Sharif Digital Repository

Selective Laser Melting (SLM) process is a powder-based metal Additive Manufacturing (AM) technique. This developing industry has many advantages like generation of geometrically complex shapes with high density. High Cost, production and characterization of powders, limited material choices and process parameters optimization are some of the challenges associated with SLM. Stainless steel 316L due to its unique properties, like corrosion resistance, high strength, biocompatibility, availability and cost is indeed a commonly used material in SLM. In this research, the characterization of the powder produced by the flame spraying device, which is a new method, was discussed. Wire with 3mm... 

In this thesis, nanocomposites based on magnetic graphene oxide and iron oxide nanoparticles coated with smart polymeric materials (by polymerization of monomers such as glycidyl methacrylate, acrylic acid, and N-isopropyl acrylamide) via Reversible Addition−Fragmentation Chain-Transfer (RAFT) polymerization were successfully synthesized. The combination of large surface area in nanoparticles and different functional groups in polymeric layers can give unique properties to nanocomposites. Therefore, we synthesized various smart nanocomposites with this perspective. After synthesizing these nanocomposites, smart magnetic nanoparticles were characterized by FT-IR, NMR, XPS, TGA, DLS, VSM, GPC,... 

Gray Cast Irons are the most important engineering Cast Irons. Gray color of fracture surface and morphology of graphite flakes are the reasons of this naming. Gray iron is relatively cheap with easy production; because of wide chemical composition range rather other cast irons. Furthermore, shrinkage and feeding in the casts from gray iron, besides surface finishing by machining are easy. The other properties of gray iron are resistance against sliding wear, high thermal conduction coefficient, low module of elasticity and thermally shock resistance. In this research, the effects of added nitrogen as an alloying element and cooling rate on microstructure, hardness and tensile properties of... 

This projct includes the following sections: In the first section, Michael addition reaction of anthrone to nitroolefins is described in water without using any catalyst to prepare 9-(2-nitro-1-arylethyl)anthracene-10(9H)-ones. This method is green, efficient and gives high yields of products. The solvent effect is also investigated. In the second section, Considerable efforts have been directed in recent years towards the transition metal complex catalyzed oxidation of organic compounds such as olefins, sulfides, benzylics alcohols and phenolics. And due to the various advantages of supported heterogeneous catalysts and in our aim to develop a simple, more efficient and eco-friendly... 

The primary purpose of acidizing operations in the oil and gas industry is to enhance hydrocarbon production. Acidizing has been a common and conventional method for years, especially when production engineers face issues like declining reservoir pressure leading to reduced production rates. Initially, the treatment solution is referred to as matrix acidizing. In acidizing operations, different additives are combined with the acid to control its behavior in the reservoir. These additives may include iron control agents, corrosion inhibitors, friction reducers, and more. Incompatibility among these additives, the acid, and reservoir fluids can lead to severe damage to the reservoir.... 

Currently, one of the most important problems in the field of drilling is the issue of drilling fluid loss in different formations. The problem of mud loss has been evident since the beginning of oil and gas well drilling operations, so that oil companies spend millions of dollars annually to solve the problem of mud loss. Problems such as pipe jamming, loss of rig production time, well blowout, loss of a large volume of drilling mud and damage to reservoir formations due to loss of drilling fluid are caused. Regarding the drilling variables, many factors cause the decrease or increase of the loss, the most important of which are the weight on the drill bit, drilling speed, the rate of... 

Gears are a major component of many transmission systems. nowadays, improving the operating conditions and reducing the weight of the gears is one of the most needed issues in the industry. This dissertation aims to find the optimal structure of gear under different load cases and reduce its weight optimally. In this regard, topology optimization is used to develop the gear structure.In this research, two areas of bio-inspired design and additive manufacturing are used to achieve goals. These two areas can make good use of each other's potentials and achieve results that were not previously possible with traditional methods of design and manufacturing. First, an introduction and history of... 

In this study, standard composite laminate specimens with micro and nano sized particle additives are made to study the effect of the additives on the fracture toughness of the specimens in standard tests. The composite laminates are made from epoxy resin and unidirectional glass fibers. The mode I and mode II fracture toughness of the specimens are measured under various loadings in standard tests. The fracture surface is then, fractogaphed by microscopic instruments. In conclusion, the fracture behavior of laminated composites, toughened by micro and nano particles is discussed. The results show that using rubber particles will improve fracture toughness of neat epoxy resin and laminated... 

Dental implants should be biocompatible. This ability cause bone growth beside implant and increases stability of implant. Manufactoring method and materials used in implants are main parameters affectig biocompatibility of implants. Fabrication of functionally graded structures is a novel method to increase biocompatibility. Stress shielding is one of the main causes of failures in current dental implants. This phenomenon takes place due to different young modulus of dental implants and host bone. Pouros structures remedial this problem and implant’s young modulus comes closer to host bone. The aim of this project is to study feasibily of fabrication of functionally graded titanium dental... 

