فهرست مطالب payam saraeian

Due to the difficulties and limitations in grinding hard materials, the use of nanoparticles in the Minimum Quantity Lubrication method can be effective as an appropriate solution to improve the efficiency of lubricating fluids. In this study, the effect of using a combination of carbon nanotubes and copper nano oxide on the surface quality of Inconel 718 alloy during grinding by Minimum Quantity Lubrication has been investigated. The results showed that the use of nanoparticles in Rapeseed oil reduced the roughness and improved the surface health of the samples. The best surface topography with the least amount of pits and Furrows was obtained by combining nanoparticles with 3wt% in rapeseed oil, so that the surface roughness of the samples was reported 0.255 μm during this method, which is compared to the net use of CNT and CuO decreased by 14% and 3% respectively. Also, during the use of nanoparticles in minimum quantity lubrication, the amount of surface roughness compared to dry, flood and minimum quantity lubrication with rapeseed oil, decreased by about 35%, 13% and 18%, respectively.

Today, a variety of implants with different applications are used to replace or support a damaged biological structure, the most common of which are dental and orthopedic implants. Due to the widespread use of stainless steel 316 L in the manufacture of implants and the occurrence of cracks and residual stresses during the process of electrical discharge machining for the production of these products, the use of effective and economical polishing methods such as burnishing in It is effective in increasing the surface properties and compatibility of these products with living tissue. In this study, after performing the electrical discharge machining process on the surface of the sample and making the ball burnishing, the burnishing operations were performed by changing the input parameters and in accordance with the experiments designed using the mini tab software. Thus, the effect of variable burnishing force, feed speed and number of tool passes on surface roughness properties, micro-hardness and corrosion resistance of the final surface of the work piece were investigated. During the optimization of the response surface methodology, the optimal value for surface roughness, micro-hardness and surface corrosion rate of the samples were obtained, respectively, 0.108 μm, 435.34 Vickers and 2.18*105 respectively. Compared to the control sample, the surface roughness of the samples decreased by about 97% and the micro-hardness and corrosion resistance of the samples increased by about 2 and 11 times, respectively.

Due to the increasing expansion of products made of plastic materials, high percentage of plastic waste enters the waste and waste annually, and the recycling of these plastic wastes is usually accompanied by decrease in their mechanical properties. One of the simplest and the most affordable ways to overcome the decline in mechanical properties during use recycled polymer, is achieving optimal combination virgin polymer and recycled polymer via mixing together. In order to produce products with both high quality and optimal mechanical properties will be desirable. Accordingly is beneficial for both environment and economic point of view, reducing use of virgin polymer.  In this study, in order to investigate the effect of weight percentage of recycled polyamide 6.6 with virgin polyamide 6.6 on the mechanical properties by injection molding proses, mix recycled polyamide 6.6 and virgin polyamide 6.6 with different weight percentages is prepared and then is injected. The results of mechanical tests on injected samples showed that adding more than 50% by weight of recycled polyamide 6.6 to virgin polymeric materials increased melt flow index, glass transition temperature and crystal temperature. While, the mechanical properties of samples decreased with increasing weight percentage of recycled polyamide in the composition. These changes were less for some properties such as tensile and flexural strength and more for impact resistance. Tensile and flexural strength and impact resistance in samples with 50% by weight of recycled polyamide in the composition, respectively, decreased by about 6%, 9% and 34% compared to the new polyamide sample.

Advanced ceramics have special applications in the manufacture of special and strategic parts due to their characteristics such as high strength, stability at high temperatures, high corrosion resistance and unique magnetic and electrical properties. Boron carbide is a dark crystalline material that is the hardest known material after diamond and cubic boron nitride. Due to the high characteristics and hardness of boron carbide and the special ability of the electrical discharge machining process in machining hard materials and creating complex shapes, in this study, the effect of peak current parameters and pulse -on time on surface roughness and material removal rate of samples prepared from boron carbide has been investigated experimentally and statistically. The results of the experiments showed that the peak current had the greatest effect on the surface roughness and material removal rate of the samples and also the comparison of microscopic images of the surface of the machined samples showed that the peak current has increased the cracks and the size of the cavities. Thus, with the increase of peak current from 16 ampere to 24 ampere, the average size of the cavities has increased by about 30% and the continuation of the process of increasing the current intensity to 32 ampere has increased the average size of the cavities by about 8 %. Also, during the factorial optimization, the optimal values for the sampling material removal rate and surface roughness of the samples were 2.45 mm3 / min and 4.30 μm, respectively.

