Mechanical Engineering Commons^™

On The Opening Of A Class Of Fatigue Cracks Due To Thermo-Mechanical Fatigue Testing Of Thermal Barrier Coatings, M. T. Hernandez, D. Cojocaru, M. Bartsch, Anette M. Karlsson

Mechanical Engineering Faculty Publications

The evolution of fatigue cracks observed in thermal barrier coatings (TBCs) subjected to an accelerated test scheme is investigated via numerical simulations. The TBC system consists of a NiCoCrAlY bond coat and partially yttria stabilized zirconia top coat with a thermally grown oxide (TGO) between these two coatings. The cracks of interest evolve in the bond coat parallel and near the interface with the TGO during thermo-mechanical fatigue testing. In their final stage, the cracks lead to partial spallation of the TBC. This study focuses on why the cracks open to their characteristic shape. To this end, finite element simulations …

Characterization Of Fracture Toughness G (Sub C) Of Pvc And Pes Foams, Elio E. Saenz, Leif A. Carlsson, Anette M. Karlsson

Mechanical Engineering Faculty Publications

The fracture behavior of polyvinyl chloride (PVC) and polyethersulfone (PES) foams has been examined using the single-edge notch bend and the double cantilever beam (DCB) tests. PVC foam densities ranging from 45 to 100 kg/m³ and PES foam densities ranging from 60 to 130 kg/m³ were examined. The PVC foams failed in a linear elastic brittle manner, whereas the PES foams displayed much more ductility and substantially larger toughness at a comparable foam density. The cell wall thickness of the PES foams was almost twice the thickness of the PVC foams which may have contributed to the high …

Detecting Cracked Rotors Using Auxiliary Harmonic Excitation, Jerzy T. Sawicki, Michael I. Friswell, Zbigniew Kulesza, Adam C. Wroblewski, John D. Lekki

Mechanical Engineering Faculty Publications

Cracked rotors are not only important from a practical and economic viewpoint, they also exhibit interesting dynamics. This paper investigates the modelling and analysis of machines with breathing cracks, which open and close due to the self-weight of the rotor, producing a parametric excitation. After reviewing the modelling of cracked rotors, the paper analyses the use of auxiliary excitation of the shaft, often implemented using active magnetic bearings to detect cracks. Applying a sinusoidal excitation generates response frequencies that are combinations of the rotor spin speed and excitation frequency. Previously this system was analysed using multiple scales analysis; this paper …

Mechanical Behavior Of Bio-Inspired Laminated Composites, Liang Cheng, Adam Thomas, James L. Glancey, Anette M. Karlsson

Mechanical Engineering Faculty Publications

To investigate if the relative high strength and stiffness of biological composites can be translated into man-made materials, innovative bio-inspired laminated composites with commercial materials (glass epoxy prepreg) were designed and manufactured by incorporating the distinctive helicoidal morphology observed in the exoskeletons of crustaceans. The helicoidal structure is characterized by a stacking sequence consisting of a gradual rotation of each lamina in the multi-layered laminated composites. Variations of the helicoidal structure were designed and produced to address some important issues encountered in the practical composites manufacturing process, including mid-plane symmetry. In addition, composite structures with a general quasi-isotropic configuration were …

Fabrication And Testing Of A Nonstandard Thin-Film Heat Flux Sensor For Power System Applications, Scott D. Wilson

ETD Archive

Stirling convertors are being operated by NASA Glenn Research Center for many years to demonstrate a Radioisotope Power System (RPS) capable of providing reliable power for potential multi-year space missions. Techniques used to monitor Stirling convertors for change in performance include measurements of temperature, pressure, energy addition, and power output. It is difficult to measure energy addition to Stirling convertors due to the complex geometries of the hot components, temperature limits of sensor materials, and invasive integration of sensors. A thin-film heat flux sensor was used to directly measure heat energy addition to a Stirling convertor. The one micron thick, …

Modeling And Performance Investigation Of A Rotor With Dissimilar Bearing Support System, Yunlu Li

ETD Archive

Different types of bearings have different dynamic characteristics. By using one type of bearing at one end of a rotor and another type of bearing at the other end of the rotor, it is possible to exploit the advantages of both types in the same system. One example of such combination is a bronze bushing and active magnetic bearing (AMB). In the available literature, there are examples of such systems but are not fully explored with regard to how to model the system to fully utilize both support type properties. This thesis investigates the modeling and performance of such a …

