Wright-Patterson Air Force Base

About: Wright-Patterson Air Force Base is a other organization based out in Wright-Patterson AFB, Ohio, United States. It is known for research contribution in the topics: Laser & Mach number. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

Coarsening behavior of an alpha-beta titanium alloy

Abstract: The static-coarsening behavior of the alpha-beta titanium alloy, Ti-6Al-4V, was established via a series of heat treatments at typical forging-preheat and final-heat-treatment temperatures followed by quantitative metallography. For this purpose, samples of an ultra-fine-grain (UFG) size billet with a microstructure of equiaxed alpha in a beta matrix were heated at temperatures of 843 °C, 900 °C, 955 °C, and 982 °C for times between 0.25 and 144 hours followed by water quenching. The coarsening of the primary alpha particles was found to follow r 3-vs-time kinetics, typical of volume-diffusion-controlled behavior, at the three lower temperatures. At the highest temperature, the kinetics appeared to be fit equally well by an r 3 or r 4 dependence on time. The observations were interpreted in terms of the modified LSW theory considering the effect of volume fraction on kinetics and the fact that the phases are not terminal solid solutions. Prior models, which take into account the overall source/sink effects of all particles on each other, provided the best description of the observed dependence of coarsening on the volume fraction of primary alpha. In addition, the volume-diffusion kinetics derived for the UFG material were found to be capable of describing the coarsening behavior observed for industrial-scale billet of Ti-6Al-4V with a coarser starting equiaxed-alpha microstructure.

Modeling of Aerodynamic Coupling Between Aircraft in Close Proximity

Abstract: A method is developed for modeling the aerodynamic coupling between aircraft Hying in close proximity. Velocities induced on a trailing aircraft by vortices from an aircraft upstream are written as a function of the relative separation and relative orientation between the two aircraft. The nonuniform vortex-induced wind and wind gradients acting on the trail aircraft are approximated as effective uniform wind and wind gradients. In a dynamic simulation, the effective wind can be used directly in the equations of motion, whereas the wind gradient can be used in the standard buildup equations for the aerodynamic moments. This removes necessity to explicitly compute the induced forces and moments. Various vortex models for estimating induced velocities and averaging schemes for computing effective wind components and gradients are assessed