Showing 3 results for Saeidi
A.b. Kabiri Samani, M. Borgheie and M.h Saeidi,
Volume 24, Issue 2 (1-2006)
Abstract
The study of two-phase fluid flow behavior in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions and other similar conduits is of great importance. A two-phase mixture flowing in a pipe can exhibit several interfacial geometries such as bubbles, slugs or films, depending on the fluid and hydrodynamic properties of flow. The main variables, giving rise to a variety of flow patterns, include relative discharge rate of fluids and the pipe slope. The
flow patterns mostly attainable with air and water include stratified include and slug patterns. In this paper, the experimental results of pressurized water tunnel model are presented. The results include pressure transient and its variations for different hydraulic and geometric properties. It is shown that trapped and released air can cause tremendous pressure surges in the system and, eventually, may cause failure in systems (e.g. the maximum pressure inside the pipe would reach up to 10 times of upstream hydrostatic pressure). Finally, relations for forecasting maximum and minimum pressure in these situations are presented as a function of mean pressure, flow characteristics and pipe geometry.
M. Meratian, N. Saeidi,
Volume 28, Issue 1 (Jun 2009)
Abstract
In cast aluminum and its alloys, the microstructure varies under different solidification conditions, causing variations in their mechanical properties. These materials are basically produced in sand and metallic molds or through die casting, each of which is associated with a unique solidification regime with significantly different cooling rates so that the resulting microstructure strongly depends on the casting method used. In the present study, the effects of such important solidification parameters as cooling rate, solidification front velocity, and thermal gradient at the solid-liquid interface on secondary dendrite arm spacing were investigated. By a directional solidification system, the mathematical relation between cooling rate and dendrite spacing was extracted for several commercially important aluminum alloys. A neural network model was trained using the experimental values of cooling rates and secondary dendrite arm spacing. Reliable prediction of these values was made from the trained network and their corresponding diagrams were constructed. A good agreement was found between simulation and experimental values. It is concluded that the neural network constructed in this study can be employed to predict the relationship between cooling rate and dendrite arm spacing, which is difficult, if not iompossible, to accomplish experimentally.
S. Asghari, A. M. Eslami, A. Taheri Zadeh, N. Saeidi,
Volume 39, Issue 3 (Journal of Advanced Materials-Fall 2020)
Abstract
In this study, the effect of welding heat input on microstructure and mechanical properties of dissimilar joints of API-X42 and API-B pipeline steels was investigated. Evaluation of the microstructures showed that increasing the welding heat input decreased acicular ferrite in weld metal microstructure, while amount of Widmanstatten ferrite, polygonal ferrite and grain boundary ferrite increased. Also, results of microhardness test showed that by increasing the heat input, hardness of weld metal and the heat affected zone decreased. Tensile test results showed that as the heat input increased, fracture transferred from base metal of API-B to the heat affected zone. Impact test results also showed that increasing the welding heat input could sharply drop the impact energy of the heat affected zone for both base metals due to extensive grain growth.
