ahmad afsari

Friction stir processing (FSP) is a method of changing the properties of a metal through intense, localized plastic deformation. The influence of FSP on the mechanical properties of AA7075-T6 aluminum alloy welded by Gas Tungsten Arc Welding (GTAW) was investigated. The original and friction Stir-processed welds were assessed, and their microstructure and mechanical properties were compared. FSP was found to produce a great extent of refinement in microstructure accompany with uniformly distributed fine particles. Using FSP improved the mechanical properties of the welds, particularly those joined by GTAW, through grain refinement in the fusion zone (FZ). The FSP at 1600 rpm and 80 mm/min improved the elongation, tensile strength, and hardness of 7075-T6 aluminum alloy. FSP increased the tensile properties of 7075-T6 GTAW due to grain refinement of the weld zone by 14 percent. Elongation increased about 200 percent for the joint fabricated using WS of 80 mm per min and RS of 1600 rpm compared to unprocessed weld. Hardness decreased from 120 Hv to 60 Hv after welding and then increased to 90 Hv after FSP. Decreasing hardness attributed to welding heat effects, which increase after FSP, is related to grain refinement. This work showed that FSP is an effective method for improving the mechanical properties of fusion welds in 7075 Al-Zn alloy through microstructural modification.

Several factors influence the quality of the final parts of the plastic injection process, as many variables play a role in controlling this process. These factors can include the machine, mold, operator, raw materials, and working environment. An extensive study revealed that molding machines significantly impact quality compared to other factors. Adjusting and optimizing the machine parameters makes it possible to achieve parts with the desired or acceptable quality. The main goal of this project is to develop an application system that selects the regulatory parameter values for machines handling polycarbonate and other polymers. Additionally, the defects will be predicted in injected parts, and their properties will be analyzed using Moldflow software. Another software, based on practical data, will take initial user input and provide the necessary machine parameters to the operator from a reliable information source. During the production stage, if a defect occurs, the software will generate instructions tailored to the defect type and the conditions and parameter values. If the defect persists after following the provided instructions or if the nature of the defect changes, the software will adapt its guidance until defects are resolved, creating perfect parts without any flaws.

The Diesel Engine Test Stand Structure (DETSS) is crucial in industries like automotive, agriculture, shipbuilding, military, and aerospace for engine testing and repair, ensuring safety for technicians. This study designed a steel structure in INVENTOR software, considering the engine's weight, power, and torque. Static and dynamic analyses were conducted using ABAQUS. Static analysis revealed maximum von Mises stress (300–617 MPa) in the motor mount and chassis and minimum stress (100–175 MPa) in the radiator mount, fuel tank, and control panel. Vibrational analysis showed maximum displacement (0.08 mm at 7.20 Hz) in the chassis and mounts, and minimum displacement (0.05 mm at 9.45 Hz) in the control panel, fuel tank, and battery holder. The findings highlight the need for reinforcement and optimization of the motor mount and engine holder.

In this research, the weld zones resulting from friction stir welding (FSW) and arc welding with shielding gas and non-consumable tungsten electrodes (TIG) on AL-5754 alloy were compared. The input parameters for both processes were selected based on the Taguchi method, and the welding operations were performed accordingly. To achieve optimal input parameters, tensile, ultrasonic, and hardness tests were conducted on the samples. The results indicated that the weld created by the TIG method exhibited higher tensile strength for samples 3, 4, and 9, with values of 195, 152, and 151 MPa, respectively. However, in FSW, the finer granularity of the base material (44 microns) resulted in a better microstructure (30 microns) compared to the TIG method. This characteristic leads to enhanced mechanical properties, such as toughness, fatigue strength, and flexibility, in the FSW method. Since the hard work done on the base metal is lost with this method, and there is no possibility of increasing the strength of the weld, as can be done with the TIG method by changing the filler material, the TIG method is preferred in this comparison.

