Browsing by Author "Dr. Gregory Buckner, Committee Member"

Now showing 1 - 8 of 8

Automated Method For Fiber Length Measurement
(2006-08-04) Tompkins, Michael; Dr. Jon Rust, Committee Co-Chair; Dr. M.K. Ramasubramanian, Committee Co-Chair; Dr. Jeffrey Joines, Committee Member; Dr. Gregory Buckner, Committee Member
The price of cotton is dictated by quality and the most significant factor of contributing to the fiber quality is the length distribution of the fibers contained within the population. Therefore it is of importance to accurately and repeatably measure the length of fibers within a population so that it is graded properly. Current methods are inadequate and thus prior work focused on designing a machine to directly measure individual cotton fibers using digital imaging. The current work begins with the evaluation of the effectiveness of the digital imaging machine. The machine was evaluated and sources of error identified. Modifications were implemented in an attempt to improve the error. After multiple modifications with little success an entirely new design was conceptualized. The new design aimed to eliminate all major sources of error with the existing machine while not creating new sources of error. The new design is discussed and the results are compared to those obtained by the original imaging machine. The new machine was better able to accurately measure the length of cut length fibers. The variation between fibers within a sample and entire samples of cut length fiber was significantly decreased when compared to the variation of the previous system.
Development of a Ground-based Test Facility for Studying Reel-in Dynamics of Tethered Satellite Systems.
(2006-12-06) Newsome, Justin Carlyle; Dr. Andre Mazzoleni, Committee Chair; Dr. Gregory Buckner, Committee Member; Dr. Larry Silverberg, Committee Member
Tethered Satellites offer benefits for the space industry. Several applications are being found which utilize their unique dynamics; from sensing characteristics of the atmosphere to providing a propellantless mode of propulsion. Ground-based experimentation is useful as a cost effective means to develop a thorough understanding of tether dynamics. A number of experiments are required to fully investigate the behavior. After examining a number of experiments previously conducted, a new experiment is devised and tested. The experiment consists of designing a low friction representation of a satellite, the design of a stationary post to be tethered to the satellite representation, choosing an adequate test facility, and developing a means of acquiring data from the experiment. In order to check that the experiment is a useful tool for tether analysis, a mathematical model for the system is developed and then the experimental and mathematical results are compared.
Experimental Characterization and Modeling of Electro-Mechanically Coupled Ferroelectric Actuators
(2008-11-13) York, Alexander; Dr. Stefan Seelecke, Committee Chair; Dr. Gregory Buckner, Committee Member; Dr. M.K. Ramasubramanian, Committee Member; Dr. Ralph Smith, Committee Member
Piezoelectric actuators used in nano-positioning devices exhibit highly non-linear behavior and strong hysteresis. The rate-dependence of piezoelectric materials resulting from the kinetics of domain switching is an important factor that needs to be included in realistic modeling attempts. This thesis provides a systematic study of the rate-dependent hysteresis behavior of a commercially available PZT stack actuator. Experiments covering full as well as minor loops are conducted at different electro-mechanically coupled loading conditions with polarization and strain recorded. In addition, the creep behavior at different constant levels of the electric field is observed. These experiments provide evidence of kinetics being characterized by strongly varying relaxation times that can be associated with different switching mechanisms. Finally, an electro-mechanically coupled free energy model for polycrystalline ferroelectrics is presented that is based on the theory of thermal activation. It is capable of predicting the hysteretic behavior along with the frequency-dependence present in these materials. The electro-mechanically coupled model also predicts the behavior of spring coupled actuators under various pre-stress levels. The model will be coupled with a SDOF model of a commercial nano-positioning stage (Nano-OP30, Mad City Labs) and is the basis for future control applications.
Experimental Investigation of Rate-Dependent Inner Hysteresis Loops in PZT
(2005-04-27) York, Alexander; Dr. M. K. Ramasubramanian, Committee Member; Dr. Stefan Seelecke, Committee Chair; Dr. Gregory Buckner, Committee Member
The rate-dependence of piezoelectric material resulting from the kinetics of domain switching is an important factor that needs to be included in realistic modeling attempts. This paper provides a systematic study of the rate-dependent hysteresis behavior of a commercially available PZT stack actuator. Experiments covering full loop as well as first, second, third and forth order reversals are conducted at different loading rates with polarization and strain recorded. Creep behavior at different constant levels of the electric field is also observed. The kinetics are characterized by strongly varying relaxation times that can be associated with different switching mechanisms. Inner hysteresis loops in the (P, E) diagram are also shown to have different characteristics depending on the electric field level at the reversal points.
