جستجوی مقالات مرتبط با کلیدواژه « شبیه سازی المان محدود » در نشریات گروه « مکانیک »

This paper investigates the effect of die clearance on the quality of the cutting edge in the fine blanking process of a part with a complex geometry made of CK15 steel. The fine blanking process was simulated using the finite element method through DEFORM 3D software and the results were compared with the experimental results. Cutting force, distribution of stress and strain, dimensions of the radial area, surface quality, and dimensional accuracy of the workpiece were considered as fine blanking criteria. By examining the results, it was found that with increasing the die clearance, the range of equivalent strain and stress on the raw material increases and plastic deformation occurs in the material at the clearance zone. Therefore, by reducing the clearance, these areas become more concentrated, as a result, the strain of the cutting line is reduced and the cutting edge has higher precision and quality. Also, by increasing the punch force, the phenomenon of non-flatness and surface defects of the final part reduces. The results have shown that by increasing die clearance from 0.4 to 0.6 sheet thickness, the stress of the sheet increased to 25%, and the average strain increased about 82%.

To fix the femoral neck fracture using screws, there are different opinions among orthopedic surgeons about screw placement. Also, the parameters of bone drilling, including the angle of the drill tip and the rotational speed of the drill, can also have an effect on the fixation strength. In this research, experimentally and with the help of simulation, the effect of three types of arrangement including triangle, inverted triangle and linear, and parameters of rotational speed and angle of the drill tip on the strength of femoral neck fracture fixation has been investigated for the first time. In experimental tests, the maximum force tolerated by for the inverted triangle arrangement is 25% and 37% higher than the triangle and linear arrangements, respectively. The rotational speed of the drill 2000 rpm compared to 1000 rpm and the tip angle of the drill 60° compared to 118° have increased the connection strength by 11 and 7.5 percent, respectively. The analysis of variance showed that the effect of the type of screw arrangement, respectively. the rotational speed of the drill and the angle of the drill tip on the fixation strength is 83.26, 6.98 and 3.24%, respectively. The results obtained from the numerical simulation showed that the proper arrangement is the inverted triangle with the drilling parameters of the rotational speed of the 2000 rpm and the tip angle of the 60°, which has endured N4782 force.

One of the most widely used metal forming processes is Ironing, which is usually used as a secondary process after the deep drawing process. The Ironing process is used to reduce the wall thickness, equalize the thickness distribution of the wall, and also increase the length of the workpiece. Among the developed methods, the constrained Ironing method has provided the highest thickness reduction ratio. This method is based on converting the tensile stress to compressive stress in the deformation area. The thickness reduction percentage of 65% has been considered for this research which is simulated by the FEM method and after that experimental sample has been made by this method. Finally, due to the conversion of stress in the deformation area, this method provides the possibility of achieving a higher thickness reduction, and the mechanical properties of the sample were improved. This process, due to the application of compressive stress and high strain to the shell, has led to the reduction of the grain size and also its stretching, which has affected the mechanical properties in such a way that the microhardness of the sample has reached from 48 Vickers to 130 HV. Also, this process leads to a 120% increase in tensile strength.

In this paper, the effect of including SiC nanoparticles in the weld zone on the maximum shear strength of friction stir lap welded 7075 aluminum alloy is investigated, both experimentally and numerically. This objective is carried out by studying the effects of rotational and transverse speeds, tilt angle, the shape of the tool and the penetration depth. The numerical investigation is based on developing an FE model by means of Deform and ABAQUS to simulate the welding procedure, which results are verified by the experimental findings. Experimental procedure is designed based on Taguchi method. The verification of the developed FE model shows that the simulation results are in proper agreement with the experimental findings. In general, including SiC nanoparticles in the weld zone can increase the maximum shear strength up to 24%, compared to the case of where the specimens are welded without SiC. Furthermore, applying the threaded tapered tool leads to higher shear strength in comparison with the squared shape tool, i.e., the strength of the specimens welded by threaded tapered tool are 4 to 5% higher without SiC inclusion and 4 to 7.5% higher with SiC, compared to the same case welded by squared tool. In addition, while the rotational speed has the highest influence on the findings, the tilt angle does not affect the results that much.

