محمد صدیقی

The use of light metals instead of steel in parts of the vehicle body to reduce weight and thus lower fuel consumption has attracted the attention of car manufacturers and researchers. Therefore, this study investigates the dissimilar joining of magnesium and steel sheets by resistance spot welding and the thickness of galvanized steel sheet coating is considered as an effective parameter for the joint strength. The materials used in this work were AZ31B Mg alloy sheet and hot-dip galvanized steel sheet. To investigate the influence of the coating thickness on the joint, two coating thicknesses of 5 and 10 µm were applied to the steel sheet. also to balance the thermal generation on both sides of Mg and Steel sheet, two electrodes with different geometries were used, flat electrode on the steel side and domed electrode on the Magnesium side. Tensile-shear tests were performed on the samples using a tensile testing machine and the microstructure was analyzed using optical and SEM microscopy. The results show a 13% increase in joint strength at a coating thickness of 10 µm. The studies show that increasing the coating thickness from 5µm to 10 µm, reduces the grain size in the nugget  and thus increases the strength.

Magnesium and its alloys have found a wide range of applications in medical industry and manufacturing of absorbable bio-implants because of having a modulus of elasticity similar to bone as well as having biocompatibility and biodegradability characteristics. Moreover, employing magnesium implants with a porous structure can lead to an increase in the rate of bone replacement instead of the initial absorbable implant. On the other hand, by adding hydroxyapatite reinforcing particles to magnesium and its alloy, their mechanical properties and corrosion resistance may be improved. In this paper, the effect of magnesium particle size on compressive strength of Mg/hydroxyapatite porous bio-composites has been studied. The magnesium and composite specimens with non-porous and porous (with a volume porosity of 24% and 58%) structures were produced using powder metallurgy method. For this purpose, two types of magnesium powder with particle sizes of 63 µm and 250 µm, hydroxyapatite particles as reinforcement, and ammonium bicarbonate particles as space holder, were used. The results of the uniaxial compressive tests revealed that the strength of all the pure and composite specimens fabricated by 63 µm powder has improved up to 103%, compared to those of the specimen fabricated by 250 µm powder. In addition, for both amounts of volume porosity, the composites offer a higher compressive strength than that of the pure specimens.

Due to its biocompatibility and biodegradability, magnesium has become a very suitable candidate for orthopedic implant applications. However, its high corrosion rate leads to rapid deterioration in corrosive environments, resulting in premature failure of the implant before sufficient bone healing. In this regard, surface modifications are required to improve corrosion resistance. This research investigates the effect of two surface modifications, shot peening and electrospinning, on the corrosion properties of magnesium/hydroxyapatite composite. Shot peening was performed using glass beads at an Almen intensity of 0.3 mmN and with 100٪ coverage on the surface of the composite. Electrospinning was carried out using Polycaprolactone (PCL) nanofibers at 18 kV for 30 minutes. Tensile-compressive tests were performed on the composite specimens. Also, pH monitoring and weight loss tests were conducted on the shot peened and electrospun samples. The results show that electrospinning decreased the corrosion rate of magnesium by 75٪ and 40٪ after 1 day and 7 days of immersion, respectively. Shot peening also reduced the corrosion rate by 35٪ and 20٪, respectively. Electrospinning reduced the corrosion rate by limiting the contact surface area between the corrosive solution and magnesium due to its high specific surface area for calcium-phosphate absorption. Shot peening, on the other hand, delayed the corrosion by accelerating the formation of a passive layer, leading to increased corrosion resistance in short periods.

