جستجوی مقالات مرتبط با کلیدواژه « شبیه سازی » در نشریات گروه « مواد و متالورژی »

Precise prediction of the texture component and simulation of the microstructure evolution facilitate the control and design of the final mechanical and physical properties. Through coupling the finite element simulation and crystal plasticity modelling, the current study introduced a robust technique for predicting the texture component after warm rolling. The simulation was then performed at two temperatures of 300 and 500oC for warm rolling. To calculate the appropriate hardening parameters for the crystal plasticity simulation, the experimental flow curves were obtained from torsion tests at the same temperatures of warm rolling. The presented framework predicted the texture components and associated intensities accurately. This was confirmed followed by comparing the results with the experimental ones. The proposed approach also predicted the flow curves correctly and precisely, as further proved by comparing the simulated flow curve based on the experimental flow curves.  Revealing the effect of deformation gradient on the texture evolution, the simulation also showed that the shear components imposed by friction rotated the texture components along the ND direction of the specimen.

In addition to the inherent characteristics of explosives, the power of the detonation is affected by arrangement of the explosive train. Therefore, the correct design of the explosive train, especially for insensitive explosive charges containing aluminum, play a fundamental role in order to be more effective. In the current research work, by changing the dimensions of the booster pellet and its position relative to the main charge; the detonation behavior of the main charge has been investigated. In this study, the booster pellet (COMP-A3) is modeled with JWL equation of state and the main charge (PBXN-111) is modeled with ignition and growth equation of state. The simulations has been done using AUTODYN software. The coefficient used in the equation of state (ignition and growth) has been evaluated with experimental results. The simulation results show that by reducing the diameter of the booster pellet from 5cm to 3cm, for a certain length of the booster pellet, reaching to the steady detonation increases due to the greater divergence of pressure wave into the charge. In the case where the booster is inside the charge, the peak pressure values increase in the corners of the charge and adjust the pressure drop due to the divergence. The simulation shows that for the case where the booster and the main charge are placed on top of each other, the booster with a diameter of two centimeters with any length of the booster pellet is not able to create stable detonation in the main charge. For a submerged condition of the same diameter, the booster can produce stable detonation in the main charge. This study showed that a booster pellet with a diameter of 5 cm and a length of 4 cm can cause a complete detonation in PBXN-111. The length of the region to reach stable detonation with this booster is 15 cm.

In this study, simulation of the effect of the second pulse current on temperature distribution and nugget size of TRIP1100 steel during resistant spot welding was performed by finite element method. Then, the effect of the second pulse current on the weld nugget size, weld nugget microstructure and mechanical properties of the resistant spot welds of the above-mentioned steel was experimentally investigated. Temperature distribution, weld nugget dimensions and heating and cooling cycles during resistant spot welding were predicted by simulation. Based on the simulated thermal cycles and continuous cooling transformation diagram of the TRIP1100 steel, a fully martensitic microstructure was predicted for the weld nugget in all currents. A good agreement was obtained between the simulated and experimental results. It was observed that the nugget diameter logarithmically increases with increasing the second pulse current. Furthermore, the microstructure of weld nugget in all samples was fully martensitic. Assessment of the mechanical properties of the welded samples by shear tension test demonstrated that the maximum load increases with increasing the weld nugget diameter. Nevertheless, the fracture energy decreased with increasing the nugget diameter.

Direct Chill casting is a suitable method for the production of high diameter aluminum sheets. In this method, molten aluminum is poured into a mold and the mold is cooled by hydrogen. Despite the improvements made in the casting process, unwanted defects still appear during the production of the product. To deal with these problems, improved methods of direct refrigeration (DC) process are used, including direct refrigeration casting using hot top and casting in the presence of low frequency magnetic field (LFEC). Due to the advantages of direct refrigeration casting in the presence of a magnetic field, simulation of this process is important in order to better investigate the effect of the magnetic field on the molten pool, so that before any experimental work a numerical approximation of the magnetic field effect is obtained. Be. In this report, the direct refrigeration casting process is simulated in the presence of a magnetic field using ANSYS Fluent 19.2 software. The simulation output includes temperature distribution profiles, liquid volume fraction, velocity and steady-state flow lines for DC and LFEC casting for 70- and 14-inch diameter aluminum alloy billets and associated molds.