In recent years, ring rolling process is used to produce seamless rims in many industries, including the aviation and railway industries. The reason for this is the advantages of this process, such as saving money and materials, high quality and high efficiency. In this research, the shaping of the front and rear spools of an airplane engine compressor has been investigated using the ring rolling process. Due to the complexity of the internal and external surface shapes of these spools, it is difficult to simulate the ring rolling process for them. For the performed simulation, the stress applied to the main roller has been checked with the assumption of the shape of the rollers. Also, the forces acting on the main roller in the case where the rollers are assumed to be malleable have been extracted and compared with the previous results where all the rollers are rigid. In both spools, there are complex forms designed on the surface of the roller. If the concentration of stress created at the sharp points during elementing is ignored, the stresses created on other parts of the mold are around 400 MPa. Therefore, H13 steel can be used for the front and back spools to make all molds. But it is suggested that the surface of the shell should be as hard as possible and after making molds and using them for the mass production of shells, these surfaces should be constantly reviewed.

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.

Today, cars play an important role in people's daily lives. Therefore, ensuring the safe operation of car parts and their connections that are affected by high oscillating stresses is very important. since considering the fatigue strength is the requirement to make sure the quality and safety of the cars. Due to this reason, in this paper, the interference fit of the bushing in Triangle suspension was evaluated using a stair case fatigue test and finite element simulation. The finite element simulation of the ​​different interference fit was performed and evaluated according to Gerber and Goodman criteria. Experimental results showed that the durability life for parts with an interference fit ​​of 0.22, 0.15, and 0.30 mm is equal to 1.41, 1.17, and 1.17 times the applied force in the vehicle. Also, the average Gerber safety coefficient calculated from the finite element simulation results is 1.16, 1.12, and 1.07, respectively. According to Goodman and Gerber, the highest reliability interference of 0.22 mm was estimated, which was also consistent with the results of the experimental test. Therefore, it can be said that with small changes in the amount of interference fit of parts in the joints, the fatigue life of the parts can be effectively improved, which is completely consistent with the results of the references

Thermal and vibration stress relieving processes are among the common methods of reducing residual stresses that can be performed on the part after the manufacturing. The advantages of vibratory stress relief over thermal stress relief are no need for fixtures, time and cost savings, no weight and dimensional limitations and usability for all alloys. In this research, the numerical and experimental study of vibration stress relief process of a T-shaped weld has been done. In the first step, a T-joint was made using shielded metal arc welding . The longitudinal and transverse residual stresses equal to 251 MPa and 191 MPa were measured, respectively. The differences between the calculated and the measured residual stresses in the longitudinal and transverse direction are about 17% and 1.5%, respectively. Then, by finite element simulating the vibration stress relieving process, the optimal values of the parameters affecting the process, such as the frequency of force exertion, the amount of force and the location of force exertion, were obtained. The most effective vibration stress relief condition related to the case with the applied force equal to 20% of the yield force of the sample and the excitation frequency equal to 95% of the natural frequency of the sample. The differences between the calculated and the measured residual stresses after vibration stress relief process is about 10%. By increasing the applied load frequency to 95% of natural frequency of the sample, longitudinal and transverse residual stresses decreased by more than 55% and about 70%, respectively.

In this paper, the severe plastic deformation by twist extrusion (TE) process is investigated. In this process, the workpiece is forced through a twist channel, which develops shear strains in the material. These shear strains result in a fine-grained structure in the material. For investigating the material deformation, the TE process was simulated in the Abaqus finite element (FE) software. The effects of backpressure and friction between the sample and channel were investigated. In the FE model, a sample of AA6063 aluminum alloy was formed in a twist channel with an angle of 45 degrees and a length of 16 mm. The FE simulation results were validated by conducting experimental tests. When the backpressure of 50 MPa was used, the sample was distorted, which improved by increasing the backpressure to 70 MPa. The highest strains occurred in the corners of the sample, which was about twice of the plastic strains obtained at the side edges of the sample. Furthermore, the calculated plastic strains in the central areas of the sample were very low (0.042) in comparison to the strains developed in the corners and side edges of the sample.

Today, the use of metallic bipolar plates in the fuel cell industry has attracted the attention of many researchers due to its much lower cost than thick graphite plates produced by machining. The best method for the production of metallic bipolar plates is forming process. Among the different forming methods, the stamping process has a higher production rate, simpler process, and lower production cost. One of the major problems in the formation of the metallic bipolar plates is the springback of the sheet after forming, which causes distortion and non-uniformity in the formed channels. In this study, the effects of geometrical parameters such as draft angle, corner radius, depth of channel and process parameter such as lubricant on filling profile as well as springback of formed sheet made of stainless steel 304 with a thickness of 0.1 mm were investigated. For this purpose, the simulation was performed using ABAQUS finite element software and the results were verified by experimental analysis. Then the outputs were evaluated by changing the input parameters in the simulation. The results showed that the draft angle and channel width had the most influence on the springback value of the formed plates. The results related to the process parameter such as the lubricant effect showed that the springback value is almost independent of the lubricant parameter. However, in quite equal conditions, the stress distribution in the corners and channel walls is much more uniform when using the lubricant.

