Loading...
Search for:
finite-element-models
0.009 seconds
Total 193 records
A mathematical model for evolution of flow stress during hot deformation
, Article Materials Letters ; Volume 59, Issue 26 , 2005 , Pages 3319-3324 ; 0167577X (ISSN) ; Sharif University of Technology
2005
Abstract
A mathematical model has been proposed to predict flow behavior of steel under hot deformation conditions with regard to the effects of dynamic recovery and dynamic recrystallization. For this purpose, Kocks-Mecking dislocation model together with a first order rate equation have been utilized. To associate temperature and strain rate variations on flow behavior of deforming metal, a thermo-viscoplastic finite element model has been coupled with the proposed model. To verify the modeling results, hot rolling experiments were performed and roll forces at various temperatures and rolling speeds were recorded. A good agreement was found between the predicted and the experimental data. © 2005...
Analytical modeling of magnetic flux in superconducting synchronous machine
, Article IEEE Transactions on Applied Superconductivity ; Volume 23, Issue 1 , 2013 ; 10518223 (ISSN) ; Elhaminia, P ; Zolghadri, M. R ; Fardmanesh, M ; Sharif University of Technology
2013
Abstract
A general model for superconducting synchronous machines in which the rotor can be considered as a magnetic or a nonmagnetic material is proposed and analytically investigated. Analytical equations for magnetic flux in different regions of the machine have been developed. Furthermore, nonlinear magnetization of the iron core is studied. In order to solve the equations in the case of the iron saturation, a reiterative algorithm is proposed. Finite-element simulation has also been performed to verify the equations and the proposed algorithm. The obtained analytical results show good agreement with finite-element method results
The effects of intra-abdominal pressure on the stability and unloading of the spine
, Article Journal of Mechanics in Medicine and Biology ; Volume 12, Issue 1 , 2012 ; 02195194 (ISSN) ; Farahmand, F ; Shirazi Adl, A ; Arjmand, N ; Malekipour, F ; Parnianpour, M ; Sharif University of Technology
Abstract
In spite of earlier experimental and modeling studies, the relative role of the intra-abdominal pressure (IAP) in spine mechanics has remained controversial. This study employs simple analytical and finite element (FE) models of the spine and its surrounding structures to investigate the contribution of IAP to spinal loading and stability. The analytical model includes the abdominal cavity surrounded by muscles, lumbar spine, rib cage and pelvic ring. The intra-abdominal cavity and its surrounding muscles are represented by a thin deformable cylindrical membrane. Muscle activation levels are simulated by changing the Young's modulus of the membrane in the direction of muscle fibers, yielding...
An analytical approach for optimal design of rotor iron for superconducting synchronous machine
, Article IECON Proceedings (Industrial Electronics Conference), 7 November 2011 through 10 November 2011, Melbourne, VIC ; 2011 , Pages 1741-1745 ; 9781612849720 (ISBN) ; Yazdanian, M ; Zolghadri, M. R ; Fardmanesh, M ; Sharif University of Technology
2011
Abstract
Although iron-cored superconducting machine has been recently proposed in many papers for its advantages over conventional air-cored structure such as less cost and less perpendicular magnetic component on HTS tapes it has not been studied analytically yet. This paper analytically investigates a general model for iron-cored superconducting synchronous machine. In this paper, analytical equations for magnetic flux in different regions of machine have been proposed along with an algorithm to solve the equations. The analytical equations will be then used to optimize the thickness of rotor iron in order to maximize the machine power density. Analytical and finite element simulation results will...
Numerical and experimental investigation of the vibration of rotors with loose discs
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 224, Issue 1 , 2010 , Pages 85-94 ; 09544062 (ISSN) ; Asayesh, M ; Sharif University of Technology
2010
Abstract
In this study, the energy method has been used to develop a finite-element code for studying the effects of loose rotating discs on the rotor-bearing systems' response. A mathematical model of the loose disc has resulted in terms similar to unbalance and gyroscopic effects in the equation of motion of the system. Results of this study show that rotor response and beating phenomena are a function of measurement location, loose disc mass and inertia, ratio of rotating speed to the speed of loose disc, and clearance between the loose disc and shaft considering constant speed for loose disc and shaft. The developed finite-element model can numerically give the response of rotors with any number...
Analysis of Tall Outrigger Braced Structures on Flexible Foundations Using Finite Elements Modeling
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masood (Supervisor)
Abstract
One of the most efficient methods in stiffening tall buildings to withstand lateral loads such as wind loading is to link the shear resisting core to the exterior columns using outrigger trusses. Many tall buildings such as Taipei 101 have benefited from outriggers. In this system, the outriggers force the perimeter frame to take part in resisting the bending moment of the lateral load acting on the structure by developing axial restraining forces in the windward and the leeward columns of the perimeter frame and forming a resisting moment.Most of the present analytical methods have studied the performance of outrigger braced structures neglecting shear deformation of the shear wall core and...
