Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Miscibility and influence on each other of a UV photo-initiated thermosetting polymer blend of radical and cationic systems

Kevin Lefebvre — Fri, 03 May 2013 08:35:39 PDT

Thermoset blends engage an interest into polymer materials using photopolymerization. Our work is inscribed within a project which consists to control the degree of crosslinking in three dimensions during UV photo-curing. Two different reaction mechanisms were considered to enlarge the control of properties. The goal of this thesis was to check the miscibility between two thermosetting polymers using radical and cationic chemical mechanisms. Then their influence on each other was studied by thermal analysis. The experimental system was Bisphenol A propoxylate diacrylate for the radical curing and 3,4-epoxycyclohexylmethyl 3,4-cyclohexanecarboxylate for the cationic. They were initiated by 2-hydroxy-2-methylpropiophenone and Triarylsulfonium hexafluoroantimonate salts mixed respectively. Several polymer blends were manufactured and influence of weight proportions and process temperature were studied. As a result, high thermal stability and properties were determined and homogeneity of these materials was verified by Thermogravimetric Analysis. Differential Scanning Calorimetry showed that thermal properties of blended materials didn’t follow any linear blending law. It was also noticed that the temperature needs to be highly considered. The cationic resin, which used to be post-cured to reach a high degree of curing, was highly cured at 80°C. But the radical network, which used to crosslink very fast at ambient temperature, didn’t fully cure. We concluded that some interactions occur between the two systems but the presence of Interpenetrating Polymer Networks was not confirmed.

Design of Experimental Methods to Test the Performance of Pads and Helmets under Blast Loading Conditions

Kurtis Palu — Tue, 23 Apr 2013 10:05:38 PDT

Improvised explosive devices (IEDs) have become a primary weapon in conflicts against US and allied forces. Improvements in body armor and medicine have increased the survivability of such events. These factors have caused an increase in traumatic brain injury (TBI) and mild traumatic brain injury (mTBI) induced by primary blast waves. Injury mechanisms caused from primary blast waves are not clearly understood or defined. How primary blast waves interact with materials or between narrow gaps found between helmet pads is not known. Two novel test fixtures were developed to provide a basic understanding of these two issues.

The first fixture was developed to examine the helmet-head subspace focusing on the so called “underwash” affect. All tests were carried out in the shock tubes at UNL. A relationship between the peak pressures on the forehead and crown of the head and the gap distance between pads was established. Based on these experiments, optimal gap distances were determined to be 1.6”, 2.1” and 2.9” for incident pressures of 30 psi, 20 psi and 10 psi, respectively.

The second fixture was developed to investigate the blast mitigation performance of pads and other materials. Collaborative testing was performed with the Massachusetts Institute of Technology on sandwich samples filled with fluid or fluid-like materials. Results showed that below incident pressures of 20 psi the core material of the sandwich sample has little effect on the blast mitigation performance.

Pad materials currently used in the US Army ACH helmet were tested with the blast mitigation performance fixture. Comparison of high speed video footage and pressure profiles taken behind the pads showed that the peak pressure occurs before maximum displacement of the pads into the system. Theoretical stress wave transmission times were compared to experimental values. Results confirm that stress wave propagation is the primary mechanism in blast pressure transmission, compared to dynamic loading caused from local deformation.

In addition a novel device, AENID was designed to simulate an IED detonating under the floor of a vehicle such that occupant loading and kinematics can be studied in a repeatable fashion and is offered in the appendix.

Advisor: Namas Chandra

Passive and Actuated Grasping Using Superelastic Materials for Surgical Applications

Alan M. Goyzueta — Mon, 22 Apr 2013 08:30:49 PDT

This thesis presents two devices for passive and actuated grasping for surgical applications, both using superelastic materials. The first section of the thesis discusses the design, finite element analysis, and qualitative testing of a passive retainer subassembly for a Material Handling System for Natural Orifice Translumenal Endoscopic Surgery (NOTES). The purpose of the MHS is to shuttle necessary surgical items between miniature in vivo robots working inside the peritoneal cavity and surgeons outside the body through a natural orifice. The retainer subassembly is part of the actual shuttle and serves the purpose of securing the items that are loaded into the shuttle for transportation. The second part of this thesis discusses the design and quantitative testing of a laparoscopic grasper with fully compliant, monolithic jaws that deform as they grasp tissue. The goal of this device was to lessen the maximum pinch forces applied to soft tissues in an effort to prevent excess tissue trauma caused by excessive grasping forces.