Temperature prediction is essential for assessing the state of stresses, strains, and material flow during friction stir welding (FSW). In this context, the thermal and mechanical behavior of the AA6063-T5 aluminum alloy was simulated in FSW. This research utilized the Finite Element Method (FEM) for thermal and mechanical simulations, employing Abaqus/Explicit software. The first simulation focused on the thermal model, implemented through coding in FORTRAN using the Schmidt-Hotel reference model, which investigates the temperature distribution of the alloy. The second simulation was mechanical in nature; it utilized the output results from the thermal simulation to examine the stresses resulting from the FSW process. The samples were made of the same material and were butt-jointed for the operation. A tool speed of 60 mm/min, a force of 4000 newtons, and a coefficient of friction of 0.4 were applied during this process. The parameters for thermal conductivity, specific heat, coefficient of expansion, and Young's modulus were defined as temperature-dependent. The results indicated that the temperature distribution diagram at a specific point along the welding path closely matched practical examples of the FSW process. The temperature distribution contours at the beginning, middle, and end of the welding path, as well as the temperature distribution across the cross-sectional surface of the weld in the middle of the piece, were consistent with the samples. Additionally, the diagram and contour of the longitudinal residual stress in the workpiece aligned well with the completed samples.

This paper analyzes the nonlinear dynamic response of truncated conical shells reinforced with carbon nanotubes with functional graded ceramic-metal matrix subjected to harmonic excitation. Carbon nanotubes are distributed with three different patterns along the length and thickness of the conical shell. The matrix material of the shell is considered to be a combination of metal and ceramic, whose properties change as a power function along the thickness of the shell. In order to analyze the dynamic of this system, firstly, the nonlinear dynamic equations of the conical shell are derived based on the first order shear deformation theory and von Karman's strain-displacement relations. Then, with the help of Galerkin discretization method, partial differential equations of the system are converted into time-dependent ordinary differential equations. Adams-Bashforth numerical method is used to solve the system of nonlinear differential equations. Finally, a parametric study is presented to investigate the effects of some parameters of the system, such as the power index, volume fraction and distribution pattern of carbon nanotubes, the geometric characteristics of the shell, and amplitude of the excitation force on the nonlinear dynamic response of the conical shell. In order to validate, the results of this article are compared and presented with the results of previous valid references.

The braking system in cars is directly deals with the issue of safety, and as a result, it is essential to pay attention to this matter. One of the materials used to make disc and brake pads in disc brakes is a ceramic material. This research aims to simulate and analyze the dynamic-thermal ceramic brake disc during the braking operation using the finite element method. Currently, the conventional brake disc is used in the Peugeot 206 car (domestic production), which has low efficiency in terms of life, wear, etc. Therefore, in this research, considering the significant production of Peugeot 206 car in the country, the disc and brake pads of this car have been selected, which were first modeled by Catia software, and after transferring the model to Abacus software and defining the types of ceramics and Cast iron was analyzed by finite element method. Compared the results of the Peugeot 206 ceramic brake disc and pad analysis were with the results of the standard (cast iron) discs in this car. The results showed that the maximum von Mises stress in the ceramic disc was 260.7 MPa, while the maximum von Mises stress in the cast iron disc was 293.3 MPa. The amount of heat produced in the ceramic disc during the braking action in 4 seconds was almost 84% less than the cast iron disc in the same period. Also, the results showed that the ceramic disc has a higher safety factor (1.98) than the cast iron disc (1.45).

The correct selection of input parameters in the electric discharge machining (EDM) process leads to improvements in the material removal rate (MRR), dimensional accuracy of the parts, quality of the surface finish, and reduction of tool wear. The main goal of the research was to investigate the type and extent of the influence of input on output parameters in EDM operations. Experimental data and the contribution of parameters were obtained using the Taguchi test design with three levels. The tool used was made of copper. Samples were selected from three types of alloy steel: 4340, Ti6Al-4V, and AISI D2 steel. The test variables included maximum current (Ip), gap voltage (Vg), and duty factor (DF). In these experiments, Ip values of 5, 10, and 15 amps, Vg values of 25, 50, and 75 volts, and DF values of 0.3, 0.6, and 0.9 were selected. The number of machining operations was 81 tests, and the L9 orthogonal array related to the Taguchi approach used for Design of Experiments (DOE) reduced the number of machining operations from 81 to 27 tests. The results indicated that the current parameter of 5 amps had the highest effect on surface roughness (SR) in samples of AISI4340 steel. The current of 15 amps had the greatest impact on MRR, while the duty factor (DF) of 0.6 played the highest role in electrode wear rate (EWR). Maximum Ip contributed 36.77%, Vg contributed 31.03%, and DF contributed 32.18% to EWR.

