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Friction Stir Welding of Commercially Purity Titanium and its Effect on Microstructure and Mechanical Properties using Different FSW Tools
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor)
Abstract
The objective of this investigation was obtaining sound Friction Stir Welded (FSWed) Commercially Purity Titanium using suitable Tool’s Materials (for Shoulder and Pin) in order to be able to work in high temperature (>1000 ˚C) with great mechanical properties and minimum wear during process. Consequently, different materials and designs for Tool, such as High Speed Steel tool, Tungsten based tool, Tungsten Carbide (WC-Co) based tool and diverse tool geometry and designs like simple design, threaded design, fixed pin and inserted pin (adjustable pin) was used. The results demonstrated that using simple cylindrical WC-Co for pin and Tungsten for shoulder resulted in joints with the best...
Recovery of drop in heat transfer rate for a rotating system by nanofluids
, Article Journal of Molecular Liquids ; Volume 220 , 2016 , Pages 961-969 ; 01677322 (ISSN) ; Rashidi, S ; Abolfazli Esfahani, J ; Sharif University of Technology
Elsevier
Abstract
This paper simulates Al2O3-water nanofluid flow and forced convection around a rotating circular cylinder. The governing parameters are Reynolds number (1 ≤ Re ≤ 100), solid volume fraction of nanoparticles (0 ≤ φ ≤ 0.05) and non-dimensional rotation rate (0 ≤ α ≤ 3). The simulations are performed to study the effects of mentioned parameters on the heat transfer rate and fluid flow characteristics. The governing equations including the continuity, momentum, and energy equations are solved with a finite volume method. It is observed that the reduction of heat transfer with increase in rotation rate is in the vicinity of 6.9% and 32% for Re = 5 and 100, respectively at φ = 0.05. Furthermore,...
Physical properties of near-Earth asteroid (2102) Tantalus from multiwavelength observations
, Article Monthly Notices of the Royal Astronomical Society ; Volume 515, Issue 3 , 2022 , Pages 4551-4564 ; 00358711 (ISSN) ; Lowry, S. C ; Rozitis, B ; Dover, L. R ; Taylor, P. A ; Virkki, A ; Green, S. F ; Snodgrass, C ; Fitzsimmons, A ; Campbell-White, J ; Sajadian, S ; Bozza, V ; Burgdorf, M. J ; Dominik, M ; Jaimes, R. F ; Hinse, T. C ; Hundertmark, M ; Jorgensen, U. G ; Longa-Pena, P ; Rabus, M ; Rahvar, S ; Skottfelt, J ; Southworth, J ; Sharif University of Technology
Oxford University Press
2022
Abstract
Between 2010 and 2017, we have collected new optical and radar observations of the potentially hazardous asteroid (2102) Tantalus from the ESO NTT and Danish telescopes at the La Silla Observatory, and from the Arecibo planetary radar. The object appears to be nearly spherical, showing a low-amplitude light-curve variation and limited large-scale features in the radar images. The spin-state is difficult to constrain with the available data; including a certain light-curve subset significantly changes the spin-state estimates, and the uncertainties on period determination are significant. Constraining any change in rotation rate was not possible, despite decades of observations. The convex...