Advisor: Carl A. Nelson

Predicting Vehicle Dynamics for Roadside Safety Using Multibody Systems Simulations

Brett D. Schlueter — Thu, 06 Dec 2012 12:20:38 PST

Accurate means for predicting vehicle dynamics is required in the design and testing of roadside safety hardware. Past research has used finite element (FE) modeling to this end, but multibody systems (MBS) modeling may provide a more efficient way to solve these problems. MBS modeling using Adams/Car was investigated by first compiling an introduction to the program, then performing basic vehicle dynamics simulations using a supplied model. Next, a model of a 2270 kg pickup was created and validated against physical test data involving impact with a speed bump. Finally, pickup trajectories in 4H:1V and 6H:1V V-ditches were predicted for widths of 24, 30, 38, and 46 ft.

A poor tire model and the inability to account for bumper contact led to inaccuracies in the results, and guidelines are established for scaling damper rates to compensate. For small obstacles and low impact scenarios, scaling damper rates by two produces good results. As large tire deformations and bumper contact become important, scale factors of 30 are required. Unfortunately, even high damper rates cannot fully compensate for all factors. MBS modeling may prove useful in vehicle dynamics simulations relating to roadside safety, but only for low impact events at least until a better tire model can be acquired and bumper contact definitions can be included.

Adviser: John D. Reid

Modular Joystick Design for Virtual Reality Surgical Skills Training

Michael Head — Thu, 06 Dec 2012 12:00:48 PST

A modular control interface and simulated virtual reality environment was designed and created in order to determine how the kinematic architecture of a control interface affects minimally invasive surgery. A user is able to selectively determine how many, the type, and location of degrees of freedom they require for the specific surgical simulation through the use of modular joints and constraint components. Furthermore, passive locking was designed and implemented through the use of inflated latex tubing around rotational degree of freedom joints. It is believed these features will have the ability to effectively simulate a variety of surgical simulations and thus improve surgical skills.

Advisor: Carl A. Nelson

A Study of HDPE in High Pressure of Hydrogen Gas—Measurement of Permeation Parameters and Fracture Criteria

Sompong Prachumchon — Mon, 03 Dec 2012 12:08:32 PST

The permeation parameters of hydrogen gas in high density polyethylene (HDPE) system are sought by comparison with a diffusion model. The method of Green’s functions is used to obtain solutions for the diffusion model. Permeation parameters are found from transient experimented data during two processes; pressurization followed by depressurization. The mechanical compression of HDPE during the pressurization process resulted in lower diffusivity coefficient values and higher solubility values. The results show that the diffusivity coefficient value in the pressurization process is 37% of that during the depressurization process. At the start of the depressurization process, a short-duration fast flow rate of the hydrogen gas that is observed experimentally is explained by the addition of a contact conductance to the diffusion model.

Study of the behavior of a pre-existing flaw under depressurization process of the HDPE and hydrogen gas system is included. Under quasi-static assumption, a prediction of internal pressure inside the flaw caused by diffusion using a constant volume model and a varying volume model is given. The results from these models are verified by FEM software COMSOL with a good agreement. Determination guild line of the safety of an HDPE with a pre-existing flaw with various sizes from failure by yielding, and the critical energy release rate , and the critical stress intensity factor is provided. The flaw with radius of 4 micron, 20 micron, 40 micron, 80 micron, and 100 micron located at various positions inside the Sample is used in the simulation. The results of calculation show that the Sample embedded with spherical flaw is safe from yielding. However, the Sample embedded with circular shaped flaw is fail to crack propagation when the flaw has radius greater than and equal to 20 micron while the flaw with radius of 4 micron is safe from failure. The maximum internal pressure depends on the location of the flaw in the HDPE. The time to reach the maximum internal pressure depends on the size of the flaw.

Study of 1D model and 2D model during pressurization process in COMSOL shows relative percentage difference of the diffusive flux magnitude of 16.23 percent.