Friction stir process (FSP) was used to improve hardness and tribological properties of Al-5083 aluminum alloy through formation of metal matrix composite (MMC) material. The process involved the use of titanium diboride powder (TiB2) and carbon nanotubes reinforcing materials. The number of passes during the process was varied. Observations of the microstructure of the composite materials were made using scanning electron microscopy (SEM), while the composited surface layers were examined using microhardness testing. After conducting four passes using FSP, the surface nanocomposite obtained from carbon nanotubes and TiB2 yielded a maximum increase in hardness of 32.3%, and 21.6% compared to the base alloy respectively. Moreover, the samples produced with four passes, containing carbon nanotubes, showed a hardness 8% greater than the samples produced with the same number of passes, but with TiB2. Additionally, the highest wear resistance was also obtained using four passes. The wear resistance exhibited by the carbon nanotube-reinforced composite was approximately 45% greater than the TiB2 powder-reinforced composite. Hence, the use of FSP can potentially increase the working life of the part in wear conditions by up to 3.5 times.

Cryogenics is a field that involves producing, storing, transporting, and using materials at freezing temperatures. One application of this technology is in the shrinkage fitting process, where coolant materials like liquid nitrogen are used to reduce the dimensions of parts so that they can be joined together. This technique is often utilized in sub-assemblies to create a strong fit between the internal and external surfaces of components, which eliminates relative movement between parts, allowing force to be directly transferred from one part to another. In a recent study, we investigated different methods for fitting bush and axle parts with precise dimensions. Cryogenic, pressing, and thermal methods were utilized for assembly fitting. The cryogenic and thermal methods utilized contraction and expansion of parts for assembly fitting, while no dimensional changes occurred in press fitting.  Results from the study showed that the cryogenic method required less force for the assembly and disassembly of parts, and the surface quality of the parts after disassembly was better compared to the other methods. Metallographic tests demonstrated that the microstructure of the parts did not change, and impact tests showed that there was no decrease in the toughness of the parts after the cryogenic operation. Based on these findings, the researchers concluded that the cryogenic method is an excellent technique for fitting SAE4140 Steel parts.

Connecting parts through welding as permanent connections can play an important role in various industries. Despite the favorable load-bearing capabilities of joints resulting from welding dissimilar parts, they have some limitations that need to be identified and checked to optimize their use. One of the limitations is the behavior of parts under thermal stresses caused by the welding process. Thus, it is important to consider the welding conditions of the dissimilar parts in the contact area of the electrode and the welding seam, as this can significantly affect the mechanical performance of the welds. The research conducted in this study involved using the electric welding method with non-consumable tungsten electrodes under shielding gas (TIG) to connect aluminum and carbon steel parts. Ansys software was utilized to investigate the effect of thermal stress in the welding process for different joints. To ensure accuracy, parts were welded together practically under similar conditions, and the results obtained were compared with the results of the modeled method. First, the behavior of a steel sheet under the butt and Tee Joint and then the role of various factors on welding performance were investigated by modeling the process for a pipe in different conditions. Finally, due to the significant role of T-shaped joints in various industries, heat distribution, behavior, and stress analysis were investigated.

The FSP is a method for solid state processing of metal alloys. FP4M milling machine and non-consumable rotary-tools were used to create the necessary heat and further mix copper with titanium-dioxide powder. The base plate is made of copper with a purity of 99.9%. The heat created during the process on the copper piece and the titanium-dioxide nanoparticles in the groove leads to metallurgical changes in the microstructure of the base metal and leads to changes in the size and shape of the grains. The samples were subjected to metallography and microstructure investigations by OP, XRD, corrosion and wear tests. The results show that in the HAZ area, the grains were in the form of a fine grain structure of copper solid solution, containing twin regions with an average grain size of 14, but in the process area, the grains were formed as a distorted and disturbed structure of copper solid solution. The average friction coefficient in the base copper wear diagram is less than one. By matching with the corrosion graph, the base copper sample has better corrosion resistance.

