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Tubular components, such as stepped tubes, conical tubes and box-shape tubes, are mainly produced by tube hydroforming process. Obtaining a sharp corner is the main goal in some of these components. In this paper, corner filling in stepped tubes is studied using a new multistage hydroforming die. The proposed die was simulated and filling of the die cavity was investigated. The finite element software, ABAQUS 6.4, has been used for simulation. In order to verify the simulation results, the new die of stepped tube was manufactured and then experiments have been performed on it. The results of the experiments verified the simulation results. It was shown that by using the new die, parts with sharp corners could be produced. The simplicity of the die and the low internal pressure are among the advantages of this die.Thickness distribution was also examined by FE simulation and via experiments and it is shown that a better distribution could be obtained by the proposed die set.

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In order to produce shell parts with diffrents applications using the new method in sheet metal forming is inevitable. In this article is intruduced a new process that movement of forming tool is compeltely gradual and controlled. In this method can creat complicated shapes in sheet metal. Also in order to create movement of tool is used Computer numerical Controlled (CNC) machine. In this process with inserting a punch under the sheet and gradual movement of tool in the special path creates a deformation in accoddance to punch shape. In this research by using experimental tests and theoretical analysis (slab analysis) is presented a comprehensive study of the governing equations in process. With calculating of stress field can present applied load at tool and sheet. ge for Calculation of this force is a suitable gauge for choosing kind of CNC machine equipment, sheet type and etc. Also according to analysis results can make decision about the effect of immeasurable important parameters in this process.

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In this paper, the role of isotropic and kinematic hardening models are discussed in cold forming of a U-channel considering the springback phenomenon. The effect of influential parameters on the springback is also studied. For this purpose, a cold roll forming machine was built using a milling machine. The effects of forming angle’s changes, sheet material, roll geometry and sheet thickness are studied experimentally and numerically. The results show that the isotropic work hardening model is more precise in prediction of the springback. 304 stainless steel and AISI 1015 are used in experimental verification. Comparison of the simulation results with experimental values demonstrates the accuracy of the modeling.

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Present study describes the approach of applying Response Surface Methodology (RSM) with a Pareto-based multi-objective genetic algorithm to assist engineers in optimization of sheet metal forming. In many studies, Finite element analysis and optimization technique have been integrated to solve the optimal process parameters of sheet metal forming by transforming multi objective problem into a single-objective problem. This paper aims to minimize the objective functions of fracture and wrinkle simultaneously. Design variables are blank-holding force and draw-bead geometry (length and Diameter). Response surface model has been used for design of experiment and finding relationships between variables and objective functions. Forming Limit Curve (FLC) has been used to define the objective functions. Finite element analysis applied for simulating the forming process. Proposed approach has been investigated on a cross-shaped cup drawing case and it has been observed that it is more effective and accurate than traditional finite element analysis methods and the ‘trial and error’ procedure.

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In tube hydroforming, the loading path, that is the relationship between axial feeding and internal fluid pressure, is of important significance. Researchers have employed various optimization approaches to find an optimum loading path. In this research a statistical method based on finite element analysis has been developed. An accurate FEA has been used to simulate the process and to find the response of the process to the loading. The Response Surface Method (RSM) has been used to model the responses from the finite element analysis. The behavior of the process can be predicted using this model. The obtained model then used to optimize the process. Since The RSM model was initially obtained for a predefined domain of variables multilevel optimization was employed to improve the accuracy of the model. The multilevel optimized curve yielded the best thickness uniformity, the result of which are reported.

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The Incremental Sheet Metal Forming (ISMF) process is a new and flexible method that is well suited for small batch production or prototyping. In this study, after the process simulation with ABAQUS software and verification of results through experimental tests, the effects of three parameters including friction coefficient, tool diameter and vertical step size on three objectives including vertical force, minimum thickness of deformed sheet and amount of spring-back are investigated. A neural-network model is developed based on simulation data and the effects of parameters are studied on each objective. Also multi-objective genetic algorithm is performed to get the Pareto front of optimum points.

