Master of Science, The Ohio State University, 2020, Aero/Astro Engineering

This research investigates the strategic design of elastomeric metamaterials to induce controllable mechanical properties and sensing capabilities. Elastomers have been utilized in the creation of flexible electronics due to the inherent ability to nondestructively deform. When a malleable, conductive material, such as liquid metal, is incorporated into an elastomeric host structure, a flexible electronic material is created that may maintain electrical conductivity during high strain loading. While research has uncovered ways of utilizing deformation of flexible electronics to achieve functionality such as resistance change and self-healing, there are few studies that explore mechanical and electrical properties of such systems when subjected to compression. The material responses may be made more versatile by exploiting principles of elastic metamaterials. Such metamaterials contain void architectures that create elastic truss networks capable of reversible buckling, and have shown ability to provide impact and vibration attenuation capabilities. Methods of controlling the mechanical properties of these metamaterials, such as functionally grading layers of beams, or incorporating magnetic microparticles into the elastomer matrix to modify the stiffness in real-time with an externally applied magnetic field, have been explored. Yet, research is lacking on the interplay of design parameters and magnetic field that result in mechanical behaviors. Motivated by these needs, this research explores foundations of new generations of smart metamaterials by establishing methods for sensing and control of material behavior. A new approach to liquid metal-based sensing in elastomeric materials is built up, leveraging mechanical deformation to induce a digital logic sensing modality. Then, the interplay of mechanical design and magnetoelasticity is explored for metamaterials with properties governed by ferromagnetic particle filler and the presence of magnetic field. The findi (open full item for complete abstract)

Committee: Ryan Harne Dr. (Advisor); Marcelo Dapino Dr. (Advisor) Subjects: Electromagnetism; Engineering; Materials Science; Mechanical Engineering; Mechanics; Polymers

Doctor of Philosophy, University of Akron, 2015, Mechanical Engineering

This research comprised of a multi-stage effort to create a hydrodynamic journal bearing design that had capability to be actively controlled through the use of magnetorheological fluids. An arrangement of electromagnets was designed and a modified Reynolds equation was derived to evaluate the performance of the bearing design; where the fluid was modeled as a Bingham plastic, whose yield strength is proportional to the strength of the applied magnetic field. Bench tests were then utilized to provide a proof of performance for the bearing design and to quantify the rheological properties of the magnetorheological fluids created for the study. The evaluation of the performance of the bearing design consisted of 15 steady state conditions with operational parameters of speed and applied magnetic field as the key variables; while the bearing performance was analyzed by measuring eccentricity, torque and fluid pressure. The results of the experimental testing indicated that, a decrease of 15% in the eccentricity ratio was achievable relative to the baseline eccentricity ratio for all speeds. Given that the applied load remained constant, a decrease in eccentricity correlates to an increase in load capacity when a magnetic field is applied. The analysis also showed that an increase of up to 4.5% in the bearing torque, which represents reduction in operating efficiency when a magnetic field is applied. These results validated both the advantages and disadvantages of this bearing design. This proves the bearing design gives the ability to control the bearing performance with the expected consequence of increased heat generation and power consumption from the electromagnets as well as the bearing torque.

Committee: Minel Braun Ph.D. (Advisor) Subjects: Aerospace Engineering; Mechanical Engineering

Master of Science in Engineering, University of Toledo, 2010, Mechanical Engineering

Hybrid vehicles have been developed to increase the fuel economy of existing vehicles. Examples include hydraulic and electric hybrid vehicles. A common issue in hybrid vehicles is the additional vibration and vibration-caused noise. This vibration is primarily caused by the switching of power modes, i.e. from the conventional gasoline engine to the electric or hydraulic motor. In certain cases, this vibration, due to the wide frequency range characteristics, cannot effectively be isolated through the use of conventional isolation technologies. In this thesis, a mixed mode magnetorheological mount has been investigated to mitigate this and similar wide-frequency vibration. In order to effectively isolate vibration, a mount should be designed for a specific application. Different engines however are required for each application; a designer therefore must alter the engine mount with the desired stiffness and damping characteristics. In this work a parametric analysis has been performed on one of the main components of the mount, the elastomeric top. The analysis and comparison to the experimental results are discussed in detail. Three different parameters were the focus of this investigation. The rubber thickness (by two means) and height were studied. It was found that varying the mount diameter (thickness) is the most influential parameter that was investigated. The initial analyses to validate the finite element model showed at most a ~5% difference. The results of this study will be instrumental for designing and optimizing different mounts including magnetorheological and hydraulic mounts.

