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Use of Forming limit diagrams (FLD) in process design of metal forming is a conventional method. Therefore many experimental and theoretical efforts have been carried out in order to investigate the FLDs. Many ways to obtain this FLDs and their effective parameters have been studied. But the stress state at these studies is planar which lead to an untrue model for several metal forming process such as incremental sheet forming. With this technique, the forming limit curve (FLC) appears in a different pattern, revealing an enhanced formability, compared to conventional forming techniques. Therefore, in this study, the effect of through thickness shear stress has been examined on the prediction of the forming limit diagrams (FLDs). Determination of the FLD is based on the Marciniak and Kuczynski (M–K) model with some modifications on the stress states for consideration of the through thickness shear stress effects. Also, the effective range of this stress has been investigated. The results showed that if the through thickness shear stress has a 10 per cent of yield stress value, this stress component has no effect on the FLD.

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Ironing is a conventional metal forming process for producing thin walled cans with uniform thickness components manufactured from deep drawn cups. The most important drawback of the conventional ironing is the lower thickness reduction ratio (TRR) causes needing annealing process and multi stage ironing. Recently, a new ironing process named constrained ironing was presented by the current authors to achieve an extra TRR to solve the conventional ironing problems. This process that is based on the compressive stresses makes it possible achieving high TRR without interruption for additional processing such as multi-stage ironing and annealing. In this paper, FEM simulation was performed to investigate the effective parameters. The simulation results showed that process the process load increases with increasing the friction coefficient. Also, the state of the stresses is fully compressive in constrained ironing process while it is tensile in the conventional ironing method. Thus, compressive stress components minimize formability problems, and higher thickness reduction ratio is achievable in the new ironing method. Also, experimental results showed that the tensile strength and hardness increased after constrained ironed of the deep drawn cup.

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In this work static analysis of isotropic rectangular plates with variable thickness are presented using three dimensional electricity theory and for first time using radial point interpolation method. Using this numerical method, the field variables are interpolated just using nodes scattered arbitrarily in the plate domain. As there is no connection between any two nodes, their number can be increased in any area and direction to get more accuracy. It is assumed that, the plate thickness varies linearly in y direction or it has parabolic convex/concave lower surface in the y direction. The horizontal upper surface of the plate is subjected to the transverse uniform load in the z direction. Shape functions in this method have Kroneker delta function property and different boundary conditions can be applied easily using elimination approach. Convergence of results for simply supported isotropic rectangular plates with linearly variable thickness is presented for different thickness ratios and compared with available results. Distributions of the deflections and stresses for the plates with parabolic convex/concave lower surface in the y direction and under different boundary conditions are presented in numerous graphs. It has been showed that this numerical method is so appropriate to analyze such plates and have rapid convergence and high accuracy.

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The incremental forming process which can be used in low quantity production of the components is a relatively new forming process for sheet metal components. One of the problems of this method is thinning and non-uniform thickness distribution of the component in radial direction. In the incremental forming process, the sheet thickness in the wall of the formed cup is reduced considerably while the thickness in the bottom of the formed cup is unchanged. This problem is hindering the wide application of the incremental forming process in the industry. In this paper, a new method is presented for the improvement of the thickness distribution in the incremental forming process. In the presented method, a new preform is added to forming stages which reducing the sheet thickness in the bottom of the formed cup, increases the minimum thickness in the wall of the formed cup and improves its thickness distribution. The incremental forming process are simulated using the software ABAQUS and verified using the experiments available in the literature. Then the proposed method is simulated which its result indicates the capability of the presented method in thickness improvement.

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In this paper, the behavior of cylindrical shells with uniform thickness and functionally graded thickness distributions subjected to axial quasi-static loading is investigated experimentally and subjected to axial impact is investigated experimentally and numerically. Steel cylindrical shells with uniform thickness and functionally graded thickness distributions have same inner diameter, length and weight. Cylindrical shells are impacted by the drop hammer apparatus and experimental axial force-time curves are obtained by using a load cell; in addition, impact simulations are done by Abaqus finite element software. The effect of thickness distributions on the shortening, energy absorption, buckling shape and axial force-time curve of cylindrical shells is investigated. It is found that for axial quasi-static loading, a change in thickness distribution of cylindrical shell is able to convert the buckling shape from mixed buckling (a combination of axisymmetric and diamond modes) to progressive buckling, also for axial impact loading, a change in thickness distribution of cylindrical shell can affect the number of complete folds. The studies also suggest that at same impact energy, functionally graded thickness distribution cylindrical shell compared with uniform thickness distribution cylindrical shell absorbs approximately the same energy with more shortening and transforms less mean load and peak load to under protected specimen, thus, functionally graded thickness distribution cylindrical shell is a better energy absorption specimen. It is found that there is a good agreement between the experimental and numerical results.

