Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 6 of 6
Full-Text Articles in Mechanical Engineering
Characterization Of Residual Stress In Microelectromechanical Systems (Mems) Devices Using Raman Spectroscopy, Lavern A. Starman
Characterization Of Residual Stress In Microelectromechanical Systems (Mems) Devices Using Raman Spectroscopy, Lavern A. Starman
Theses and Dissertations
Due to the small scale of MEMS devices, the inherent residual stresses during the deposition processes can affect the functionality and reliability of the fabricated devices. Residual stress often causes device failure due to curling, buckling, or fracture. Currently, few techniques are available to measure the residual stress in MEMS devices. In this dissertation, Raman spectroscopy is used to measure and monitor the residual and induced stresses in MUMPs polysilicon MEMS devices. Raman spectroscopy was selected since it is nondestructive, fast, and provides potential in situ stress monitoring. Raman spectroscopy scans on unreleased and released MEMS fixed-fixed beams, cantilevers, and …
Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel
Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel
Theses and Dissertations
Effects of Shot-peening on High Cycle Fretting Fatigue behavior of Ti-6Al-4V were investigated. Experiments were performed with 6.35 mm thick specimens which provided S/N curves. After the tests, it was observed that the specimens failed near the trailing edge of contact. Scanning Electron Microscopy showed that cracks initiated on the contact surface for 6.35 mm, and at the depth of specimen ranging from 200 to 300 microns for 3.81 mm thick specimens. Initial crack orientation was around 37 and 42 degrees respectively for 6.35 and 3.81 mm thicknesses. Finite Element Analysis (FEA) was conducted, and using FEA results, Smith-Watson-Topper, Findley, …
Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley
Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley
Theses and Dissertations
This thesis studies selective etching techniques for the development of AlxGa1-xAs micro-opto-electro-mechanical systems (MOEMS). New MEMS technology based on materials such as AlxGa1-xAs enables the development of micro-systems with embedded active micro-optical devices. Tunable micro-lasers and optical switching based on MOEMS technology will improve future wavelength division multiplexing (WDM) systems. WDM vastly increases the speed of military communications and sensor data processing. From my designs, structures are prepared by molecular beam epitaxy. I design a mask set for studies of crystal plane selectivity. I perform a series of experiments on the selective …
Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey
Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey
Theses and Dissertations
Tunable micro-optical devices are expected to be vital for future military optical communication systems. In this research I seek to optimize the design of a microelectromechanical (MEM) structure integrated with a III-V semiconductor micro-optical device. The resonant frequency of an integrated optical device, consisting of a Fabry-Perot etalon or vertical cavity surface emitting laser (VCSEL), may be tuned by applying an actuation voltage to the MEM Flexure, thereby altering the device's optical cavity length. From my analysis I demonstrate tunable devices compatible with conventional silicon 5V integrated circuit technology. My design for a Fabry-Perot etalon has a theoretical tuning range …
Fretting Fatigue Behavior Of A Titanium Alloy Ti-6al-4v At Elevated Temperature, Onder Sahan
Fretting Fatigue Behavior Of A Titanium Alloy Ti-6al-4v At Elevated Temperature, Onder Sahan
Theses and Dissertations
The purpose of this research is to investigate the fretting fatigue behavior of the titanium alloy Ti-6Al-4V at elevated temperature is investigated. Fretting and plain fatigue experiments are conducted at 260 °C. Crack initiation location and crack initiation orientation is measured and fretting and plain fatigue life data of the specimens from these tests are obtained. Fatigue parameters capable of predicting the number of cycles to specimen failure, the crack location and the crack orientation along the contact surface are analyzed. The parameters are calculated by using the computed stresses and strains obtained from the finite element analysis. The mechanisms …
Examination Of Contact Width On Fretting Fatigue, Russell S. Magaziner
Examination Of Contact Width On Fretting Fatigue, Russell S. Magaziner
Theses and Dissertations
The primary goal of this study was to find the effects on the fretting fatigue life when systematically holding the fretting fatigue variables, peak contact pressure, maximum/minimum nominal bulk stress, and the ratio of shear traction to pressure force constant while varying the contact semi-width through changes in pad radius and normal load. Experimental tests were performed on a test setup capable of independent pad displacement. Analytical and finite element simulations of the different experimental tests were performed. The local mechanistic parameters were inspected. Five different critical plane based fatigue predictive parameters lacked effectiveness in predicting changes in life with …