Committee: Mohammad Elahinia PhD (Advisor); Mehdi Pourazady PhD (Committee Member); Sorin Cioc PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy in Engineering, University of Toledo, 2009, Mechanical Engineering

In recent years, the higher price of fossil fuels and green house effects has been the motivating factors for the automotive industry to introduce more efficient vehicles. Today evolution in automobiles is mostly to reduce fuel consumption and emissions. Variable cylinder management has been employed in V6 & V8 engines to allow the vehicles to operate with only 3 or 4 active cylinders. Hybrid technologies including hybrid electric and emerging hydraulic hybrid equip the vehicles with additional power sources which work at higher efficiency than that of internal combustion engines. The proven advantages of the hybrid vehicles or variable cylinder management also come with challenging problem of noise, vibration and harshness (NVH). This issue has to be properly addressed in order for the technologies to find consumer acceptance. The NVH in modern vehicles is mainly due to the involvement of multiple power sources working in different modes and the switching among them. This feature can lead to shock and vibration over a wide range of frequencies. It has been proven that passive vibration isolators, e.g. elastomeric and hydraulic, are not sufficient to deal with this problem. Active mounts are effective, but they are expensive and can lead to stability problems. Research has shown that semi-active vibration isolators are as effective as active mounts while being significantly less expensive In this study, a novel shock and vibration isolator in the form of a magnetorheological (MR) mount is introduced. MR fluids are smart fluids which respond to magnetic fields. Using these fluids it is possible to transform a passive hydraulic vibration isolator to a semi-active device one. The semi-active MR mount presented in this dissertation is unique because it utilizes the MR fluid in two configurations flow (or valve) and squeeze modes to mitigate shock and vibration over a wide range of frequencies. The new mount was designed following a thorough literature review of the s (open full item for complete abstract)

Committee: Mohammad Elahinia PhD (Advisor); Walter Olson PhD (Committee Member); Nagi Naganathan PhD (Committee Member); Maria Coleman PhD (Committee Member); Abdollah Afjeh PhD (Committee Member) Subjects: Automotive Materials; Engineering; Experiments; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2012, Industrial and Systems Engineering

Vibration control is a critical function of the bar feeders which are used to automatically feed stock to high-volume computer-numeric-controlled turning operations. Current technology employs continuous rigid support along the length of the bar; however, the need to quickly load fresh bar stock and change between stock sizes makes the physical implementation cumbersome, which in turn introduces process challenges. Specifically, each different stock diameter requires a specially matched guide channel, introducing a significant amount of changeover time between jobs as well as a significant capital investment. This research investigates how the rheology of a single discrete support might be tuned to affect the dynamics of the bar, providing comparable vibration control without these disadvantages. The bar stock is modeled as a Bernoulli-Euler beam, and a method of predicting the natural frequencies with a general viscoelastic support is developed. Magnetorheological fluids in direct contact with the bar are evaluated as an alternative for implanting the variable-rheology support. Theoretical and experimental results are presented, and a control algorithm is proposed. Finally, the viscoelastically supported beam model is used to explore how various support configurations, without regard to their physical manifestation, may be located and tuned to avoid resonant vibration in beams.