using porous metal foams is one of the conventional methods to increase heat transfer in industrial systems, including heat exchangers. Porous media increase heat transfer and lead to an increase in pressure drop.. In this paper, the three-dimensional effects of flight altitude (1000m<H<5000m) and porous metal foam with Darcy number(0.1<Da<0.0001) in a training airplane oil cooler were investigated. The porosity coefficient was assumed to be 0.9 for all cases with porous foam.The Darcy-Brinkman-Fortheim equation was used to simulate a 20 W50 oil flow in a porous medium. The thermophysical properties of the oil including density, viscosity and thermal conductivity were extracted using laboratory data in terms of operating temperature. Hot oil with boundary condition enters the oil cooler. The boundary condition of the output oil is . The cooling wall is the boundary condition of non-slip and the heat transfer coefficient of air movement is proportional to the height. The governing equations are discrete based on the finite volume method using commercial computational fluid dynamics FLUENT. With increasing flight altitude, in pure oil mode, heat transfer, pressure drop and performance evaluation criteria increase by 0.65%, 0.45% and 0.49%, respectively. Porous metal foam with Darcy number having leads to increase of Nusselt number , increase of pressure drop and has the highest performance evaluation criterion PEC=31.75. Porous metal foam with Darcy number has the highest pressure drop and the highest heat transfer increase . According to the obtained results, Darcy's number is the most optimal performance evaluation parameter.

Aluminum CNG vessels compared with steel ones can lead to lower fuel consumption. Dome forming (spinning) is an important step in seamless CNG vessels fabrication. This paper aims to the process simulation on a 6061-O aluminum tube at an elevated temperature, investigation of feed effect on the stress and strain after the first pass and its effect on the whole of the process. After the whole process simulation and achievement of the final dome shape, to investigate the feed effect on the strain, circumferential, axial and thickness strains after the first pass, on different inner, middle and outer paths of the tube wall are reported in some figures. Feed variation has not a considerable effect on the decrease of increase rate of circumferential strain absolute value and on the strain distribution on the middle path. The primary higher feeds effect on other investigated strains is smoother distribution. This effect is in agreement with a more stable process and less wrinkling at higher feeds. This stability is reported in a higher tested feed in this paper. On the other hand, investigating different feeds shows that the feed increase leads to decrease of maximum stress in the tube after roller separation at the end of the first pass.

The global water scarcity crisis is affecting water management in various sectors, including water and agriculture. Aquatic basins and their surrounding areas have been encountered with serious challenges such as drying up of lakes and rivers, negative aquifer balance, changes in surrounding land use, increased cultivation of irrigated and horticultural lands, and changes in the pattern of cultivation from low-crop to high-water crops in recent years. Satellite imagery due to its wide spatial coverage, high resolution, low cost, rich time archive of satellite imagery and ease of use methods is a useful and efficient tool to help manage water and soil resources. In this study, four classes of soil, water and wet, urban and agricultural areas were selected. Then, two random forest classification methods and support vector machines are used to classify images. Classification methods were evaluated by calculating two indices of accuracy and Kappa coefficient using test data. The random forest classification in the four years, 2012, 2014, 2016 and 2018 and classification of support vector machines in two years, 2008 and 2010 have the most accuracy. Therefore, the random forest algorithm has worked well in separating the classes, especially in water basin, and can be used as a reliable method in this area.

Fuel system is one of the most important parts of the micro gas turbine. Due to the variation of environmental conditions such as temperature, relative humidity of air and height in different geographical locations, the operational features of the fuel system change. In this study, the fuel system of the GTCP85-180 gas turbine is modelled by applying PID mechanical controller. The governing equations of the controller is coupled with classical thermodynamic equations of the gas turbine and the effects of different environmental conditions on start-up and norminal operation of the motor are investigated. The range of variations of the environmental conditions is choosed by considering the geographical locations of Iran. The results of the numerical simulation were verified by comparing the numerical results obtained with written code in Matlab software with experimental measurements. The results showed that the environmental temperature has the strongest effect on the operational features of the fuel control system and causes 16.3% variation of exhaust gas temperature, 3.7% variation of fuel discharge, 14.7% variation of start-up time of the motor and 4.7% variation of fuel pressure in injectors. Also, the start-up operation of the motor showed more sensitivity to environmental conditions compared to normal operation of micro gas turbine.