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Fuel consumption, emissions and output power are some of the very important factors for automotive engine design. Since the combustion efficiency depends on the quality of the air-fuel mixture and mixture quality depends on the fuel injection parameters, the investigation of spray features is an overall goal in direct injection engines. In this paper, simulation of GDI spray is carried out in a constant volume chamber contains nitrogen in four different injection pressure using the AVL Fire software. The results are validated against the Istituto Motori-CNR experimental data. The log-normal probability distribution as an initial droplet diameter and Huh-Gosman model as secondary breakup were used. Then the combustion of EF7 Engine with direct injection was studied and wall film thickness was compared at different injection pressures and injector angles. Also, the effects of wall temperature and single-stage and two-stage fuel injection with different ratios of injected fuel mass were evaluated on the wall film. Since the fuel can be injected into the combustion chamber in both intake and compression stroke according to engine operating conditions in gasoline direct injection engines, the simulation was done for open cycle engine.

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One of the very important issues in designing hand prosthesis is to consider their cover or cortex. The purpose of this research is to design a cover to have a similar behavior, as much as possible, to the human natural skin, in power transmission and deformation pattern. A layer made of Lorica®, which has similar properties to natural skin, has been added to the conventional cover which composed of three layers. Using finite element analysis Software, ANSYS V.15, the new four-layered cover has been investigated on three dimensional model of the hand prosthetics with different thickness for the outer layer, and the pattern of deformation and internal stresses in the prosthesis are measured. Optimal thickness of the outermost layer is evaluated due to stress and strain distribution and their transformation to prosthesis metallic core. The relationship between the thickness of this layer and the distribution of stress and deformation of the cover is not linear and direct and the thickness of 1.5mm shows better results among the measured values in this section. In this study, the fourth layer was added to improve the frictional and elastic properties of formerly used prosthetic covers, and its effects on stress and strain distribution in the prosthesis was investigated. It is determined that due to lack of linear correlation between the thickness and stress distribution, the optimal thickness of each layer must be selected based on design limitation like the ability of embedding tactile sensors in future for the minimum thickness.

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In this paper, cold roll forming process of a high strength steel pipe using four types of flower pattern including circular, edge, double radius and reverse bending is simulated with finite element method in MSC Marc Mentat software. Due to importance of quality of final pipe and in order to achieve the desired geometry in high strength steel pipes, selecting the appropriate flower pattern to design the pipe roll forming production line is considered. Using finite element simulation results, deformation of sheet in this process is studied and effect of flower pattern type on geometry of final product, which includes curvature distribution, spring back and thickness distribution of pipe, is investigated. Results show that implementing reverse bending flower pattern, leads to reduction in deviation from mean curvature at edge of the sheet up to about 65 percent. Thickness distribution analysis shows that circular and edge flower patterns cause upsetting and thinning of edge of the sheet up to 0.2 millimeters, respectively. But, use of double radius and reverse bending patterns cause average thickness of edge to be well adjusted to reach 2.8 millimeters. Also, circular flower pattern has the lowest value of spring back in terms of variation of mean relative curvature of 0.69 percent and edge deviation of 0.15 millimeters. To validate the finite element simulation, experimental tests were designed and conducted using one forming stand. By comparing resultant data of experimental tests with simulation results, validity of finite element simulation confirmed.

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Micro end-milling is one of the main manufacturing processes of creating miniaturized parts which are increasingly demanded in many industries. Using tools with diameter less than 1 mm results in rising the so-called “size effect” and problems due to ploughing at low feeds per tooth. It is therefore crucial to estimate value of minimum chip thickness which helps to reduce or eliminate the ploughing. In this study role of scaling down is investigated with regard to milling operation in micro- and macro-scale. A titanium alloy Ti-6Al-4V is used as workpiece. Two-flute endmills with diameters of 0.8 and 2 mm are used representing micro and macro-scale, respectively. Effects of axial depth of cut and feed rate as input parameters were evaluated on such output characteristics as specific cutting energy, microhardness, surface roughness, topography and chip formation. Results show higher values of microhardness and specific cutting energy in micro-scale. Microhardness and specific cutting energy in micro-scale were found to be 6 times and 150% greater than the macro-scale, respectively. The study suggests that minimum chip thickness can be varied approximately between 0.25 and 0.49 of the cutting edge radius.

