Mechanical Engineering Commons^™

Load Path Uncertainty In A Wood Structure And The Effect On Structural Reliability, Wenqi Wang, Christopher D. Eamon

Civil and Environmental Engineering Faculty Research Publications

The roof truss bearing points of a light-framed wood house were instrumented with load cells. It was found that under dead load alone, symmetric and theoretically identical truss reactions have significant variation. A similar degree of reaction discrepancy was found under the application of uplift pressures caused by hurricane winds. Analysis revealed that the majority of this discrepancy is caused by inherent uncertainties in load path. Although uncertainties in load magnitude and material resistance are accounted for in design by use of appropriate load and resistance factors, load path is generally taken to be deterministic. In this study, load path …

Reliability Analysis Of Reinforced Concrete Columns Exposed To Fire, Christopher D. Eamon, Elin A. Jensen

Civil and Environmental Engineering Faculty Research Publications

A reliability analysis is conducted on reinforced concrete columns subjected to fire load. From an evaluation of load frequency of occurrence, load random variables are taken to be dead load, sustained live load, and fire temperature. Resistance is developed for axial capacity, with random variables taken as steel yield strength, concrete compressive strength, placement of reinforcement, and section width and height. A rational interaction model based on the Rankine approach is used to estimate column capacity as a function of fire exposure time. Various factors were considered in the analysis such as fire type, load ratio, reinforcement ratio, cover, concrete …

Reliability-Based Design Optimization Of Concrete Flexural Members Reinforced With Ductile Frp Bars, Bashar Behnam, Christopher D. Eamon

Civil and Environmental Engineering Faculty Research Publications

In recent years, ductile hybrid FRP (DHFRP) bars have been developed for use as tensile reinforcement. However, initial material costs regain high, and it is difficult to simultaneously meet strength, stiffness, ductility, and reliability demands. In this study, a reliability-based design optimization (RBDO) is conducted to determine minimum cost DHFRP bar configurations while enforcing essential constraints. Applications for bridge decks and building beams are considered, with 2, 3, and 4-material bars. It was found that optimal bar configuration has little variation for the different applications, and that overall optimized bar cost decreased as the number of bar materials increased.

Analysis Of Alternative Ductile Fiber-Reinforced Polymer Reinforcing Bar Concepts, Bashar Behnam, Christopher D. Eamon

Civil and Environmental Engineering Faculty Research Publications

Steel-reinforced concrete structural components are often associated with significant maintenance costs as a result of reinforcement corrosion. To mitigate this problem, fiber-reinforced polymer (FRP) bars have been used in place of traditional steel reinforcement for some applications. The non-ductile response of typical FRP bars is a concern, however. To overcome this problem, hybrid ductile FRP (HDFRP) bars have been developed for use in concrete flexural members with resulting ductility indices similar to sections reinforced with steel. In this study, five different HDFRP bar concepts are analyzed and compared in terms of ductility, stiffness, and relative cost. Of primary interest is …

Resistance Factors For Ductile Frp-Reinforced Concrete Flexural Members, Bashar Behnam, Christopher D. Eamon

Civil and Environmental Engineering Faculty Research Publications

To prevent damage caused by corroding reinforcement, fiber reinforced polymer (FRP) reinforcing bars have been used in place of steel in a relatively small but increasing number of structures in the civil infrastructure. A concern with the use of traditional FRP bars, however, is the resulting lack of ductility. This problem has been overcome with the development of a new generation of composite reinforcement, ductile hybrid FRP (DHFRP) bars. However, standards that address the design of DHFRP bars are unavailable, and appropriate resistance factors for the use of DHFRP reinforcement are unknown. In this study, a reliability analysis is conducted …

Reliability Analysis Of Rc Beams Exposed To Fire, Christopher D. Eamon, Elin A. Jensen

Civil and Environmental Engineering Faculty Research Publications

A procedure for conducting reliability analysis of reinforced concrete beams subjected to a fire load is presented. This involves identifying relevant load combinations, specifying critical load and resistance random variables, and establishing a high-temperature performance model for beam capacity. Based on the procedure, an initial reliability analysis is conducted using currently available data. Significant load random variables are taken to be dead load, sustained live load, and fire temperature. Resistance is in terms of moment capacity, with random variables taken as steel yield strength, concrete compressive strength, placement of reinforcement, beam width, and thermal diffusivity. A semi-empirical model is used …

