Browsing by Author "Dr. Eric Klang, Committee Member"

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Advancement of Online Systems in Engineering by Expert TA
(2006-09-04) Morton, Jeremy Andrew; Dr. Thomas Honeycutt, Committee Member; Dr. Kevin Lyons, Committee Member; Dr. Larry Silverberg, Committee Chair; Dr. Eric Klang, Committee Member
This dissertation introduces a new online system called Expert TA. The system was developed based on the hypothesis that expressions are key elements in engineering problems and that the treatment of expressions is critical to the advancement of online systems. This dissertation identifies ergonomic problems with expression entry that Expert TA overcomes through the use of a problem-customize integrated expression editor, called a palate. Then the dissertation shows, using an expression analyzer that operates in the background of Expert TA, that specific mathematical mistakes within an entered expression can now be located. Emulating standard instructional practices, detailed feedback pertaining to specific mistakes and grading on the basis of specific mistakes is now possible.
Behavior of GFRP Bridge Decks for Highway Bridges
(2005-12-06) Nelson, James Lee; Dr. Eric Klang, Committee Member; Dr. Emmett Sumner, Committee Member; Dr. Sami Rizkalla, Committee Chair
This research presents the results of an experimental program undertaken at the North Carolina State University (NCSU) Constructed Facilities Laboratory (CFL) to evaluate the performance of a new innovative glass fiber reinforced polymer (GFRP) bridge deck. This bridge deck is produced commercially by Martin Marietta Composites of Raleigh, NC under the trade name of DuraSpan. The experimental program involved examining the behavior of 5.00 inch deep and 7.66 inch deep DuraSpan bridge deck profiles. The program included numerous quasi-static flexural tests, testing of connection details to facilitate the development of a railing system, evaluation of the performance of the bond lines in negative moment regions, and an evaluation of the coefficient of thermal expansion. A finite element model was developed to predict the stiffness of the bridge deck at service load levels. Finite element optimization techniques were used in conjunction with coupon test data and the large scale flexural test data to calibrate the model.
Characterization of Epoxy-hybrid nano-particle Resins for ambient cure VARTM Processes
(2008-05-10) Caldwell, Mary Kathryn; Dr. Eric Klang, Committee Member; Dr. Kara Peters, Committee Chair; Dr. Jeffrey Eischen, Committee Member
This thesis presents the mechanical characterization of fire resistant epoxy-hybrid resin systems suitable for ambient cure VARTM processes. Several new epoxy-hybrid nano-particle resins were developed and tested for use in large scale composite structures. Based on the viscosity, Tg, and cure time requirements twelve of these resins systems were pre-selected for mechanical testing. Neat resin castings were tested in tension to determine the elastic modulus, tensile strength and maximum elongation. From these results, six of the resin systems were further cast in unidirectional glass fiber laminates. Transverse tension and short beam shear testing was performed on all laminates to determine the mechanical properties of the glass/epoxy systems. Two of the epoxy-hybrid resin systems showed promising behaviors, having a higher transverse modulus and ultimate strength than the original benchmark vinyl-ester resin. Additionally, fiber Bragg grating sensors were embedded in one benchmark vinyl-ester laminate and one epoxy-hybrid laminate during the cure cycle. Taking advantage of both the extrinsic and intrinsic properties of these sensors, residual strains, temperature changes, and degree of cure of the resin were monitored. In addition to having a higher modulus of elasticity and ultimate strength, these new epoxy-hybrid nano-particle resin laminates showed minimal temperature increases during cure and smaller residual strains than the comparable vinyl-ester resin laminates.
The Design, Analysis, Construction and Testing of an Uninhabited Aero Vehicle Platform
(2003-12-31) Burgun, Robert Scott; Dr. James Selgrade, Committee Member; Dr. Eric Klang, Committee Member; Dr. Charles E. Hall Jr, Committee Chair
An uninhabited aero vehicle platform design is presented. This encompasses the landing gear system and the structures of the vehicle. The landing gear system consisted of the design, construction and testing of the main and nose gears. The testing of the landing gear resulted in a valid system that could then be integrated into the vehicle. The vehicle structures are composed of various configurations of composite sandwiches. Extensive material testing was conducted to experimentally produce the physical properties of the materials. These properties and techniques can be utilized by other vehicle designs. The structural design was refined and ultimately verified within a finite element analysis program, ANSYS. This analysis implemented a composite shell element that utilized all of the material properties gained from the material testing. This work resulted in an analyzed and constructed vehicle. Ultimately the vehicle was load tested to verify the analytical results.
The effects of sloped ground on the hip, knee, and ankle joint kinetics and kinematics during manual lifting tasks.