Incremental forming method with lower cost and more flexibility can be a suitable alternative for traditional methods of the hole-flanging. In this study, the possibility of square hole-flanging of AL1050 aluminum sheet using incremental forming method has been investigated and the quality of the pyramid flange has been compared with conical flange. The final shape of the flange is defined so that wall angle increases with raising height. The process simulation was performed using Abaqus software and an experimental test was done to validate the simulation results. After performing the experimental tests, flange features such as the final size of the hole, flange height, and wall thickness were measured. The results showed that at the created flange around the circular hole, there is less spring back and more dimensional accuracy, however, it can be flanged a square hole by incremental approach with consideration of the height and hole size. The dimensional measurements showed that the final size of the hole will increase after the hole-flanging. By investigation of the various holes, it was found that in the larger initial hole, increasing the hole size after the flanging will be lower.

In this paper, the dynamic response of electro actuated viscoelastic microbeam is investigated and micropolar theory of elasticity has been used to consider the effects of size in microstructure. Euler-Bernoulli beam theory and Hamilton’s principle with considering viscoelastic integral constitutive equations, the midplane stretching effect, the axial residual stress and electrostatic force has been used to obtain the equation of motion and the boundary condition of fixed-fixed viscoelastic microbeam. Therefore, the nonlinear integro-differential equation in Volterra integral equation form is obtained. Galerkin method will be used, in order to solve the nonlinear partial integro-differential governing equation and then it converted to the ordinary integro-differential equation. By using the fourth order Runge - Kutta method, we can obtain the response (transverse displacement) of the electro actuated viscoelastic microbeam. In the following, the effect of initial gap value and material length scale parameter on the viscoelastic microbeam behavior are investigated. In the end, the viscoelastic microbeam is simulated in the FE software and the problem is analyzed in quasi-static form. In order to validate, the simulation result is compared with the result obtained from the quasi-static solution of the viscoelastic microbeam.

Explosion is fast chemical reaction that alters primary explosive material to gas. Explosion process include two general part of starting explosion and interaction between environment and explosion products. Study of plate performance and investigation elastic – plastic behavior and plate rupture is essential to determine relation of those with plate geometric parameter. Shock tube is used for modeling and simulation of loading explosion. In this paper, Experimental and FEM modeling are used to Investigation of Explosive Wave blasting on the Aluminum Plate. Simulation is done by ANSIS Autodyn software. Shock tube was designed and fabricated in order to experimental study.

In this paper, a novel high speed forming process called warm electrohydraulic forming (WEHF) process is introduced. In this new forming process, the blank is heated before the forming process and then formed using the Electrohydraulic forming process. In order to investigate the formability improvement in this hybrid process, first the electrohydraulic forming of aluminum alloy AA5182-O at room temperature is simulated using the commercial software LS-DYNA and the results of simulation are verified with the experimental results available in the literature. After verification, the warm electrohydraulic forming process in different temperatures is simulated and the Forming Limit Diagrams (FLD) are obtained and compared to each other. The results indicate that considerable improvement in formability of the aluminum alloys in warm electrohydraulic forming process in different forming paths. Due to the ability of the WEHF in formability improvement, a novel WEHF is introduced and its formability improvement is investigated. In the experimental tests 23.6% increasing in failure strain of aluminum alloy is observed at WEHF in comparison with EHF. Therefore the formability improvement in WEHF process can be concluded.

Productions of metallic ultra-fine and Nano microstructure have been addressed by researchers and engineers in recent years. The purpose of the production of these materials with specific procedures is to achieve lightweight parts with high strength and capabilities. Various methods for manufacturing solid round or square sections using equal channel angular pressing have been offered by researchers. However, few researches have been reported the production of pipes with high strength-to-weight property. A direct extrusion method is proposed for the production of high-strength tubes. Aluminum alloy 3003 that is widely used in industries because of the structural characteristics of a cold working is used in this study. Previous studies have been focused on channel angle of 90o, but in this study, angles above 90o are investigated. Strain and stress distribution results in finite element simulation have been used to obtain the optimal internal and external channel angles. The optimal channel angles are first investigated by simulation results. The required die with optimal channel angles was then manufactured and the samples were experimentally tested. The results showed that the use of these angles with optimal channel angels in equal channel angular presses for aluminum 3003 tube increases significantly the tensile strength and hardness.

