Showing 7 results for Eslami
M. T. Sattari, S. S. Eslamian and A. Abrishamchi,
Volume 21, Issue 2 (1-2003)
Abstract
Limitations on water resources and the high costs of new hydraulic structure construction intensify the need for an optimum operation of Iranian reservoir systems. For appropriate water distribution and management in a 9-reservoir system on the Kalamarz river, Mianeh basin optimizing mathematical models are applied. Considering the stochastic nature of river discharges and the constant amount of reservoir volume and farmland area, an optimum linear chance constrained model is programmed and run by GAMS software. This model is only used for within-year regulation. Using a linear yield regulation, operation parameters for request months and all reservoirs are derived by the model. Also, the model computes portions of river discharge diverted to each reservoir in different months and outflow from downstream for different months. Results show greater than 60 percent deficit that indicates the lack of sufficient attention to constructing an optimum reservoir volume and extensive development of farmlands for each reservoir.
Keywords: Multi-reservoir system, optimal operation optimizing Models, linear chance constrained model
A. Eslami, M. Karimpoor Fard and N. Shariatmadari,
Volume 24, Issue 1 (7-2005)
Abstract
In recent years, determining bearing capacity of piles from in-situ testing data as a complement to static and dynamic analysis has been used by geotechnical engineers. In this paper, different approaches for estimating bearing capacity of piles from SPT data are studied and compared. A new method based on N value from SPT is presented. Data averaging,
failure zone and plunging failure of piles are revisited in the light of this new method. A data bank was compiled including 42 full scale pile load tests in sites where SPT was performed close to pile locations. Comparison of current methods by error investigation with statistical and cumulative probability approaches demonstrates that the new method predicts pile capacity with more accuracy and less scatter than others. Therefore, it can be applied as a suitable solution in geotechnical design.
M. Veis Karami, A. Eslami, M. M. Ranjbar and T. Riyazi,
Volume 26, Issue 1 (7-2007)
Abstract
Application of pile-raft foundations, which are known as “compound foundations”, is a suitable alternative in the case of heavy load structures. The interaction behavior of pile raft foundations makes these systems very complex to analyze. Different methods have been proposed to determine the bearing capacity of piled raft systems and distribution of loads between the components, i.e. pile group and mat. These methods are generally categorized into computer-based and conventional methods. In most of these methods, the bearing capacity of the mat, which is often a great portion of the total capacity, is neglected. Also, some model parameters used in these methods, as well as pile group or raft stiffness, cannot be determined by routine tests or calculations. In this study, a number of recent analytical methods of piled raft system are presented. A new method is then proposed which is based on settlement analysis of piled raft foundation and distribution of load between pile group and mat foundation, which regards the interaction of compound systems as an equivalent block foundation. In this approach, settlement is computed based on the concept of neutral plane according to which relative settlement of soil and pile group become the same. Two practical case studies are implemented for validation of the method. The comparison demonstrates favorable results for the proposed method.
A. Eslami, H. Modaraei, and H. Ahmadi,
Volume 26, Issue 2 (1-2008)
Abstract
M. Ghasemian Malakshah, F. Ashrafizadeh, A. Eslami, F. Fadaeifard,
Volume 38, Issue 2 (Journal of Advanced Materials-Summer 2019)
Abstract
Since martensitic precipitation hardened 17-4pH stainless steel has been widely used in corrosive environments, evaluation of its corrosion fatigue behavior is important. In this research, after microstructural studies, mechanical, corrosion, fatigue and corrosion fatigue tests were performed on 17-4pH specimens. Fatigue and corrosion fatigue tests were carried out at the stress ratio of -1 and the stress frequency of 0.42 Hz (to increase the effect of corrosive solution), and corrosion fatigue tests were conducted in 3.5% NaCl solution, an environment similar to corrosive sea water. Fatigue limit of 17-4pH stainless steel was 700 MPa in air and 415 MPa in corrosive environment. Comparing the S-N curves of this alloy at the optimal heat treatment cycle in two modes of fatigue and corrosion fatigue revealed the reduction of fatigue limit up to 40 % in the presence of corrosive environment. This reduction was due to the effect of observed corrosion pits on the surface and Damaged passive layer.
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.
M. Ghalambaz, M. Shamanian, A. M. Eslami, M. Abdollahi, E. Abdoulvand,
Volume 41, Issue 1 (Journal of Advanced Materials-Spring 2022)
Abstract
This research investigated the bonding properties of AISI 321 austenitic stainless steel from microstructural, mechanical, and corrosion points of view. To obtain the optimal parameters of pulsed current gas tungsten arc welding (PCGTAW), the Taguchi method was used. A cyclic potentiodynamic polarization test evaluated the corrosion resistance of the welded samples. The optimal conditions were achieved when the background current, the pulse current, the frequency, and the percentage of the pulse on time were 50 amps, 140 amps, 5 Hz, and 50, respectively. On the other hand, the analysis of variance showed that the percentage of pulse on time equal to 36 and the background current equal to 46 amperes were the most influential factors on the surface current density of the austenitic stainless steel 321 connection using the PCGTAW process. The mechanical properties were assessed using punch shear testing. In the optimal condition, the maximum shear force and strength were 3200 N and 612 MPa, respectively. The results showed that the most critical factor affecting the bonding properties of 321 steel was the heat input.
