Master of Sciences (Engineering), Case Western Reserve University, 2017, EMC - Mechanical Engineering

A Mini-Whegs vehicle was designed, fabricated, and assembled consisting predominantly of 3D printed parts. 3DP Mini-Whegs is a fully functional, Bluetooth controlled, mobile quadruped approximately 6 ½ inches long. It's a member of the Whegs family of robots, which all utilize rotating, spoked appendages, called wheel-legs. The unique geometry of these appendages introduces considerable vibrations to the system, making it difficult to integrate vibration sensitive equipment, such as cameras or sensors. A vibration analysis model was developed to simulate vibrations in the moving robot. Three wheel-leg designs were developed and analyzed to determine that stiffer spokes provide less vertical displacement and less stiff ones offer less angular displacements, and that four spoked wheel-legs are considerably more stable than three. Different front-to-back wheel-leg phase angles vary the vibrations but an optimal angle depends on application. Experiments investigated the validity of the simulation and verified the difference in stiffness of compared wheel-legs.

Committee: Roger Quinn (Advisor); Richard Bachmann (Advisor); Clare Rimnac (Committee Member) Subjects: Design; Mechanical Engineering; Mechanics; Robotics; Robots

PhD, University of Cincinnati, 2011, Engineering and Applied Science: Mechanical Engineering

Prolonged exposure to tool vibration causes vascular, neurological and musculoskeletal abnormalities in hand-arm system, which is collectively known as hand-arm vibration syndrome (HAVS). HAVS is a major musculoskeletal disorder (MSD) affecting large numbers of construction workers and miners. One of the major symptoms of HAVS is vibration white finger (VWF) caused by exaggerated vasoconstriction of the arteries and skin arterioles. A significant number of construction workers, miners and even dentists are affected by HAVS. The precise mechanism or pathogenesis of the syndrome still remains unclear, and there is a need for better understanding of various biodynamic responses induced by vibration. Accurate analysis of hand-arm vibration response is very difficult due to the complexity of the hand-arm structure such as redundancy of the musculo-tendon unit, active participation from central nervous system, inherent non-linearity and heavy damping effect. Three fundamental modeling methods are developed in this study to understand the cause of musculoskeletal responses and vascular system responses of the hand-arm system. The first model is a musculoskeletal kinematic model developed by adopting a modified Hill's model to describe the behavior of the muscle and tendon. At first, the force in each muscle necessary to generate the grip force is determined by a quadratic optimization process. Using the force determined, the activation level of the muscle is found by assuming that the muscle-tendon undergoes an isometric contraction during the gripping. With the activation level known, the muscle-tendon system is simplified by a set of spring-mass-damper based on the assumption that the muscle response to the vibration is passive. From dynamic analysis it is shown that smaller intrinsic muscles are vulnerable to high frequency vibrations even if the overall response of the hand-arm is small. The second model addresses vasospasm in finger artery caused by vibration, there (open full item for complete abstract)

Committee: J. Kim PhD (Committee Chair); Rupak Banerjee PhDPE (Committee Member); Yijun Liu PhD (Committee Member); Dong Qian PhD (Committee Member) Subjects: Biomechanics

Master of Sciences (Engineering), Case Western Reserve University, 2009, EMC - Mechanical Engineering

The damping force and the self-excited force, which are a part of Heat Exchanger tube vibrations, act in the same (transverse) direction. The wedging process introduces alternating longitudinal coulomb forces that act at double the frequency of transverse vibrations and is defined by the wave equation. The transverse vibrations and the alternating longitudinal coulomb forces are coupled and act orthogonal to each other. Physical observations show that the transverse vibrations cannot exist without longitudinal vibrations. The governing constitutive equations for coupling can be shown theoretically through material non-linearities by considering higher order terms for the elastic energy, and geometric non-linearities by considering non-linear strain displacement relations. This non-linear constitutive equation when used in the equation of motion for transverse vibrations, the Gol'dberg tensorial result emerges. Energy reorganization due to this coupling results in reduced transverse vibration amplitudes. A simple experimental setup simulating this wedging process validates that transverse vibrations cannot occur without longitudinal vibrations.

