, M.Sc. Thesis Sharif University of Technology Farshid, Saman (Author) ; Adib Nazari, Saeed (Supervisor)

Abstract

First stage blades tempreture in the turbine rotor section for the advanced turbines has increased up to 1100oc. The blades should be under mentioned condition for the long times up to 70000 hours and accordingly creep happens. Fatigue–creep interaction is the main reason for the failures of many engineering components under high temperature and cyclic loading. In this thesis, a model for the life prediction of fatigue–creep interaction which was developed by other investigators has been modified to predict fatigue–creep interaction on the nickel-based superalloys. In this model, the law of energy conservation and the momentum conservation principle are used to describe the process of...

Molecular dynamics simulation of manipulation of metallic nanoclusters on double-layer substrates [electronic resource]

, Article Physica E: Low-dimensional Systems and Nanostructures ; 2010, Vol. 42, No. 9, pp. 2364-2374 Mahboobi, H. (Hanif) ; Meghdari, Ali ; Jalili, Nader ; Amiri, Farshid ; Sharif University of Technology

Abstract

Molecular dynamics simulations are carried out to investigate the manipulation of metallic clusters on double-layer surfaces. The system parts are made of transition metals. The conditions which are subjected to change in the tests are material combinations for cluster, main substrate and lubricant layer (adlayer). In addition to qualitative observations, two criteria which represent the particle deformation and substrate abrasion are utilized as evaluation tools and are computed for each case. Obtaining this sort of knowledge is highly beneficial for further experiments in order to be able to plan the conditions and routines, which guarantee better success in the manipulation process

Exponential stabilization of flexural sway vibration of gantry crane via boundary control method

, Article JVC/Journal of Vibration and Control ; Volume 26, Issue 1-2 , 2020 , Pages 36-55 Entessari, F ; Najafi Ardekany, A ; Alasty, A ; Sharif University of Technology

SAGE Publications Inc 2020

Abstract

This paper aims to develop a boundary control solution for complicated gantry crane coupled motions. In addition to the large angle sway motion, the crane cable has a flexural transverse vibration. The Hamilton principle has been utilized to derive the governing partial differential equations of motion. The control objectives which are sought include: moving the payload to the desired position; reducing the payload swing with large sway angle; and finally suppressing the cable transverse vibrations in the presence of boundary disturbances simultaneously. These simultaneous boundary control objectives make the problem challenging. The proposed control approach is based on the original...

Boundary control of a vertical nonlinear flexible manipulator considering disturbance observer and deflection constraint with torque and boundary force feedback signals

, Article International Journal of Systems Science ; 2021 ; 00207721 (ISSN) Entessari, F ; Najafi Ardekany, A ; Alasty, A ; Sharif University of Technology

Taylor and Francis Ltd 2021

Abstract

In this paper, boundary control (BC) laws are designed to find a BC solution for a single-link nonlinear vertical manipulator to suppress the link’s transverse vibrations and control the rigid body nonlinear large rotating motion. The governing equations of motions and boundary conditions, which all consist of a set of PDEs and ODEs have been derived based on the Hamilton principle. It is desired to regulate large angular orientation, suppress the flexible link’s transverse vibrations and compensate the boundary disturbance simultaneously. The amount of elastic boundary vibration has remained within the constraint range. By considering novel Barrier-Integral Lyapunov functional in order to...

Boundary control of a vertical nonlinear flexible manipulator considering disturbance observer and deflection constraint with torque and boundary force feedback signals

, Article International Journal of Systems Science ; Volume 53, Issue 4 , 2022 , Pages 704-725 ; 00207721 (ISSN) Entessari, F ; Najafi Ardekany, A ; Alasty, A ; Sharif University of Technology

Taylor and Francis Ltd 2022

Abstract

In this paper, boundary control (BC) laws are designed to find a BC solution for a single-link nonlinear vertical manipulator to suppress the link’s transverse vibrations and control the rigid body nonlinear large rotating motion. The governing equations of motions and boundary conditions, which all consist of a set of PDEs and ODEs have been derived based on the Hamilton principle. It is desired to regulate large angular orientation, suppress the flexible link’s transverse vibrations and compensate the boundary disturbance simultaneously. The amount of elastic boundary vibration has remained within the constraint range. By considering novel Barrier-Integral Lyapunov functional in order to...

Condition Monitoring of Wind Turbine Blade Using Fiber Optics

, M.Sc. Thesis Sharif University of Technology Entessari, Farshid (Author) ; Zabihollah, Abolghasem (Supervisor) ; Behzad, Mehdi (Co-Advisor)

Abstract

Over the last decades the attention of the most modern countries about usage of wind has grown due to the recent crisis of energy. This renewable energy source offers a cost effective solution for electricity production. Wind energy is the best candidate among other sources due to wind turbines technology reliability. In order to gain maximum power from wind turbines, their size becomes relatively large, which creates more complexity in their repair and maintenance, furthermore Wind turbine downtime is outside the expectations, which is more costly than corrective maintenance, therefore in order to minimize sudden downtimes and related huge maintenance, a reliable monitoring technique must...

Boundary Stabilization and Motion Control of Flexible Crane Systems

, Ph.D. Dissertation Sharif University of Technology Entessari, Farshid (Author) ; Alasty, Aria (Supervisor) ; Najafi Ardekany, Ali (Supervisor)

Abstract

In recent years, boundary control (BC) approach for distributed parameter systems and their applications has demonstrated that it can be a well-intentioned candidate for control system design. In this approach, the main focus is on the boundary actions, where the actuators are aligned on the boundaries of the media. BC may be considered as an ideal approach, especially from applied and engineering point of view, because it deals only with actuators and sensors along the boundaries. Moreover, the problem of boundary stabilization and motion control of flexible crane systems has been one of the remarkable problems for control engineers. In this research, we contemplate the boundary control...

Planar molecular dynamics simulation of Au clusters in pushing process

, Article International Journal of Nanomanufacturing ; Vol.5, No.3/4 , 2010 , pp.288-296 Mahboobi, S. H ; Meghdari, A. (Ali) ; Jalili, N. (Nader) ; Amiri, F. (Farshid) ; Sharif University of Technology

2010

Abstract

Based on the fact that the manipulation of fine nanoclusters calls for more precise modelling, the aim of this paper is to conduct an atomistic investigation for interaction analysis of particle-substrate system for pushing and positioning purposes. In the present research, 2D molecular dynamics simulations have been used to investigate such behaviours. Performing the planar simulations can provide a fairly acceptable qualitative tool for our purpose while the computation time is reduced extremely in comparison to 3D simulations. To perform this study, Nose-Hoover dynamics and Sutton-Chen interatomic potential will be used to investigate the behaviour of the aforementioned system. Pushing of...

Molecular dynamics simulation of manipulation of metallic nanoclusters on stepped surfaces

, Article Central European Journal of Physics ; Volume 9, Issue 2 , 2011 , pp 454-465 ; 1644-3608 Mahboobi, S. H ; Meghdari, A. (Ali) ; Jalili, N. (Nader) ; Amiri, F. (Farshid) ; Sharif University of Technology

2011

Abstract

Molecular dynamics simulations are carried out to investigate the manipulation of metallic clusters on stepped surfaces. Five surface forms are considered in the simulations. The system parts are made of pure transition metals and Sutton-Chen many-body potential is used as interatomic potential. The conditions which are subjected to change in the tests include: materials used for particles and substrate, and surface step conditions. In addition to qualitative observations, two criteria which represent the particle deformation and substrate abrasion are utilized as evaluation tools and are computed for each case. Simulation results show the effect of the aforementioned working conditions on...