The investment casting process is a reliable way to produce complex and delicate shapes , with good surface quality and high dimensional accuracy. The main advantage of investment casting is the ability to produce a wide variety of products from different industries, and non-machinable components can be cast in the same predetermined way, so that the final component generally does not need to be welded and assembled, thus saving time and money. This method was used in ancient times to produce weapons, jewelry and artistic sculptures. Over the centuries, this technology has advanced and is used in the casting of various works of art, industrial parts and the production of turbine blades. The present article is an overview of the application of investment casting process in the production of artistic pieces. In this article, investment casting history, model wax properties, adhesives, additives and fillers, ceramic shell fabrication process for non-ferrous alloys, comparison of microwave and autoclave dewaxing methods, smelting and final operations, 3D printing method for Model construction and finally the simulations used to predict defects and model optimization will be reviewed separately.

It is very important to study the collision of high-energy material HMX in the form of simulations in order to increase safety and prevent a possible explosion, as well as to increase the quality of the product, in situations that practical testing may be very dangerous.
In this study, due to its high consumption in the military industry and the important role of the size of the material in military equipment, the high-energy HMX material has been used to simulate and evaluate the results. In this article, the energy production rate during the breakage of energetic solid particles in the size of 40 to 150 microns has been investigated. The purpose of this study in the first step is to find the optimal operating conditions in the breakage machine and then to investigate the various parameters caused by the collision of particles of energetic materials during breakage in the introduced jet mill machine. Therefore, in this study, first the designed jet mill in different operating conditions (different inlet pressures) was simulated and investigated using the DPM model. Gas flow behavior, particles moving path and HMX particle temperature were simulated by Ansys-Fluent software. The results showed that The operating pressure of 4 (bar) provides the possibility of maximum breakage in the jet mill machine without the risk of explosion.

Flow line model as an efficient model in ECAP process analysis is based on functions that evaluate the material plastic flow inside the die. Among the various flow functions, the general flow function has the highest ability in analyzing of ECAP process. All parameters of this function have so far been considered as fixed parameters in calculating velocity and velocity gradient fields. Previous studies have shown a relatively linear relationship between the power in the function and the initial position of the flow lines. Accordingly, in the present work, the mentioned fields have been calculated based on the variable power and in order to investigate its effect, the experimental results of the ECAP process with an angle of 90 degree of aluminum alloy AA2124 have been used. The experimental flow lines were analyzed to find the linear relationship between the function’s power and the initial position of the flow lines. Simulations of the texture evolution were carried out subsequently using the general flow function in both constant and variable power conditions. Comparison of the simulated textures with the experimental results showed a much better performance of the variable power mode; in such a way that compared to the constant power condition, the deviation in the position of the simulated texture components in the variable power mode is significantly lower. However, the change in the power mode of the function did not show a significant effect on the intensity of the simulated texture.

The optimal design of sprue well in of aluminum sand casting process is considered ‎in the present study. The lack of is appropriate design for this component of gating ‎system could cause filling defects such as sand erosion, oxide films and gaseous ‎bubbles trap within the melt. In this study, formerly suggested designs in the ‎literature are firstly examined and then a new optimal design, based on logical try-‎and-error using computer simulation, is introduced to avoid their limitations. The ‎performance of new design is compared to former ones by means of computer ‎simulation. Finally, to validate simulation results, experimental studies are conducted ‎using water and molten metal fluid flow in side transparent sand mold. A high speed ‎camera is employed to capture the fluid flow pattern in the transparent mold. The ‎reasonable agreement between experimental results and computational ones support ‎the validity of numerical simulation and feasibility of presented new design.‎‎

In this study, a finite element numerical method was developed to simulate the stress distribution in the conventional and functionaly graded NiCrAlY / YSZ (GZ) plasma sprayed thermal barrier coating on the Inconel 738 substrate. Residual stress was measured using the nanoindentation method and the results used for verification of the numerical results. The results showed that with increasing the amplitude of the interface, the maximum stress decreases and then increases with further amplitude increment. The maximum residual stress increases with increasing thickness. Comparison of stress distribution in YSZ and GZ coatings showed that the use of GZ coating increases residual stress.