Probabilistic Stress Analysis Of Circular Fins Of Different Profiles, Sridhar Madhira Venkata

ETD Archive

The temperature distribution and thermal Stresses induced by a temperature difference for steady state heat transfer in silicon carbide (SiC) ceramic tube heat exchanger with circular fins was computationally simulated by a finite element method and probabilistically evaluated in view of the several uncertainties in the performance parameters. Cumulative distribution functions and sensitivity factors were computed for Hoop and Radial stresses due to the structural and thermodynamic random variables. These results are used to identify the most critical design variables in order to optimize the design and make it cost effective. The probabilistic analysis leads to the selection of the …

Model Identification, Updating, And Validation Of An Active Magnetic Bearing High-Speed Machining Spindle For Precision Machining Operation, Adam C. Wroblewski

ETD Archive

High-Speed Machining (HSM) spindles equipped with Active Magnetic Bearings (AMBs) are envisioned to be capable of autonomous self-identification and performance self-optimization for stable high-speed and high quality machining operation. High-speed machining requires carefully selected parameters for reliable and optimal machining performance. For this reason, the accuracy of the spindle model in terms of physical and dynamic properties is essential to substantiate confidence in its predictive aptitude for subsequent analyses.This dissertation addresses system identification, open-loop model development and updating, and closed-loop model validation. System identification was performed in situ utilizing the existing AMB hardware. A simplified, nominal open-loop rotor model was …

A Cfd Model Of Mixing In A Microfludic Device For Space Medicine Technology, Terri Lynn Mckay

ETD Archive

The DNA Medicine Institute (DMI) is currently developing a device to be used for blood analysis to satisfy the unique requirements of space medicine applications. A key component of that device is the micromixer, which will ensure mixing and dilution of reagents utilized for detection assays. As part of the device design process, the micromixer was modeled, and the mixing characteristics were analyzed and compared to experimental data. The experimental data was based on a top-view of the system and, lacking data throughout the fluid domain, could not provide the insight into the mixing process that modeling could readily provide. …

Cfd Simulations For The Effect Of Unsteady Wakes On The Boundary Layer Of A Highly Loaded Low Pressure Turbine Airfoil (L1a), Samuel J. Vinci

ETD Archive

The study of a very high lift, low-pressure turbine airfoil in the presence of unsteady wakes was performed computationally and compared against experimental results. The experimental data were collected in a low speed wind tunnel under high (4.9 ) and then low (0.6 ) freestream turbulence intensity conditions on a linear cascade with wakes that were produced from moving rods upstream of the cascade. The flow coefficient was kept at 0.7 while the rod to blade spacing was changed from 1 to 1.6 to 2 blade spacings. These cases were conducted for Reynolds number equal to 25,000 and 50,000, based …

Evaluation Of Lean Systems In Rail Maintenance Operations, Mert Baykut

ETD Archive

The recognized strength of lean systems is its broad applicability to every process industry even though they include some complicated and time-intensive processes. However, this conception is based on the tools and philosophy of Lean systems and the nature of the industry. The required craftsmanship and repetitive processes in rail maintenance define the uniqueness of this research The objective of this thesis was to research the opportunities and applicability for lean systems in rail maintenance. During the research a unique system, consisting of Lean systems and systems engineering tools, is realized and tried to integrate instead of a pure Lean …

A Systems Engineering Reference Model For Fuel Cell Power Systems Development, T. L. Blanchard

ETD Archive

This research was done because today the Fuel Cell (FC) Industry is still in its infancy in spite over one-hundred years of development has transpired. Although hundreds of fuel cell developers, globally have been spawned, in the last ten to twenty years, only a very few are left struggling with their New Product Development (NPD). The entrepreneurs of this type of disruptive technology, as a whole, do not have a systems engineering 'roadmap", or template, which could guide FC technology based power system development efforts to address a more environmentally friendly power generation. Hence their probability of achieving successful commercialization …

Fea Analysis Of Novel Design Of Cylindrical Roller Bearing, Prasanna Subbarao Bhamidipati