Advisor: Kevin D. Cole

Optimal Reduction of Electrical Energy Consumption by Supply Air AC Motors

Keyhan Rafiee — Mon, 29 Oct 2012 06:30:42 PDT

The Nebraska Center for Energy Sciences Research (NCER) at the University of Nebraska-Lincoln (UNL) strives to be energy efficient through Green Energy. Of course, in meeting some of the requirements for different types of Leadership in Energy and Environmental Design (LEED) certification, certain minimum levels of energy efficiency practices must be met. One such level of energy efficiency, in particular, is reduction in the consumption of electrical energy in buildings. This thesis is a study of methods of reducing the consumption of electrical energy (measured in kW of electrical power) in the UNL Jorgensen Hall (JH) air handling unit 2 (AHU2) ‘fan wall’ of supply air AC motors/fans.

An analysis of the experimental results showed that the numerical values obtained for the total head loss (and the consequential power loss) from the equations employed in each energy method were sufficiently close to each other. This led to the conclusion that the equations employed in the energy methods were properly constructed. A comparison was made between the magnitudes of the head losses (and consequential power losses) associated with the work done by different motor combinations. Furthermore, this comparison was made while, in every combination, the AC motors were operating at a specific speed to move a mass of air through the AHU2 intake air duct system. The

optimal performance of the AHU2 supply air AC motors was achieved through this comparison. The specific power consumption, for every different AHU2 supply air AC motor combination tested, was also taken into consideration in order to determine the combined optimum level of performance for these motors in every setting.

The effects of friction factor on major and minor head losses and consequently on total head loss were considered. A scheme was constructed for the linear optimization of the curve for the total head loss against major head loss. It was also concluded that a particular function developed to describe the relationship between friction factor and Reynolds number is not the only relationship through which friction factor can be determined. Friction factor can be determined independent of Reynolds number.

Finally, recommendations were made so as to bring about the transitioning from one motor combination to another as smoothly as practical in order to meet the specific air supply requirements in different seasonal weather conditions. This can be achieved by way of modifying the appropriate segments of an energy management system software program in constant communication with (field) controllers at all times in order to command these AC motors (operating in different combinations) to run as closely as possible to their peak efficiencies only within a rather narrow range of speed and switching them on and off as needed at all times.

Advisor: C. W. Solomon To

Sustainability for Die Manufacturing: Comparative Study of WEDM and Milling

Matthew S. Kalus — Fri, 05 Oct 2012 13:40:42 PDT

Sustainability is more important in today's culture due to the increasing demand for a more eco-friendly society. Concentrations in minimizing and reducing environmental impacts, energy and natural resources have been forthcoming in industry. The tool, mold and die industries are the most well known industries that machine harder materials using mills and WEDM. The objective of this thesis was to compare the sustainability differences in both of these machines utilizing the accepted standards for evaluating the manufacturing process performance for sustainability. These standards include the evaluation of the process parameters, raw materials, power, tools and fluids which all contribute to different effects in the environment, machining performance and operator safety. An experiment was conducted on both machines to study the power differences by altering the machines' cutting parameters on a D2 tool steel workpiece. Current, surface roughness, metal removal rates and tool wear were documented. Increases in power and tool wear can be controlled by varying process parameters such as using cutting fluids and changing the metal removal rate. A higher metal removal rate increased the amount of power used but did not improve surface roughness. Milling and WEDM operations exhibited a similar specific energy trend which is considered another way of comparing both machines. Surface roughness was shown to be better at higher specific energies for WEDM. In milling, lower surface roughness numbers were seen in a broad range of specific energies. Overall, a correlation between the metal removal rate, power and surface roughness affected sustainability.

Advisor: Robert Williams

Improving Health Care Quality and Safety: The Development and Assessment of Laparoscopic Surgery Instrumentation, Practices and Procedures

Bernadette McCrory — Wed, 03 Oct 2012 14:30:39 PDT

Adverse events due to medical errors are a leading cause of death in the United States exceeding the mortality rates of motor vehicle accidents, breast cancer and AIDS. Improvements can and should be made to reduce the rates of preventable surgical errors since they account for nearly half of all adverse events within hospitals. Although minimally invasive surgery has proven patient benefits such as reduced postoperative pain and hospital stay, its operative environment imposes substantial physical and cognitive strain on the surgeon increasing the risk of error. In order to mitigate errors and protect patients, a multidisciplinary approach was taken to improve minimally invasive surgery. Clinical, human factors, and biomedical engineering principles and methodologies were used to develop and assess laparoscopic surgery instrumentation, practices and procedures. First, the foundational understanding and the imperative to transform health care into a high quality and safe system is discussed. Next, a generalized perspective is presented on the impact of the design and redesign of surgical technologies and processes on human performance. The remainder of this dissertation presents the experimental results of four studies used to develop and assess laparoscopic surgery instrumentation, practices and procedures. In the first experiment, a novel hand-controlled electrosurgical laparoscopic grasper was developed and evaluated to eliminate the use of foot pedals, reduce surgery-related discomfort, and minimize the risk of actuation errors. The final three studies compared the emerging technique of single-incision surgery to conventional laparoscopic surgery to determine whether there were any technical, physical or subjective performance differences across the two surgical techniques. In all, these studies contribute towards the improvement of the quality and safety of minimally invasive surgery.