An Investigation on the Behavior of Bolted Connections using Friction Drilling in Shear and Tension
, M.Sc. Thesis Sharif University of Technology ; Ahmadizadeh, Mehdi (Supervisor)
Abstract
Friction drilling or flow drilling is a method of making holes in metal sheets, in which the material is pushed with the aid of heat from friction. This procedure allows making holes in sheet metal, with a sleeve formed as the hole is created. This sleeve is then threaded and used as the nut, thus eliminating the need for access to the interior faces of hollow steel sections. On the other hand, with the development of advanced manufacturing techniques, larger and thicker hollow structural sections are becoming more popular in mid-rise and multistory structures. onsequently, flow drilling can be considered as a viable alternative for traditional drilling techniques, where the material is...
Optimization of Scan Algorithms in Selective Laser Sintering
, M.Sc. Thesis Sharif University of Technology ; Movahhedi, Mohammad Reza (Supervisor) ; Khodaygan, Saeed (Supervisor)
Abstract
One of the most important manufacturing methods using technologies AM, is the SLS method. This method because it would significantly reduce the construction time is the ability to build a variety of materials, is pervasive. The SLS devices input is part CAD file which is then part layered, a layer of powder is poured on the bed. Each layer is defined contour on the part and then scanned by laser inner layer is hatched by laser. Scanning algorithms and hatching in the SLS is an important part of building that has an impact on properties part and a lot of research has been done about it. synthetic scan algorithms presented in this study. The purpose of this algorithm is that part warpage and...
Damage Detection of Lapjoints with Piezoelectric Wafer Active Sensor
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
Structural Health Monitoring (SHM) is a multidisciplinary emerging research field. SHM assesses the health state of the structure through processing and interpreting of signals and can predict remain life of the structure. Damage detection with Piezoelectric Wafer Active Sensors (PWAS) is one of the effective and emerging methods of SHM. One of the most critical parts of aerial structures is lap joints in which SHM could be very effective. In this research, damage detection of lap joints using lamb wave propagation has been studied. A 3D model of an aluminum lap joint presented. The PWAS are modeled separately and bonded to the host structure and coupled electromechanically with the...
Scrutiny of a Semi-rigid End-plate Splice Connection under Monotonic and Cyclic Loading
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masood (Supervisor)
Abstract
Existing design methods for steel frames has been improved over the last three decades in order to incorporate the behavior of semi-rigid steel connections in furtherance of frame design and since the analysis and design of structures is often done based on the assumption of completely rigid or pinned behavior,therefore, the actual behavior of connections and their modeling can help to understand the actual behavior of structures.Knowledge of the initial rotational stiffness of the connection is important for elastic analysis of structures. Investigations show that structures with semi-rigid connections have many features which are the causes to prefer these kinds of connections to the...
Modeling and Structural Health Monitoring of 5 MW Wind Turbine Based on Moving Principal Component Analysis
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
Nowadays, the structural health monitoring is considered as an essential element in improving the performance of the structures. The role and importance of the issues in this area have been reached to the point that different ideas and policies are developed for the safety margin over the useful life of the structures. To analyze more accurately, a real model of a turbine blade is required. This issue would be taken into more consideration when the scale of the turbine gets larger. Changing of the design philosophies over time results in effective changes in the design process and maintenance procedures. Any single of these inspections has different importance according to users' demands. In...
Numerical Modeling of the Behavior of Base Plates with Various Degrees of Rigidity
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)
Abstract
Connections have a crucial role in the behavior of every structure. Amongst various types of connections used in steel structures are those used to connect the columns to the foundations, namely Base Plates. As other types of connections, base plates control the behavior of the structure in various respects including affecting the effective length of columns. The main task of any base plate is to distribute the forces of the column on the foundation in such a manner that the stresses in concrete are below their allowable values. Different configurations, with or without various attachments, are used for designing the base plates hence achieving various types of behavior with various levels...
Parametric Finite Element Modeling of the Vertebral Trabecular Bone Behavior Based on Cellular Solids Theory
, M.Sc. Thesis Sharif University of Technology ; Jalali, Mir Abbas (Supervisor) ; Parnianpour, Mohammad (Co-Advisor)
Abstract
Spine column is the most important musculoskeletal structures. One of the serious health problems in societies, especially among aged population is osteoporosis. Loss of bone density in bone structures is called osteoporosis which increases the risk of fracture due to a decrease of bone stiffness and bone strength. Spine is the most common sites for osteoporosis-related fractures. Current assessment of osteoporosis status is based on bone densitometry tools like QCT (Quantitative Computed Tomography) or DEXA (Dual Energy X-ray absorptiometry). With these methods it is only possible to estimate density without any consideration the morphology of trabecular making parts like rods and plates....