Effect Of Intake Temperature And Boost Pressure On The Auto-Ignition Of Fuels With Different Cetane Numbers And Volatilities, Chandrasekharan Jayakumar

Wayne State University Dissertations

The aim of this research is to investigate the effect of air inlet temperature and boost pressure on the auto-ignition of fuels that have different CNs and volatilities in a single cylinder diesel engine. The inlet air temperature is varied over a range of 30°C to 110°C at a constant intake pressure of 1.1 bar. The boost pressure is varied from 1.1 bar to 1.5 bar at a constant intake temperature of 60°C. All engine tests are run at steady-state conditions. The fuels used are ultra-low-sulfur-diesel (ULSD), JP-8 (two blends with CN 50 & 31) and F-T SPK. Detailed analysis …

Exergetic Analysis Of Hydrogen Combustion Involving Electronically Excited Species, Devon Alan Washington

Wayne State University Dissertations

Plasma-assisted combustion (PAC) is a growing field of research that involves using nonthermal plasma (NTP) to enhance combustion. PAC research involves modeling reaction mechanisms and chemical kinetics. Exergy analysis of combustion devices focuses on combustion irreversibility, including mixing, internal heat transfer, and oxidation. This novel research project merges these two branches of research.

The focus of this work is the application of exergy analysis to PAC systems, to analyze the effect introducing NTP has on trends in exergy destruction associated with oxidation during hydrogen combustion. This was accomplished by developing a plug flow reactor model using the chemical simulation tool …

Simulations And Experiments Of Fuel Injection, Mixing And Combustion In Di Gasoline Engines, Yi Zheng

Wayne State University Dissertations

Direct Injection (DI) has been known for its improved performance and efficiency in gasoline spark-ignition engines. In order to take all the advantages of the GDI technology, it is important to investigate in detail the interactions of fuel spray and combustion system, such as air-fuel mixing, in-cylinder flow development, surface wetting, and turbulence intensity. The characterizations of the internal nozzle flow of DI injector are first studied using the multidimensional computational fluid dynamic (CFD) simulation. In the meanwhile the numerical and experimental studies are carried out to observe the external spray and wall impingements in an optical constant volume vessel. …

Characteristics Of Cold Start Of A Diesel Engine Using Jp8 And Ulsd Fuels, Madhushankar Palanisamy

Wayne State University Theses

This study involves the cold start testing of ULSD and JP8 fuels on the 6 cylinder 7.2 liter turbocharged diesel engine at various ambient temperatures as low as 0oF for JP8 fuel and 10oF for ULSD fuel. Cycle by cycle analysis of the cold start transient data, along with the effects of variation in ambient temperature on the engine cranking speed and in cylinder motoring pressure were analyzed and presented. It was found that the reduction in ambient temperature resulted in prolonged cranking periods along with the longer time taken to reach idling speed as well as increased combustion instability. …

Structure Borne Noise Analysis Using Helmholtz Equation Least Squares Based Forced Vibro Acoustic Components, Logesh Kumar Natarajan

Wayne State University Dissertations

This dissertation presents a structure-borne noise analysis technology that is focused on providing a cost-effective noise reduction strategy. Structure-borne sound is generated or transmitted through structural vibration; however, only a small portion of the vibration can effectively produce sound and radiate it to the far-field. Therefore, cost-effective noise reduction is reliant on identifying and suppressing the critical vibration components that are directly responsible for an undesired sound. However, current technologies cannot successfully identify these critical vibration components from the point of view of direct contribution to sound radiation and hence cannot guarantee the best cost-effective noise reduction.

The technology developed …

Ionization In Diesel Combustion For On-Board Diagnostics And Engine Control, Tamer Hassan Badawy

Wayne State University Dissertations

Diesel engines have been known for their high thermal efficiency and specific power output, but there is concern about engine-out NOx and particulate matter emissions. To meet the current emission standards, advanced diesel engines are fitted with electronically controlled fuel injection systems and sophisticated and expensive after-treatment devices. Further improvements are still needed to meet future goals in better fuel economy and the more stringent emission standards. In order to meet these goals, there is a need for the control of the combustion process to reduce engine-out emissions in real-time and reduce the demand on the after-treatment devices. This requires …

Impact Damage Analysis Of Balsa Wood Sandwich Composite Materials, Suof Abdalslam

Wayne State University Dissertations

No abstract provided.