ETD Archive

This work presents a finite element stress analysis of a novel design of cylindrical roller. The focus of this study is to create a uniform contact-stress distribution along the length of the roller and to recommend a roller bearing design which is easier to fabricate. The new design relies on creating symmetric cylindrical cavities at both ends of a roller. The cavity is concentric with the main body of the roller. The new roller design reduces overall mass of the typical assembly with helps to improve bearing life and its overall performance. The FEA results published herein shows that new …

Vibratory Behavior Of Rolling Element Bearings: A Lagrangian Approach, Phani Krishna Kalapala

ETD Archive

Vibratory behavior of a rolling element bearing on a horizontal rotor is studied in this work. This Thesis analyzes the dynamics of a typical roller bearing as a result of internal excitations. These internal excitations stem from the geometric deviations of the interacting surfaces from their ideal geometry. Such deviations in turn are the results of either manufacturing limitations or normal wear of the bearing surfaces. Lagrangian approach is implemented to derive the dynamic equations of motion. Matlab is used to solve the equation of motion of governing the vibrations of the system. Parametric studies are conducted to provide results …

Adaptive Sliding Mode Control For Aircraft Engines, Kathryn C. Ebel

ETD Archive

Aircraft engine control has been evolving since its beginning. With advancements in technology more and more control methods are being applied to this area. This thesis presents the design of an adaptive PID sliding mode control (A-SMC) for a turbofan engine. The controller design methodology is presented. Using an aircraft engine simulation environment developed by NASA, called Commercial Modular Aero-Propulsion System Simulation, the developed controller is tested. The results from three simulations are analyzed to investigate the application of this new design scheme. The A-SMC is able to follow the demanded fan speed for short flight simulations. However, some of …

Multivariable Sliding Mode Control Design For Aircraft Engines, Sirirat Sangwian

ETD Archive

Many control theories are used in controlling aircraft engines. However, the multivariablesliding mode control is not yet established in this application even though ithas a lot of potential in dealing with complex and nonlinear systems such as aircraftengines. Therefore, a guideline in developing multivariable sliding mode control law for an aircraft engine is presented in this thesis. The problem of chattering in thesliding mode control is suppressed by the use of the boundary layer method. The controllogic is tested by implementing NASA's Commercial Modular Aero-PropulsionSystem Simulation 40k (C-MAPSS40k). Simulation results are analyzed and comparedto the results obtained from the baseline …

Application Of Active Magnetic Force Actuator For Control Of Flexible Rotor System Vibrations, Volodymyr Mykhaylyshyn

ETD Archive

The purpose of this work was to develop and experimentally demonstrate a novel approach to minimize lateral vibrations of flexible rotor. The applied feed forward control approach employed magnetic force actuator to inject a specially designed force to counteract the rotor unbalance force. By specific selection of frequency and phase as functions of the rotor running speed and rotor natural frequency, the proposed simplified injection waveform has been shown to be effective both in reducing the rotor's vibrations and for hardware implementation. A model of the test rig was constructed using the finite element (FE) method and was validated using …

Probabilistic Structural And Thermal Analysis Of A Gasketed Flange, Atul G. Tanawade

ETD Archive

Performance of a flange joint is characterized mainly by its 'strength' and 'sealing capability'. A number of analytical and experimental studies have been conducted to study these characteristics under internal pressure loading. However, with the advent of new technological trends for high temperature and pressure applications, an increased demand for analysis is recognized. The effect of steady-state thermal loading makes the problem more complex as it leads to combined application of internal pressure and temperature. Structural and thermal analysis of a gasketed flange was computationally simulated by a finite element method and probabilistically evaluated in view of the several uncertainties …

Implicit Methods For Efficient Musculoskeletal Simulation And Optimal Control, Antonie J. Van Den Bogert, Dimitra Blana, Dieter Heinrich

Mechanical Engineering Faculty Publications

The ordinary differential equations for musculoskeletal dynamics are often numerically stiff and highly nonlinear. Consequently, simulations require small time steps, and optimal control problems are slow to solve and have poor convergence. In this paper, we present an implicit formulation of musculoskeletal dynamics, which leads to new numerical methods for simulation and optimal control, with the expectation that we can mitigate some of these problems. A first order Rosenbrock method was developed for solving forward dynamic problems using the implicit formulation. It was used to perform real-time dynamic simulation of a complex shoulder arm system with extreme dynamic stiffness. Simulations …