Direct metal deposition (DMD) process is an additive manufacturing technology that is rapidly gaining laser importance due to its various capabilities in applications such as coating, repairing high-value damaged parts, rapid prototyping and even production in small quantities. Among the equipment needed for this process, nozzle is perhaps the most important component because its performance affect the efficiency of powders trapped in the molten pool, and is crucial to the quality of the deposited layer. The existing nozzle designs can be categorized in two groups; lateral and coaxial nozzles; and the coaxial ones are divided into continuous and discontinuous types. Coaxial nozzles have... 

Formation acidizing is one of the best well stimulation methods to remove reservoir damage and improve recovery of oil and gas well. The proper design of acidizing operations can significantly improve the production of a formation. In the meantime, causing formation damage and precipitation in oil flowlines, which may be caused by the incompatibility of the stimulation fluid with the reservoir fluid and rocks, is one of the most serious problems in the operation, which reduces permeability and oil/gas production. As a result, the success of the acidizing operation requires to study the interaction of components of operation (acid, reservoir water, formation rock, and acid additive)... 

Direct Metal Deposition is one of the methods of Additive manufacturing that has seen the most spread in recent years. In this method metal powder is directed towards the free surface of the workpiece through a nuzzle, and is simultaneously heated to become molten in a melting pool by a laser beam and begins the deposition process. One of the parts that make up a DMD system is powder feeding nuzzle. These nuzzles usually encounter a similar fundamental problem: that the effect of gravity on the stream of metal powder and the carrier fluid causes this stream to deviate from its intended position. To prevent this, nuzzles are usually designed with a fixed downward angle and the angle of the... 

Additive manufacturing technology (AM) is one of the new methods of rapid prototyping. Experts claim that using this process can produce a prototype of the product with any complex geometry in the shortest possible time. Among the methods of metal additive fabrication, the direct metal layering method with the powder coaxial nozzle has different capabilities and has received much attention by researchers. In this research, we intend to find a relationship between device parameters and the geometry of samples made by direct metal layer method. According to the research, many parameters affect the quality of the samples made by this method, the most effective of which are the three parameters... 

In this study, the zirconia antistatic coating was synthesized by dip coating sol-gel route on glass substrate. The solution contains ZrCl4 as precursor and isopropanol as solvent to synthesize zirconium oxide. The effects of environmental humidity and solution concentration on the coating characterization were analyzed. MPTS and primer binder were added as binding agents in the solution to observe the effect of binding agents on the coating adhesion. Solution stability and antistatic coating characterization were analyzed by zita potential test, FTIR spectroscopy, EDX analysis, FESEM and AFM microscopy, pencil hardness test, thickness test, antidust ability and spectrophotometer. The... 

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... 

Selective Laser Sintering (SLS) is one of the powder-based Additive Manufacturing (AM) technology in which parts built by CO2 laser. In this research work, Titanium-PMMA-Stearic Acid powders are mixed together to produce parts by Indirect Metal Laser Sintering (IMLS) method. The optimum process parameters such as energy density, Percentage composition of Titanium-PMMA and Scan Sintering are obtained by adopting the Taguchi method for getting the maximum density and minimum porosity. Experiments are planned by Taguchi’s Mix-L8 orthogonal array. According to the results obtained from this study, the percentage of combination Ti-PMMA and Energy density, respectively, are a major parameters that... 

One of the major challenges in Additive Manufacturing is the creation of residual stresses due to the high temperature gradient in the solidification zone. This will cause problems such as cracks in the structure, metallurgical defects as well as deformation and dimensional accuracy reduction in the finished product. The purpose of this study is to perform mathematical modeling and computer simulation of the selective laser melting process (SLM) to predict these stresses as well as identify the effective parameters on this phenomenon. The conditions were adjusted in this model with the actual coefficients of the device. Additionally, the powder used in this project is Ti6Al4V material. By... 

The following thesis is concerned with the effect of channel feedback in tracking and stability of linear Gaussian systems over Additive White Gaussian Noise (AWGN) channel when the decoder is the Kalman filter and encoder is the innovation encoder. When the feedback channel is described by a noisy link or a random switch, it is shown that stability is not possible for unstable systems. But for stable systems, an innovation encoder, Kalman filter decoder and a certainly equivalent controller for tracking and stability are presented. When the feedback channel is described by a deterministic switch, for both stable and unstable systems, an innovation encoder, Kalman filter decoder and a... 

In this thesis after the study of the reported works on butterfly network, we improve the rate region of full duplex butterfly network. We use a simple specification of lattice codes to break code book into two code books. By selection of the coded message of the two transmitters in symetric butterfly channel from these two code books, we can decode the sum of the two messages and recover each messages by simple mod operation. The simulation shows that the rate region is improved  

Steel shear wall systems have been introduced as a lateral load resisting system since 1970s. Based on the designer’s choice, this system can be used with or without stiffeners. Employing stiffeners prevents the elastic buckling of steel plates which can enhance the system to absorb more energy. The design code for using stiffeners has not developed yet in Iran since this kind of systems is not common practice. In this study, the Response Modification Factor (R), as an important factor in the design procedures of structures, is investigated for 1,3,5,7 and 10-story regular and irregular building structures which have un-stiffened steel shear walls with 3, 4.5 and 6 millimeters thickness with...