Nowadays, due to the need of composite structures with thin walls in industry and due to low weight ratio to high strength, has received more consideration than before. Composite laminates are cause of more problems and damages in machining process. This problems are especially in thin wall composite structures. One of the best ways for preventing damage during machining process in thin wall composite structures is use of machining process with high speed. In this study effect of milling parameters in high speed on surface roughness, material removal rate, and deflection in thin wall composite structures was studied. For this purpose, firstly were made samples of glass- epoxy composite with thicknesses 2mm, 4mm and 6mm and then milling process with high speed and changing spindle speed, feed rate, and cutting depth was done. To get test results using an experimental design. Comparison of the optimization results on composites with different thicknesses by the response surface methodology, showed that the optimal values of surface roughness 2.12 μm and material removal rate 5.99 mm3/min and deflection of 0.082 mm is for the sample with a thickness 6 mm. In composites with a thickness 6 mm due to higher rigidity, better results were obtained. Also, the predicted error rate was calculated in comparison with the experimental values obtained for the surface roughness parameters, material removal rate and deflection rate 6%, -5.22% and 2.5%, respectively, which indicates the favorable agreement between the experimental results and statistical analysis.

Due to the increasing need of industries to prototyping with the highest accuracy and lowest cost, the application of rapid prototyping technology as a modern and rapid method has been considered to reduce the time between design to production and market to product. Fused deposition modeling is one of the most common methods in 3D printing and rapid prototyping, but the components produced in this way are usually of poor geometric accuracy and surface quality. Circularity error in the cavities is one of the important geometrical and tolerances errors. In this study, the experimental study the effect of process parameters such as layers thickness, temperature and speed of nozzle on the surface roughness and circularity error of the samples is investigated. The sample is a rectangular that has three holes in three different plates and the measurement of circularity error and surface roughness have been done in three directions and three different plates, respectively.The results showed that the lowest values were obtained for the surface roughness of the holes in the XY plane for a nozzle temperature 270 °C, printing speed 30 mm / s and layer thickness 0.2 mm. Also, the minimum value for the circularity error of the holes was obtained on the XY plate for the nozzle temperature 210 °C, printing speed 30 mm / s and layer thickness 0.4 mm. During the response surface optimization, the model optimized value was 1.174 μm for the surface roughness and 0.114 mm for the circularity error.

Nowadays Polymer Matrix Composites are replaced by metal as composite structures in petroleum industry due to their lightness and high strength ratio. Usually, the resin used to make these composite structures is a polyester resin and because of the use of this resin, in addition to its good physical and chemical properties, its price is lower than other resins. but one of the disadvantages of polyester composites is to expose it and to create a hazard in the petrochemical and refinery industries. Therefore, in order to solve this problem, four anti-inflammatory filler materials, including nanoclay with a weight percentage of 1,2,3%, aluminum hydroxide with a weight of 2,5,7,10%, magnesium hydroxide with a weight percentage of 2, 5,10,15% and zinc oxide with a weight percentage of 1,3,5,7%. In this research, the resistance to fire extinguishing by combustibility test (burning rate) and mechanical properties of composite by using tensile, hardness and impact tests is investigated. Finally, by comparing and checking the results, it was found that with 2% nanoclay weight, the maximum tensile strength, 58.33% improvement and with 39.11% hardness of glass / polyester composite would be improved. Also, by adding 2 wt% magnesium hydroxide, the impact strength is improved by 125%, and by adding 5% by weight of aluminum hydroxide, the burning rate of glass / polyester composite is reduced by 59.12%. It is the cause of the burning down rate in the sample containing aluminum hydroxide due to the reaction of hot forming and the release of water molecules.