Committee: Joseph Mansour (Advisor); Winston Perera (Committee Co-Chair); Vassilis Panoskaltsis (Advisor); Joseph Prahl (Committee Member); Roger Quinn (Committee Member) Subjects: Engineering

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

With an explosion of the internet of things, energy harvesting provides an environmentally friendly solution to replace consumable batteries in powering wireless sensors. The goal of the research is to bridge a fundamental disconnection in the state-of-the-art understanding of dynamic, multiphysics interplay in vibration energy harvesting systems. In this spirit, vibration energy harvesting systems that integrate structural and electrical nonlinearities are examined to create knowledge on intricate dynamics when subjected to complex vibration environments. The revealed principles may build foundations for techniques to capitalize on synergistic dynamic responses and deliver sustainable robust DC power. In the dissertation, theoretical frameworks that synthesize the mechanical and electrical nonlinearities have been established to examine the intricate dynamics of the integrated nonlinear energy harvesting system. The proposed analytical formulations have been validated by experiments and present particular efficacy to probe the nonlinear dynamics and regulated electrical power, which may help guide the design and deployment of nonlinear energy harvesting systems under complex vibration environments. Moreover, the principles of impedance have been employed to scrutinize the energy transfer in the complex and nonlinear multiphysics network to shed light on strategies for maximizing the energy conversion efficiency of the integrated nonlinear energy harvesting system. The uncovered dynamical characteristics and optimal strategies facilitate insights on the suitable integration of sub-systems and assist in the development and deployment of high-efficiency and sustainable energy harvesting systems. The new knowledge on the system-level harvester implementation may also guide the advancements of other fields, where wireless sensor networks are possibly deployed, such as medical implantation, civil infrastructure health monitoring, and wildlife tracking.

Committee: Ryan Harne (Advisor); Kahraman Ahmet (Committee Member); Srinivasan Manoj (Committee Member); Rodgers Emily (Committee Member) Subjects: Mechanical Engineering

Master of Science, Miami University, 2020, Mechanical and Manufacturing Engineering

Vibration based monitoring techniques are widely used to detect damage, monitor the growth of inherent defects, system identification, and material parameter estimation for various engineering applications. These techniques present a non-invasive and relatively inexpensive tool for various biomedical applications, for example, in characterizing the mechanical properties of the bone and muscles of humans as well as animals. In recent years, it has been shown that fundamental natural frequencies and corresponding damping ratios can be correlated to the bone health quality indicators as associated with osteoporosis, osteoarthritis etc. In this research, through the investigation of clinical data, an analysis procedure is developed to investigate the correlation between the damping properties associated with both lower and higher modes of vibration and bone health quality. Subsequently, a data-driven system identification tool for reconstructing the parameters (mass, stiffness, damping distributions) in a low-dimensional human model is developed which utilizes selected measurements from the clinical study. It is anticipated that the analysis process and parameter identification techniques presented here can be developed and tuned for any individual human model and can be can be used as osteological monitoring tool for predicting early diagnostics pre-cursors of the bone or muscle related conditions or diseases.

Committee: Kumar Singh (Advisor); James Chagdes (Committee Member); Mark Walsh (Committee Member) Subjects: Biomechanics; Biomedical Engineering; Mechanical Engineering; Osteopathic Medicine

Doctor of Philosophy, University of Toledo, 2019, Engineering

The internal combustion engine cold test is becoming one of the main tests performed during the late stage of the product development and production quality inspection. Analyzing the status of the engine is required before releasing it to the consumers market. The cold test is a station with a highly optimized design, where it is capable of inspecting the functionality of various components and properties of the engine in a relatively short period of time during the production process. The studies included in the coming sections are trying to achieve an accurate engine testing data which leads to a reliable decision regarding the engine health and efficiency. The cold testing stand is a vibratory source with a high complexity, for the fact of having many parameters and assemblies that play a role in forming the noise, vibration, and harshness (NVH) of the testing stand. A better understanding of the machine dynamics behavior can be achieved by creating a torsional vibratory model and calculating the driveline natural frequencies. Calculating the natural frequencies of the system is crucial for avoiding resonance excitations during the testing phase. Eigenvalue problem solution was constructed; the natural frequencies and the mode shapes were obtained. The calculated natural frequencies are showed a deviation of less than 5% of the measured values. Engine cold testing process depends mainly on the feedback of the mounted sensors on the driveline and the engine itself. Feedback signals carry information about the rotating speed, the engine noise and vibration, the manifold pressures and the torque values. The clarity of these signals affects the accuracy and the utility of the cold test during the engine development. The engine, the driveline, and the electric motor system operate at high speeds that generate axial and lateral vibrations. The failure of any part of the assembly distorts the signals and induces backlash or harmonic amplification. A backlash study is c (open full item for complete abstract)

