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State functions: the milestone of fracture
, Article Archive of Applied Mechanics ; Volume 86, Issue 7 , 2016 , Pages 1311-1324 ; 09391533 (ISSN) ; Ranjbaran, M ; Sharif University of Technology
Springer Verlag
2016
Abstract
The fracture phenomenon is defined via the change of state of structure (entity) between the intact and the fractured end states as the function of the state variable. The twin state functions are defined for the transition of unit of the entity between its two end states. The state ratio is defined as the ratio of the two state functions. The property of the cracked structure is defined as the product of the structure property and the state ratio. The work is then used to derive the main parameters of the fracture mechanics. The work is verified via five examples. © 2016, Springer-Verlag Berlin Heidelberg
State-based buckling analysis of beam-like structures
, Article Archive of Applied Mechanics ; Volume 87, Issue 9 , 2017 , Pages 1555-1565 ; 09391533 (ISSN) ; Ranjbaran, M ; Sharif University of Technology
2017
Abstract
Beam, column, plate, and any other structure, under full or partial compressive loading, are prone to failure by the buckling phenomenon. At the instant of failure, the structure may be in unpredictable elastic, elastic–plastic, full plastic, cracked, or other forms of deterioration state. Therefore, in spite of so much study, there is no definite solution to the problem. In this paper a unified, simple, and exact theory is proposed where buckling is considered as the change of state of structure between intact and collapsed states, and then the buckling capacity is innovatively expressed via states and phenomena functions, which are explicitly defined as functions of state variable. The...
Innovative theory for the compliance computation in rotors
, Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 1779-1788 ; 10263098 (ISSN) ; Ranjbaran, M ; Sharif University of Technology
2017
Abstract
The conventional energy release rate approach to the computation of the crack compliance in rotors is critically reviewed and its shortcoming is highlighted. The state functions and the generic compliance are introduced, defined, and verified. The proposed functions are defined based on the end states' conditions and are exact. The crack compliance of the shaft in torsion is explicitly defined as the function of the crack depth ratio and recommended as a good alternative to the classical procedure of the energy release rate method. The accuracy and efficiency of the work are verified by concise mathematical formulation and comparison of the results of the work with the others in four...
A Model for Supplier Selection by Considering Buyer and Supplier Benefits
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad (Supervisor)
Abstract
Supply chain problems consist of a large number of issues. One of the key problem in this area is supplier selection in supply chain. Several criteria must be considered in the supplier selection. So, multi criteria decision making approach, neural network, mathematical programming and etc. are used for solving this problems. In most of these problems, supplier selection is done according to the buyer’s objectives.
So far, several methods are provided for supplier selection problem. In majority of them, supplier selection problem is surveyed from buyer’s viewpoint and in those have only been considered the buyer’s benefit maximization that will not necessarily lead to optimal condition...
So far, several methods are provided for supplier selection problem. In majority of them, supplier selection problem is surveyed from buyer’s viewpoint and in those have only been considered the buyer’s benefit maximization that will not necessarily lead to optimal condition...
An interface tool for finite element–based optimal design
, Article International Journal on Interactive Design and Manufacturing ; Volume 18, Issue 1 , 2024 , Pages 375-383 ; 19552513 (ISSN) ; Khodaygan, S ; Sharif University of Technology
2024
Abstract
Optimal design of engineering systems with complex geometry under multiple loadings is always a challenging procedure. This paper introduces a computational interface tool between ABAQUS® and MATLAB® that can be used for carrying out the parametric optimal design of complex mechanical components. The software is developed entirely in MATLAB® environment which can handle constrained optimization problems without the need for the user to explicitly define the constraints using mathematical equations or functions. In this software, the design variables are proposed for selection through a user-friendly environment and the objective function can be iteratively evaluated by the finite-element...
Investigating the Influence of a Silty Layer on the Liquefaction of Saturated Sandy Soils through Numerical Methods
, M.Sc. Thesis Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
One of the main geotechnical phenomena that causes severe damage during earthquake is liquefaction. This incident occurs due to the undrained behavior of loose sandy soils. In this occurrence, the interaction between the solid and liquid phases in a cyclic motion leads to an increase in pore water pressure and a decrease in interactive forces (effective forces) between grains in the solid grains. Therefore, shear strength decreases. Different aspects of the aforementioned phenomenon is investigated, namely, field, laboratory, and numerical; nevertheless, the study is largely focused on the numerical modelling. Most studies in this field are carried out on a one-layer saturated sand. However,...
