finite element simulation

In the present research, the effective parameters of ultrasonic horns in the ultrasonic-assisted simple shear extrusion process and the selection of the best choice are discussed. At first, the main input parameters (horn type, material, and dimensions) were determined to be used in the design of the experiments. Then, the experiments for input parameters were designed using the Taguchi method in Minitab software. The output results of the forming force for each level were obtained using finite element simulation in Abaqus/Explicit software. The optimization of the input values was investigated based on the-lower-the-better condition of the signal-to-noise (S/N) ratio. The optimal levels of the horn input variables were determined to achieve the minimum forming force during the ultrasonic-assisted simple shear extrusion process. After the design of experiments and the finite element simulations, the proposed horn was manufactured according to the optimal input values and then it was connected to the simple shear extrusion die. In the presence of ultrasonic vibrations, an 11% reduction in forming force was reported compared to the process without ultrasonic vibrations. A comparison of experimental and simulation results in the ultrasonic-assisted simple shear extrusion process showed a 9% error, which validated the numerical simulation.

In tube hydroforming, by applying internal pressure using a fluid such as water or oil, bulging is created in the tube and the tube conforms to the inner walls of the die. In this paper, using hydroforming process in manufacturing of a branched joint with two branches on copper tubes has been investigated. This type of joint is used in various fluid transmission lines. Simulation of the forming process has been done in Abaqus finite element software. The effect of four important process parameters on the quality of the formed product has been studied. Considering the complex shape of the desired product, effect of four parameters of initial feeding, final feeding, yielding pressure and bursting pressure have been investigated and the effect of these parameters on the height of the formed branches and the maximum thinning has been determined. The results showed that with the appropriate selection of process parameters, a product with two branches with good quality can be obtained in one forming step. The most effective parameter on the height of the formed branch is the final feeding, so that increasing final feeding leads to more height of formed branches. On the other hand, bursting pressure has the most important parameter affecting the thinning. The initial feeding has the least effect on the thinning and the height of the formed branch.

Polymer electrolyte membrane (PEM) fuel cells, as an energy generator, convert the chemical energy of the fuel directly into electrical energy. An important component of polymer fuel cells are bipolar plates, which are responsible for the distribution of fuel and oxidants and facilitate the management of water inside the cell and transmission of electric current. In this study, the fracture method of graphite-based composite bipolar plates of polymer fuel cells under bending loads was investigated experimentally and numerically. Simple and perforated composite bipolar plates were tested and simulated with the approach of determining flexural stability under static load. In numerical analysis, mechanical simulation using finite element method and Abaqus software were used. Then, after making the laboratory samples, the experimental test of three-point bending was performed on them with the aim of validating the simulation results. Finally, results of numerical and experimental analyzes of the flexural behavior of composite bipolar plates were compared with each other. Comparison of the results of numerical and experimental analyzes showed that the results of these two methods had an acceptable agreement with each other. In addition, the presence of a high percentage of graphite as well as high fragility weakens the body and beams of this material increase the specimen of the sample, which occurs only due to the molecular bond of graphite, which causes the graphite to slip.

In this paper, the error of tool deflection in perpendicular to a milling process feed direction is investigated and novel compensation method to this error is proposed. While the end mill tool is machining, due to the existence of perpendicular disturbing force on the feed path while the endmill tool is machining, a deflection which reduces machining accuracy. If a compensation force is exerted to the middle of tool, the deflection can be reduced. By using a hydraulic actuator, the compensation force would be proportional to the disturbing machining force, in the opposite direction so that this error can be reduced. It is necessary to estimate disturbing forces and tool deflection magnitude in lateral side of machining precisely before applying the proportional force to the endmill. The first step endmill is modeled on SolidWorks and in the next step The machining operation is simulated to calculate the error causing force in which both the milling tool and the workpiece are 3D flexible. By obtaining the force results of the tool under different machining modes from Abaqus, a semi -analytical model is established on Simscape Multibody module of matlab software. By comparing Abaqus results the parameters of the lumped model are adjusted. The output force is extracted from Abaqus and put in tabular form the tool deflection is extracted from MATLAB SimScape which calculation speed is faster than the numerical model in this method. To find the compensating force, the beam theory obtains a factor of 3.2 times the machining force applied to the middle of the tool. This force is applied in open loop to the MATLAB model and the result indicates almost 70 percent reduction in the tool tip lateral deflection.

The main objective in this study is to model the hydroforming process for Mg tube and obtain the forming limit diagram (FLD) using finite element method. In the first step, three -dimensional finite element modeling of hydroforming process of AL-7020-T6 tube was performed to plot FLD. In order to identify the appropriate criterion for the onset of necking, the hydroforming process modeling was performed by considering the four criteria including of the second derivative of minimum principal strain, maximum principal strain, thickness strain and equivalent plastic strain. Comparison between simulation and experimental results indicated that the second derivative of minimum principal strain, max principal strain and equivalent plastic strain were appropriate criteria for simulation. After validation of the hydroforming process modeling with experimental result, the FLD of the Mg tube was extracted. The results show that in the loading with different axial feeding, the necking time and the amount of stress and strain change. Therefore, various limit strains are obtained by changing the loading conditions. Also, according to the FLD, the higher ratio of axial feed to internal pressure causes the limit strain shifts to the left in FLD plane.