Committee: Dr. Jerald Brevick PhD (Advisor); Dr. Jose Castro PhD (Committee Member); Dr. C. H. Menq PhD (Committee Member); Dr. Kevin Hubbard PhD (Committee Member) Subjects: Industrial Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2010, Mechanical Engineering

Carbon-based nanoparticles have the potential to significantly enhance mechanical, electrical and thermal properties of polymer materials through a controlled process-induced anisotropy and inhomogeneity at the nanometer scale to optimize material properties. In order to model the processing of carbon nanofiber composites adequately it is essential to have an accurate measure of the distribution of fiber orientation within the material. A new technique based on transmission electron microscopy (TEM) image analysis is proposed that provides a complete 3D description of the material structure. This method is bench-marked with numerically generated samples. A model based on the Folgar-Tucker equation is developed to predict the rheological behavior of the carbon nanofiber/polystyrene composite. The nanocomposite stress response is derived from the combined effects of the pure polymer stress and the stress resulting from the nanofiber interactions. Model predictions of the nanofiber orientation evolution due to the flow field are compared to the experimental measurements. Magnetorheological (MR) fluids are smart materials with rheological properties, such as viscosity and yield stress that can be altered by an external magnetic field. These changes are significant, relatively fast and nearly completely reversible, which are suitable for a wide range of applications. MR fluids typically consist of micron-sized magnetizable solid particles suspended in a non-conducting carrier fluid such as mineral or silicone oil. The Brownian dynamics theory has been adapted to describe the behavior of the magnetorheological fluids subjected to external magnetic fields. The model proposed intends to be helpful in developing a fundamental understanding of the relation between the macromolecular motions and the rheological characteristics of MR fluids.

Committee: Stephen Bechtel Prof (Advisor); Kurt Koelling Prof (Committee Member); Gregory Washington Prof (Committee Member); John Yu Prof (Committee Member) Subjects: Mechanical Engineering

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

In recent years there has been increased interest in the broad areas of micro- and nano-technology due to the potential to create materials with unique properties which were previously unattainable. One area of special interest has been the use of nanoparticles such as nanoclays, nanofibers and carbon nanotubes and microscale carbonyl iron particles. Nanoclays and nanofibers have received attention due to their ability to be incorporated into polymer matrices and impart functionality such as electrical conductivity, increased tensile strength and modulus, and a reduction of gas and moisture permeability at much lower particle loadings when compared to traditional fillers such as carbon black and glass fibers. The addition of these nanoparticles also has a significant effect on the rheological properties of the composite. The rheological behavior of polystyrene/nanoclay composites under steady state shear flow and polystyrene/carbon nanofiber composites under transient shear and uniaxial extension is investigated. A constitutive model is developed that is capable of predicting the shear and extensional rheology of both types of composites and predicts orientation changes to the nanoparticles due to flow. The model is validated through comparison to the experimental rheological measurements of both composite types and experimental measurements of carbon nanofiber orientation in the polystyrene/carbon nanofiber composites under uniaxial extension.The addition of magnetizable carbonyl iron particles to a non-magnetizable carrier fluid has been done to create a smart fluid, known as a magnetorheological fluid, whose rheological properties can be modified through the application of a magnetic field. This added functionality is being utilized in applications such as shock absorbers, dampers, brakes, and clutches. The use of these fluids in engineering applications requires rheological models capable of capturing their complex flow behavior under various flow conditions. Th (open full item for complete abstract)

Committee: Dr. Kurt Koelling (Advisor); Dr. Stephen Bechtel (Committee Member); Dr. L. James Lee (Committee Member) Subjects: Chemical Engineering

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

The overall goal of the research done in this dissertation is to develop next generation force feedback systems by combining novel Magnetorheological (MR) fluid based electromechanical systems with microstructural analysis and advanced control system design. Four MR fluid based systems are designed, prototyped and tested with medical applications: A two degree of freedom (2-DOF) force feedback joystick and a 5-DOF force feedback manipulator for telerobotic surgery application, a passive and a semiactive orthopedic knee brace for rehabilitation application. Furthermore, a force feedback steering wheel is modified using MR damper with application to steer-by-wire automobiles. The test results show the appropriate performance of MR fluid based systems used in haptic and force feedback applications.