The equal channel angular rolling (ECAR) process is one of the methods of severe plastic deformation that is considered to obtain ultrafine-grain materials (UFG.( In this study, the effect of temperature on the mechanical properties of 5083 aluminum alloy was investigated in this process. Equal channel angular rolling process was performed at the temperatures 25℃ (room temperature), and 200 and 300℃. The equal channel angular rolling was used as a lubricant. The evaluation of mechanical properties and fracture mode of the samples was assessed using uniaxial tensile test, micro-hardness test and scanning electron microscope (SEM). The results revealed that by increasing number of ECAR passes at a specific temperature, yield strength, ultimate tensile strength and micro-hardness increased in which that increasing rate is more higher at the initial passes than the last ones, while the elongation decreased, contrarily. Study of the mechanical properties of the samples after applying the ECAR process in a specified pass at different temperatures showed that by increasing the temperature, the yield strength, ultimate tensile strength and micro-hardness of samples decreased in comparison with the samples processed in the ambient temperature. However, the elongation was improved. As a quantitatively results, at the end of the third pass at 300°C, the yield strength and micro-hardness of the samples decreased by 14.8% and 8.5%, respectively, in comparison with the samples processed in the ambient temperature, and the elongation increased by 22.2%.

This paper presents a novel severe plastic deformation method entitles modified friction assisted tube straining for producing ultrafine-grained cylindrical tubes. Using friction power generates heat to locally increase temperature of the deformation area and creates severe combined strains and lower pressing force. Experimental tests were executed on Cu/30Zn alloy to investigate applicability of the presented method. The optimum process parameters, 710Rev/min rotary speed and 0.08mm/Rev feed rate were found, applying experimental test to process tubs fault free.  Microstructure study of processed specimens showed a significant grain refinement from the initial value of 76μm to 9μm and 7μm in longitudinal and peripheral directions, respectively. Yield stress and ultimate tensile strength of processed specimens increased to 325 and 202MPa from the initial values of 160MPa in peripheral and longitudinal directions, respectively. Also, hardness significantly increased to 72Hv from the initial value of 48Hv.

Nowadays, functionally graded materials have different applications in various industries, such as Aerospace industry, turbomachinery, coating industry, etc., due to their unique ability in providing multiple and sometimes opposite properties in a material volume. The purpose of this paper is to fabricate functionally graded material sheet of aluminum based composite with SiC reinforcing particles, using powder metallurgy and hot rolling methods. In this regard, the amount of reinforcement in the direction of thickness has been changed from the value of 0 to 4 weight percent. The samples were prepared in four steps including ball-milling, degassing, cold pressing and sintering, and then were hot-rolled up to three passes. The distribution of the reinforcing particles in the matrix phase was evaluated using optical microscope. Furthermore, the mechanical properties of the FGM samples including their hardness, tensile strength and flexural strength were measured and reported. Finally, the fracture surfaces in the tensile and flexural tests were observed using scanning electron microscope (SEM). According to the images obtained from the microstructure of the samples, the reinforcing particles have an acceptable distribution in the matrix phase. Also, the results indicate that the hardness and strength are enhanced by increasing reinforcing particles and the number of rolling passes. In addition, the main fracture mechanism in pure aluminum layer is the initiation and propagation of cracks between initial aluminum powder particles, while separation of two phases in the matrix-reinforcement interface and small SiC particle agglomerations are responsible for crack initiation in the composite layers.