In recent years, numerous investigations have been conducted on self-healing process using vascular network in composites. Since the vascular network in the composites leads to a decrease in virgin tensile properties, it is important to determine the optimal design of the vascular network in order to achieve minimum tensile properties loss. In this research, experimental and numerical studies on the effect of hollow glass fiber (HGF) presence and orientation on tensile behavior in epoxy/glass fiber composite are carried out. The orientations of HGFs were selected at three levels of 0, 45 and 90°, and the distance of HGFs was kept at 200 μm. The experimental results indicated that the presence of blank HGFs in composite lowered the tensile strength. The lowest decrease in tensile strength was observed in the composite containing HGF at angle of 45°. The presence and failure of HGFs in composite specimens were studied using scanning electron microscopy. Next, three-dimensional simulations of composite containing vascular HGF were performed using ABAQUS software and representative volume element (RVE). To simulate the interface of HGFs and epoxy matrix, a combination of cohesive zone and Columb’s friction models was used. A good agreement between FEM and experimental results for tensile strength of different specimens was observed. Next, the healing performance for composite containing self-healing HGFs at angle of 45° was investigated.

The structural and hardness developed in advanced high-strength steel DP590 have been investigated with the help of optical microscopy and scanning electron microscopy on resistance spot welded specimens. The hardness diagram of the weld sections was prepared by microhardness test and the temperature peak and heat distribution were simulated by menas of the Abaqus software. The results show that according to the temperature generated in each region of the weld nugget, the HAZ and base metals have different microstructures, and these difference affects the hardness of the regions. The presence of tempered martensite islands with a fraction of 44% in ferrite matrix in base metal, mainly martensitic structure in the nugget, and martensitic structure along with scattered areas of ferrite in the HAZ was observed. The results of the microhardness tests showed difference in hardness values of the regions, and also it was observed that the hardness values increased in the HAZ and weld zone. The hardness values measured in the nugget, base metal, and HAZ were around 400, 200, and 450 HV which were in accordance with the observed structures

The mode and rate of agitation of the particles is one of the effective variables for dissolving solid particles in the aqueous solution. In the present study, a computer software has been used for simulation of the particle agitation in the pilot mixer reactor. The stirrer speed, pulp density, particle size and solid particles density were selected variables. The effect of above factors on velocity of particles and their accumulation was investigated. The stirrer speed has significant effect on the particle velocity, but by increasing the pulp density, average speed of the particles is more limited. Increasing the size and density of particles can reduce the speed of moving parts. Particle accumulation has increased with increasing pulp density and particle size. The stirrer speed significantly decreases the amount of inactive areas in the reactor. The density of particles does not effect on particle accumulation.

Detonation initiation by shock is an important issue in the explosive safety assessment , design of the explosive train and explosive devices. Experimental studies in this area are very difficult, expensive, and require advanced equipment. Therefore, simulation is a useful and suitable way for studying this phenomenon. The purpose of this article is to develop a one-dimensional computer code for simulation of the direct initiation of energetic materials. The Fortran SIN hydrocode, was used for this purpose and the I&G burn model was added to this code. The developed code was used to simulate the direct initiation of the Comp-B by sustained shock pulses. A good agreement was observed between the present simulation results and the results of other references. For example, in the simulation of the initiation of Comp-B by 3.78 GPa shock, the run distance to detonation was 14.8mm, which the difference between this value and the reported experimental data is 5.7%.

In this study, the effect of tool's advance velocity on the mechanical behavior of the Al-7075 alloy during friction stir welding was simulated. In this simulation, the Lagrangian method with rigid-Visco-plastic material was used. The results of the process temperature obtained by the simulation method were verified by the experimental welding test. Using the characteristic stress, strain and temperature relationships in the Al-7075 alloy, the changes and the relationship between the material strength during the welding process by simulation was studied. The generated simulation defects was verified by experimental test.