Numerical Modeling of the Behavior of Base Plates with Various Degrees of Rigidity Under Cyclic Loads
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Co-Advisor)
Abstract
Due to the important role of base plates, both in transferring forces from the structure to the foundation, and also in transferring vibrations from soil to the structure, it is necessary to have sufficient knowledge on their behaviour and performance under monotonic and cyclic loading regimes. In fact, the behaviour of the supports of any structure cannot be identified without identifying the behaviour of its base plates. Numerous configurations with/without various types of attachments have been proposed and used for base plates. In this work, altogether six commonly-used types of base plates were studied and their behaviour under monotonic and cyclic loadings was obtained using commercial...
Introduction to Developing, Modification, and Customization of the Guidelines for Replacement of Metal Patch Repairs with the Composite Patches
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
The phenomenon of aging causes a great deal of damage to the airborne structures for which there is a specific maintenance instruction, or if an unexpected damage occurs in specific area of a structure, this damage must be repaired and a special repair process must be designed for it. However, due to the diversity of damages and also variations of the implemented loads, the load is transferred to other structural elements, hence, it is necessary to extend the life of the structure in order to identify these loaded elements and reinforce the applied forces. First, this phenomenon involves a design of a large number of metal patches, where a large number of drills have to be made in the body...
Investigation of the Sensitivity of Perforated Plates in Fracture and their Growth of Strain
, M.Sc. Thesis Sharif University of Technology ; Alijani Moghaddam, Hassan (Supervisor)
Abstract
The present study looks into the fracture of perforated steel plates and their sensitivity in ductile fracture. It also examines the effects of strain rise phenomenon in these specimens. The main employed fracture model is VGM, which was first introduced by Rice and Tracey, and later enhanced by Kanvinde et al.. The general methodology includes finite element simulation and lab experiments on perforated plates, to determine ductility, strain concentration in hole periphery and model sensitivity. Fot thid purpose 86 steel sheet specimen with different holes and cuts were manufactured and tested. With the acquired data, the impact of strain concentration on the load carrying capabilities and...
Analysis of Brushless Doubly-Fed Motor under Various Operating Modes
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor)
Abstract
The Brushless Doubly-Fed Machine (BDFM) is a machine which incorporates the robustness of the squirrel cage induction machine and the speed and power factor control of a synchronous machine. All of these advantages are obtainable from a relatively low rating power electronic converter (e.g. 30% of the machine’s rating). The stator of a BDFM is furnished with two balanced three phase windings of conventional design (power and control winding). These windings differ in pole number and are often excited at different frequencies. Hence, there is no direct magnetic coupling between them. The power winding is connected to a constant-voltage, constant-frequency source and the control winding is...
Harmonic Analysis of Brushless Doubly-Fed Machines
, M.Sc. Thesis Sharif University of Technology ; Oraee, Hashem (Supervisor)
Abstract
The Brushless Doubly-Fed Machine (BDFM) is a machine which incorporates the robustness of the squirrel cage induction machine and the speed and power factor control of a synchronous machine. All of these advantages are obtainable from a relatively low rating power electronic converter (e.g. 30 % of the machine’s rating). The stator of a BDFM is furnished with two balanced three phase windings of conventional design (power and control winding). These windings differ in pole number and are often excited at different frequencies. Hence, there is no direct magnetic coupling between them. The power winding is connected to a constant-voltage, constant-frequency source and the control winding is...
A Detailed Nonlinear Finite Element Model of the L4-L5 Motion Segment to Predcit Spinal Loads during in Vivo Activities
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor) ; Parnianpour, Mohammad (Supervisor)
Abstract
Several geometrically-detailed passive finite element (FE) models of the lumbar spine have been developed and validated under in vitro loading conditions. As these models are devoid of muscles, they are either not used to simulate in vivo activities or muscle forces are modeled by a hypothetical compressive follower load (FL). A number of symmetric and asymmetric static tasks were first simulated using a validated musculoskeletal model of the thoracolumbar spine to predict trunk muscle forces. The predicted muscle forces along with the gravity loading were then applied to a passive FE model of the L4-L5 motion segment (developed and validated here) to estimate load sharing among the disc,...
Investigation of Activation Mechanism of Mechanosensitive Nano Ion Channels
, Ph.D. Dissertation Sharif University of Technology ; Vosoughi, Manochehr (Supervisor) ; Jamali, Yusef (Supervisor) ; Naghdabadi, Reza (Supervisor)
Abstract
Mechanosensitive (MS) channels are ubiquitous molecular force sensors that respond to a number of different mechanical stimuli including tensile, compressive and shear stress. One of the main mechanisms to functionally study these channels is the patch clamp technique. Here we use continuum mechanics to probe the question of how curvature, in a standard patch clamp experiment, at different length scales (global and local) affects a model MS channel. Firstly, to increase the accuracy of the Laplace’s equation in tension estimation in a patch membrane and to be able to more precisely describe the transient phenomena happening during patch clamping, we propose a modified Laplace’s equation. In...