In the deep drawing process, the optimal design of the initial blank shape has many advantages such as reducing the cost of production and waste and improving the quality of the process and thickness distribution. The deep drawing process is highly nonlinear due to the large deformation, plastic deformation of the material and the contact phenomenon. Therefore, the general solution to such problems is to use iterative methods based on numerical simulation. The present study implements a similar approach and presents a new algorithm to make geometrical corrections to the external boundaries of a blank, as well as its internal boundaries, in several iterations. A computer program was developed to automatically run these iterations to study the features of the proposed algorithm. Next, an example problem was solved, and the results are compared with other studies. The results showed that the proposed algorithm is sufficiently robust against the initial guesses for the blank, which is an advantage of the present algorithm over those from other algorithms. Because in other algorithms presented in the articles, if the appropriate initial guess is not selected, the algorithm will not converge to the answer. The proposed algorithm also has a higher convergence speed in achieving optimal blank. پرونده مقاله

Hardox-400 with an extra-high yield strength of ~1000 MPa and excellent abrasion resistance is a good candidate for several industrial applications including automotive parts, working tools, barges, loaders, etc. Due to high dimensional precision and to avoid mechanical abrasion of the work-piece, electrical discharge machining (EDM) is a proper machining technique for such steel. The influences of important process parameters, i.e. discharge current and spark pulse cycle on the electrode wear, material removal, surface roughness, and integrity of the machined material is investigated. It was observed in this work that as the discharge current increased, the electrode wear also increased but this occurred with a gradually decreasing rate. On the other hand, increasing the ratio of pulse-on to pulse-off time decreased material removal. Furthermore, it was observed that increasing both the discharge current and the pulse-on time led to a thicker solidified so-called white layer which is more susceptible to cracking and thus is detrimental to the material integrity. پرونده مقاله

The imperialist Competitive Algorithm (ICA) is one of the recent meta-heuristic algorithms proposed to solve optimization problems. The Imperialist Competitive Algorithm is based on a socio-politically inspired optimization strategy. This paper presents an Imperialist Competitive Algorithm (ICA) to optimize the performance of a surface grinding operation. Moreover, the multi-objective optimization of a surface grinding process is suggested by using an evolutionary algorithm. Factors like depth of dressing, lead of dressing, workpiece speed and wheel speed are considered to minimize the production cost, surface roughness and to maximize the production rate. The suggested approach presents two constraints handling techniques: constraints handling strategy of ICA and penalty function method. The effectiveness of this algorithm for grinding operation is investigated by comparing the results to other algorithms available in the literature. Results show that the proposed algorithm in this work gives a better performance in a shorter time for the optimization of machining parameters in comparison to other works. پرونده مقاله

One of the most important methods to reduce metal corrosion and improve erosion resistance is to use strip cladding with electro slag welding. Applying the strip electrode (E316l), cladding performed on the layer of steel (5A-516) with this process. With changes in the thickness of cladding layers and the number of these layers, the percentages of ferrite and carbon in samples obtained by WRC equipment were analyzed. The optical microscopy is used to investigate the microstructure of different cladding layers in this research work. Hence, with the increase in the percentage of carbon, the sensitivity of stainless steel to grain boundary corrosion increases. With the reduction of ferrite percentage, the sensitivity to hot cracking increased too, so the overall results indicate that with an increase in the thickness of the first cladding layer, the amount of carbon in this layer increases, this phenomenon reduces the percentage of ferrite in it. Hence, by increasing the number of cladding layers, the amount of carbon percentage reduces considerably while the ferrite percentage reaches the desired amount. پرونده مقاله