Committee: Efstratos Nikolaidis Dr. (Committee Chair) Subjects: Mathematics; Mechanical Engineering; Physics

PHD, Kent State University, 2019, College of Arts and Sciences / School of Biomedical Sciences

Falls among older adults over 65 years is the leading cause of injuries and fatalities. There has been a demonstrated correlation between number of falls, muscle activity and cognitive impairment in older adults. With increasing age, muscle weakness with executive function and attention declines while motor tasks such as balance and walking become less automated and more cognitively taxing. For example, maintaining postural balance while performing a cognitive task (dual-tasking postural control) requires integration of multi-sensory feedback and cognitive attention. Older adults show increased instability during dual-tasking postural balance due to deficits in proprioceptive sensitivity, muscle weakness and/or cognitive decline. Whole body vibration (WBV) has been used shown to improve balance and muscle strength and muscle activation in older adults. In addition, WBV can improve cognitive function, particularly inhibitory control as a measure of attention in adults with attention deficit hyperactivity disorder (ADHD). The primary objective of this study is to determine if three sessions of segmental vibration therapy (SVT) of the lower legs improve muscle activation, executive function and dual-tasking (DT) postural balance in older adults. We hypothesized that SVT will provide a sensory stimulation that acts on muscle spindles and mechanoreceptors that could stimulate neural activity of the leg muscles and improve balance. Twenty participants over the age of 60 were randomized into either a vibration therapy (SVT) or control (CON) group. Segmental vibration therapy was applied to the soleus, gastrocnemius and tibialis anterior muscles for 2 minutes at 20Hz for 3 sessions on 3 consecutive days. Muscle activity of the mentioned muscles were measured using surface electromyograms. Inhibitory control and attention, working memory and processing speed was measured using the NIH Toolbox. The Biodex Balance System was used to assess sensory integration capabilities and (open full item for complete abstract)

Committee: Angela Ridgel Ph.D. (Advisor); Eric Mintz Ph.D (Committee Member); Colleen Novak Ph.D. (Committee Member); Kimberly Peer Ph.D. (Committee Member) Subjects: Biomechanics; Biomedical Research; Neurosciences

MS, University of Cincinnati, 2018, Engineering and Applied Science: Mechanical Engineering

An engine assembly's dynamic characteristics bear a heavy influence on the performance and structural life of engine mounted components and the engine itself. The characterization and measurement of vibration response of the assembly therefore becomes an integral part of processes such as design and development, performance evaluation and failure mode investigations. The vibration testing of an engine assembly can be performed in free-free, constrained or actual operational boundary conditions. Engine testing and response characterization often is conducted in controlled environments such as engine test cells, which approximate the boundary condition of an engine on a customer application at the engine to test cell floor or skid mounting connection. As a manufacturer of diesel engines with different test cell arrangements, Cummins was interested in developing metrics to compare between the results of the engine in different test cell mounting configurations. The motivation of this thesis was to propose metrics to assess the difference in response of the engine system between different mounting arrangements. Existing modal parameters as potential assessment metrics have been discussed. New metrics for comparison of vibration response were developed specifically for an engine assembly in a test cell environment. Representative analytical models of the engine assembly were created to model the effects of change in boundary condition, and to demonstrate the application of the assessment metric. A DOE study was performed to study the sensitivity of the response by varying the structural parameters in the analytical model, and the proposed metrics were applied to evaluate the effect of mounting arrangement for each model. Impedance modeling is shown as an optional predictive tool to forecast the change in the frequency response function characteristics due to structural modification in the mounting arrangement.