Committee: Gregory Washington PhD (Advisor); Stephen Bechtel PhD (Committee Member); Vadim Utkin PhD (Committee Member); Giorgio Rizzoni PhD (Committee Member) Subjects: Mechanical Engineering

Bachelor of Science, Miami University, 2012, School of Engineering and Applied Science - Mechanical Engineering

Magnetorheological elastomers (MREs) are an emerging branch within the smart materials field that consists of hard or soft magnetic particles embedded in a rubber compound. Current applications and research have been focused on changing the stiffness of these materials by applying an external magnetic field. Components of vibration absorbers and base isolation systems that employ this material have shown the capability of offering improved performance over conventional solutions. These particular applications use soft magnetic material; however, MRE materials containing hard magnetic filler materials (those that remain permanently magnetized) were the primary focus of this project and are referred to as H-MREs. When a magnetic field is applied perpendicularly to these particles, the filler particles generate a net torque and these samples can be used as a controlled actuator. Preliminary work has been conducted to characterize these H-MREs (since their properties are significantly different than “soft” MREs) and this work has shown their usefulness in engineering applications. However, unlike comparable smart materials such as piezoelectrics and electroactive polymers (EAP), additional modeling and experimentation needs to be conducted in order to develop usable models and better understand their behavior. The first portion of this paper focuses on developing experimental models to predict the behavior of H-MRE materials as cantilevered beam actuators for use in future applications. Two additional, newer applications for which H-MREs could be useful are energy harvesting and sensing. Sensors are utilized almost everywhere today as they are used to monitor the performance of a system (whether it is fluid flow, vibration measurements, etc.). Piezoelectric materials, those that respond to electric stimuli, and Galfenol, an engineered material similar to MREs, have been studied extensively for their application as self-sensing actuators. It is hypothesized that H-MREs c (open full item for complete abstract)

Committee: Jeong-Hoi Koo PhD (Advisor); Amit Shukla PhD (Committee Member); Kumar Singh PhD (Committee Member) Subjects: Materials Science; Mechanical Engineering

Doctor of Philosophy, University of Akron, 2012, Polymer Engineering

The magneto-optical and rheological behaviors of magnetic fluids and magnetorheological (MR) fluids have been investigated. A magneto-optical apparatus was constructed which enabled us to investigate the birefringence and dichroism of ferrofluids at various levels of applied magnetic field. Specifically, the effects of the film thickness of oil-based ferrofluids and the concentration of surfactant in the oil-based ferrofluids on their magneto-optical behavior were investigated. A commercial magneto-rheological instrument (Physica MCR 301, Anton Paar) equipped with a cone-and-plate fixture was employed to investigate the transient and steady-state shear flow of both ferrofluids and MR fluids as a function of shear rate at various levels of applied magnetic fields. The rheological investigation has enabled us to determine the effect of applied magnetic field on the shear viscosity and yield stress of ferrofluids and MR fluids. A special ferrofluid was prepared by filtering out nearly all of the surfactant and small particles in an oil-based ferrofluid. We then compared its magneto-optical and rheological behaviors with those of an unfiltered ferrofluid. Further, we have found that the ferrofluid with a lower concentration of surfactant gave rise to larger birefringence and yield stress, and stronger shear thinning behavior than the ferrofluid containing a higher concentration of surfactant. This observation has lead us to conclude that an increase in unbound surfactant in a ferrofluid hindered chain formation of magnetic particles, leading to a decrease in the optical and rheological behaviors of the ferrofluid. Optical microscopy confirmed no visible chain formation of magnetic particles in the ferrofluid having a high concentration of surfactant owing to weak yield stress, birefringence, and shear thinning. On the other hand, we observed from optical microscopy that the filtered ferrofluid gave rise to larger yield stress, birefringence, and stronger shear thinning (open full item for complete abstract)

Committee: Chang Dae Han Dr. (Advisor); Alamgir Karim Dr. (Committee Member); Thein Kyu Dr. (Committee Member); David Perry Dr. (Committee Member); Timothy Norfolk Dr. (Committee Member) Subjects: Polymers