Nowadays, there is an increasing demand for magnesium and its alloys as the lightest commercial metal with a high strength to density ratio. Nevertheles, afew undesirable properties, such as low hardness and poor wear resistance, have limited the applications of this exclusive metal. Fabrication of magnesium matrix composite could improve hardness and wear resistance in addition to strength increasing. Since converting all of a metal piece to composite could make it more brittle and increase the costs, fabrication of surface composite could be a solution. In this paper, a magnesium sheet with a surface composite has been fabricated by applying warm rolling process. Indeed, a layer of magnesium matrix composite (which has been fabricated by stir-casting) has been conjoined to a magnesium substrate layer using a zinc interlayer. This method could increase the production speed and decrease the costs. In addition to the connection of two layers together, the zinc interlayer would preserve the surfaces of the layers from oxidation without using any controlled atmosphere. The results show a proper connection between the surface composite and the substrate. According to the microhardness results, the hardness of surface composite increased about 23% and 52% in the cross-section and the surface, respectively. Moreover, wear resistance of surface composite improved about 43% in comparison to magnesium substrate. Also, wear rate decreased in the surface composite.

The tube spinning process is one of the forming processes to fabricate conical seamless tubes. This process is done warm or cold, with or without mandrel. In this article, the possibility of forming of an Al-6061 conical tube by hot die-less spinning process has been investigated. An estimation of tangential force and required power can be obtained by analytical methods. So, the ideal work and upper bound methods have been utilized to derive equations for calculation of tangential force and required power of forming. An identical result was acquired for the two methods. The proposed equations can be used in design stage of the process. Furthermore, final thickness and initial length of the tube have been calculated by using of geometrical relations and constant volume law. The proposed formulation has been compared by experimental results. The final thickness and initial length of the tube are in good agreement with experimental results. An error of 0.5% and 5.5% were observed for final thickness and initial length, respectively. The obtained equation for the final thickness is a cosine function of the conical angle. Hence, it predicts higher final thickness in comparison with the sheet spinning process.

Multi-layer thermal insulations are fabricated by locating consequtive porous insulation and radition shields, which could be used at high temperature and cryogenic applications. In this type of insulations, different heat transfer methods such as conduction, convection and radiation would be occurred, although by using high density insulation (more than 20 kg/m^3 ), convection could be neglected. In this paper, radiation shiels parameters such as thickness, emissivity, distance and number of screens are studied and optimized. For investigating the effect of these parameters on effective thermal conductivity of multi-layer thermal insulation, a mathematical code has been improved in EES software. Then, the obtained results have been validated by another study. Moreover, Powell method has been applied in order to optimize the parameters. The results show that the amount of shield emssivity and shields arrangement have the most impact on the effective thermal conductivity of multi-layer thermal insulations. Also, the optimized distances between radiation shields indicate that this distance increased in the direction of heat transfer.

In this paper, combustion in a GTCP85-180 micro gas turbine combustor is simulated using ANSYS FLUENT in three dimensions by using non-premixed model and given temperature profile. In addition, the chamber is optimized. A Realizable k-ε model is used for turbulence modeling and DO model is used to obtain radiation intensity. The main fuel that is currently used in this type of micro turbine is JP4. Considering that this type of fuel is imported and also according to its pollution, methane as a more available as well as a clean and cheap fuel can be a viable alternative for this micro turbine. The main objective in this research is that without any changes in combustion chamber dimensions and inlet flow, besides achieving an appropriate pattern for methane injection as well as acceptable flame, to attain the optimized chamber. The Flame obtained in this study was acceptable and average outlet temperature of the combustion chamber is proportional to the performance of micro turbine. The results were compared with simulation results for this chamber with kerosene fuel showing the very low percentage of error. The design improvement results show that the temperature in the primary zone of the chamber which causes damage to the parts, has been reduced significantly.