Committee: Randall Allemang Ph.D. (Committee Chair); Allyn Phillips Ph.D. (Committee Member); David Thompson Ph.D. (Committee Member) Subjects: Mechanical Engineering

PhD, University of Cincinnati, 2018, Engineering and Applied Science: Mechanical Engineering

A detailed summary of the extensive studies on the feasibility and practicality of utilizing high-speed 3-dimensional digital image correlation (3D-DIC) for various random vibration measurement applications is presented. Demonstrated capabilities include finite element model validation and updating utilizing full-field 3D-DIC static displacements, modal survey natural frequencies, damping, and mode shape results from 3D-DIC are baselined against laser Doppler vibrometry (LDV), a comparison between foil strain gauge and 3D-DIC strain, and finally the unique application to a high-speed wind tunnel fluid-structure interaction study. Results indicate good agreement between 3D-DIC and more traditional vibration measurement techniques. Unfortunately, 3D-DIC vibration measurement is not without its limitations, which were also identified and explored in this study. The out-of-plane sensitivity required for vibration measurement for 3D-DIC is orders of magnitude less than LDV making higher frequency displacements difficult to sense. Furthermore, the digital cameras used to capture the DIC images have no filter to eliminate temporal aliasing of the digitized signal. Ultimately it is felt DIC was demonstrated as a valid alternative means to measure structural vibrations while providing full-field noncontacting results not possible with other methods. Furthermore, one unique first of its kind application in a high-speed wind tunnel achieved success where more traditional methods would fail.

Committee: Randall Allemang Ph.D. (Committee Chair); Allyn Phillips Ph.D. (Committee Member); S. Michael Spottswood Ph.D. (Committee Member); David Thompson Ph.D. (Committee Member); Yongfeng Xu Ph.D. (Committee Member) Subjects: Mechanical Engineering

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

Magnetostrictive materials transfer energy between the magnetic and mechanical domains as they magnetize in response to applied stresses and deform in response to applied magnetic fields. The deformation that arises from this coupling directly causes the material's effective elastic moduli to depend on stress and magnetic field. This phenomenon, known as the Delta E effect, can be electrically modulated using electromagnets. Devices having an electrically-tunable stiffness can be developed by harnessing this effect. Such devices have broad application to the field of vibration control, particularly in instances where the vibration source or operating regime change over time. Although the static Delta E effect has been extensively measured in many man-made magnetostrictive materials, such as Galfenol (FeGa) and Terfenol-D (TbDyFe), this tunability has been seldom applied to the development of vibration control devices. Real-time tuning of the elastic moduli (i.e., the dynamic Delta E effect) has not been studied. Further, the effects of dynamic stress on the constitutive behavior of magnetostrictive materials are largely unknown, despite their critical importance to the modeling and design of many magnetostrictive systems, including dynamic sensors, energy harvesters, vibration dampers, and stiffness tuning devices. This work analytically, numerically, and experimentally explores the effects of dynamic stress on magnetostrictive materials and the use of the static and dynamic Delta E effect in the development of novel vibration control devices. Measurements of the quasi-static elastic response of Galfenol reveal that the Young's modulus and Delta E effect are stiffer and smaller, respectively, for small amplitude applied stresses than for large amplitude applied stresses. The static Delta E effect in Galfenol-based composite beams that are applied as adaptive vibration absorbers is studied by constructing nonlinear, dynamic models of their vibratory response. The (open full item for complete abstract)

Committee: Professor Marcelo Dapino (Advisor); Professor Giorgio Rizzoni (Committee Member); Professor Krishnaswamy Srinivasan (Committee Member); Professor Junmin Wang (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2014, Engineering and Applied Science: Mechanical Engineering