Advisor: M. Susan Hallbeck

Analysis of Mechanically Milled Exchange Coupled Nanocomposite Permanent Magnets

Santanu Mukherjee — Mon, 30 Jul 2012 10:11:39 PDT

Nanocomposite permanent magnets have recently evoked wide interest because of their interesting properties. They usually consist of a hard magnetic phase having superior coercivities and a soft magnetic phase having improved values of magnetization and when they are coupled together, we get a permanent magnet with enhanced values of both the parameters and thus can be put to a lot of applications. Also to make this possible we can take advantage of the principle of exchange interaction which has been discussed subsequently in detail.

Also the microstructure plays a major role in obtaining good magnetic properties and the microstructure is usually controlled by the cooling rates i.e. the wheel speeds during the melt spinning process as well as heat treatment process i.e. annealing. Both these experimental techniques have been used to study the variation of magnetic properties of Nd12Fe82B6 and Nd10Fe84B6 which were formed using different wheel speeds. They were also annealed to study the changes in their magnetic properties. Mechanical milling was employed to improve the coercivities of the as cast system.

The next project was to build a non-rare earth permanent magnet using MnIr-Fe. Mechanical milling and subsequent annealing was used to study the changes in phase and the subsequent improvement in magnetic properties. The principle behind this was the exchange coupling of the antiferromagnetic MnIr alloy with the soft ferromagnetic Iron.

Advisor: Jeffrey E. Shield

DESIGN, ANALYSIS AND TESTING OF HAPTIC FEEDBACK SYSTEM FOR LAPAROSCOPIC GRASPERS IN IN VIVO SURGICAL ROBOTS

Nikhil Salvi — Thu, 26 Jul 2012 06:34:26 PDT

Laparo-Endoscopic Single Site (LESS) Robotics Surgery is an advanced technology in the field of Minimally Invasive Surgery (MIS). The LESS surgical robots significantly improve the surgeon’s accuracy, dexterity and visualization, and reduce the invasiveness of surgical procedure results in faster recovery time and improved cosmetic results. In a standard robotic endosurgery, the palpation of tissues is performed by laparoscopic graspers located at the end effectors. The master-slave configuration in robotic surgery leads in remote access to the operation site. Therefore, surgeon’s ability to perceive valuable sensory information is severely diminished. Sensory information such as haptics, which is essential for safe tissue and organ palpation, is not possible due to absence of direct access. Therefore, unknowingly excessive grasping forces are exerted by the laparoscopic graspers could lead to tissue trauma and vital tissues and organs damage.

This thesis presents the several aspects of haptic feedback system including a design and analysis of force sensing forearm to measure grasping forces exerting on tissues during palpation tasks, 4-CH bilateral teleoperated Impedance-Impedance based robotic control architecture for haptics and design and developments of Surgical Haptics-User Interface Devices (H-UID). The entire haptics feedback system has been implemented in miniature in vivo surgical robots and tested in animal surgeries at University of Nebraska Medical Center (UNMC). The results of bench-tops and animal surgeries in the presence of haptics were discussed. The haptic feedback system has established the ability to differentiate the different objects of different stiffness, provide appropriate grasping force control and reduce tissues palpation time as a result improve performance of the surgeon.

Advisor: Shane M. Farritor

Automated Resonant Wireless Power Transfer to Remote Sensors from an Unmanned Aerial Vehicle

Brent Griffin — Thu, 26 Jul 2012 06:19:38 PDT

Wireless magnetic resonant power transfer is an emerging technology that has many advantages over other wireless power transfer methods due to its safety, lack of interference, and eﬃciency at medium ranges. In this thesis, we develop a wire- less magnetic resonant power transfer system that enables unmanned aerial vehicles (UAVs) to provide power to, and recharge batteries of, wireless sensors and other electronics far removed from the electric grid. We address the difficulties of implementing and outﬁtting this system on a UAV with limited payload capabilities and develop a controller that maximizes the received power as the UAV moves into and out of range. We experimentally demonstrate the prototype wireless power transfer system by using a UAV to transfer nearly 5W of power to a ground sensor. Motivated by limitations of manual piloting, steps are taken toward autonomous navigation to locate receivers and maintain more stable power transfer. Novel sensors are created to measure high frequency alternating magnetic ﬁelds, and data from experiments with these sensors illustrate how they can be used for locating nodes receiving power and optimizing power transfer.