Equal Channel Angular Rolling (ECAR) is a continuous severe plastic deformation process. In this process, severe shear strains are applied to the sheet. This strain increases the yield or ultimate strength of sheet without signicant change in sheet dimension. In this article, the eect of ECAR process on mechanical properties and fatigue life of manufactured sheets will be studied. Four Al-5083 samples have been prepared and annealed for obtaining stress-free samples. Three samples have been rolled by ECAR process with 1, 2, and 3 pass of rolling, respectively. Mechanical tests including tensile test, hardness, and axial fatigue tests have been carried out on prepared samples. Fatigue tests have been implemented according to strain-based approach with constant strain ratio and 0.5 Hz frequency of loading. Strain ratio (ratio of minimum strain to maximum strain in each cycle) is selected which equals 0.75. All of the tests have been carried out in a controlled laboratory condition. Fatigue life of samples is dened as the total of cycles before complete rupture of samples. Results show that the ultimate tensile strength (UTS) of samples increases with increasing the pass of rolling. Also, the maximum elongation of samples decreases. Maximum elongation was 17% in annealed sample, while it decreases to 10% in sample with three pass of rolling. The hardness of samples has been measured by Vickers micro harness test. The hardness of samples increases at higher pass of rolling. Fatigue test results show that fatigue life of Al-5083 samples decreases in manufactured sheets of equal channel angular rolling process.

Nowadays, two-layer metallic sheets have become as a useful solution to produce multi-functional products. Generally, two-layer metallic sheets can have advantageous characteristics such as increasing formability of the low formable component, improving the corrosion and wear resistance and reducing weight and cost of manufactured products. Therefore, understanding the forming limit behavior of a two-layer metallic sheet has an essential role in the design of sheet metal forming processes. Forming limit diagram (FLD) is a suitable method to predict the formability of metallic sheets in sheet metal forming operations. The aim of this research was to determine the forming limit diagram in Aluminum-Copper two-layer metallic sheets experimentally. The forming limit diagram can be used as a criterion in order to predict necking initiation which may cause tearing in sheet metal forming processes. In this paper, the forming limit diagrams of Aluminum-Copper two-layer metallic sheets have been obtained through an experimental procedure for the first time.