Feasibility Study of Laser Ablation using Long Pulsed 300W, CW Single Mode Fiber Laser
(2005-06-27) Dilwith, Jason; Dr. Juei-Feng Tu, Committee Chair; Dr. Eric Klang, Committee Member; Dr. Gregory Buckner, Committee Member
Many applications now require micro sized holes that are difficult to produce with conventional methods. The entrance of lasers in the industry has brought about a better method for producing these holes. However the ultra-short pulse lasers that are normally used are extremely expensive and require many pulses to remove the material due to the small amount of energy they deposit. The objective of this research is to examine the feasibility of laser ablation using a 300W, CW Single Mode fiber laser which has high continuous power output for each pulse and has excellent beam quality. The results show that laser ablation occurs when a 100mm lens is used with pulse durations at 40 microseconds or below. Using one 18 microsecond pulse, a blind hole of 43.6 microns in diameter and 23.6 microns in depth with an aspect ratio of 0.54 can be created with little heat affected zone. This performance is comparable to nanosecond lasers, but with much higher hole depth per pulse. It was also found that the pulse duration must be short enough so that the ablating effect of the initial spike of an enhanced pulse is not nullified due to melting. At longer pulse durations (50 microseconds or more), raised surfaces are created instead of holes.
Force modeling and deflection compensation of miniature ball end mills
(2003-07-25) Clayton, Stuart Harold; Dr. Ronald Scattergood, Committee Member; Dr. Thomas Dow, Committee Chair; Dr. Gregory Buckner, Committee Member
The primary objective of this research is to increase the quality and productivity of precision milling operations. More specifically, increased accuracies and reduced costs are desired for die fabrication of injection molds when small flexible tools are required. The problem with miniature tools is their radial compliance. Typical machining forces in die materials such as hardened steels can cause significant tool deflection. When features on the order of 100 μm are desired, tool deflections can cause form errors exceeding 20% of the desired geometry. There were two main goals of this research: 1) to develop an accurate cutting force model and 2) to design and implement a spindle actuation system utilizing real-time forcefeedback machining. The first goal was to gain knowledge and understanding of the machining process by predicting cutting forces for miniature tools. The second goal involved the design of a closed loop actuated spindle system that can manipulate a tool path in one dimension. A precision actuated spindle allows real-time implementation of deflection compensation algorithms to reduce geometric form errors from tool deflection. The results from this research indicate that machining forces for miniature ball end mills are both predictable and repeatable. Experimental tests were conducted using a variety of two-flute ball end mills, workpiece materials, chip areas, upfeeds, and tool tilts. It was shown that the cutting force model provides a complete dynamic understanding of the machining forces and paves the way for the actuation system that was built into the tool spindle. Two different control algorithms were tested and proven successful as feature errors were reduced with each technique. The first algorithm involved an open loop technique where the force model was used to create an altered tool path that compensated for tool deflection. This was accomplished by predicting the machining forces, dividing by the appropriate tool stiffness to obtain deflection, and superimposing the deflection onto the original tool path. The second algorithm entailed closed loop control with forcefeedback machining using a newly designed PZT actuated spindle. The machining forces, which were used to predict tool deflection, were measured with a force transducer. The tool was moved in response to the deflection using a PID controller that regulated the voltage to a pair of PZT actuators. Errors produced from tool deflection were reduced with both control techniques. Experimental results showed that both control techniques, open and closed loop, reduced errors. The open loop compensation methods reduced error by approximately 65%, while the closed loop compensation methods reduced errors by 80%.
Improving The Dye House Through The Removal Of Unwanted Bottlenecks By Modernization And Energy Conservation
(2002-10-31) Hollar, Edward Eugene; Dr. Gregory Buckner, Committee Member; Dr. James W. Leach, Committee Co-Chair; Dr. Herbert M. Eckerlin, Committee Co-Chair
The purpose of this research has been to find ways to improve a package dye house through modernization and energy conservation. The research involved six months of floor studies done at the dye house, two assessments done by the Industrial Assessment Center, and research into ways to save energy and increase productivity. The dye house does not have any energy conservation systems in place, and there is a lot of opportunity to save energy if one was in place. This thesis details an energy conservation program that will help conserve energy with very little cost. The total energy savings recommended for this program is 18,579 MMBtu per year. The total cost savings is $81,258 per year. In addition to the energy conservation program, this thesis recommends a major modernization project. The dye house produces 200,000 lb a week, but its limiting factor is not the dye machines. The dryers at this facility control production levels. These dryers are very old and inefficient. The dye house should install two super dryers to replace all existing dryers. The project will take less than 3 years to implement and presents a simple pay back of 3 months. The energy savings are 84,856 MMBtu per year. This is a cost savings of $481,711 per year. In addition to the energy savings, the super dryer will save an estimated $3,141,759 per year in productivity savings. The total cost savings for this project is $3,623,470 per year. The implementation cost is $914,253.
Surface Finish and Form Fidelity in Diamond Turning
(2008-08-11) Lamonds, Donald Lucas; Dr. Thomas Dow, Committee Chair; Dr. Gregory Buckner, Committee Member; Dr. Ronald O. Scattergood, Committee Member