Personal Navigation Via High-Resolution Gait-Corrected Inertial Measurement Units, Özkan Bebek, Michael A. Suster, Srihari Rajgopal, Michael J. Fu, Xuemei Huang, M. Cenk Çavu¸So˘Glu,, Darrin J. Young, Mehran Mehregany, Antonie J. Van Den Bogert, Carlos H. Mastrangelo

Mechanical Engineering Faculty Publications

In this paper, a personal micronavigation system that uses high-resolution gait-corrected inertial measurement units is presented. The goal of this paper is to develop a navigation system that uses secondary inertial variables, such as velocity, to enable long-term precise navigation in the absence of Global Positioning System (GPS) and beacon signals. In this scheme, measured zerovelocity duration from the ground reaction sensors is used to reset the accumulated integration errors from accelerometers and gyroscopes in position calculation. With the described system, an average position error of 4 m is achieved at the end of half-hour walks.

Concurrent Muscoskeletal Dynamics And Finite Element Analysis Predicts Altered Gait Patterns To Reduce Foot Tissue Loading, Jason P. Halloran, Marko Ackermann, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Current computational methods for simulating locomotion have primarily used muscle-driven multibody dynamics, in which neuromuscular control is optimized. Such simulations generally represent joints and soft tissue as simple kinematic or elastic elements for computational efficiency. These assumptions limit application in studies such as ligament injury or osteoarthritis, where local tissue loading must be predicted. Conversely, tissue can be simulated using the finite element method with assumed or measured boundary conditions, but this does not represent the effects of whole body dynamics and neuromuscular control. Coupling the two domains would overcome these limitations and allow prediction of movement strategies guided by …

Auxiliary State Variables For Rotor Crack Detection, Zbigniew Kulesza, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

In the present study, a new model-based method for rotor crack detection and crack location is proposed. The finiteelement model of the rotor-bearing system accounts for the breathing mechanism of the crack. The model of the rotor system is augmented with an auxiliary single-degree-of-freedom oscillator. The observer is designed and the estimates of its two auxiliary state variables are proposed as crack indicators. The crack location along the shaft is determined by designing a set of observers, which calculate the values of these indicators for different possible crack locations along the shaft. The proposed method is validated numerically and the …

Longitudinal Sex Differences During Landing In Knee Abduction In Young Athletes, Kevin R. Ford, Robert Shapiro, Gregory D. Meyer, Antonie J. Van Den Bogert, Timothy E. Hewett

Mechanical Engineering Faculty Publications

Purpose—

The objective of this study was to determine if biomechanical and neuromuscular risk factors related to abnormal movement patterns increased in females, but not males, during the adolescent growth spurt.

Methods—

315 subjects participated in two testing sessions approximately one year apart. Male and female subjects were classified based on their maturation status as pubertal or post-pubertal.Three trials of a drop vertical jump (DVJ) were collected. Maximum knee abduction angle and external moments were calculated during the DVJ deceleration phase using a 3D motion analysis system. Changes in knee abduction from the first to second year were compared among …

High Strength And Light-Weight Materials Inspired By The Exoskeleton Of Arthropods, Anette M. Karlsson

Mechanical Engineering Faculty Publications

This work investigates the multiscaled structure and the constitutive behavior of the exoskeleton of arthropods (Japanese beetle) along with the response of biomimicked structures. Image analysis (SEM and TEM) revealed three load-bearing regions comprised of chitin-protein fiber layers orientated parallel to the cuticle surface. The chitin fibers in the exocuticle and mesocuticle are organized in a helicoidal structure (layers stacked with a small rotational angle relative to their adjacent layers). The endocuticle has a distinct pseudo-orthogonal pattern, characterized by a thin transitional helicoidal region inserted between two orthogonal layers. Idealized mechanics based models showed that the pseudo-orthogonal structure redistributes the …

Optimization And Evaluation Of A Proportional Derivative Controller For Planar Arm Movement, Kathleen M. Jagodnik, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