Experimental Investigation And Development Of An Extended Two Color Method (Etcm) With Application To Internal Combustion Engines, Elena Florea

Wayne State University Dissertations

The internal combustion engine is on a continuous path of improvement to reduce exhaust gaseous emissions and improve fuel economy. While recent trends in diesel engine development have lowered the EGR requirements, future regulatory pressure will likely result in a reversed trend in the future.

Given this, it is of interest to improve the application range of diagnostic tools such as the two color method (TCM) typically used in evaluating the properties of engine soot, such as temperature and volume fraction. This optical diagnostic method relies on the use of the light emitted by the soot particles along with a …

Ion Current Signal Detection During Cold Starting And Idling Operation In A Diesel Engine, Sanket Anil Gujarathi

Wayne State University Theses

Cold starting of diesel engines is characterized by inherent problems such as long cranking periods and combustion instability leading to an increase in fuel consumption and the emission of high concentrations of hydrocarbons which appear as white smoke. Accordingly, a signal indicative of combustion during cold starting and idling operation is important for combustion and emission control. The ion current signal has been considered for the feedback control of both gasoline and diesel engines. However, the ion current signal produced from the combustion of the heterogeneous charge in diesel engines is weaker compared to that produced from the combustion of …

Fatigue Behavior And Microstructure Examination Of Aisi D2 Trim Dies, Xinchen Wang

Wayne State University Theses

AISI D2 steels are widely used as tools for forming, drawing and trimming dies due to its high wear resistance, high compressive strength and low distortion, and its performance as a trim die material for cutting ultra-high strength steels (at 1GPa or above) is investigated in this study.

To simulate the production trimming process under a laboratory accelerated fatigue condition, a trim die simulator and testing technique have been developed. In this test 1" cubic die samples were used that offers total 12 cutting edges of 6 different material grain orientations in shearing, and with adjustable die clearance. A non-contact …

Mechanical And Electro-Chemical Investigation Of Carbon Farbric/Epoxy And Aluminum Foam Sandwich Composite Beams, Narin Sara Fatima

Wayne State University Theses

In this study the mechanical and electrochemical response of a sandwich composite comprising of carbon fiber fabric skin and aluminum foam core was evaluated. The three point flexural test was chosen to investigate the mechanical behavior in terms of finding the deformation and failure behavior. The flexural test exhibited an excellent bond between the skin and the core. The specimens mainly failed in three different modes - indentation, core shear and face yielding and showed three distinct regions: a linear rise in load with displacement region, a rapid load drop region and a plateau region followed by a densification region. …

Developing A System For Blind Acoustic Source Localization And Separation, Raghavendra Kulkarni

Wayne State University Theses

This dissertation presents innovate methodologies for locating, extracting, and separating multiple incoherent sound sources in three-dimensional (3D) space; and applications of the time reversal (TR) algorithm to pinpoint the hyper active neural activities inside the brain auditory structure that are correlated to the tinnitus pathology. Specifically, an acoustic modeling based method is developed for locating arbitrary and incoherent sound sources in 3D space in real time by using a minimal number of microphones, and the Point Source Separation (PSS) method is developed for extracting target signals from directly measured mixed signals. Combining these two approaches leads to a novel technology …

Induced Damping And Its Relationship To Beneficial Energy Harvesting In Dielectric Elastomers With Application To Walking, Heather L. Lai

Wayne State University Dissertations

This dissertation presents a novel, interdisciplinary research which addresses the potential of applying soft polymeric materials to strategically harvest biomechanical energy in a beneficial manner for use as a viable, low power source for on-board electronics. Of particular interest are electroactive polymers (EAP), which unlike other types of electromechanical smart materials such as piezoelectric ceramics, which are often brittle, have low elastic modulus and can exhibit large strains without substantial stress generations. One type of EAP, the dielectric elastomer (DE), which utilizes electrostatic forces built up across the dielectric polymer to convert between electrical and mechanical energy, is employed in …