Advisers: Carl Nelson and Carrick Detweiler

Identification of a Maximum Guardrail Height for the Midwest Guardrail System Using Computer Simulation

Ramen D. Julin — Fri, 29 Jun 2012 11:11:39 PDT

W-beam guardrails are by far the most common restraint system used along both local and major roadways. Traditionally, these restraint systems have been full-scale crash tested with a rail height ranging between 27 in. and 32 in. However, the maximum rail height which allows for safe performance of guardrails, especially in impacts involving small vehicles, has never been identified.

The main concern associated with an increase of the rail height is that small vehicles, because of their low profile, may have a tendency to lift the rail and penetrate the barrier. The objective of this project was to determine the critical rail height at which small vehicles start under-riding the barrier. A potential increase of the rail location could provide several benefits in terms of an improved safety of the system with vehicles characterized by a high center of mass, economic advantages related to the maintenance of the roadside, and accommodation of potential frost-heave and erosion.

This study used computer simulations to investigate the safety of the Midwest Guardrail System (MGS) with the rail located higher than 32 in. from the ground level, considering various impact angles and grading scenarios ranging from flat terrain to minor slopes. Also, the potential problems and the influences of different frontal geometry of vehicles were considered.

With consideration given to current small car design trends, this study showed that on level terrain the MGS would satisfy MASH TL-3 evaluation criteria with rail heights up to 36 in. Furthermore, it was shown that successful containment of errant cars and trucks may be achieved on 6:1 approach slopes when the rail is mounted at 36 in., and improved pickup truck redirection was shown on 8:1 approach slopes with increased rail mounting height.

Full-scale vehicle crash tests are necessary to confirm these simulation results before these taller systems can be deemed crashworthy according to MASH and implemented.

Advisor: John D. Reid

THE INTEGRATION OF PROPANE FLAMING AND MECHANICAL CULTIVATION FOR EFFECTIVE WEED CONTROL IN AGRICULTURE

Brian D. Neilson — Thu, 26 Apr 2012 06:55:52 PDT

Flaming is a thermal weed control method that can kill weeds within or between crop rows using heat. Mechanical cultivation is another weed control method which undercuts weeds between crop rows to kill them. A combination flamer/cultivator implement was designed to take advantage of the good qualities of both flaming and cultivation to provide excellent organic weed control.

Flaming hoods were designed in the spring of 2010 and retrofitted on an existing row crop cultivator. The hoods were tested in corn and soybean field studies in the summer of 2010. Of the seven treatments tested, a treatment of flaming combined with cultivation applied twice during a season produced the highest weed control and crop yield, while maintaining low crop injury and weed dry matter.

The flaming hoods were redesigned in the spring of 2011 to be easier to manufacture. New torches were developed to replace the commercial torches previously used. A flow mixer enhanced heat transfer by reducing or eliminating film evaporation. Reducing the primary air intake decreased flame liftoff length and improved stability.

The new hoods and torches were tested in the same seven field treatments during the summer of 2011. Flaming combined with cultivation twice performed best overall again, although the actual values of the performance parameters were lower than in 2010. There are several factors which may have caused worse results in 2011 than in 2010. These include changes in weed composition and density, equipment, climate, and planting date.

Gas temperature measurements were conducted on three of the hood/torch configurations used in the field studies, as well as on open, unhooded torches. Thermocouple heat losses due to radiation were accounted for, and ranged from 0.9 percent to 29.4 percent. The hooded torches were far superior to the open torches, increasing the high-temperature region length by approximately 200 mm. The 2010 hood provided temperatures that were 36 percent higher at the hottest cross-section than the 2011 hood, but the latter performed better overall.