Hand-Arm Vibration Syndrome (HAVS) collectively refers to diseases associated with prolonged, intensive exposure to hand-transmitted vibrations. Millions of construction workers who use hand-held power tools are affected by HAVS in the United States. Numerous dynamic models of the hand-arm system were developed to better understand the injury mechanism. One of the problems in dynamic response analysis of the hand-arm system has been difficulty in finding the excitation forces generated by the operation of hand-held tools. Especially, the force transmitted to the hands from the tool and the force interacting between the tool and work-piece are very useful information in hand-arm vibration study; however, they cannot be measured directly. Methods to estimate these forces are developed in this work by utilizing a hand-arm model, the acceleration measured at the hand, and two measured transfer functions of the tool. Experimental validation procedures of the methods are devised, which show the estimated forces are accurate enough to be used for practical applications. The method developed in this work enables estimation of the force acting between the tool and workpiece in a hand-held power tool in operation for the first time. There are many potential applications of the method developed in this work. For example, the methods can be used to make design changes in the handle bar of a grinder to reduce vibration transmission to the hands, ultimately leading to a lower frequency of HAVS.

Committee: J. Kim Ph.D. (Committee Chair); Thomas Richard Huston Ph.D. (Committee Member); David Thompson Ph.D. (Committee Member) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 2014, Mechanical Engineering

The topic of this scholarly research is motivated by the need for superior control of vehicle powertrain vibration, commonly accomplished using 3 or 4 passive mounts. However, emerging design trends (such as higher power density powertrains and lightweight structures) necessitate a hybrid approach utilizing active and passive methods to meet more stringent system performance targets. The chief research objective is to acquire fundamental understanding of dynamic interactions among multiple active and passive paths in a powertrain mounting system for improved control of multi-dimensional motion, in the presence of a rigid frame placed on four bushings. All hybrid paths are assumed to be an actuator in series with an elastomeric mount; and discrete linear time-invariant deterministic systems are assumed with small motions, harmonic excitations, steady state behavior, and no kinematic nonlinear effects. Also, passive elements are assumed massless while active elements possess mass. Additionally, passive torque roll axis motion decoupling concepts are explored to enhance active control capabilities given certain practical constraints. Analytical, computational, and experimental methods are utilized though no real-time control is done. First, the torque roll axis motion decoupling concept is studied in a 12 degree of freedom model of a realistic powertrain and coupled frame. Deficiency of prior literature neglecting the need for a physically realizable system is overcome by deriving improved mount compatibility conditions, implemented in new decoupling paradigms to ensure more realistic mount positions. It is mathematically shown that full decoupling is not possible for a practical system, and partial decoupling paradigms are pursued to ensure that only the powertrain roll motion is dominant. This constitutes as a major contribution. The interaction between hybrid paths is studied next as part of a resonating two path source-path-receiver system with 6 degrees of (open full item for complete abstract)

Committee: Rajendra Singh Dr. (Advisor); Jason Dreyer Dr. (Committee Member); Manoj Srinivasan Dr. (Committee Member); Vishnu Sundaresan Dr. (Committee Member); Vadim Utkin Dr. (Committee Member) Subjects: Mechanical Engineering

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

Background – Although extensive research has been reported on the relationship between lower back pain and whole-body vibration (WBV) in the occupational health environment,less is known about the effects of mechanical shocks associated with the operation of heavy equipment. Objectives – The main objective of this research is to characterize mechanical shocks caused by forklift operation using objective methods such as the International Organization of Standardization ISO 2631-1, ISO 2631-5, British Standard BS 6841, and American Conference of Governmental Industrial Hygienists ACGIH and comparing them, also comparing the results to the European Union action level and vibration levels recommended by different authors. Specific aims- There are two specific aims for this research which are outlined below: Specific Aim 1: To Characterize Mechanical Shocks using Different Methods. The VATS is capable of measuring mechanical shocks according to different standards such as the ISO 2631-1, BS 6841, ACGIH and finally the new ISO 2631-5 which was introduced in 2004. Specific Aim 2: To assess significant difference if any among the different methods.To our knowledge only one study compared the new ISO 2631-5 method to old ISO 2631-1 standard (Alem N. 2005). Only the VDV method which is recommended by ISO 2631-1 for measuring mechanical shocks was compared to the new ISO 2631, results showed that ISO 2631-5 is more sensitive to measuring mechanical shocks then the VDV method. Results from different methods measured by VATS will be compared and investigated. Methods – An instrumentation based method using a commercially available (WBV) measurement system employing a seat pad sensor is used to measure WBV for each forklift operator according to different standards and methods such as the ISO, British Standard and the ACGIH standard. The vibration instrument was used to measure the vibration accelerations for four forklift operators in a packing factory; the resulting raw data wa (open full item for complete abstract)