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In the new sheet metal forming process as incremental sheet forming and spinning forming, this is not perfectly true in Marciniak-Kuczyinski model to assume that sheet deformation occurs in the plane-stress state indispose there are normal compressive stress and through-thickness stress. In this type of forming processes, the obtained limit strains refer to improving the sheet forming. However, in researches the effects of through-thickness shear stresses, also known as out-of-plane shear, has been studied less. The generalized forming limit diagram is a great curve that includes all six components of the stress tensor. In this paper, the effect of normal comprehensive and through-thickness shear stresses on the limit strain AA6011 aluminum sheet using a modified M-K and the anisotropic Yield function, Hill 48 and by using numerical solutions of nonlinear equations, Newton-Raphson method. The first the forming limit diagram was drawn with the assumption that the through-thickness shear stresses and then the effects of normal comprehensive stress and through-thickness shear stress on the limit strains were proved and the generalized forming limit curves were obtained. The results show that forming limits can be increased significantly by both normal compressive stress and through-thickness shear stresses. Also, the effects of normal stress on increasing the formability of sheet compared with the effects of through-thickness shear stress is greater.

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In the present work, experimental and numerical results of the effects of different pressure curve on the thickness variation of sheet metal and distribution of radius and hoop strain for effective stress-strain curve have been presented. A series of experiments are carried out using a hydroforming apparatus by exerting different pressure curves including pendulous, steeped, saw and continuous. In each series, the effect of changes in pressure curve on thickness distribution was quantitatively measured. Different pressure curves such as continuous, stepped, and pendulous was produced in experiments. The ABACUS software was implemented to simulate the effect of changes in pressure curve. A good agreement between the experimental and numerical results was observed. The results show that stepped pressure produces more uniform distribution in sheet metal thickness. Mechanical behavior of sheet metal during plastic deformation phase under stepped pressure, produced satisfactory results, and using this type of pressure could control the effects of friction between the die surface and sheet metal specimen much better. Also, constant time duration of pressure pulses in stepped and pendulous curves leads to decreasing of maximum pressure needed for deformation of sheets.

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With increasing amount of pollution by thermal power plants in Industrial and developing countries, tend to use small-sized hydroelectric plants increased. In complex terrain regions there are usually a significant height difference between refineries and using place, the pressure can to produce electricity by power plants pressure reducer. The power plant is due to the relatively high initial cost less were used. Gradually, with the possibility of using pump as turbine and reducing the cost of building a micro power plant use the plant was expanded. Therefore, in this study centrifugal pump by CFturbo software was designed and for Numerical analysis of the three-dimensional fluid, the simulation was performed using the CFX software on SST k-ω turbulence model. The numerical results were compared with experimental in pump and turbine modes and showed good agreement. In order to increase the efficiency of the turbine pump (reverse pump), the decrease in the diameter of the impeller blades at different flow rates was investigated, which resulted was decrease in the amount of separation phenomenon around blades and causing increase in hydraulic quantities nearby the turbine bep point, but reducing the diameter at the flow rates very lower from bep point, didn’t have great impact at improvement of efficiency, at the bep point reducing the diameter, caused to increase 11.86 and 13.65 percent of the head and torque, and improved efficiency 1.26 percent.

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In this paper, the single point incremental forming (SPIF) of friction stir welded (FSWed) 5083 aluminum alloy sheets are investigated experimentally and numerically. The aluminum sheets with 2mm thickness are friction stir welded with the same FSW parameters. In order to obtain the effect of FSW on the formability of SPIF, the base sheets and FSWed sheets are formed to conical shapes with different forming angles and then the limiting wall angles are determined for each condition. The experimental results indicate that the limiting forming angle of FSWed sheet is not so much different than the base sheet and FSW does not have a negative effect on the sheet metal formability in SPIF. To study the effect of SPIF and FSW in mechanical and microstructural properties of the formed parts, the effects of these process on the grain size and micro-hardness is investigated. Furthermore, the incremental forming is numerically simulated using the ABAQUS software and the sheet thickness distribution, obtained from the simulation, is compared with the experimental results. After verification of the numerical simulation model, the effect of FSW on the thickness distribution and strain distribution in SPIF is studied. The results indicate that in weld region and base metal region, the distributions of thickness and major strain are uniform while the distribution of minor strain is non-uniform.