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Bipolar plates are the most important and expensive components used in fuel cells. Metallic bipolar plates are the best choice to replace graphite or machined thick metal plates due to their lightweight and low cost. Selection of suitable forming process is one of the main subjects in fuel cell technology. Nowadays, hydroforming process is commonly used for the production of metallic bipolar plates because of its capability in forming light weight and complex parts. Among the various patterns of bipolar plates, serpentine flow field pattern inevitably brings two main defects of rupture of material during forming process and uneven flow distribution in practical operations. In this research, forming of a slotted interdigitated serpentine pattern on SS304 stainless steel sheet by hydroforming process has been examined using finite element simulation and experimental approach. The effects of process parameters and die geometry on the thickness distribution and filling percent are also studied. It is concluded that by increasing the forming pressure, filling percent of the die increases and the thickness of critical region is more reduced due to the increasing of drawing ratio. Also, it was found that hydroforming process has high repeatability.

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Incremental sheet metal forming process is considered as one of methods which able manufacturer to produce parts without dedicated die in low and rapid prototype production, and many researches have been done to improve it. Using of ultrasonic vibration is one of the modern approaches in forming processes which reduce friction and forming force. The purpose of this study is to investigate the effect of ultrasonic vibration applied to the tool in single point incremental sheet metal forming process. For this, first theory of single point incremental forming has been studied; its principle has been investigated and analytical relations have been modified then analytical relations in the case of applying ultrasonic are derived from those. To practical evaluation of applying ultrasonic to this process a set can be installed to the head of CNC milling machine is designed and manufactured. According to results of analytic compared to experimental results a reasonable approximation of forming force variation in normal single point incremental forming process and applying ultrasonic can be offered. Based on tests results forming force in applying ultrasonic compare to normal mode reduces between 33 to 63.5 percent depend on test circumstances.

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In the present paper, drawing process of metal plates through a wedge-shaped die, by proposing new velocity field, has been analyzed by upper bound method and simulated by finite element method (Abaqus software). Among the important cases in upper bound analysis of the forming processes is selection the appropriate boundaries for the deformation zone and offering admissible velocity field that in addition to satisfy the incompressibility condition and boundary conditions, is consistent by the behavior of metal flow in the deformation zone. The entrance boundary of deformation zone has been assumed exponential curve surface and boundary at exit has been assumed cylindrical surface. In the past analyses, metal flow lines in the deformation zone have been assumed straight but in reality it is not. In the present work, velocity field and also geometric shape of the deformation zone, justify that metal flow lines are non-straight. Base on proposed velocity field, internal powers, shear and frictional and also total power have been calculated. Then, according to the plate pulling velocity, required drawing force has been obtained. Finally, analytical results have been compared with the obtained results of FEM. In order to validate the present analysis, obtained results have been compared with other researchers. Also, the effect of various parameters, such as percentage reduction in thickness and shear friction constant on the drawing force and die optimum angle have been investigated.

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Forming media in metal forming processes is so important. Since the forming media in Ball deep-drawing process is discrete, it is quite flexible. In this paper, thickness distribution and required force for forming of conical part by ball deep-drawing and conventional deep-drawing processes using finite element simulation and experimental stages, were studied. In this research, sheets were used made St14 steel and brass wit 1mm thickness. The experimental results are in good agreement with simulation results. The results showed the sample formed by conventional deep-drawing process had more uniform thickness distribution than ball deep-drawing, but the maximum thinning in the parts of ball forming process was less than conventional deep-drawing process. Also it was observed that required force for ball deep drawing process is more than the conventional deep-drawing process. It was observed that with increasing radius of the input die, the force required to stretch the ball deep-drawing and ball processes is decreased, also with increasing radius of the input die is reduced thinning amount. It was noted that one of the advantages of ball deep drawing process than traditional deep drawing process is achieved a negative slope part.

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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.

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A Forming Limit Diagram (FLD) is a graph which depicts the major strains versus values of the minor strains at the onset of localized necking. Experimental determination of a FLD is usually very time consuming and requires special equipment. Many analytical and numerical models have been developed to overcome these difficulties. The Gurson- Tvergaard- Needlemann (GTN) damage model is a micromechanical model for ductile fracture. This model describes the damage evolution in the microstructure with physical equations, so that crack initiation due to mechanical loading can be predicted. In this work by using the GTN damage model, a failure criterion based on void evolution was examined. The aim is to derive constitutive equations from Gurson's plastic potential function in order to predict the plastic deformation and failure of sheet metals. These equations have been solved by analytical approach. The Forming Limit Diagrams of some alloys which studied in the literatures have been predicted using MATLAB software. The results of analytical approach have been compared with experimental and numerical results of some other researchers and showed good agreement. The effects of GTN model parameters including 〖 f〗_0 〖,f〗_C 〖,f〗_N,f_f , as well as anisotropy coefficient and strain hardening exponent on the FLD and the growth procedure of void volume fraction have been investigated analytically.

