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Full-Text Articles in Engineering
Electrical Capacitance Measurements To Assess European Corn Borer Infestation In Maize, Mavrik D. Thomas
Electrical Capacitance Measurements To Assess European Corn Borer Infestation In Maize, Mavrik D. Thomas
Theses and Dissertations
The European Corn Borer (ECB), Ostrinia nubilalis, is an agricultural pest which bores small holes in the rind of maize stalks and then proceeds to consume the pith. Because most of the damage to the stalk is internal, it is difficult to quantify the damage to an individual stalk without time-consuming, manual examination. This work explored the hypothesis that internal damage could be detected and quantified using non-destructive, electromagnetic measurements. Laboratory experiments and numerical simulation studies predicted changes in capacitance of stalks due to hollow core ECB damage. A guarded probe device to measure electrical impedance from 500 Hz to …
Surface Roughness Of Electron Beam Melting Ti-6al-4v Effect On Ultrasonic Testing, Evan T. Hanks
Surface Roughness Of Electron Beam Melting Ti-6al-4v Effect On Ultrasonic Testing, Evan T. Hanks
Theses and Dissertations
Experimental research was conducted on the effects of surface roughness on ultrasonic non-destructive testing of Electron Beam Melted (EBM) additively manufactured Ti-6Al-4V. Additive Manufacturing (AM) is a developing technology with many potential benefits, but certain challenges posed by its use require further research before AM parts are viable for widespread use in the aviation industry. Possible applications of this new technology include, Aircraft Battle Damage Repair (ABDR), small batch manufacturing to fill supply gaps, and replacement for obsolete parts. The research presented here assesses the effectiveness of ultrasonic inspection in detecting manufactured flaws in EBM manufactured Ti-6Al-4V. EBM products are …
Test And Evaluation Of Ultrasonic Additive Manufacturing (Uam) For A Large Aircraft Maintenance Shelter (Lams) Baseplate, Daniel H. Gartland
Test And Evaluation Of Ultrasonic Additive Manufacturing (Uam) For A Large Aircraft Maintenance Shelter (Lams) Baseplate, Daniel H. Gartland
Theses and Dissertations
Additive manufacturing is an exciting new manufacturing technology that could have application to Air Force Civil Engineer (CE) operations. This research replicates a Large Area Maintenance Shelter (LAMS) baseplate design for ultrasonic additive manufacturing (UAM). Due to production problems the test section was not built as designed. Instead, a smaller block of material was submitted for evaluation. After the UAM build, ultrasonic inspection was conducted to identify anomalies in the test piece. The results of this proof of concept study indicate that UAM is not yet ready for CE expeditionary applications requiring a high degree of mechanical strength. The machine …
A High Bandwidth Non-Destructive Method For Characterizing Simple Media, Matthew L. Szuster
A High Bandwidth Non-Destructive Method For Characterizing Simple Media, Matthew L. Szuster
Theses and Dissertations
The relative complex permittivity can be extracted with time domain data from a perfect electrical conductor (PEC) backed sample of a low-loss, non-dispersive dielectric using dual ridged waveguide aperture probes with attached PEC flange plates of the same geometry and different dimensions. The temporal domain measurement of interest is the ability to detect the reflection from the edge of the flange plate in the parallel region created by the flange plate and the PEC backing on the dielectric sample. Signal processing windows are applied to the data in order to exploit this edge reflection. The types of signal processing methods …
An Enhanced Fuselage Ultrasound Inspection Approach For Ishm Purposes, Francisco Ospina
An Enhanced Fuselage Ultrasound Inspection Approach For Ishm Purposes, Francisco Ospina
Theses and Dissertations
This effort constitutes a systems engineering approach in which the materials science, ultrasound structural health monitoring, flight and maintenance operations, and relevant aeronautical policies and programs are involved to explore the evolution and characterization of structural cracks in aircraft fuselage structures in which the loads are varying. During flight, an aircraft fuselage skin and structure are subjected to varied cyclic loads, which can cause embedded cracks and other damage features to change their characteristics due to loading effects. The current research is based in the application of finite element modeling techniques using COMSOL and PZFLEX software to characterize the behavior …
Changes In Structural Health Monitoring System Capability Due To Aircraft Environmental Factors, Jeffrey D. Kuhn
Changes In Structural Health Monitoring System Capability Due To Aircraft Environmental Factors, Jeffrey D. Kuhn
Theses and Dissertations
Structural Health Monitoring (SHM) promises to decrease the maintenance cost and increase the availability of aging aircraft fleets by fundamentally changing the way structural inspections are performed. But this promise can only be realized through the consistent and predictable performance of a SHM system throughout the entire remaining life of an aircraft. In a sensor-based SHM system, sensor signal changes are analyzed and interpreted to identify structural flaws. But aircraft environmental factors such as temperature fluctuations, cyclic strain and exposure to various aircraft fluids also have the potential to change SHM sensor signals, raising questions about long term SHM system …
Inverse Scattering Image Quality With Noisy Forward Data, Thomas J. Sorensen
Inverse Scattering Image Quality With Noisy Forward Data, Thomas J. Sorensen
Theses and Dissertations
Image quality metrics for several inverse scattering methods and algorithms are presented. Analytical estimates and numerical simulations provide a basis for poor image quality diagnostics. The limitations and noise behavior of reconstructed images are explored analytically and empirically using a contrast ratio. Theoretical contrast ratio estimates using the canonical PEC circular cylinder are derived. Empirical studies are conducted to confirm theoretical estimates and to provide examples of image quality vs SNR for more complex scatterer profiles. Regularized sampling is shown to be more noise sensitive than tomographic reconstructive methods.
Finite Element Analysis Of Lamb Waves Acting Within A Thin Aluminum Plate, Sejin Han
Finite Element Analysis Of Lamb Waves Acting Within A Thin Aluminum Plate, Sejin Han
Theses and Dissertations
Structural health monitoring (SHM) is an emerging technology that can be used to identify, locate and quantify structural damages before failure. Among SHM techniques, Lamb waves have become widely used since they can cover large areas from one single location. Due to the development of various structural simulation programs, there is increasing interest in whether SHM data obtained from the simulation can be verified by experimentation. The objective of this thesis is to determine Lamb wave responses using SHM models in ABAQUS CAE(a Finite Element Analysis(FEA) program). These results are then compared to experimental results and theoretical predictions under isothermal …
Lamb Wave Propagation In Varying Thermal Environments, Jennifer P. Andrews
Lamb Wave Propagation In Varying Thermal Environments, Jennifer P. Andrews
Theses and Dissertations
During flight, launch, and reentry, external surfaces on aerospace vehicles undergo extreme thermo-acoustic loads resulting in structural degradation. Structural health monitoring techniques are being devised to evaluate the health of these structures by locating and quantifying structural damage during and after flight. One such technique uses Lamb wave propagation to assess damage on the surface and through the thickness of thin materials. The objective of this study was to assess the sensitivity of piezo-generated Lamb wave propagation to isothermal and thermal gradient environments using both theoretical and experimental methods. Experimental isothermal tests were conducted over a temperature range of 0-225 …