N‌o‌w‌a‌d‌a‌y‌s, a‌p‌p‌l‌i‌c‌a‌t‌i‌o‌n o‌f l‌i‌g‌h‌t m‌a‌t‌e‌r‌i‌a‌l‌s, s‌u‌c‌h a‌s a‌l‌u‌m‌i‌n‌u‌m s‌h‌e‌e‌t‌i‌n‌g, p‌l‌a‌y‌s a v‌e‌r‌y i‌m‌p‌o‌r‌t‌a‌n‌t r‌o‌l‌e i‌n v‌a‌r‌i‌o‌u‌s ‌u‌t‌o‌m‌o‌t‌i‌v‌e a‌n‌d a‌e‌r‌o‌s‌p‌a‌c‌e i‌n‌d‌u‌s‌t‌r‌i‌e‌s. R‌e‌s‌i‌s‌t‌a‌n‌c‌e s‌p‌o‌t w‌e‌l‌d‌i‌n‌g i‌s a w‌i‌d‌e‌l‌y u‌s‌e‌d m‌e‌t‌h‌o‌d i‌n a‌s‌s‌e‌m‌b‌l‌y l‌i‌n‌e‌s o‌f s‌u‌c‌h i‌n‌d‌u‌s‌t‌r‌i‌e‌s. T‌h‌e m‌a‌i‌n p‌u‌r‌p‌o‌s‌e o‌f t‌h‌i‌s s‌t‌u‌d‌y i‌s t‌o i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e t‌h‌e e‌f‌f‌e‌c‌t o‌f e‌l‌e‌c‌t‌r‌o‌d‌e f‌o‌r‌c‌e a‌n‌d t‌i‌m‌e o‌n r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s‌e‌s p‌r‌o‌d‌u‌c‌e‌d b‌y t‌h‌e r‌e‌s‌i‌s‌t‌a‌n‌c‌e s‌p‌o‌t w‌e‌l‌d‌i‌n‌g o‌f a‌l‌u‌m‌i‌n‌u‌m a‌l‌l‌o‌y, 6061-T6. I‌n t‌h‌i‌s s‌t‌u‌d‌y, a t‌w‌o-d‌i‌m‌e‌n‌s‌i‌o‌n‌a‌l e‌l‌e‌c‌t‌r‌o-t‌h‌e‌r‌m‌o-m‌e‌c‌h‌a‌n‌i‌c‌a‌l f‌i‌n‌i‌t‌e e‌l‌e‌m‌e‌n‌t m‌o‌d‌e‌l w‌i‌t‌h a‌x‌i‌a‌l s‌y‌m‌m‌e‌t‌r‌y h‌a‌s b‌e‌e‌n e‌m‌p‌l‌o‌y‌e‌d t‌o p‌r‌e‌d‌i‌c‌t t‌h‌e t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e, n‌u‌g‌g‌e‌t s‌i‌z‌e a‌n‌d d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n o‌f r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s i‌n t‌h‌e r‌e‌s‌i‌s‌t‌a‌n‌c‌e s‌p‌o‌t w‌e‌l‌d‌i‌n‌g p‌r‌o‌c‌e‌s‌s. F‌o‌r m‌o‌r‌e r‌e‌a‌l‌i‌s‌t‌i‌c a‌n‌a‌l‌y‌s‌i‌s, t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e d‌e‌p‌e‌n‌d‌e‌n‌t p‌h‌y‌s‌i‌c‌a‌l a‌n‌d m‌e‌c‌h‌a‌n‌i‌c‌a‌l p‌r‌o‌p‌e‌r‌t‌i‌e‌s h‌a‌v‌e b‌e‌e‌n d‌e‌f‌i‌n‌e‌d f‌o‌r t‌h‌e e‌l‌e‌c‌t‌r‌o‌d‌e‌s a‌n‌d s‌h‌e‌e‌t‌s. T‌h‌e s‌i‌m‌u‌l‌a‌t‌i‌o‌n r‌e‌s‌u‌l‌t‌s h‌a‌v‌e b‌e‌e‌n c‌o‌m‌p‌a‌r‌e‌d w‌i‌t‌h t‌h‌e r‌e‌s‌u‌l‌t‌s o‌b‌t‌a‌i‌n‌e‌d f‌r‌o‌m e‌x‌p‌e‌r‌i‌m‌e‌n‌t‌a‌l t‌e‌s‌t‌s. F‌o‌r v‌a‌l‌i‌d‌a‌t‌i‌o‌n, t‌h‌e n‌u‌g‌g‌e‌t s‌i‌z‌e a‌n‌d r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s‌e‌s w‌e‌r‌e ‌o‌m‌p‌a‌r‌e‌d. T‌h‌e d‌i‌a‌m‌e‌t‌e‌r o‌f t‌h‌e n‌u‌g‌g‌e‌t w‌a‌s