(2002-08-21) Shin, Gwanseob; Dr. Eric Klang, Committee Member; Dr. Carolyn Sommerich, Committee Member; Dr. Gary A. Mirka, Committee Chair
The biomechanical effects of sloped ground on hip, knee, and ankle joint moments and lifting posture during sagittally symmetric manual lifting were investigated using a two-dimensional five-segment dynamic biomechanical model. Subjects' motions were traced and recorded at 60Hz by Flock of Birds magnetic tracking system as they lifted a 10 kg cubic box on five sloped grounds; two declined slopes (-20°, -10°), two inclined slopes (+20°, +10°), and flat ground (0°), using three lifting techniques; back lift, freestyle lift, and leg lift. Fifteen trials were tested and each trial involved repetitive lifting (6 to 9 lifts per trial) for 50 seconds. The kinetic and kinematic effects were examined by computing the peak net reactive moments at the hip, knee, and ankle joints, and measuring peak segment flexion angles of the trunk, thigh, and leg (shank). Results indicated that the peak joint moments and peak segment angles were significantly affected by slope angle and lifting technique (α = 0.05). The inclined slope angles (10° and 20°) caused up to 6.8 % and 14.3 % larger peak hip moments than flat ground during the freestyle and leg lifts, respectively. The lowest peak hip moment (236.48 Nm) was observed during the leg lift on flat ground and the largest peak hip moment (302.62 Nm) occurred during the back lifts on flat ground. The components contribution analyses showed that the two static components (vertical reaction static force on the shoulder joint and the trunk mass) were main contributors to the responses of peak hip moment to changes in slope angle. The leg lift technique produced significantly less peak joint moments than other lifting techniques regardless of slope angle. The mean peak hip moment was 16.0 % and 10.5 % less in the leg lift technique (251.0 Nm) than in the back (298.8 Nm) and freestyle lift (280.4 Nm) respectively. Specifically, trunk angular acceleration acted as a major contributor to the significant difference in peak hip moments between the back lift and the leg lift. The trunk angular acceleration, peak flexion angles of the trunk, thigh, and shank separated the leg lift from the back lift.
Electronically Towed Micro Vehicles
(2003-09-25) Sanders, Keith; Dr. Larry Silverberg, Committee Member; Dr. M. K. Ramasubramanian, Committee Chair; Dr. Eric Klang, Committee Member
In recent years, tremendous advancements have been made in the area of intelligent vehicle systems, autonomous vehicles, and remote navigation. Applications of such advancements vary from highway transportation systems, to military convoys, to unmanned exploration of dangerous environments. The evident benefits of these intelligent vehicle systems include more efficient travel, transportation of multiple vehicles by a single driver, and remote exploration of hazardous or otherwise dangerous terrain. The purpose of this research is to develop and implement an electronically towed micro vehicle system using a 1/10 scale R/C car as the platform. The system will use minimal external sensors and will be capable of following a lead vehicle through various maneuvers at various speeds. The scope of the project includes modifying an R/C car for autonomous control by a microprocessor, establishing a wireless link between two vehicles for direct communication, and developing a control algorithm that will enable the towed vehicle to follow a leader operated by radio control. The towed vehicle will rely on information transmitted from the leader as well as from on board sensors to determine the path of the leader and follow accordingly. Several experimental tests have been conducted to test the performance and determine the limits of the system. The results of these experiments demonstrate a working leader follower system implemented on 1/10 scale vehicles. Future development and research will be aimed at implementing this system on full scale automotive vehicles for transportation or military applications.
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.
Mechanics of fabric drape
(2004-07-08) Pandurangan, Pradeep; Dr. Eric Klang, Committee Member; Dr. Traci May-Plumlee, Committee Member; Dr. Jeffrey Eischen, Committee Chair
Three dimensional virtual representations of fabrics done based on particle modeling lack accuracy in their representation of various fabrics due to very little understanding of how fabric mechanical properties affect drape. Particle models represent cloth as a mesh of particles connected by springs. The springs exert forces on the particles causing them to move thus representing the deformation of fabric. The spring constant values input to the simulation correspond to the mechanical properties of the modeled fabric. Fabric mechanical property values obtained from standard testing like the Kawabata evaluation cannot be input directly to the particle modeling software to produce simulations resembling reality. A systematic way of selecting various input parameters to the particle model is developed by comparison of 3D scans of the drape of simple forms of various fabrics to matching simulations produced by the particle model. Since drape is a complex function of many unpredictable variables a simple way of varying only a few parameters in simulations without compromising on their resemblance to reality has been developed. Subtle and not-so-subtle differences in drape shapes occur each time a fabric is draped. This nearly random behavior presents a challenge for deterministic modeling approach. Criterions are developed based on drape variability studies for the classification of a simulation as a good match to reality or not and a relationship is developed between measured fabric material properties and simulation input parameters. The relationship was then tested on more complex apparel and found to produce excellent results. A theoretical approach was developed to determine how various spring constants that are input to the particle model simulation affect drape shapes. A simplified 2D (a strip of particles) version of the particle model was programmed in order to compare its deformation with that of a cantilever beam undergoing large deflections. By comparing the deflection of the particle model beam to the theoretical results a relationship was developed between material constants input to the simulated particle model beam and the standard material constants for a beam such as modulus of elasticity.
Modeling of the Damping Contributions of O-rings in a Submergible Six-Axis Load Cell.
