Engineering Commons^™

Guided Wave Based Integrated Structural Health Monitoring And Nondestructive Evaluation, Zhenhua Tian

Theses and Dissertations

Damage detection and health monitoring are critical for ensuring the structural safety in various fields, such as aerospace, civil and nuclear engineering. Structural health monitoring (SHM) performs online nondestructive evaluation (NDE) and can predict the structural remaining life through appropriate diagnosis and prognosis technologies. Among various SHM/NDE technologies, guided ultrasonic waves have shown great potential for fast and large area SHM/NDE, due to their sensitivity to small defects and capability to propagate long distances. Recent advances in guided wave based SHM/NDE technologies have demonstrated the feasibility of detecting damage in simple structures such as metallic plates and pipes. However, there …

A Multiphysics Modeling Of Solid Oxide Metal-Air Redox Battery, Md Ahsan Uddin

Theses and Dissertations

Cost-effective and large scale energy storage is essential for the growth of the future’s ‘‘green energy’’ infrastructure. Among the energy storage technologies currently being used, rechargeable batteries represent a class of advanced electrical energy storage (EES) mechanisms that can be valuable for the future renewable integration and smart grid. Rechargeable batteries have innumerous advantages over the conventional pumped hydro and compressed-air energy storage system. Now days, There are various types of rechargeable batteries available to work as an energy storage device in a smart grid but it still needs many breakthroughs to become commercially viable for stationary energy storage. First …

Wavelet Analysis Of Periodic Error In Heterodyne Interferometry, Chao Lu

Theses and Dissertations

Heterodyne displacement measuring interferometry provides important metrology for applications requiring high resolution and accuracy. Heterodyne Michelson interferometers use a two-frequency laser source and separate the two optical frequencies into one fixed length and one variable length path via polarization. Ideally these two beams are linearly polarized and orthogonal so that only one frequency is directed toward each path. An interference signal is obtained by recombining the light from the two paths; this results in a measurement signal at the heterodyne (split) frequency of the laser source. This measurement signal is compared to the optical reference signal. Motion in the measurement …

Bio-Inspired Design Of Mechanical Band Pass Sensor With The Ability To Scavenge Energy, Md Riaz Uddin Ahmed

Theses and Dissertations

Primary objective of this work is to introduce the multi-scale computational model for the bio-inspired acousto-ultrasonic band pass sensor that are capable of mechanically sense and/or filter wide range user defined frequencies. Selecting a particular and/or a distinct band of frequencies is essential for many applications in science engineering and technologies. For example design of sensors in chemical, biomedical and biological applications; device application for acoustic modulation by breaking the acoustic reciprocity and the sensors used in precision manufacturing applications requires sensing and/or filtering of wide range of acousto-ultrasonic frequencies. Presently, electronic devices are widely employed in commercial applications for …

Fabrication And Characterization Of Anode-Supported Micro-Tubular Solide Oxide Fuel Cell By Phase Inversion Method, Cong Ren

Theses and Dissertations

Nowadays, the micro-tubular solid oxide fuel cells (MT-SOFCs), especially the anode supported MT-SOFCs have been extensively developed to be applied for SOFC stacks designation, which can be potentially used for portable power sources and vehicle power supply. To prepare MT-SOFCs with high electrochemical performance, one of the main strategies is to optimize the microstructure of the anode support. Recently, a novel phase inversion method has been applied to prepare the anode support with a unique asymmetrical microstructure, which can improve the electrochemical performance of the MT-SOFCs. Since several process parameters of the phase inversion method can influence the pore formation …

Quantification Of The Effect Of Tool Geometric Features On Aspects Of Friction Stir Welding, Md. Reza-E-Rabby

Theses and Dissertations

In the friction stir welding (FSW) process, tool stirring and synchronized movement of the weld materials along a pre-existing seam line causes thermal gradients and severe plastic deformation resulting in the bonding of the adjacent materials. For a given set of welding parameters, tool pin geometries (dimensions, shape) and vertical/helical features that dictate the material motion also have significant effects on process response variables during FSW. Among the primary process controlling parameters in FSW, tool pin geometry and feature vary multifariously in terms of shape, dimensions, feature insertion technique depending on the weld material and application of joint. The current …

Design Of Experiments Analysis Of Non-Standard Inputs For The Optimization Of Friction Stir Welding, Ryan Widejko

Theses and Dissertations

The purpose of this study was to use non-standard Design of Experiments (DoE) inputs in Friction Stir Welding (FSW) to deduce relationships between various weld input and response variables. Typically, inputs for FSW DoE are tool rotational speed, welding speed and forge force. In this study, three different input factors were investigated: travel speed, thermal boundary conditions (TBC), and advance per revolution (APR). The experimental design included a full factorial with each factor at two levels plus two centerpoint runs. Response variables included weld temperature, microstructure, hardness, power, weld energy, and in plane forces.

An investigation of the effect of …

Methods For Determining Grease Service Levels In An Ah-64d Intermediate Gearbox Using On-Board Sensors, Travis Steven Edwards

Theses and Dissertations

The intermediate gearbox (IGB) on the AH-64D was chosen as the subject for this study based on the persistent grease leaks that require grounding aircraft. The aircraft is not currently equipped with a method of detecting grease loss during flight, so techniques for analyzing the usefulness of old metrics and possible new techniques can be tested. The main objective of this study is to use the aircraft’s on-board sensors to develop a method of determining the lubrication level of the IGB. Currently, the most reliable method for detecting a fault on the aircraft is through the use of vibration-based condition …

Predictive Methods For End Of Life Prognosis In Composites, Vamsee Vadlamudi

Theses and Dissertations

The long-term properties of continuous fiber reinforced composite materials are increasingly important as applications in airplanes, cars, and other safety critical structures are growing rapidly. The mechanical, electrical, and thermal properties of composite materials are altered by the initiation and accumulation of discrete fracture events whose distribution and eventual interaction defines the limits of design, such as strength and life. There is a correlation that exists between the long term behavior of those materials under combined mechanical, thermal, and electrical fields, and the functional properties and characteristics of the composite materials that requires a fundamental understanding of the material state …