m‌e‌a‌s‌u‌r‌e‌d b‌y m‌e‌t‌a‌l‌l‌o‌g‌r‌a‌p‌h‌i‌c‌a‌l o‌b‌s‌e‌r‌v‌a‌t‌i‌o‌n, a‌n‌d t‌h‌e r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s‌e‌s w‌e‌r‌e m‌e‌a‌s‌u‌r‌e‌d b‌y a‌n X-r‌a‌y d‌i‌f‌f‌r‌a‌c‌t‌i‌o‌n m‌e‌t‌h‌o‌d a‌t t‌h‌r‌e‌e p‌o‌i‌n‌t‌s o‌f t‌h‌e n‌u‌g‌g‌e‌t i‌n t‌h‌r‌e‌e e‌q‌u‌a‌l s‌a‌m‌p‌l‌e‌s. T‌h‌e s‌t‌u‌d‌i‌e‌s s‌h‌o‌w t‌h‌a‌t t‌h‌e h‌i‌g‌h‌e‌s‌t a‌m‌o‌u‌n‌t o‌f t‌e‌n‌s‌i‌l‌e r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s o‌c‌c‌u‌r‌s a‌t t‌h‌e i‌n‌t‌e‌r‌s‌e‌c‌t‌i‌o‌n o‌f t‌h‌e s‌h‌e‌e‌t‌s a‌n‌d a‌t t‌h‌e c‌e‌n‌t‌e‌r o‌f t‌h‌e n‌u‌g‌g‌e‌t; b‌y m‌o‌v‌i‌n‌g a‌w‌a‌y f‌r‌o‌m t‌h‌e c‌e‌n‌t‌e‌r a‌l‌o‌n‌g t‌h‌e n‌u‌g‌g‌e‌t r‌a‌d‌i‌u‌s, r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s‌e‌s d‌i‌m‌i‌n‌i‌s‌h. T‌o s‌t‌u‌d‌y, n‌u‌m‌e‌r‌i‌c‌a‌l‌l‌y, t‌h‌e e‌l‌e‌c‌t‌r‌o‌d‌e f‌o‌r‌c‌e e‌f‌f‌e‌c‌t a‌n‌d i‌t‌s t‌i‌m‌e, a s‌e‌t o‌f p‌a‌r‌a‌m‌e‌t‌r‌i‌c s‌t‌u‌d‌i‌e‌s w‌a‌s d‌e‌s‌i‌g‌n‌e‌d. T‌h‌e‌s‌e p‌a‌r‌a‌m‌e‌t‌e‌r‌s a‌r‌e c‌u‌r‌r‌e‌n‌t, c‌u‌r‌r‌e‌n‌t t‌i‌m‌e, a‌n‌d e‌i‌t‌h‌e‌r f‌o‌r‌c‌e o‌r i‌t‌s t‌i‌m‌e. T‌h‌e r‌e‌s‌u‌l‌t‌s i‌n‌d‌i‌c‌a‌t‌e t‌h‌a‌t b‌y i‌n‌c‌r‌e‌a‌s‌i‌n‌g t‌h‌e e‌l‌e‌c‌t‌r‌o‌d‌e f‌o‌r‌c‌e a‌n‌d i‌t‌s t‌i‌m‌e, t‌h‌e r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s‌e‌s i‌n‌c‌r‌e‌a‌s‌e. B‌u‌t t‌h‌e e‌f‌f‌e‌c‌t o‌f e‌l‌e‌c‌t‌r‌o‌d‌e f‌o‌r‌c‌e i‌s l‌e‌s‌s t‌h‌a‌n i‌t‌s t‌i‌m‌e o‌n r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s‌e‌s. T‌h‌i‌s f‌a‌c‌t r‌e‌f‌e‌r‌s t‌o h‌i‌g‌h‌e‌r h‌e‌a‌t t‌r‌a‌n‌s‌f‌e‌r a‌n‌d c‌o‌o‌l‌i‌n‌g r‌a‌t‌e a‌t t‌h‌e w‌e‌l‌d‌i‌n‌g z‌o‌n‌e. A‌n i‌n‌c‌r‌e‌a‌s‌e i‌n f‌o‌r‌c‌i‌n‌g t‌i‌m‌e c‌a‌u‌s‌e‌s a h‌i‌g‌h‌e‌r c‌o‌o‌l‌i‌n‌g r‌a‌t‌e, a‌n‌d m‌o‌r‌e c‌o‌l‌u‌m‌n‌a‌r d‌e‌n‌d‌r‌i‌t‌e s‌t‌r‌u‌c‌t‌u‌r‌e c‌a‌n b‌e o‌b‌s‌e‌r‌v‌e‌d i‌n t‌h‌e n‌u‌g‌g‌e‌t a‌r‌e‌a. T‌h‌i‌s w‌i‌l‌l c‌r‌e‌a‌t‌e c‌o‌n‌c‌e‌n‌t‌r‌a‌t‌e‌d r‌e‌s‌i‌d‌u‌a‌l s‌t‌r‌e‌s‌s‌e‌s a‌t t‌h‌e n‌u‌g‌g‌e‌t z‌o‌n‌e.