Committee: Dr. Richard Shell (Advisor) Subjects: Engineering, Industrial

Master of Science, The Ohio State University, 2010, Mechanical Engineering

Passive hydraulic engine mounts are commonly employed for motion control and vibration isolation in vehicle powertrain systems. Such devices are often tuned in terms of their low frequency resonance and damping ratio (say corresponding to the engine bounce mode) to control noise and vibration and improve the ride comfort, quality, and safety of the vehicle. Mount tuning concepts with one inertia track and one decoupler using the track length or diameter are well understood, but the dynamic response with multiple tracks, orifices, or decouplers is not. To overcome this void in the literature, dynamic tuning concepts of hydraulic engine mounts, with emphasis on multiple (n-) inertia tracks, fixed decoupler-type designs, are analytically and experimentally examined in this thesis. Since a wide variety of n-inertia track configurations is possible, dynamic stiffness models are developed to explain a family of such configurations, based on linear time-invariant lumped fluid system theory. Furthermore, a new n-track prototype mount concept is designed, built, and tested in a controlled manner, with the capability of varying the type (capillary tube, orifice) and number (n) of inertia tracks, in addition to length and diameter of each. This prototype is used to examine several designs with alternate n-track configurations for improving performance compared to the n = 1 track case. Three narrowband devices are designed and tested to refine existing theory for predicting peak frequency of loss angle, in addition to examining and validating an n = 3 track mount for the first time. Two broadband devices are designed and tested successfully by tuning damping ratios of the mount with orifice-type tracks for the first time. Several n-track mount designs with orifice-type tracks are also proposed, which successfully describe a special broad-tuned design utilizing a controlled ‘leakage' path flow area for the first time. Lastly, a quasi-linear dynamic stiffness model is developed (open full item for complete abstract)

Committee: Dr. Rajendra Singh (Advisor); Dr. Ahmet Kahraman (Committee Member) Subjects: Acoustics; Design; Engineering; Mechanical Engineering

Master of Science (MS), Ohio University, 2012, Civil Engineering (Engineering and Technology)

Many variable stiffness and damping devices have been proposed in an attempt to mitigate the effects of unwanted vibrations in civil engineering structures. This work proposes a novel variable stiffness or damping device called the Continuously Variable Amplification Device (CVAD) that improves upon past limitations. It consists of a sphere and rollers in series with a spring or damper, and is able to produce a large, continuous, and rapidly varying range of stiffness or damping values. A series of relationships and equations are derived and validated to describe the amplification of the device. A numerical simulation is developed that pairs the CVAD with SSASD and RSASD devices and places it in a seismically excited eight story structure in a supplemental damping role. In addition, centralized control laws are created and applied to the CVAD devices. The results demonstrate the device and its centralized control laws are a marked improvement over the state-of-the-art.

Committee: Kenneth Walsh Ph.D (Advisor); Eric Steinberg Ph.D (Committee Member); Deboriah McAvoy Ph.D (Committee Member); Douglas Green Ph.D (Committee Member) Subjects: Civil Engineering

Master of Science (MS), Ohio University, 1984, Civil Engineering (Engineering)

The purpose of this study is to experimentally determine the behavior of structural plates with elastically suspended vibration absorbing plates attached. Three major factors under study are mass of the vibration absorber, stiffness of the elastic connectors, and flexural rigidity of the vibration absorbing plate. The single panel simply supported square plate is tested to determine the vibration attenuation effects of three different vibration absorbers. These vibration absorbers are also square plates and are suspended by springs at the four corners. The tests were conducted with a custom designed and con- structed model and testing frame and standard structural dynamics laboratory equipment. A data acquisition system consisting of a personal computer with an analog-to-digital converter was used. The experimental results were compared to theoretical and numerical analyses and experimental modeshapes were determined. The results show that heavy vibration absorbers, i.e., weight of the secondary plate greater than one-half the pri- mary plate weight, shift the fundamental and lower order primary plate natural frequencies. Absorber plates about one half the weight of the primary plate tend to have a wide range effect. Lightweight absorbers, i.e., less than one- half the primary plate weight, affect higher order primary plate frequencies. The elastic connectors serve to fine tune the system to a desired effect. Secondary plate flex- ion has little affect on the behavior.