Aluminum based composites are manufactured in a variety of methods, such as mixing in liquid state, mechanical alloying and so on. Explosive welding is one of the modern ways of producing Aluminum based composite. Explosive welding is used for excellent bonding of similar and dissimilar materials with a wide variety of thicknesses, area dimensions and different thermal and mechanical properties. In this study, Aluminum plates were reinforced by steel wires by explosive welding. The steel wires are placed between two Aluminum plates and joint between plates and reinforcement were made by explosive welding process. The quality and morphology of the interface depend on standoff, the geometry of the welded plates, the properties of the metals, etc. In this paper, the appropriate parameters were determined using the numerical simulation and drawing of weldability window and layout of explosive welding was designed. The produced parts were examined by optical microscope. The simulation results showed that in the constant stand off by increasing the explosive ratio in constant standoff, velocities collision and dynamic collision angle increased. The metallography results showed that the composite obtained excellent bonding quality of interface without void and fracture.

The destructive corrosion phenomenon has been identified as one of the major problems in the Iranian gas refineries, which is often found in the amine regenerator tower and the steam condensate regions of carbon dioxide. One of the most important causes of this problem is the lowering of the amine temperature below the safe operating temperature range. According to the simulation of the process performed using ProMax software, in the event of a drop in the temperature of the amine entering to the regenerator tower, mainly at the bottom of the tower, as well as the reboiler, which according to the body (carbon steel 516), the corrosion is likely to occur. Examining the corrosion coupon installed in this gas sweetening indicates an increase in the corrosion rate, which can increase up to 1.27 mm/year if the process conditions in the amine cycle are not controlled. Stereo microscope images and identification corrosion product by x-ray diffraction used in this study confirm the above item. Finally, different strategies for controlling the temperature of the amine to the tower in the operational safe area are presented in accordance with the strategies of each refinery, as well as considering the cost of the life cycle. The above solution may include designing and adding a new heat exchanger or periodic cleaning to identify the sediment formed in the amine-amine plate converter.

Electron Beam Welding (EBW) is a high-efficiency, high-precision welding method that its application is increasing rapidly in various industries, including car manufacturing, aviation and aerospace. The simulation of the electron beam welding process with the aim of predicting the residual stress in the work piece and analyzing the temperature and stress profiles during the welding process has always been of interest to the researchers for the purpose of welding engineering and prediction of optimal conditions. In this research, the Finite Element Method (FEM) model of electron beam welding was prepared in 3D and loaded on the Abaqus software. This model includes thermal and mechanical interaction, and metallurgical phenomena. The thermal analysis is unilaterally coupled with mechanical analysis. The heat source that is used is a combined heat source that is attached to Abaqus using the subroutine and the Fortran coding. Welding is in a vacuum environment and the thermal dissipation due to thermal conductivity and radiation is applied in different parts as boundary conditions on the model. The workpiece is made of Ti-6Al-4V alloy and has thermal and mechanical properties which are defined dependent on temperature. The temperature variations during welding and the residual stress of the base metal which is obtained from the numerical simulation are comparable to the results recorded in the practical studies and an acceptable adaptation was made that shows the accuracy of the combined heat source model used in this research for modeling of electron beam welding.

The jet formation caused by the collapse of a liner is dependent mainly upon the explosive characteristics loaded in shaped charge warhead. In this study, the purpose was to compare the influence of Octol and PBXN-110 fillers on performance of a specific shaped charge warhead. This material loaded into the aluminum-cased shaped charge having a 35° copper  liner and 510 cm3 in capacity. Results obtained by numerical simulation (LS-Dyna) indicated that the most effective stand-off is 50 cm. Based on simulation data, octol has a higher penetration compared to PBXN-110 for the same stand-off. Results from the experimental tests also showed that the warheads loaded with octol and PBXN-110 have penetration about 444 mm and 324 mm respectively. PBXN-110 exhibit a weak penetration effect due to its lower density and detonation velocity compared to Octol.

The study purpose was to evaluate the effect of initial billet temperature, extrusion speed, extrusion ratio and angle on the tube extrusion process of AISI304, particularly the extrusion force, and achieve optimal parameters. Abaqus software was used for the simulation purpose. 12 samples were evaluated with different initial conditions. Two-dimensional axisymmetric model was used to simulate the process, due to the axial symmetry of the process. Mechanical-thermal coupled solution was used for process solution. Also, CAX4RT elements were used for achieving all the degrees of freedom. The initial temperature was found to have the strongest effect on the force.