In this research the designed mechanism for chasing and repoussé of sheet metal is studied. This mechanism is similar to incremental sheet metal forming. In this kind of sheet metal forming, sheet is fixed and forming tool pastes desired pattern incrementally. The major difference between designed mechanism and traditional incremental forming is as follows: control on the punch energy and sequence, and fixing sheet by using protectant material behind it instead of clamping sheet sides. In this mechanism, the solenoid is used as a hammer. The plunger moves to the center of the coil while energized. Striking energy could be controlled by controlling the excitement voltage and punching sequence thus could be adjusted by manipulating the excitement algorithm. In this paper, the utilized solenoid is simulated. The mechanical and magnetic relations are merged for this. And the effect of core head geometry and plunger mass and coil covers on the strike energy and hence power is studied.

A study was conducted to investigate performance of a GTCP85-180 gas micro-turbine. It was concluded that hot compartment defects are significant in numbers. Due to the long time performance¡ this engine has many limitations; ignoring these limitations will cause severe damages to the hot compartment of the engine. Using numerical method which has both sufficient accuracy and low cost in comparison to experimental tests¡ temperature distribution and output temperature for this micro-turbine were computed. Afterward¡ by proposing a new geometry for the combustion chamber and conducting new simulation¡ a better performance was achieved. Changes in cooling holes and diluting holes configuration resulted in smoother temperature profile near the wall boundary and also output of the combustion chamber. This smoother temperature resulted in the reduction of the defects in combustion chamber and turbine blades. By comparing the temperature profile of both geometries it is evident that the proposed geometry has fewer temperature peaks in compare to the original one and it also has a smoother temperature distribution. According to the fact that mean output temperature of the original combustion chamber and proposed chamber is 950K and 1000k respectively¡ it is concluded that by using the proposed geometry¡ thermal efficiency is improved by 8 percent.

Due to the increasing use of multilayer sheets in various industries, the study of widely used blanking operation on these sheets is necessary. In this paper a study on the process of fine blanking of a multilayer sheet of Al / Cu / Al is done. In order to get accurate numerical results, finite element simulations of multilayer plate are conducted by using Johnson–Cook model and ALE formulation in ABAQUS/ Explicit commercial finite element code. The results are in good agreement with experimental results. The results show that with increasing counter punch force the surface quality is improved and the shear force is increased. Microscopic examination of the lateral edges show that below the aluminum layer edge, relatively large amount of plastic deformation is observed.

In this paper، the effect of Equal Channel Angular Pressing (ECAP) process on the structure and mechanical properties of AM30 magnesium alloy was studied. The results showed a considerable effect of ECAP process on creating an ultrafine grain size structure. Scanning Electron Microscope indicated that the grain size dropped from 20. 4 µm in the extruded form to 7. 2 µm in the first pass and 3. 9 µm in fourth pass. The fourth pass presented higher ductility and lower yield stress in comparison with the extruded case. This behavior can be explained based on higher rate of texture softening versus the effects of the grain refinement on strength. The hardness test on the samples cross-section showed an increase in hardness and a uniform strain distribution at higher ECAP passes.

New trends have been observed in recent years for rapid prototyping of sheet metal parts by Incremental Forming process particularly at low quantity production. Recent ideas have been presented for a new type of this process known as Incremental sheet metal hammering (ISMH) method. In ISMH process, by sequence moving of a hammering punch over a clamped sheet metal, a three-dimensional work piece is produced without using a die. In this paper, the effect of tool parameter on the formability of Al-1100 will be studied. To investigate this issue, the sheet is clamped. Then by considering the cone angle, hammering is applied at a certain diameter and frequency until the failure happens. By recording the angle and the height values at failure point, a correlation has been extracted between the diameter and the frequency. Analysis of the results shows that by decreasing the diameter of the punch, maximum strain in the direction of thickness is observed at higher height. Also, by increasing the diameter of the punch, formability of Al-1100 increases. Also, it is shown that by increasing the impact frequency, the formability of the sheet will be decreased.