Showing papers by "Vaughn College of Aeronautics and Technology published in 2006"

Some hypersonic intake studies

Abstract: A ‘two dimensional’ air intake comprising a wedge followed by an isentropic compression has been tested in the Cranfield Gun Tunnel at Mach 8·2. These tests were performed to investigate qualitatively the intake flow starting process. The effects of cowl position, Reynolds number, boundary-layer trip and introduction of a small restriction in the intake duct were investigated. Schlieren pictures of the flow on the compression surface and around the intake entrance were taken. Results showed that the intake would operate over the Reynolds number range tested. Tests with a laminar boundary layer demonstrated the principal influence of the Reynolds number on the boundary-layer growth and consequently on the flow structure in the intake entrance. In contrast boundary layer tripping produced little variation in flow pattern over the Reynolds number range tested. The cowl lip position appeared to have a strong effect on the intake performance. The only parameter which prevented the intake from starting was the introduction of a restriction in the intake duct. The experimental data obtained were in good qualitative agreement with the CFD predictions. Finally, these experimental results indicated a good intake flow starting process over multiple changes of parameters.

Effects of aeronautical conditions on passivation cracking of micro-structures of IC packages

Abstract: Passivation cracking is one of the main failures of ICs and thermo-mechanical failures are the root cause. A major cause for these failures is due to the different Coefficients of Thermal Expansion (CTE), different Young's modulus, Poisson's ratios of package materials under different temperatures and some mechanical loadinds. Therefore the working conditions of compound materials used here is expected to have a pronounced influence on the local stress distribution in the passivation layer. The aeronautical conditions mainly include different temperatures and overloads as well as the vibration conditions. Here the finite element simulations and the maximum principal stress theory are applied here to investigate the effects of aeronautical conditions on passivation cracking of microstructures of IC packages, and the result will pave the way for compound materials selection in IC packages and usage under aeronautical conditions.