Committee: Fathy Akl (Advisor) Subjects: Engineering, Civil

Master of Science (MS), Ohio University, 1995, Mechanical Engineering (Engineering)

Optimal control theory has been particularly successful in the evolution of techniques for solving dynamic problems. Problems of a dynamic nature have long been of interest to industry. Classical mathematical tools have been applied to their solution, in particular; these have included variational methods including the classical calculus of variations approach and more general methods associated with recent development of the maximum principle. In this research, the calculus of variations is applied to optimize the motion of a rod and a membrane, and to determine the boundary conditions for optimality of the axial vibration of a rod and the transverse vibration of a membrane. The procedure for finding the distribution of the control input over the domain (fixed ends and fixed time) of the rod and membrane and the minimization of a cost function are also introduced.

Committee: Sunil Agrawal (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy, Case Western Reserve University, 2009, EMC - Mechanical Engineering

In this research, the fault detection and diagnosis using a model-based technique for the cracked rotor vibration system is developed and implemented. More specifically, the observer based or filter bank approach is employed in the fault detection and diagnosis process in order to detect the occurrence of a crack and diagnose the position and the depth of the crack in rotating machinery. The fault detection and diagnosis process is consisted of two parts. The first part is the filter bank or the residual generation which generates the residual vectors corresponding to each observer. The second part is a voting algorithm which searches the observer that corresponds to the behavior of the real system. The type of filter contained in the filter bank is the discrete time-variant Kalman filter. The filter is specifically designed to track the cracked rotor vibration system. Since the filter is time-variant, the state matrix at the current time step of the filter is updated by the state estimated value from the previous time step. Constructing the filter bank with the presented filter allows the fault detection and diagnosis process to perform very well under the environment of the process and measurement noises which is unavoidable in real systems. The voting algorithm evaluates every observer to find the observer behaving the closest to the real system based on the score achieved by each observer. The score is calculated by the information of the residual mean, the residual autocorrelation of each observer, the correlation coefficient between the real system measurements, and the observer outputs. In order to evaluate the fault detection and diagnosis process performance, the fault detection and diagnosis process is tested with the simulated real system containing various sets of system parameters. The results and discussions are presented.

Committee: Kenneth A. Loparo PhD (Committee Chair); Dario Gasparini PhD (Committee Member); Robert L. Mullen PhD (Committee Member); Maurice L. Adams PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science, University of Akron, 2006, Mechanical Engineering

Flow induced vibrations of single and double-walled carbon nanotubes are studied using pipe models. The solutions to flow induced vibrations of pipes are well known. Buckling and flutter are two instabilities of concern. The problem formulation, governing differential equation and dimensionless frequency response for single-walled nanotubes are the similar to that of pipes conveying fluids. The van der Waals forces between the layers of multiwalled nanotubes are modeled as springs. This changes the governing differential equation and the dimensionless frequency response for the double-walled nanotubes. The following results are for fixed-fixed boundary conditions. The first instability encountered for the single-walled nanotubes was buckling. This occurred at a dimensionless velocity of 2ð. Larger mass ratios would buckle in the first mode then regain stability before the onset of flutter. Small mass ratios would buckle in the first and second modes followed by flutter. This corresponds with previous solutions to flow induced vibrations of pipes. Results for double-walled nanotubes show that buckling will also occur before the onset of flutter, but at larger dimensionless velocities then the single-walled nanotubes. The examples studied here regained stability in the first mode before the onset of flutter.

Committee: S Kelly (Advisor) Subjects:

Master of Science, The Ohio State University, 1965, Graduate School

Committee: Not Provided (Other) Subjects: