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    Robust Design Optimization for Fatigue Life with Geometric and Material Uncertainties of Mechanical Parts Under Random Loading Based on Maximizing Fatigue Life and Minimizing Uncertainty in Fatigue Llife Prediction

    , M.Sc. Thesis Sharif University of Technology Esfahani, Saeed (Author) ; Khodaygan, Saeed (Supervisor)
    Fatigue life prediction of a mechanical part is one of issues which a group of engineers are engaged with it and always they try to design the parts with the maximum of lifetime. Although many researches have been done in this field but yet we can see that predicted life are different from that happens in the reality because there are some uncertainties in the phenomena. Our effort in this project is creating an algorithm design so that the parts are designed by it, have the maximum fatigue life and the minimum uncertainty in prediction. In this project we have considered geometrical, material and random loading uncertainties as error resources. Older methods those are presented in this... 

    Reliability Based Robust Design Optimization of Mechanical Systems with Uncertain Parameters Using Bayesian Inference

    , M.Sc. Thesis Sharif University of Technology Hassani, Hossein (Author) ; Khodaygan, Saeed (Supervisor) ; Asempour, Ahmad (Supervisor)
    This world’s commercial and competitive space force’s designers and manufactures to produce and supply products with high quality and low price at desirable level of reliability. On the other hand, during the design and production process, Engineers are always faced with uncertainty. Essentially, uncertainties can be divided into two categories: aleatory and epistemic. Aleatory uncertainties are due to changes in design conditions, material properties, physical dimensions of components and operating conditions. This kind of uncertainty will not be reduced during the life.on the otherhand, Epistemic uncertainties that are due to lack of knowledge about physical nature of systems can be... 

    Numerical Modelling and Experimental Validation of Nano Colloid Droplet Formation in the Electrohydrodynamic 3D Printer

    , Ph.D. Dissertation Sharif University of Technology Mohammadi, Kaivan (Author) ; Movahhedy, Mohammad Reza (Supervisor) ; Khodaygan, Saeed (Supervisor) ; Simchi, Abdolreza (Co-Supervisor) ; Mofrad, Mohammad Reza (Co-Supervisor)
    The electrohydrodynamic (EHD) 3D printing technology is an Additive Manufacturing (AM) method that can be used in the manufacture of submicron-size structures. Due to the multiphysics dynamics and the multiphase nature of the microdroplet formation in the EHD printers, modeling of this phenomenon is complicated. In this thesis, the formation of a droplet in an EHD printer—under a pulsed electrical field—is simulated using a new numerical model which couples the fluid flow, the electric field distribution and the movement of the electric charges under dynamic and transient conditions. The level-set method is applied to the entire multiphysics domain in order to study the formation of the... 

    Optimization of Scan Algorithms in Selective Laser Sintering

    , M.Sc. Thesis Sharif University of Technology Manshoori Yeganeh, Ahmad (Author) ; Movahhedi, Mohammad Reza (Supervisor) ; Khodaygan, Saeed (Supervisor)
    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... 

    Tolerance Analysis of Rotating Mechanical Systems in Presence of Dimensional and Geometrical Errors

    , M.Sc. Thesis Sharif University of Technology Fallahzadeh, Hamed (Author) ; Khodaygan, Saeed (Supervisor)
    Because of increasing demands for using of rotating systems in high accuracy and high speed applications, in addition of specific condition of rotating systems, it is necessary to analysis these rotating systems characteristics. In addition to the dimensional and geometrical errors of mechanical system parts and assembly errors, manufacturing quality directly depends on Non Repetitive Run-Out (NRRO) errors; so the results of NRRO errors as an ultra-precision characteristic should be studied in required outputs. In this paper by analyzing dimensional and geometrical tolerances as tolerance zone, the variations of system outputs because of tolerances is calculated in both static and dynamic... 

    Optimal Design of the High Speed Spindle Bearings to Reduce Non Repeatable Run Out

    , M.Sc. Thesis Sharif University of Technology Farahani, Mohammad Reza (Author) ; Khodaygan, Saeed (Supervisor) ; Movahhedy, Mohammad Reza (Co-Advisor)
    Creating synchronous conditions of precision and speed in rotating systems is a requirement for the design of these systems. The requirement to create these conditions is essential in various applications, such as machine tools and computer equipment. One of the main sources of error in the motion of the high speed spindles is the occurrence of non-repetitive runouts. The presence of non-repetitive runouts at high speeds greatly affects the accuracy of the rotating motion of rotating systems and reducing its effects is always considered in the design of high speed rotary systems. Usually, one of the most important factors in the occurrence of non-repetitive runouts is related to spindle... 

    Selection of the Optimal Orientation of Parts in Rapid Prototyping Processes

    , M.Sc. Thesis Sharif University of Technology Amir Hossein Golmohammadi (Author) ; Khodaygan, Saeed (Supervisor)
    Additive manufacturing (AM), also known as Rapid prototyping or D printing, is a new technology for the manufacturing of the physical parts through an additive manner. In the AM process, the orientation pattern of the part is one of the most important factors that significantly affects the product properties such as the build time, the surface roughness, the mechanical strength, the wrinkling, and the amount of support material. The build time and the surface roughness are the more imperative criteria than others that can be considered to find the optimum orientation of parts. In this research, Two method is used to optimize part build orientation (PBO). In the first method a new combined... 

    Effect of Superhydrophobic Materials Application on the Car Body to Reduce Drag

    , M.Sc. Thesis Sharif University of Technology Valizadeh, Mahsa (Author) ; Moosavi, Ali (Supervisor) ; Khodaygan, Saeed ($item.subfieldsMap.e)
    Considering the importance of environmental issues and the limitation of fuel supplies in the world, car issues have become one of the most important debates of the day. The methods used to reduce fuel consumption and emissions of greenhouse gases are primarily aimed at changing vehicle structure to reduce drag. An external body shape has been developed to reduce drag forces over the years. Due to the existence of limitations in the actual conditions of the theory, such as the beauty and convenience production, other methods should be examined. In this study, the structure of superhydrophobic properties materials with the emphasis on innovation has been considered. In order to investigate... 

    Finite Element Simulation of Machining Chatter in Turning and Milling with Orthogonal Geometry, Taking into Account of Two-Dimensional Machine Tool Dynamics

    , M.Sc. Thesis Sharif University of Technology Jafarzadeh, Ehsan (Author) ; Movahhedy, Mohammad Reza (Supervisor) ; Khodaygan, Saeed (Co-Advisor)
    Chatter vibration is a major obstacle in high quality machining. This undesirable vibration decreases the production rate, surface quality, tool life and machine tool life. In the last few decades, a lot of models have been presented to predict chatter. Most of the models, whether linear or nonlinear, have focused on modeling of machine tool dynamics and either disregard the effective parameters of chip formation process or apply some of these parameters through simplified equations. In this research, a finite element simulation of chip formation is combined with the dynamics of machine tool to investigate chatter and its effective factors. The proposed approach, unlike common mathematical... 

    Device on a Chip, in Order to Control and Separation of Circulating Tumor Cells

    , M.Sc. Thesis Sharif University of Technology Masoudi, Mohammad Mahdi (Author) ; Shamloo, Amir (Supervisor) ; Khodaygan, Saeed (Supervisor)
    The process of separating cells from a laboratory sample, is a crucial step in biotechnology and medical science. Cells separation is important for various reasons, including the identification and treatment of diseases, as an example, separation of Circulating Tumor Cells (CTCs) from patient blood sample. CTCs are cells that shed from a tumor and diffuse into blood vessels. These cells are the starters of metastasis, the process in which cancer spreads in body, and are main reason of deaths caused by cancer. Extremely low percentages of target cells in the blood, clarify the importance of highly accurate and sensitive separation. Currently, conventional separation methods are of macro-order... 

    Optimal Design of Tolerances in the Non-rigid Assemblies under the Thermal Impact

    , M.Sc. Thesis Sharif University of Technology Hemati Nik, Javad (Author) ; Khodaygan, Saeed (Supervisor)
    Tolerance allocation in the recent mechanical assembly is significant because it straightly affects product performance and cost. Loose tolerances may cause the quality defect while tight tolerances can increase the cost. Thermal effects and the temperature gradients are one of the factors that caused changes in the size and geometry of the components during the performance of mechanical assemblies. This thesis proposes a new approach for tolerance design considering the thermal effects, to achieve lower manufacturing cost and good product quality. Finite element analysis is used to determine the deformation of components in an assembly. The neural network is trained using experimental... 

    Laser-Based Inspection of Internal Geometry of Industrial Pipes in Pigging Procedure

    , M.Sc. Thesis Sharif University of Technology Hadavand, Majid (Author) ; Khodaygan, Saeed (Supervisor)
    Along with improvement of technology and need for access to energy resources, existence of pipelines such as gas, oil and water pipes is vital for our lives. These pipes will be eroded and damaged over time. With the prediction of the defects and tracking of pipeline paths, the probability of sudden damages is greatly reduced. In this research, at first various non-destructive methods of monitoring the pipelines are investigated and it is shown that the laser method is the most comprehensive and non-destructive inspection method and then the background of the chosen method is examined. Also, the hardware aspect of the system and the proper layout of the laser sensors are determined on the... 

    Tolerance Design of Mechanical Systems based on Reliability Modeling under Bayesian Inference

    , M.Sc. Thesis Sharif University of Technology Ghaderi, Aref (Author) ; Khodaygan, Saeed (Supervisor) ; Assempour, Ahmad (Supervisor)
    Mechanical production centers are seeking to produce the highest quality products at the lowest cost. Intrinsic processes of manufacturing are not precise processes, and factors such as tool wear, tool vibration and fixation, fixing defects, and other factors that occur during production, make the pieces deviate from the designer's desirable geometry. Usually, due to deviations of parts from their size, their dimensional and geometric characteristics change. Because the components are rarely just a part, often in the majority of parts of the assembly, the operation of the set may be impaired due to the accumulation of changes. Errors that are usually caused during component assembly due to... 

    A new Approach in Reliability Based Robust Optimization

    , M.Sc. Thesis Sharif University of Technology Sharafi, Mohammad Hossein (Author) ; Khodaygan, Saeed (Supervisor)
    A mechanical system inherently affected by the conditions, factors and parameters of uncertainty. Without including the uncertainty effects in the optimal design procedure, the mechanical system will not be reliable. To include uncertainty effects in an optimum design, there are two different approaches; the robust design optimization and the reliability based design optimization. In robust design optimization process, the main aim is to enhance the system performance by minimizing the variations. In reliability based design optimization process, the target is that the optimal design variables to be in appropriate reliably levels. In this paper, a new model for the reliability based robust... 

    Tolerance Design of Mechanical Parts Considering Degradation and Quality Loss in Manufacturing Process and Operating Conditions

    , M.Sc. Thesis Sharif University of Technology Dehghani Tafti, Mohammad Saleh (Author) ; Khodaygan, Saeed (Supervisor) ; Asempour, Ahmad (Supervisor)
    The tolerance stack-up in mechanical assemblies is closely related to the quality of finished products and to the costs of production. In practice, choosing a large tolerance range will result in performance reduction. On the other hand, with small tolerances considered, production costs will increase. Tolerance allocation is a useful tool to control the dimensional and geometric variables of the product, so design engineers can control the final product quality level, production cost, and other variables. The proposed method for tolerance design considers the effects of degradation and quality loss over time and allocates tolerances so that, the functional key characteristic satisfies, as... 

    Automatic System Identification Algorithm Including Uncertainty Estimation based on Operational Modal Analysis

    , M.Sc. Thesis Sharif University of Technology Shakeri, Mohammad Sajad (Author) ; Khodaygan, Saeed (Supervisor) ; Movahedi, Mohammad Reza (Supervisor)
    Modal analysis is very important in determining the physical properties of structures and mechanisms. This field is divided into two general parts: Experimental Modal Analysis (EMA) and Operational Modal Analysis (OMA). In the operational modal analysis, there are more challenges for the analyst due to the lack of inputs to identify the system. Many of the mechanical structures can not be analyzed experimentally and under specific loadings, but should be identified under actual operating conditions and in situations where the inputs of the system are not measurable. For this purpose, a modal analysis method called "Random Sub-Space Identification" (SSI) is intoduced, which uses only output... 

    Optimization of Resonator’s Acoustic Performance in the Muffler Set

    , M.Sc. Thesis Sharif University of Technology Asadi, Alireza (Author) ; Khodaygan, Saeed (Supervisor)
    Noise pollution is one of the major issues in automative industry. Many of these noises are caused by the internal combustion engine. Using reactive mufflers in the car's exhaust path can effectively reduce this annoying noises. Imposed pressure drop caused by installation this mufflers must be within an acceptable range for the car engine. Resonators, despite having a much lower pressure drop than other components of the exhaust system, can be used to cover the weaknesses of the muffler in the acoustic performance of the noise reduction set. One of the most common methods for designing a resonator is to use perforated plates. In this study the effect of various geometric parameters of a... 

    A Path Planning Method Based on Basic RRT* Algorithm and Cagd-Based Curves Ffor Non-Holonomic Wheeled Mobile Robots

    , M.Sc. Thesis Sharif University of Technology Eshtehardian, Ali (Author) ; Khodaygan, Saeed (Supervisor)
    Throughout recent decades, one of the most important and challenging problems in robotics has been robot's path planning. Path planning means a robot must find its way from start to the goal point and track it without any collision to the obstacles. For this aim during the recent decades a wide variety of algorithms such as A*, Dijkstra and … have been proposed that some of which generate an optimal path as their output while others tend to create only a path regardless of its optimality. One of the most practical path planning methods is RRT algorithm which is executable in real-world applications, and by generating some nodes randomly then creating a tree-based graph, thereby outputting a... 

    Robust Orientation Estimation Using Imu and Online Machine Learning Based Calibration in the Presence of Distortions

    , M.Sc. Thesis Sharif University of Technology Golmohammad, Sadjad (Author) ; Khodaygan, Saeed (Supervisor)
    In this project an optimized and robust orientation estimation method using IMU and magnetic sensors is presented. Magnetic distortion effects in orientation estimation is also one of the main purposes. Proposed sensor fusion algorithm is based on a complementary filter which provides a quaternion estimation as the algebraic solution of a system from inertial/magnetic observations. To develop the basic sensor fusion algorithm some procedures including a simple calculation to deal better with non-gravitational accelerations, decrease the effect of magnetometer in the presence of distortions and online gyroscope bias estimation is added. Also, a method for classification the different types of... 

    Optimal Process Planning for Automated Robotic Assembly of Mechanical Assembles based on Reinforcement Learning Method

    , M.Sc. Thesis Sharif University of Technology Raisi, Mehran (Author) ; Khodaygan, Saeed (Supervisor)
    Nowadays, the assembly process is planned by an expert and requires knowledge and it is time-consuming. The flexibility and optimality of the assembly plan depend on the knowledge and creativity of the expert, and therefore expertise is an important parameter in developing the assembly plan. Therefore, the use of intelligent methods to plan the assembly process has been considered by many researchers. . The reinforcing learning approach has the potential to solve complex problems due to the use of experience gained from interacting with the environment and Has been successfully implemented in controlling many robotic tasks. However, due to the inherent complexity of the assembly, as well as...