In most clinical applications of functional electrical stimulation (FES), the timing and amplitude of electrical stimuli have been controlled by open-loop pattern generators. The control of upper extremity reaching movements, however, will require feedback control to achieve the required precision. Here we present three controllers using proportional derivative (PD) feedback to stimulate six arm muscles, using two joint angle sensors. Controllers were first optimized and then evaluated on a computational arm model that includes musculoskeletal dynamics. Feedback gains were optimized by minimizing a weighted sum of position errors and muscle forces. Generalizability of the controllers was evaluated by performing movements …

Optimality Principles For Model-Based Prediction Of Human Gait, Marko Ackermann, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Although humans have a large repertoire of potential movements, gait patterns tend to be stereotypical and appear to be selected according to optimality principles such as minimal energy. When applied to dynamic musculoskeletal models such optimality principles might be used to predict how a patient's gait adapts to mechanical interventions such as prosthetic devices or surgery. In this paper we study the effects of different performance criteria on predicted gait patterns using a 2D musculoskeletal model. The associated optimal control problem for a family of different cost functions was solved utilizing the direct collocation method. It was found that fatigue-like …

On The Effective Elastic Properties Of Macroscopically Isotropic Media Containing Randomly Dispersed Spherical Particles, D. Cojocaru, Anette M. Karlsson

Mechanical Engineering Faculty Publications

computational scheme for estimating the effective elastic properties of a particle reinforced matrix is investigated. The randomly distributed same-sized spherical particles are assumed to result in a composite material that is macroscopically isotropic. The scheme results in a computational efficient method to establish the correct bulk and shear moduli by representing the three-dimensional (3D) structure in a two-dimensional configuration. To this end, the statistically equivalent area fraction is defined in this work, which depends on two parameters: the particle volume fraction and the number of particles in the 3D volume element. We suggest that using the statistically equivalent area fraction,introduced …

Structure-Property Relationship In Ionomer Membranes, Ahmet Kusoglu, Anette M. Karlsson, Michael H. Santare

Mechanical Engineering Faculty Publications

Perfluorosulfonic acid (PFSA) ionomer membranes are ion-conducting polymers with high water sorption capacity and thermo-mechanical stability. The morphology of PFSA changes during sorption affecting the mechanical and physical properties of the membrane. In this work, we investigate the structure-property relationship in swollen PFSA membranes using three proposed nanostructural descriptions and determine Young's modulus of the membrane at a wide range of temperatures (−20–85°C) and water volume fractions (0–0.5) for these configurations. Comparing the mechanics-based models with experimental data we propose that ion-rich water domains in PFSA membrane are spherical at low water content, spherical with connecting channels at intermediate water …

Modeling Disk Cracks In Rotors By Utilizing Speed Dependent Eccentricity, Andrew L. Gyekenyesi, Jerzy T. Sawicki, Wayne C. Haase

Mechanical Engineering Faculty Publications

This paper discusses the feasibility of vibration-based structural health monitoring for detecting disk cracks in rotor systems. The approach of interest assumes that a crack located on a rotating disk causes a minute change in the system’s center of mass due to the centrifugal force induced opening of the crack. The center of mass shift is expected to reveal itself in the vibration vector (i.e., whirl response; plotted as amplitude and phase versus speed) gathered during a spin-up and/or spin-down test. Here, analysis is accomplished by modeling a Jeffcott rotor that is characterized by analytical, numerical, and experimental data. The …

Design And Validation Of A General Purpose Robotic Testing System For Musculoskeletal Applications, Lawrence D. Noble, Robb W. Colbrunn, Dong-Gil Lee, Antonie J. Van Den Bogert, Brian L. Davis

Mechanical Engineering Faculty Publications

Orthopaedic research on in vitro forces applied to bones, tendons, and ligaments during joint loading has been difficult to perform because of limitations with existing robotic simulators in applying full-physiological loading to the joint under investigation in real time. The objectives of the current work are as follows: (1) describe the design of a musculoskeletal simulator developed to support in vitro testing of cadaveric joint systems, (2) provide component and system-level validation results, and (3) demonstrate the simulator’s usefulness for specific applications of the foot-ankle complex and knee. The musculoskeletal simulator allows researchers to simulate a variety of loading conditions …