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open access

Mechanical Characterization of A2 and D2 Tool Steels By Nanoindentation

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 failu… more
Date: May 2012
Creator: Okafor, Uzochukwu Chimezie
Partner: UNT Libraries
open access

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

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 be… more
Date: May 2012
Creator: Coelho, Gavin
Partner: UNT Libraries
open access

Effects of Minimum Quantity Lubrication (Mql) on Tool Life in Drilling Aisi 1018 Steel

Description: It has been reported that minimum quantity lubrication (MQL) provides better tool life compared to flood cooling under some drilling conditions. In this study, I evaluate the performance of uncoated HSS twist drill when machining AISI 1018 steel using a newly developed lubricant designed for MQL (EQO-Kut 718 by QualiChem Inc.). A randomized factorial design was used in the experiment. The results show that a tool life of 1110 holes with a corresponding flank wear of 0.058 mm was realized.
Date: August 2012
Creator: Maru, Tejas
Partner: UNT Libraries
open access

Mist Characterization in Drilling 1018 Steel

Description: Minimum quantity lubrication replaces the traditional method of flood cooling with small amounts of high-efficient lubrication. Limited studies have been performed to determine the characteristics of mist produced during MQL. This study investigated the mist concentration levels produced while drilling 1018 steel using a vegetable based lubricant. ANOVA was performed to determine whether speed and feed rates or their interactions have a significant effect on mist concentration levels and partic… more
Date: August 2012
Creator: Cole, Ian
Partner: UNT Libraries
open access

Corrosion Protection of Low Carbon Steel By Cation Substituted Magnetite

Description: Surfaces of low carbon steel sheet were modified by exposure to highly caustic aqueous solutions containing either chromium or aluminum cations. Corrosion resistances of such surfaces were compared with that of steel surfaces exposed to plain caustic aqueous solution. In all cases a highly uniform, black coating having a spinel structure similar to magnetite (Fe3O4) was obtained. The coated steel surfaces were characterized using X-ray photoelectron spectroscopy (XPS), scanning electron micros… more
Date: May 2013
Creator: Phadnis, Ameya
Partner: UNT Libraries
open access

Direct Strength Method for Web Crippling of Cold-formed Steel C-sections

Description: Web crippling is a form of localized buckling that occurs at points of transverse concentrated loading or supports of thin-walled structural members. The theoretical computation of web crippling strength is quite complex as it involves a large number of factors such as initial imperfections, local yielding at load application and instability of web. The existing design provision in North American specification for cold-formed steel C-sections (AISI S100, 2007) to calculate the web-crippling str… more
Date: May 2013
Creator: Seelam, Praveen Kumar Reddy
Partner: UNT Libraries
open access

The Measurement of the Third-order Elastic Constants for La3ga5sio14 (Lgs) and La3ga55ta05o14 (Lgt) Single Crystal

Description: Recently, the development of electronic technology towards higher frequencies and larger band widths has led to interest in finding new piezoelectric materials, which could be used to make filters with larger pass band widths and oscillators with better frequency stability. Langasite (La3Ga5SiO14, LGS) and its isomorphs have enticed considerable attention of researchers as a potential substrate material for piezoelectric device applications because of its high frequency stability and fairly goo… more
Date: December 2013
Creator: Karim, Md Afzalul
Partner: UNT Libraries
open access

Development and Test of High-Temperature Piezoelectric Wafer Active Sensors for Structural Health Monitoring

Description: High-temperature piezoelectric wafer active sensors (HT-PWAS) have been developed for structure health monitoring at hazard environments for decades. Different candidates have previously been tested under 270 °C and a new piezoelectric material langasite (LGS) was chosen here for a pilot study up to 700 °C. A preliminary study was performed to develop a high temperature sensor that utilizes langasite material. The Electromechanical impedance (E/M) method was chosen to detect the piezoelectric p… more
Date: December 2014
Creator: Bao, Yuanye
Partner: UNT Libraries
open access

Direct Immersion Cooling Via Nucleate Boiling of HFE-7100 Dielectric Liquid on Hydrophobic and Hydrophilic Surfaces

Description: This study experimentally investigated the effect of hydrophobic and hydrophilic surfaces characteristics on nucleate boiling heat transfer performance for the application of direct immersion cooling of electronics. A dielectric liquid, HFE – 7100 was used as the working fluid in the saturated boiling tests. Twelve types of 1-cm2 copper heater samples, simulating high heat flux components, featured reference smooth copper surface, fully and patterned hydrophobic surface and fully and patterned … more
Date: December 2014
Creator: Joshua, Nihal E.
Partner: UNT Libraries
open access

Application of Cyclic Polarization of Aluminum 3003 Used in All-Aluminum Microchannel Heat Exchangers

Description: All-aluminum microchannel heat exchangers are designed to significantly reduce refrigerant charge requirements, weight, reduced brazed joints, and decreased potential for leakage by increasing reliability. Al 3003 alloy is corrosion resistant and can be formed, welded, and brazed but the issue with all-aluminum heat exchangers is localized corrosion (pitting) in corrosive environments. Currently, there is no universally accepted corrosion test that all coil manufacturers use to characterize the… more
Date: May 2015
Creator: Barnes, Javier
Partner: UNT Libraries
open access

Direct Strength Method for Web Crippling of Cold-formed Steel C and Z Sections Subjected to Interior One Flange Loading and End One Flange Loading

Description: The main objective of this research is to extend the “Direct strength method” for determining the web crippling strength of cold-formed steel C and Z sections subjected to End one flange loading and Interior one flange loading conditions. Direct strength method is applied for designing the columns and beams earlier. The existing specifications equation for calculating the web crippling strength of cold-formed steels designed by American Institute of Iron and Steel is very old method and it is b… more
Date: December 2015
Creator: Dara, Martin Luther
Partner: UNT Libraries
open access

Spray Cooling with HFC-134a and HFO-1234yf for Thermal Management of Automotive Power Electronics

Description: This study aims to experimentally investigate the spray cooling characteristics for active two-phase cooling of automotive power electronics. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. Two types of refrigerants, HFC-134a (R-134a) and HFO-1234yf, are selected as the working fluids. The test section (heater), made out of oxygen-free copper, has a 1-cm2 plain, smooth surface prepared following a consistent procedure, and would… more
Date: December 2015
Creator: Yaddanapudi, Satvik Janardhan
Partner: UNT Libraries
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