscus. These models describe the mechanical response under intensive sports and unexpected accidents. -Specific aim 3: Conduct experiments to model damage and fracture behavior of the meniscus. This would help in establishing damage criteria for the meniscus and help prevent potential meniscus injuries. Results from specific aim 1 d (open full item for complete abstract)

Committee: Chia-Ying Lin Ph.D. (Committee Chair); Yongfeng Xu Ph.D. (Committee Member); Woo Kyun Kim Ph.D. (Committee Member); Kumar Vemaganti Ph.D. (Committee Chair) Subjects: Mechanical Engineering

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Mechanical Engineering

A human's interaction with the outside world begins with the human skin and therefore, contact mechanics of human skin is an important area of research. The applications are all-encompassing, from medical technology in the form of drug delivery mechanisms and prosthetics to the digital world in the form of touchscreens or even personal care. The variations in morphological and physiological features in combination with the properties of counter surfaces make human skin contact a complex problem. There are several aspects of this complex tribological system that need to be addressed. These include characterizing the surface topography of human skin, enhancing the predictability of contact parameters, and understanding the mechanics at the interface of such interactions. In this study, as the first specific aim, a method is developed to characterize the directionality of skin tension lines using statistical methods of characterizing rough surfaces. The method is able to capture the increasing anisotropy of human skin with aging. The method can be applied to the surface coordinates of the skin and the pixel intensity data from skin images. The second specific aim is to predict the coefficient of friction considering the changes in the skin's morphological and physiological features. To achieve this, a fractal-based finite element model in combination with an interfacial condition-enhanced empirical method is used. Results show that the proposed approach can replicate several experimental findings from the literature. Human skin in general is a soft material. Therefore, the recent understanding of contact mechanics of soft materials is applicable to skin. The third specific aim is to understand the contact mechanics at the interface of skin interactions. To this end, we use finite element models to first extend the current single asperity studies to three-dimensional soft materials. Specifically, we investigate the role of surface roughness and mate (open full item for complete abstract)

Committee: Kumar Vemaganti Ph.D. (Committee Chair); Bhargava Sista Ph.D. (Committee Member); Manish Kumar Ph.D. (Committee Member); Woo Kyun Kim Ph.D. (Committee Member) Subjects: Mechanical Engineering