The main purpose of using scaffolds replacement tissues of the body. The most important part is to choose the type and steel scaffolding so that eventually will replace the damaged tissue. One of the mechanisms proposed to reshape the bone is based on its piezoelectric properties. It seems that the use of piezoelectric materials is an option for use in the body, is a unique privilege. Therefore, the ceramic barium titanate (BaTiO3) having good piezoelectric properties, Curie temperature of about 125˚C and laboratory observations that non-toxic in the body, as a candidate to replace and simulate the performance of bone tissue, has been proposed. In this study, the design and produce of barium titanate piezoelectric ceramic as a bone scaffold with foam casting method and become coated with gelatinous and nanostructured HA composite for bone tissue engineering. Then test its properties by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and mechanical properties were studied. In the end, it was concluded that the barium titanate scaffold produse with foam casting method coated with gelatin nano hydroxyapatite composite structure suitable for use in bone tissue engineering.

Ultrasonic Assisted Magnetic Abrasive Finishing (UAMAF) is the combination of magnetic abrasive finishing (MAF) and ultrasonic vibrations to finish the surfaces in nanometer scale. In this work, the experimental setup for UAMAF was prepared to finish inner surface of tube workpiec. By using experimental setup, the effect of experimental parameters such as ultrasonic vibrations, mesh number, the type of abrasives (SiC and diamond) and finishing time has been investigated on the changes in the surface roughness of AL6061 tube workpiece. The experimental results showed that the use of ultrasonic vibrations has a significant effect on reducing the surface roughness. The changes in surface roughness increases with the mesh number from 90 to 800 and finishing time from 30s to 5 min. Among two types of abrasives, diamond showed the best performance in finishing. Optical microscopy images showed that the dominant finishing mechanism in MAF for coarse grains (with mesh size of 90 and 120) is two body and for fine grains (with mesh size of 220, 400 and 800) is three body. In UAMAF for both of the coarse and fine grains the dominant finishing mechanism is three body.

The vibratory finishing is one of the important mass finishing processes. This can be applied for finishing many metallic and non- metallic components using abrasive materials such as steel, ceramic, natural materials and etc. The vibratory finishing process is used for some purposes such as surfaces polishing, deburring, oxide layer removing and rounding the edges. Evaluation of surface roughness changes with time that is one of the important parameters during the vibratory finishing process. In this study, the effects of the working time and abrasive materials are investigated on the surface roughness changes of CK45 steel samples. The ceramic, glass and mixed abrasive particles are used as the abrasive media. The experiments are performed at different time from 10 to 120 minutes in the dry environment. Finally, the surface roughness values of samples were measured and then fitted by a regression equation for description of the surface roughness changes with time. According to the results, the maximum surface finish was obtained after 120 minutes by using mixed abrasive materials. The surface roughness improved approximately 60%.

Today, composite materials have extensive use in aerospace automotive and defense industries compared to metals, because of their high strength to weight ratio and good corrosive resistance. Machining of these materials regard to their composite structure is complicated. Achieve optimal machining conditions, depending on the needs, according to the type of fiber and resin used in composites, need proper analysis and careful investigation. In this study, composite pipes made of glass-epoxy to a thickness of 5 millimeters, which are often used in the body of Aerospace structures, produced by hand lay-up and their surface roughness after turning process is measured. In order to obtain the minimum roughness in the turning process, tool type in two modes, and cutting speed, feed rate, and depth of cut are studied at three different levels. So Taguchi experimental design method and experimental test samples on roughness the results analysis and performed by minitab software. Finally, concluded that the minimum value of the surface roughness is obtained by tools with chip-breaking levels, cutting speed 100 m/min, feed rate 0.05 mm/rev, and the depth of cut 1.5 mm.