Adviser: George Gogos

Error Reduction and Effect of Step Size in Adjustment Calculus for Cam Applications

Sai Siddhartha Nudurupati — Wed, 25 Apr 2012 07:48:39 PDT

Any measurement, however carefully done, will never be free from errors. Similarly, machining of cams for automobiles is prone to contain errors. These errors are naturally a part and parcel of cam manufacturing. The nature of deviations of the manufactured cam profile from the theoretical cam determines its usability. Sometimes, allowable deviations in high speed cams may be in the order of 2540 µm. Larger deviations will disqualify the cams for applications.

Velocity and acceleration of the cam are estimated from the measured displacement of the cam follower during quality control implementation. This data helps in eliminating the unfit cams. Existing methods deal with a notorious challenge from propagation of measurement errors in the displacement data to predicted velocity and acceleration values.

J. Oderfeld developed a little known method called ‘Adjustment Calculus’ which is an alternative method for this purpose. This method combines the ‘marching point’ method that fits a polynomial to discrete data and a symmetric Stirling interpolation method. Until now, adjustment calculus has been applied to reduce errors in acceleration data. In this work, adjustment calculus is implemented to velocity predictions. ‘Weights’ for calculation of adjusted velocity are derived using a cubic polynomial fit and symmetric Stirling interpolation formula. The effect of step size on application of adjustment calculus to different cam profiles is probed using the Monte Carlo method.

Effective step size for practical applications in automotive cam quality control is suggested for each cam profile. Practical pointers for application to cam inspection for velocity and acceleration analysis are formulated.

Adviser: Wieslaw M. Szydlowski

A Conductivity Testing System Coupled with a Tensile Testing Machine to Measure the Surface Properties of Polymer Specimens

Nguyen T. Nguyen — Mon, 23 Apr 2012 12:43:34 PDT

Polymers play an essential role in our everyday life due to their employment in a widespread range of applications. Polymers are used in industries such as space, biomedical, electronics, etc. in which their electrical and mechanical properties are major aspects which need to be investigated prior to implementation. When subjected to mechanical stimulations, polymers may exhibit changes in electrical conductivity which can vary locally within the specimens, especially in those of conducting polymers. In mechanical investigations a tensile testing machine is used to understand polymers’ strength, elasticity or other mechanical properties. In electrical analysis, using a four-point probe to examine the electrical resistivity (conductivity) of a material is also frequently applied. However, no studies have been done to explore the relationship between mechanical manipulations and changes in electrical properties in situ. The current study explores this relationship.

An electrical conductivity testing system is designed and developed to couple with a tensile testing machine to measure the electrical conductivity of polymeric specimens while experiencing tensile loading. The system features a commercial four-point probe sensor, which is automatically controlled to approach a specimen and to measure the electrical conductivity of that specimen locally in two directions: longitudinally and transversely to the axis of stress. The method of testing is then implemented to experiment on specimens of high density polyethylene. Other types of specimens such as carbon nanotubes/polyethylene composites and metallic surface layer deposited polyethylene are also tested. Descriptions of the development process of the robotic systems and results of the execution are presented.

Advisor: Carl A. Nelson

Microstructure Selection of Sm-Co-Al Alloys to Increase Magnetization

Brian Dick — Thu, 19 Apr 2012 08:44:25 PDT

An ever increasing demand for higher performing magnets drives the need for new and innovative methods to achieve this goal. Sm-Co rare earth permanent magnets have a unique eutectic microstructure that, through refinement, could become a two-phase magnet which would significantly increase their energy product. The eutectic structure of Sm₈Co₉₂ is comprised of αCo rods embedded within a Sm₂Co₁₇ matrix. If the rods are small enough to encourage exchange coupling and the matrix is smaller than the single domain limit, then an efficient two-phase magnet is created.

Refining the Co rods and matrix size were the goal of this research. The method used to accomplish this goal was through adding Aluminum. Al was added in increments from 1-5 atomic percent. The goal of adding Al was to increase the number of nucleation sites and so increase the number of rods and decreasing their size. The Al would also act as an obstacle that the forming phases would have to push out of the way, slowing their progress. The beneficial by-product of the refinement of the microstructure is an increase in coercivty.

With the addition of Al to the alloy the average αCo rod size was reduced from 300 nm to about 70 nm. This was accomplished at a melt spinning wheel speed of 10 m/s. Therefore at higher wheel speeds this would be reduced further. Also it was shown that the volume fraction of aCo remained relatively constant throughout.