The aim of this paper is simulation of shaped charge process using Eulerian analysis. To this end, the finite element analysis was used to simulate the process of shaped charge. In this simulation, whole of the model has been considered from Eulerian elements. Verification of finite element method has been confirmed by comparing simulation with experimental tests and Birkhoff model. Comparison of penetration depth in finite element analysis with experimental samples has shown that the results are in good agreement with each other. Also comparing parameters such as liner collapse velocity, velocity distribution in jet length and jets profile has indicated that the simulation results are close to Birkhoff model. It should be noted that ABAQUS finite element software is used in this simulation to analyze the process of shaped charge.

The aim of this study, is study on the effects of flash gutter geometry on the material flow, predict of defect formation and forging process parameters in cold forging. For this purpose, effects of three flash geometry with trapezoidal, oval and square shapes were investigated on the simple frustum part. The effect of flash gutter geometry simulated using ABAQUS finite element software and then form with the optimized flash gutter was manufactured and forging process to verify the simulation results on a piece of AA3003aluminum alloy, was carried out. The results showed that trapezoidal flash gutter had more appropriate conditions for material flow than other cases. According to the simulation results, the maximum plastic strain was formed around the flash area and its value was maximum in the die with trapezoidal flash gutter, which was due to the greater flow of the material in the trapezoidal flash gutter geometry. According to the simulation results prediction, the distribution and exerted applied pressure to produce the final part on die with square flash gutter was more than others. The maximum applied pressure was on the flash area of die, which was the largest for the square flash gutter, and had the smallest amount of trapezoidal flash gutter geometry.

In this day and age, the ultra-fine materials due to their unique properties have found a special place in various industries. By reducing the grain size, the share of atoms at the grain boundaries has been increased and the increase of grain boundaries prevents the movement of dislocations and increases the strength. One method of producing ultra-fine materials is imposing severe plastic deformation. In order to apply Plastic deformation, disparate methods can be used that parallel angled channels are used in this study. ABAQUS finite element software is used to analyze the process numerically and to optimize the results, neural network and genetic algorithm methods have been used. In this study, the effects of die parameters including channel angle, tube length, increase of diameter difference and the friction coefficient are checked out. The results depicted that the coefficient of friction and pipe length which are tested, played a pivotal role in the homogenization of strain distribution separately; that by increasing the supposed friction coefficient and reducing the length of the tube, the strain distribution will be homogeneous. The difference between the increase in the diameter of pipe and the angle of die’s channel will have little impact on the improved uniformity of strain distribution. On the other hand, increasing the coefficient of friction, pipe length and diameter of pipe ends with an increase in the force of process while increasing the angle of die’s channel culminated in reducing the formation force. Additionally, considering the results obtained from optimization of parameters,

In this paper, finite element modeling of friction welding of two ASTM A106-B and AISI 4140 dissimilar pipes is investigated. The effect of the friction welding parameters including rotation speed, friction pressure, friction time, forging pressure and forging time on the axial shortening are investigated using a fractional factorial design method. Because of the extreme material deformation, an innovative remeshing technique was scripted in Abaqus CAE to prevent the creation of distorted elements. 27 models were solved and 3 validation experimental tests were carried out. Results showed that increasing the all parameters cause larger axial shortening. Friction pressure with 33.9% had the most effect on the axial shortening. Moreover, an increase in forging pressure and forging time has a limited effect on the axial shortening. After about 2 seconds from the beginning of the welding, the temperature of the interface becomes steady at about 1250°C. The validation tests revealed that the simulation error was about 5.6% which shows a good agreement between the finite element results and the experimental data.

In this study, interference fit process and its influence on fatigue life of holed specimens made of AISI4340 hardened steel were investigated experimentally. For this purpose, Tungsten carbide pins were fitted into the steel samples and putted under fatigue test with zero load ratio and 10 Hz frequency. These experiments were done for specimens with 5 interfence levels and two repetition. Results revealed that the compressive force required for interference fitting the pin in hole increases as the interference size goes up. The peak force was observed when the pin reached bottom of specimen and the maximum plastic deformation occurred. 3D finite element modeling of interference fit showed that distribution of residual stress on the hole wall and far away from it were compressive and tensile respectively. Moreover, results of fatigue experiments showed increasing the specimens fatigue life up to 1.5% interference fit. In this level, fatigue life is 2.5 times greater than specimen without fitting. However, by increasing interference up to 2%, increasing trend of fatigue life is stopped. Analysis the fracture surface of samples showed that the fatigue cracks are initiated from edge of the hole at specimens with press fit. While crack initiation site was in the middle plane of hole for specimens without fitting.