Electrical discharge machining (EDM) is a modern machining method which in pace with industrial developments, various studies are aimed at improving this process's parameters including material removal rate. In previous researches, changes in machining tool’s properties and specifications have been investigated as the solution to improve the material removal rate. A novel and efficient process to change material microstructure and properties is equal channel angular pressing (ECAP) that is appropriate method to produce fine grains materials with high strength and adequate properties. In this study, the pure copper material was processed through 4 and 8 passes of ECAP and its effect as a toolfor EDM process, on material removal rate, with different discharge current and pulse ontime was examined. Microstructure of the specimens were analyzed after ECAP operation using electron back scatter diffraction method (EBSD), and the average diameter of grains for specimens were measured using this technique. The results of the experiments indicated that processing the copper tool with ECAP through 4 passes, increases the material removal rate up to 13.2 percent. Moreover, increasing the number of passes of ECAP from 4 to 8 improved the effectiveness of this process on increasing the material removal rate up to 5.5 percent.

Uncontrolled diabetes can lead to diabetic foot ulcers and if it is not treated can lead to amputation. With suitable plantar pressure distribution, by changing material and arrangement of constituent layers for multi-layer insoles, the foot ulcers can be prevented or improved. In this study, single-layer and three-layer insoles made by Silicone Gel, Plastazote Foam, Polyfoam and Ethyl Vinyl Acetate foam have been compared. the materials behavior determined using a uniaxial pressure test. Then a custom-made insole was prepared and by a digitizer device, a scatter file obtained from machined sample. This file was imported in Catia software and the volumes and surfaces has been created by using a three dimensional nonlinear FEM model, for 4 single-layer and 18 combinations of three-layer insoles during dynamic test. For verification of FE results, experimental test has been done by using Pedar system. The results showed that among single-layer insoles, the Silicon Gel and Plastazote and between three-layer insoles arranging Plastazote, Silicone Gel and Ethyl Vinyl Acetate (from top to bottom) were recognized as the best combination. Three-layer insole stress concentration and strain can reduce 31% Von Mises constrain stress and 30% strain with respect to one layer insole. Experimental tests using Pedar system verified this result. In dynamic mode using Pedar system, Silicon Gel one layer insole and three-layer PLZ-SG-EVA decrease plantar pressure by 30% and 54% respectively in comparison with bare foot. The method used in this research can show suitable performance of these materials when used as insole. Also this research can be helpful for analyzing insoles using finite element method.

Magnetic abrasive finishing (MAF) is a micromachining process that uses magnetic field and magnetic abrasive particles to conduct the mechanism of material removal in micro-nanometer scales. In this paper, by an experimental method and statistical analysis, the effects of parameters like working gap, work-piece rotational speed and material removal mechanism (injection of abrasive slurry of Al2O3) in the MAF process, on the external surfaces of cylindrical pieces of stainless steel (AISI 440C)were investigated on surface roughness. To do the experiments, a mechanism was designed and constructed. The results of this research show that the working gap and work-piece rotational speedhave a significant effect on the improvement of the surface roughness. It has been indicated that in vitro surface roughness improved 20% as a result of the gap working of 2 mm, workpiece rotational speed of 355 rpm, using the injection of abrasive slurry of Al2O3.

In this article, the effect of parameters like working gap, work piece rotational speed and material removal mechanism(injection of the SiC Abrasive slurry and Al2O3, use of diamond paste as abrasive tool) in Magnetic Abrasive Finishing process using designing of experiments on the external surface of Cylindrical work pieces of Stainless steel AISI 440C to get minimum surface roughness has been investigated. For implementation of tests, a mechanism was designed and after carrying out the tests, the obtained data was analyzed using Minitab software. Using response surface method the predicted model, the value of surface roughness was represented. Input parameters to produce optimum have also been reached using the predicted model and desirable surface roughness. Also, results show that the surface roughness has been improved by 50% with the working gap of 2 mm and work piece rotational speed of 355 rpm and using diamond paste.

At this study, after designing and manufacturing a rotary tool, its machining parameters and their effects on surface roughness of aluminum alloy of Al99 which is one of the most consumable alloys in aerospace industry, is studied and optimized. First, the rotary tool is designed and manufactred. Then according to Taguchi method, the experiments have been designed to record surface roughness, machining temperature and exerted forces on the tool. In order to evaluate optimum condition of the experiment results, MINITAB and Genetic Programming (GP) have been implemented to obtain the best regression; then for obtaining the optimum condition of machining, the results of running Genetic Programming has been used. In the end optimum machining parameters to achieve the best surface quality is presented