Today, metal forming is considered one of the essential methods of manufacturing and producing parts. Therefore, the more accurate knowledge of it leads the industrialists to produce higher quality parts. Deep drawing is one of the most important methods in metal forming processes used to produce cup-shaped products. In this paper, numerical simulation of the deep drawing process based on the finite element method is performed using Abaqus software for a cylindrical cup. Then, the results obtained from numerical simulation are compared with the experimental results in the sources, and the validation of the simulation is performed. In the deep drawing process, effective parameters such as circumferential strain distribution, thickness strain distribution, and radial force distribution are extracted from numerical simulations and compared with experimental results in the sources. The effect of friction coefficient, blank holder force, and punch radius on the deep drawing process has also been investigated. Because experimental methods based on trial and error are time-consuming and costly to achieve the shape of the primary blank, researchers use numerical methods to simulate and design metal sheet forming processes such as deep drawing. It is necessary to compare the results with experimental works to validate the simulations performed by numerical methods. پرونده مقاله

Deep drawing is a popular process in sheet metal forming. The goal of shape optimization of the initial blank which is considered in the present work is to find the shape of the blank in a manner in which after a deep drawing process the contour of the edges of the produced part meets a target contour. Such problems are highly nonlinear because the simulation consists of large deformation, plastic deformation, and contact. Therefore, the general approach to solving such problems is using iterative methods which are based on numerical simulation. Such an approach is also followed in the present work and a new algorithm for geometry modification of initial blank in each iteration is proposed. In the proposed algorithm, the normal distance between the final contour and target contour is used as a criterion to modify the initial blank. To evaluate the proposed algorithm a computer program is developed and to automatically execute the iterative process. One numerical example solved and the results are compared with those reported in the literature. One of the benefits of the proposed algorithm is its insensitivity to the initial guess. Therefore, to evaluate the effect of the initial guess on its performance the example was solved using different initial guesses. The results show that the proposed algorithm is robust regarding the initial guess and convergence to the optimum shape will be achieved by starting from an initial guess. پرونده مقاله

The joining of dissimilar metals by Friction stir welding (FSW) is one of the newest metal joining processes. In this research, the tool was made from H13 hot working steel, which has a concave shoulder with a 3-degree inclined angle. The welding operation performed using a milling machine. The non-homogeneous workpieces joining of the Al alloy (5083) and a sheet of annealed copper (ASTM B36) with a thickness of 2 mm was investigated by the FSW method. The joining process was carried out at three tool transverse speeds of 25, 35, and 45 mm per minute and three rotational velocities of 1000, 1300, and 1600 rpm. Microstructural changes of the welded samples were analyzed by optical microscopy and scanning electron microscopy used to distinguish the type of phases. While its mechanical properties analyze according to different parameters used in the experiments. Also, the welded parts were subjected to microhardness and tensile tests. It found that the welding sample with a tool rotational speed of 1,300 rpm and a forward speed of 35 mm/min has the best mechanical properties, with a tensile strength of 82% and a yield strength of 80% of aluminum base metal. While welded components with a forward speed of 25 mm/min have tunnel defects and brittle phases of AlCu and Al2Cu formed in the stir region so that with the increase of rotational speed and forward speeds, the percentage of these brittle phases increases. پرونده مقاله

Today, one of the new approaches of researchers to produce materials with very fine grains is the application of severe plastic deformation on the prototype with coarse grains. In this method, the grain size is reduced to the nanometer scale in several stages through applying strong strains to the sample, which leads to the improvement of mechanical and physical properties in the material. One of the most important methods of applying severe plastic deformation is the constrained groove pressing (CGP) process. According to studies, little research has been done on the weight loss of structures used in the military, maritime, aviation, and medical industries. Therefore, the mechanical behavior of the sheets was experimentally studied by the CGP method. The results show that the structure of 7075-T6 aluminum particles decreased in size from 60 microns to 270 nanometers by increasing the steps of this process. Also, the yield strength in the fourth pass increased by 38% compared to the annealed sample, and the tensile strength improved by 34%. In addition, the percentage of longitudinal increases in the fourth pass is reduced to its lowest value, ie 40%. پرونده مقاله