Magnetic analysis was performed and the coercivity of Sm₈Co₉₂ with additional 3% Al was not higher than Sm-Co magnets. This could be due to several factors but not to a creation of different phases. It was shown through x-ray diffraction that no new phases were formed when higher melt spinning wheel speeds were used.

With the addition of Al, the microstructure is considerably refined with the addition of up to 5% Al.

Advisor: Jeffrey E. Shield

Effects of Approach Techniques in Place Kicking: A 3D Analysis

Chase M. Pfeifer — Thu, 19 Apr 2012 07:58:28 PDT

Various studies aim to understand the fundamentals of kicking, primarily the instep kick commonly used by soccer players. Of those studies, most are limited to a 2D analysis using high-speed cameras for position tracking and electromyography to observe muscle activity. The few studies that investigate a 3D model are limited in their position tracking capabilities and focus mainly on joint flexion potentials and foot speed. To the authors knowledge no study of this caliber has been performed on the kinematics and dynamics of place kicking in American football. This thesis uses a 12 camera high-speed motion tracking system to investigate the kicking techniques of three place kickers of different experience levels by observing several kicks from each. Results demonstrate that the quality of a place kick cannot be determined solely on foot speed but direction and location of foot velocity and the force of the kicking leg at impact. Position and orientation of the plant foot proves to be a driving factor in producing a more ideal effective kinetic energy as well as direction of foot velocity upon impact.

Advisor: Jeff A. Hawks

Development and Recommendations for a Non-Proprietary, High-Tension, Cable End Terminal System

Ryan J. Terpsma — Thu, 12 Apr 2012 10:30:44 PDT

Cable guardrail systems have been increasing in popularity in recent years due to several perceived benefits over the commonly used W-beam guardrail. A non-proprietary design was desired as an alternative to the many proprietary designs available. A non-proprietary, high-tension cable end terminal was necessary to accompany the non-proprietary, high-tension cable guardrail system under development.

The objective of this research project was to develop design recommendations for a non-proprietary, high-tension cable end terminal. An analysis of several cable guardrail end terminals was undertaken to identify any common features that may prove to be beneficial or detrimental to end terminal designs. Next, a study of the non-proprietary low-tension system was conducted to determine the cause of vehicle instabilities in full-scale testing. Since the high-tension and low-tension cable end terminal designs are similar, it is likely that any issues with the low-tension design will also be evident in testing of the high-tension design.

LS-DYNA modeling of current cable terminal anchor hardware was then accomplished and compared to bogie testing results. The anchor model proved to be sufficiently accurate to preliminarily analyze alternative cable anchor designs.

A final, optimized, high-tension cable anchor design was produced along with alternative terminal post recommendations for continuing development of the non-proprietary, high-tension cable end terminal.

Advisor: John D. Reid

Material Handling System for Robotic Natural Orifice Surgery

Jeff Midday — Tue, 10 Apr 2012 09:07:08 PDT

Natural Orifice Translumenal Endoscopic Surgery (NOTES) is a relatively new surgical approach which uses no external incisions, thereby improving cosmetic outcomes, decreasing overall recovery time and reducing the risk of external infection. In standard NOTES, flexible endoscopic tools have been used to carry out a variety of surgical procedures in the abdomen. As an alternative, miniature in vivo robots can be fully inserted into the peritoneal cavity and utilized to perform various surgical procedures. These in vivo robots eliminate tool triangulation issues, improve multi-tasking capabilities and greatly increase freedom and dexterity when compared to standard endoscopic and laparoscopic tools. One major limitation is that once inserted, the in vivo robots are isolated within the abdomen and cannot send or receive materials to the external environment. The focus of this thesis is a Material Handling System (MHS) that has been developed to bridge this deficiency.

This system features a flexible silicone overtube and an open-loop control system with manual and automatic operation capabilities. The system utilizes the helix of a spring to advance a payload along the length of the overtube. All of the design rationale, design decisions, components and materials are discussed. Additional description of all of the electronic hardware, coupled with the programming logic, provides detailed insight into the open-loop control strategy. The bench-top and in vivo testing results of the completed device are presented.

This thesis also addresses finite element modeling of the dimensional changes of silicone tubing under bending. The model looks at the complex issue of modeling a continuum rubber such as silicone, validated experimentally. The model provides general guidelines for the bending and kinking properties of a wide variety of tubing diameters and thicknesses. This tubing model can increase an engineer’s ability to properly dimension and tolerance an overtube, such as that found in the MHS, based on the bending criteria of the device.