Friction stir processing is widely used for improvement of properties and microstructure of Aluminum, Copper and Magnesium alloys but investigation on steels are limited. Due to the fact that steel alloys, in addition to aluminum, copper and magnesium alloys, have good engineering properties and vast applications in the industry, they need to be processed by friction-stirring process. In this regard, the present research examines the effect of frictional stirring process on grain size, hardness and wear resistance of Ck45 steel due to the number of passes and tool design. In this research, it was shown that the friction-stirring method can be an effective method to increase the hardness and wear resistance of this steel in such a way that increasing the number of passes causes more heat generation per unit length and also affects the grain size, hardness and probably atomic penetration. In general, with the increase in the number of passes, the size of the grains in the stirring area becomes larger, while the final hardness and wear resistance are determined under the joint effects of grain size and hardness. The results indicate that the hardness has increased by 42% and the amount of wear has decreased by 85% compared to the original sample by the frictional stirring process.Keywords

To predict static aeroelastic behavior accurately, two-way fluid and structure interaction (FSI) coupling methods are used to calculate the static deformations and aerodynamic characteristics of the deformed rocket. According to the studies, little research has been done on the weight reduction of space structures. Therefore, due to the stratigicness of the Fin of space structures, the mechanical behavior of the sheets for the construction of the Fin has been experimentally studied using a constrained groove pressing (CGP) method and a comparison has been done between the amounts of deviation caused for a rocket flying in different Mach numbers and different angles of attack, by simulating a two-way FSI Method for WAF and Flat Fins models with two types of material, the CGP 7075-T6 aluminum, and the 4130 steel. Results of constrained groove pressing show that with the increase in the steps of this process, 7075-T6 aluminum with 38% increase of yield strength in fourth transit, 34% increase in tensile strength, 40 percent decrease in elongation, and 62% increase in toughness relative to the prototype, will be produced. The total deviation in WAF Fin is much less than the flat Fin. Also, deviations of Fin made of CGP 7075-T6 aluminum is less than the Fin made of 4130 steel.

Over the last several decades, implants have been used to treat fractures and promote healing. The most important reason for deformation and shortening of the bone during healing due to loading on the nails is a lack of strength of the intramedullary nail. Materials with very fine grain dimensions are considered for such purposes. Ultrafine-grained (UFG) materials have structural elements with very fine grain sizes. Several methods for producing UFG materials have been developed, one of which is the top-down approach, which refines coarse-grained metals via severe plastic deformation (SPD). The SPD technique has several advantages that set it apart from other methods of synthesizing. Two of the SPD methods used in this study were the repetitive corrugation and straightening (RCS) process and the equal channel angular pressing (ECAP) process on a 316L stainless steel rod. Mechanical tests were performed on the rods produced using these methods. Under loading, simulation results revealed that the bone implanted by the RCS rod has greater structural stiffness than the bone implanted by an ECAPed 316L stainless steel rod.

The method of intramedullary nailing, which leads to the alignment of the diaphyseal broken bone, is one of the diaphyseal fractured bone healing novelties. The rods utilized must be strong enough to withstand the forces exerted by the transplanted bone. Today, various researchers are interested in using severe plastic deformation (SPD) methods to improve the mechanical characteristics of metals. One of the SPD procedures used in this study was repetitive corrugation and straightening (RCS) on a 316L stainless steel rod. After conducting mechanical characteristics tests on the rods produced using this approach, ABAQUS software was utilized to simulate the intramedullary nailing finite element method (FEM). The results of the experiments revealed that raising the number of pressing stages to eight significantly increases the hardness of the samples. The simulation findings revealed that the bone sample implanted by the rod manufactured by the aforementioned procedure has a higher structural hardness than the bone implanted by a basic 316L stainless steel rod under various stress conditions.

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.

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%.

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.

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.

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.

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.

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.

Titanium and its alloys (Ti-6Al-4V) are considered to be among the most promising engineering materials due to a unique combination of high strength to weight ratio, melting temperature, corrosion resistance, and biocompatibility. Anodizing is one of the coating methods that increases corrosion resistance and wear resistance and provides better adhesion of paint primers mostly applied to protect Al, Ti, Mg, and their alloys. The novel Plasma Electrolytic Oxidation (PEO) technique is gaining increased attention for depositing thick, dense, corrosion resistant, and hard ceramic coating on valuable metals (Al, Ti, and Mg). The aim of this research is a comparison between the corrosion behavior of anodized and plasma electrolytic oxidized Ti-6Al-4V at different voltages. The surface morphology, thickness, and phase composition of coatings were investigated using a scanning electron microscope and X-ray diffraction. The potentiodynamic polarization test was used to determine the corrosion behavior of the specimens. Results indicated that increasing of corrosion resistance by tests anodized sample at 50 V at 15 minutes and PEO sample at 375 V at 10 minutes.

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.