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As an effective forming method in aeronautical industries, peen forming is derived from shot peening process. Major application of this process is for production large thin components with gentle curvature such as aircraft panels and wing skins. This process can be divided into two categories; peen forming without elastic pre-strain (conventional peen forming) and with elastic pre-strain (stress peen forming). In this research, numerical and experimental study of shot peening, peen forming and stress peen forming of aluminum alloy sheets were conducted. In order to perform experimental tests, steel shots with 0.4 mm and 0.6 mm diameter and aluminum alloys Al 6061-T6 strips were used. For applying elastic pre-strain, fixtures with four pre-bending radii ∞, 500 mm, 375 mm and 250 mm were designed and manufactured. In numerical section, using same parameters as applied in experiments, first by using a 3D model with random distribution of shots, shot peening process was simulated and created stresses in sheet ( induced and residual stresses), were obtained. Next by using this model and in a three step procedure, peen forming and stress peen forming processes were simulated. The results showed that applying pre-strain is very effective in distribution of stress profile inside the sheet metal and thus in the final deformation of it. Accordingly, in compared with conventional peen forming, stress peen forming produces larger curvatures in the sheet metal. Furthermore, with increasing pre-bending moment (decreasing pre-bending radius), the resultant curvature in the sheet in the direction of the applied pre-bending, increases.

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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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Sheet Metals are widely used in different industries such as ship building. One important subject in these industries is to create the desired sheets through line heating process. In this paper, at first, the simulation of heat transfer between a gas torch and a plate during the line heating process is investigated. Impingement jet model is used to simulate the effect of a heat source (flame) and air cooling on the plate by using the commercial engineering software, FLUENT. Then, the computed temperature distribution by FLUENT is fed into the ANSYS FEM package for thermo Elasto-Plastic deformation analysis and the results are validated. Process execution needs heat paths and heat conditions. For this purpose heat paths of the cylindrical shape was obtained based on the Strain-Based Method. For thermal conditions a neural network was trained. In this regard, close to 63 different situations in different powers and torch speeds were run. Finally, to verify the thermal characteristics obtained for the cylindrical shape, paths and thermal conditions obtained was passed on a flat sheet metal by simulation and the result was compared with the desired shapes. It was shown that the Strain-Based Method in determining the thermal paths is very practical.

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Metal forming is a conventional manufacturing process that a material with simple form is subjected to plastic deformation and emerged to industrial end products. Reduction of forming forces and improving of products quality have been a promising object for investigators and artisans. To accede this purpose, primary methods such as increasing material temperature and modern methods such as use of high power low amplitude ultrasonic vibrations were introduced. In ultrasonic assisted forming, high power ultrasonic transducer produces low amplitude high frequency mechanical vibrations which transmitted to material subjected to deformation and contacting surfaces of tool/workpiece. Results show reduction of forming forces and tool wear as well as improving surface integrity and dimensional stability that lead to increasing production rate and process efficiency. By regarding to importance and capability of ultrasonic assisted metal forming, this paper is concerned with application of ultrasonic vibration on metal forming processes. To this purpose, fundamental and mechanisms of application of high power ultrasonic were introduces and discussed. Also, industrial future of this technology as well as its advantages, range of application and its restriction were mentioned.

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Incremental sheet forming is a flexible forming technology in which the sheet metal is gradually formed by the movement of tools in specified path. Due to the progressively localized deformation of the sheet and concentration of the forces on contact area of tool and sheet metal, the formability of the sheet increases compared with other common forming methods. In this study, numerical simulation of the incremental forming of AA3105-St12 two-layer sheet has been performed to calculate forming force and final thicknesses of the layers. The validity of the simulation results is evaluated by comparing them with those obtained from experiments. Numerical models for estimating the vertical force applied on the tool and the final thicknesses of the layers in terms of the process variables have been obtained using artificial neural network. Multi-objective optimization has been conducted to achieve the minimum force and the minimum thickness reduction of layers using obtained numerical models based on genetic algorithm method. Optimum thickness of the two-layer sheet and the thickness ratio the layers in different states of contact of the aluminum or the steel layers with the forming tool have been determined.