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 Department: Department of Engineering Technology
Mechanical Characterization of A2 and D2 Tool Steels By Nanoindentation

Mechanical Characterization of A2 and D2 Tool Steels By Nanoindentation

Date: May 2012
Creator: Okafor, Uzochukwu Chimezie
Description: Nanoindentation technique was used to investigate the surface properties of A2 and D2 tool steel subjected to different heat treatments. the mechanical characteristics of these two easily available tool steels were studied based on microstructural images obtained from SEM, the grain growth after heat treatment using X-ray diffraction method and nanoindentation technique. the investigation showed that a single nanoindentation result can explain how heat treatment influences reliability and failure in A2 and D2 tool steels. in this work, the causes and effects of these variations were studied to explain how they influence reliability and failure in A2 and D2 tool steel. Finally, a cube-corner indenter tip was used to determine the fracture toughness of silicon wafer. the emphasis of this research is on how nanoindentation technique is more extensive in material characterization.
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Nominal Shear Strength of Cold-formed Steel Shear Walls Using Osb Sheathing

Nominal Shear Strength of Cold-formed Steel Shear Walls Using Osb Sheathing

Date: May 2012
Creator: Li, Chao
Description: In the cold-formed steel construction, the oriented strand board is a common material for shear wall sheathing. an OSB is made by using wood chips as raw materials that undergo high temperature pressing to create a multi-larger structure material. Due to the OSB having a high strength in shear, it is an important material used in the construction field. the thesis is trying to verify published nominal shear strength in AISI-213-07 in the first part. This objective has two parts: the first part is to verify nominal shear strength (Rn) for wind and other in-plane loads for shear wall. the second part is to verify nominal shear strength (Rn) for seismic and other in-plane loads for shear wall. Secondly, the thesis verifies the design deflection equation for nominal shear strength of CFS shear walls with OSB sheathing. the test specimens were divided into eight groups which trying to verify the design deflection equation that was published in AISI-213-07 standard.
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Ota-quadrotor: An Object-tracking Autonomous Quadrotor for Real-time Detection and Recognition

Ota-quadrotor: An Object-tracking Autonomous Quadrotor for Real-time Detection and Recognition

Date: May 2012
Creator: Coelho, Gavin
Description: The field of robotics and mechatronics is advancing at an ever-increasing rate and we are starting to see robots making the transition from the factories to the workplace and homes as cost is reduced and they become more useful. In recent years quadrotors have become a popular unmanned air vehicle (UAV) platform. These UAVs or micro air vehicles (MAV) are being used for many new and exciting applications such as aerial monitoring of wildlife, disaster sites, riots and protests. They are also being used in the film industry, as they are significantly cheaper means of getting aerial footage. While quadrotors are not extremely expensive a good system can cost in the range of $3000 - $8000 and thus too costly as a research platform for many. There are a number of cheaper open source platforms. The ArduCopter is under constant development, has the largest community and is inexpensive making it an ideal platform to work with. The goal of this thesis was to implement video processing on a ground control station allowing for the ArduCopter to track moving objects. This was achieved by using the OpenCV video-processing library to implement object tracking and the MAVLink communication protocol, available on the ...
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Recommended Modified zone Method Correction Factor for Determining R-values of Cold-Formed Steel Wall Assemblies

Recommended Modified zone Method Correction Factor for Determining R-values of Cold-Formed Steel Wall Assemblies

Date: May 2011
Creator: Black, John
Description: Currently, ASHRAE has determined the zone method and modified zone method are appropriate calculation methods for materials with a high difference in conductivity, such as cold-formed steel (CFS) walls. Because there is currently no standard U-Factor calculation method for CFS walls, designers and code officials alike tend to resort to the zone method. However, the zone method is restricted to larger span assemblies because the zone factor coefficient is 2.0. This tends to overestimate the amount of surface area influenced by CFS. The modified zone method is restricted to C-shaped stud, clear wall assemblies with framing factors between 9 and 15%. The objective of the research is to narrow the gap of knowledge by re-examining the modified zone method in order to more accurately determine R-Values and U-Factors for CFS wall assemblies with whole wall framing factor percentages of 22% and above.
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Effect of Polyphosphoric Acid on Aging Characteristics of PG 64-22 Asphalt Binder

Effect of Polyphosphoric Acid on Aging Characteristics of PG 64-22 Asphalt Binder

Date: December 2010
Creator: Ramasamy, Naresh Baboo
Description: This research presents the results on an experimental investigation to identify the effect of polyphosphoric acid (PPA) on aging characteristics of an asphalt binder. Addition of PPA to asphalt binders is said to improve performance of flexible pavements. Asphalt binder PG 64-22 in modified and unmodified conditions was subjected to aging in the laboratory using a regular oven and also simulated short term aging using rolling thin film oven (RTFO) test. Aging experiments were conducted to analyze the extent of oxidation in terms of changes in molecular structure of the asphalt binder. These changes were appraised using Fourier transform infrared (FTIR) spectroscopy, dynamic shear rheometer (DSR), and epifluorescence microscopy tests. FTIR was used to determine the changes in major bands with addition of PPA. Stiffness and viscoelastic behaviors of asphalts were determined from the DSR test. The stiffness is measured by calculating the shear modulus, G* and the viscoelastic behavior is measured by calculating the phase angle, sin δ. Epifluorescence microscopy is a tool used to study properties of organic or inorganic substances. The morphological characteristics of PPA modified asphalt samples were observed through epifluorescence microscopy. Epifluorescence microscopy reveals the polymer phase distribution in the asphalt binders. Results of this ...
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Software and Hardware-In-The-Loop Modeling of an Audio Watermarking Algorithm