Prediction of Hydraulic Fracturing Technology in Naturally Fractured Rocks, by Considering Immiscible Two-phase Flow
, Ph.D. Dissertation Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Ayatollahi, Shahab (Supervisor) ; Shad, Saeed (Supervisor) ; Ranjbaran, Abdolrasul ($item.subfieldsMap.e)
Abstract
To have a deeper understanding of Hydraulic fracturing operation, in this study four important parts in this field was developed and simulated. In the first part, continuity and momentum equations for a single phase flow in a propagating penny-shaped fracture inside an impermeable matrix was revisited based on a fixed coordinate system. Its correctness was validated against experimental data and its features were compared with the well-known lubrication theory in analytical form. The new derived continuity equation caused the fracture tip to have a positive and finite pressure while, the conventional model predicted negative infinity for that. In the second part, Finite Volume method was...
Does the short-term boost of renewable energies guarantee their stable long-term growth? Assessment of the dynamics of feed-in tariff policy
, Article Renewable Energy ; Volume 159 , October , 2020 , Pages 1252-1268 ; Hamed Shakouri, G ; Mashayekhi, A. N ; Kazemi, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Feed-in tariff (FiT) is one of the most efficient ways that many governments throughout the world use to stimulate investment in renewable energies (REs) technology. For governments, financial management of the policy could be challenging as it needs a considerable amount of budget to support RE producers during the long remuneration period. In this paper, it has been illuminated that the early growth of REs capacity could be a temporary boost. And the socio-economic structure of the system will backlash the policy if some social mechanisms are not considered. Social tolerance for paying REs tax and potential investors’ trust emanated from budget-related mechanisms -which have rarely been...
A heuristic insight on end-point calculation and a new phase interference parameter in two-phase relative permeability curves for horizontal fracture flow
, Article Transport in Porous Media ; Volume 119, Issue 3 , 2017 , Pages 499-519 ; 01693913 (ISSN) ; Shad, S ; Taghikhani, V ; Ayatollahi, S ; Sharif University of Technology
2017
Abstract
Relative permeability curves of two-phase flow in a fracture have been a subject of study in recent years. The importance of these curves have been widely observed in multidisciplines, such as water subsurface resources, geothermal energy and underground hydrocarbon resources, especially fractured oil and gas reservoirs. Extensive experimental studies have been cited alongside the numerical studies in this area. However, simple analytical and practical solutions are still attractive. In the current study, wettability effects and phase interference explicitly were tried to be implemented in a simple analytical formula. The wettability effects are represented by residual saturations which...
Three-dimensional diffraction analysis of phase and amplitude gratings based on legendre expansion of electromagnetic fields
, Article Photonic Applications in Nonlinear Optics, Nanophotonics, and Microwave Photonics, Toronto, ON, 12 September 2005 through 14 September 2005 ; Volume 5971 , 2005 ; 0277786X (ISSN) ; Mehrany, K ; Rashidian, B ; Ranjbaran, M ; Morandotti R. A ; Ruda H. E ; Yao J ; Sharif University of Technology
2005
Abstract
Three-dimensional vectorial diffraction analysis of phase and amplitude gratings in conical mounting is presented based on Legendre expansion of electromagnetic fields. In the so-called conical mounting, different fields components are coupled and the solution is not separable in terms of independent TE and TM cases. In contrast to conventional RCWA in which the solution is obtained using state variables representation of the coupled wave amplitudes by expanding space harmonic amplitudes of the fields in terms of the eigenfunctions and eigenvectors of the coefficient matrix defined by rigorous coupled wave equations, here the solution of first order coupled Maxwell's equations is expanded in...
Dispersion and gain investigation of free electron laser based on legendre polynomial expansion
, Article Photonic Applications in Nonlinear Optics, Nanophotonics, and Microwave Photonics, Toronto, ON, 12 September 2005 through 14 September 2005 ; Volume 5971 , 2005 ; 0277786X (ISSN) ; Chamanzar, M ; Mehrany, K ; Rashidian, B ; Ranjbaran, M ; Morandotti R. A ; Ruda H. E ; Yao J ; Sharif University of Technology
2005
Abstract
Free electron lasers have been the subject of intensive interest during the recent decades. In this paper, free electron laser having sheet electron beam with arbitrary inhomogeneous profile of transverse distribution of the beam current density is studied in the linear regime, whereas a novel approach based on the Legendre polynomial expansion of eigenfunctions, already used in analyzing optical structures including stratified structures and diffraction gratings, is adapted to find the eigenfunctions and eigenvalues of the structure. As for this method is unconditionally stable, it works pretty well even in those cases in which the conventional transfer matrix method suffers from numerical...