(2006-04-28) Davis, Luke Allen; Dr. Eric Klang, Committee Member; Dr. Eddie Grant, Committee Member; Dr. Kara Peters, Committee Chair
The objective of this research is to provide general guidelines and calibration procedures to accurately model and improve the response time of submergible 6-axis load-cells based on multiple beam configurations sealed with compressible o-rings. This objective is achieved by adding a damping contribution to the existing stiffness model through an appropriate time derivative function. Data collection parameters are experimentally determined to control the noise and prevent the time derivative from becoming unstable. The effects of o-ring type and material properties on the stiffness of a particular submergible six-axis load cell are determined. Following the stiffness study, the damping matrix is derived from data collected during various loading cases, assuming that the damping effect can be modeled as constant in time. A comparison of the effect of material properties, results from stiffness tests, and other data are performed to determine their effect on the damping matrix. Finally, the assumption of constant damping is evaluated through the comparison of the modeled response to the measured system response.
Observations on Upstream Flame Propagation in Ignited Hydrocarbon Jets
(2006-05-09) McCraw, Jennifer Leigh; Dr. Kevin Lyons, Committee Chair; Dr. James Leach, Committee Member; Dr. Eric Klang, Committee Member
Studies are presented that examine the development of combustion in an initially non-reacting methane jet after ignition at a downstream location. Image measurements depicting the axial location of a fixed energy ignition source that permits transient flame propagation back to the nozzle are presented. The results from the experimental investigations are discussed. Nine different cases were investigated in order to determine the major parameters that impact the axial location of the ignition source at which flame propagation back to the burner was permitted. When the ignition source was located at larger axial distances than those indicated, flame propagation upstream to the burner was not possible and, instead, the flame blew out. The Reynolds number of the jet, the scalar field and the air co-flow magnitude were investigated for their contributions. A standard digital video camera was used in order to film the ignition of the jet and to determine the farthest axial location from the burner at which upstream flame propagation was possible. With the aid of computer software, the height for each case was determined. Conclusions to the effect these parameters had on the axial location are discussed as well as the implications for the physics governing the process.
Optical Property Changes in Deformable Lenses
(2007-04-24) Sigmon, Doug Jeremy; Dr. Mohammed Zikry, Committee Member; Dr. Eric Klang, Committee Member; Dr. Jeffrey Eischen, Committee Chair
The purpose of this research has been to develop a model to predict the change in optical parameters of a lens due to imposed mechanical deformation. Single curve and double curve lens models were developed using geometrical parameters taken from contact lenses. Deformation was imposed on the surface of the lens and the change in the radius of curvature and focal length were computed. Analytical models as well as two dimensional and three dimensional finite element models were developed. The finite element models consider loading situations and the impacts on the lens radius of curvature, as well as the ability of the lens to focus on a single point. The three dimensional models show a change in focal length corresponding to a power change of two diopters for modest imposed deformations. Analysis of the model suggests lens materials with lower elastic moduli have more advantageous lens properties. The model suggests larger deformation would give larger power changes if desired.
Shear Response and Bending Fatigue Behavior of Concrete-filled Fiber Reinforced Polymer Tubes
(2004-11-29) Ahmad, Iftekhar; Dr. Eric Klang, Committee Member; Dr. Amir Mirmiran, Committee Chair; Dr. James M. Nau, Committee Member; Dr. Sami Rizkalla, Committee Member
Recent field applications and research findings have demonstrated the effectiveness of concrete-filled fiber reinforced polymer (FRP) tubes (CFFT) as an efficient and promising hybrid system for designing main components such as pier columns, girders and piles for a bridge system. The vision was to provide a cost-competitive unified system composed of FRP/concrete hybrid members, which may act as a viable alternative to conventional reinforced and prestressed concrete structural systems. To achieve their broad-based implementation in civil infrastructure, understanding of their behavior and developing analytical tools under full spectrum of primary and secondary load demands are essential. Response characterizations under primary load demands namely, axial compression, flexural and axial-flexural, and seismic loadings have already been reported. However, investigations under primary shear and secondary fatigue load demands remain to be addressed. The present study consists of two phases. In the first phase, an experimental and analytical investigation was undertaken to characterize the behavior of a CFFT beam. Study on shear was primarily focused on the deep beam behavior. Comparisons of behavior of deep, short and slender beams were also highlighted. A strut-and-tie model approach, pertinent to analysis of deep reinforced and prestressed concrete members, was proposed to predict the shear strength of deep CFFT beams. Prediction showed good agreement with test results. It was concluded that shear failure mode is only critical for beams with shear span less than their depth. In the second phase, a detailed study on flexural fatigue behavior and modeling was undertaken. The main objective was to evaluate the performance of beams under four basic criteria; i) damage accumulation ii) stiffness degradation, iii) number of cycles to failure, and iv) reserve bending strength. Effects of laminate fiber architecture, reinforcement index, load range, and end restraint on the fatigue response of CFFT beams were addressed. A fiber element was developed, capable of simulating sectional strain profile and moment curvature at any given time or number of cycles under single and two stages of loading. The model can also predict deflections at mid-span, and can analyze the reserve bending response of a fatigued CFFT beam. Parametric study revealed that flexural fatigue performance of CFFT beams could be enhanced by increasing reinforcement index and the effective elastic modulus in the longitudinal direction.