Software and Hardware-In-The-Loop Modeling of an Audio Watermarking Algorithm

Date: December 2010
Creator: Zarate Orozco, Ismael
Description: Due to the accelerated growth in digital music distribution, it becomes easy to modify, intercept, and distribute material illegally. To overcome the urgent need for copyright protection against piracy, several audio watermarking schemes have been proposed and implemented. These digital audio watermarking schemes have the purpose of embedding inaudible information within the host file to cover copyright and authentication issues. This thesis proposes an audio watermarking model using MATLAB® and Simulink® software for 1K and 2K fast Fourier transform (FFT) lengths. The watermark insertion process is performed in the frequency domain to guarantee the imperceptibility of the watermark to the human auditory system. Additionally, the proposed audio watermarking model was implemented in a Cyclone® II FPGA device from Altera® using the Altera® DSP Builder tool and MATLAB/Simulink® software. To evaluate the performance of the proposed audio watermarking scheme, effectiveness and fidelity performance tests were conducted for the proposed software and hardware-in-the-loop based audio watermarking model.
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Cold-Formed Steel Bolted Connections Using Oversized and Slotted Holes without Washers

Cold-Formed Steel Bolted Connections Using Oversized and Slotted Holes without Washers

Date: August 2010
Creator: Xu, Ke
Description: In cold-formed steel (CFS) construction, bolted connections without washers for either oversized or slotted holes may significantly expedite the installation process and lower the cost. However, the North American Specification (AISI S100, 2007) for the Design of Cold-Formed Steel Structural Members requires washers to be installed in bolted connections with oversized or slotted holes. A research project (Phase 1) sponsored by American Iron and Steel Institute (AISI) was recently completed at the University of North Texas (UNT) that investigated the performance and strength of bolted CFS connections with oversized and slotted holes without using washers. The research presented in this thesis is the Phase 2 project in which the bolted CFS connections were studied in a broader respect in terms of the failure mechanism, the material thickness, and the hole configurations. Single shear and double shear connections without washers using oversized holes, oversized combined with standard or slotted holes were experimentally examined. Combined with Phase 1 results, the Phase 2 gives a comprehensive evaluation of the behavior and strength of bolted CFS connections with oversized and slotted holes without using washers. Revisions to the existing AISI North American Specification requirements for bolted connections are proposed to account for the reduction ...
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Nominal Shear Strength and Seismic Detailing of Cold-formed Steel Shear Walls using Steel Sheet Sheathing

Nominal Shear Strength and Seismic Detailing of Cold-formed Steel Shear Walls using Steel Sheet Sheathing

Date: August 2010
Creator: Chen, Yujie
Description: In this research, monotonic and cyclic tests on cold-formed steel shear walls sheathed with steel sheets on one side were conducted to (1) verify the published nominal shear strength for 18-mil and 27-mil steel sheets; and (2) investigate the behavior of 6-ft. wide shear walls with multiple steel sheets. In objective 1: this research confirms the discrepancy existed in the published nominal strength of 27-mil sheets discovered by the previous project and verified the published nominal strength of 18 mil sheet for the wind design in AISI S213. The project also finds disagreement on the nominal strength of 18-mil sheets for seismic design, which is 29.0% higher than the published values. The research investigated 6-ft. wide shear wall with four framing and sheathing configurations. Configuration C, which used detailing, could provide the highest shear strength, compared to Configurations A and B. Meanwhile, the shear strength and stiffness of 2-ft. wide and 4-ft. wide wall can be improved by using the seismic detailing.
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Effects of Rebar Temperature and Water to Cement Ratio on Rebar-Concrete Bond Strength of Concrete Containing Fly Ash

Effects of Rebar Temperature and Water to Cement Ratio on Rebar-Concrete Bond Strength of Concrete Containing Fly Ash

Date: May 2010
Creator: Pati, Ardeep Ranjan
Description: This research presents the results on an experimental investigation to identify the effects of rebar temperature, fly ash and water to cement ratio on concrete porosity in continuously reinforced concrete pavements (CRCP). Samples were cast and analyzed using pullout tests. Water to cement ratio (w/c) and rebar temperature had a significant influence on the rebar-concrete bond strength. The 28-day shear strength measurements showed an increase in rebar-concrete bond strength as the water to cement ratio (w/c) was reduced from 0.50 to 0.40 for both fly ash containing and non fly ash control samples. There was a reduction in the peak pullout load as the rebar surface temperature increased from 77o F to 150o F for the cast samples. A heated rebar experiment was performed simulating a rebar exposed to hot summer days and the rebar cooling curves were plotted for the rebar temperatures of 180o F - 120o F. Fourier transform infrared spectroscopy was performed to show the moisture content of cement samples at the rebar-concrete interface. Mercury intrusion porosimetry test results on one batch of samples were used for pore size distribution analysis. An in-depth analysis of the morphological characteristics of the rebar-concrete interface and the observation of pores ...
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Design and validation of an automated multiunit composting system.

Design and validation of an automated multiunit composting system.

Date: December 2009
Creator: Pickens, Mark Everett
Description: This thesis covers the design of an automated multiunit composting system (AMUCS) that was constructed to meet the experimental apparatus requirements of the ASTM D5338 standard. The design of the AMUCS is discussed in full detail and validated with two experiments. The first experiment was used to validate the operation of the AMUCS with a 15 day experiment. During this experiment visual observations were made to visually observe degradation. Thermal properties and stability tests were performed to quantify the effects of degradation on the polymer samples, and the carbon metabolized from the degradation of samples was measured. The second experiment used the AMUCS to determine the effect of synthetic clay nanofiller on the aerobic biodegradability behavior of poly (3-hydroxybutyrate-co-3-hydroxyvalerate).
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