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The present study investigates the effect of the mixing chamber length on the effervescent atomizer internal two-phase flow and the liquid film thickness at the exit of the atomizer at different gas-to-liquid mass ratios. Therefore, the internal flow of this atomizer simulated for three different lengths of the mixing chamber, at the gas-to-liquid mass ratios of 0.08%, 0.32%, and 1.24% and at the liquid flow rate of 0.38 L / min by the volume of fluid interface following model. The simulation results show that the mixing chamber length does not have much effect on the dominant flow regime in the discharge passage. However, by increasing the mixing chamber length, the two-phase flow inside this chamber more expanded before entering into the discharge passage. Therefore, the two-phase interface instabilities in the discharge passage are lower for the atomizer with the longer mixing chamber. In addition, based on the measuring results of the liquid film thickness at the exit of the atomizer, the effect of the mixing chamber length on the thickness of this film depends on the gas-to-liquid mass ratio. Increasing the mixing chamber length at low gas-to-liquid mass ratio increases the liquid film thickness at the exit of the effervescent atomizer. While at high gas-to-liquid mass ratio, it's inverse. At middle gas-to-liquid mass ratio, the changes of the liquid film thickness at the exit of the atomizer with the mixing chamber length do not show a steady trend.

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Aerodynamic and optimal design of a blade of a horizontal axis wind turbine (HAWT) has been performed in order to extract maximum power output with considering the strength of the blade structure resulted from different loads and moments. A design procedure is developed based on the Blade Element Momentum (BEM) theory and suitable correction factors are implemented to include three-dimensionality effects on the turbine performance. The design process has been modified to achieve the maximum power by searching an optimal chord distribution along the blade. Based on the aerodynamic design, the blade loads have been extracted and the blade mechanical strength has been investigated by analyzing the thickness of the blade surface and the blade material. The developed numerical model can be considered as a suitable tool for aerodynamically and mechanically design of a turbine blade. The results for a 500 W turbine show that the turbine performance improves by 5% approximately, by modifying chord radial distribution. Yield stress analysis shows the effect of introduced chord distribution on the blade strength, in different blade thicknesses and different blade materials. In addition, optimum tip speed ratio for having favorable mechanical safety factor is derived. Three different airfoil are examined for this investigation and comparing their mechanical safety factor.

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Concrete is one of the most widely used building materials for fragile behavior. The addition of fiber to concrete affects the behavior of tensile strength, tensile strength, flexural strength, modulus of elasticity, impact resistance and some other mechanical properties of concrete. For this purpose, an experimental research was carried out to provide an experimental model of the flexural fatigue life of reinforced concrete with macrosynthetic fibers by constructing concrete joists with three different thicknesses of 80, 100 and 150 mm. SN models (stress-loading) and HN (thickness-loading) was presented. The results showed that increasing the thickness of concrete samples and adding fibers to concrete mixture increases the fatigue life. Also, the addition of fibers to concrete samples measured the thickness of the sample for the stress level of 0.7 final stresses at 12.45-8.24%, for the stress level of 0.8, the final stress was 22.15-5.45%, and for the stress level of 0.9, the final stress decreased to 22.15% -10.18% Finds. Fiber-reinforced concrete is a type of concrete that is mixed with fiber. Various types of fibers are used to produce fiber-reinforced concrete, which include glass, polymer, carbon and steel. In the present research, macro-synthetic polymer fibers were used. Some of the consequences of applying macro-synthetic fibers in concrete include reduced shrinkage of fresh and hardened concrete, increased ductility, increased strength against fatigue stresses, increased durability and lifetime of concrete, improved concrete mechanical properties (tensile strength, flexural strength, etc.), control of secondary/thermal cracks of concrete, preventing the in-depth propagation of cracks, post-cracking chargeability and reduced permeability against chloride and sulfate ions .In most of the studies, the concrete sample's thickness is increased along with the increase in the beam's length; however, in the present work, only thickness of the beam samples with and without fibers was changed and other dimensions of the samples were kept constant in order to investigate merely the effect of increased thickness. Accordingly, effect of the size of macro-synthetic fiber-reinforced concrete sample at different thicknesses was assessed via fatigue life variations. The intertwisted fibers were added to the concrete mixture by 0.4 vol.%. Then, from each sample, three specimens were made. The obtained results were averaged and, then, recorded in the relevant tables. The following cases were considered as the research objectives: - Effect of sample size on fatigue life of concrete samples - Effect of adding macro-synthetic fibers on fatigue life In order to determine flexural fatigue of the concrete samples with the above-mentioned geometric properties, UTM device was used. The test was performed with constant sinusoidal loading at the frequency of 10 Hz. The input information for the test included loading curve shape, minimum and maximum loading values, loading frequency, and maximum number of loadings, all of which were defined as the input. To measure the values of stress levels in order for measuring the loading values, first, the average of the samples' flexural strength had to be determined; then, the stress levels could be calculated from the obtained results. also A cross sectional analysis of the broken sample showed that most of the sample failure was from aggregate and the mixture design was suitable.

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