peyman mashhadi keshtiban

The present study investigates the production process by closed die forging method of one of the sensitive and safe parts of KIA car brake, which is affected by various mechanical and thermal stresses in its operating conditions; therefore, in the present research, the application of this forming method in the Iranian automotive industry has been discussed. In this study, an attempt was made using finite element analysis in ABAQUS software to determine the maximum force required for forging this part. In addition, the influence of various parameters such as the temperature of the part during the forming process, the coefficient of friction between the part and the die, as well as the strain rate have been investigated. The results indicated that the friction coefficient has a significant effect on the maximum required force, and the maximum values of the load increase with increasing the friction coefficient; but the remarkable result is that the effect of this coefficient is negligible from a value onwards. This point is consistent with the observations in practice. Besides, a strong dependence of the results on the loading speed was observed, and the required force has increased with increasing loading speed for reasons such as the strain hardening phenomenon. Also, the force required for forging has decreased with increasing the temperature, which is due to reduced material strength. This reduction from 900°C to 1000°C is less than 2%, while it is approximately 40% from 1000°C to 1100°C, which is consistent with the experimental reports.

Nowadays, the closed die forging process is extensively applied to produce small to medium parts. The parts produced by this method show high strength, impact resistance, and toughness, which is the main advantage of this method compared to casting. Furthermore, the parts produced by this method are considerably close to the final shape of the designed part in terms of appearance compared to the open-die forging process, and the need for secondary operations such as finishing after the subjected process is significantly reduced. The present work investigates the production process with closed die forging of one of the most important parts of the gearbox of Mercedes-Benz 10-wheel truck, which is affected by various mechanical and thermal stresses in its working conditions. Finite element simulation results in ABAQUS software have been applied to analyze experiments for the purpose of evaluating the extent and type of impact of some important process parameters and also compared with the observed practical results. The results indicated that the initial temperature parameter of the workpiece has the highest effect on reducing the flow stress, and consequently, the required maximum force throughout the process. While the other evaluated parameters, i.e., press speed and mold temperature, have a smaller but undeniable impact.

One of the most popular forming processes is the shape rolling process in which the desired shape change is achieved by pressing two rollers with a special shape in the opposite rotational direction. In order to improve the product’s quality and reduce production costs, accurate analysis of the shape rolling process of the compressor blades as well as the investigation of the effective parameters have been done. First, the shape rolling process of a typical compressor blade was simulated based on the experimental data using the finite element method and Design of Experiment (DOE). Then, the effect of various process parameters, including the thickness and width of the preform, the roller diameter, the thickness and width of the flash channel, and the number of the rolling steps on two objectives, namely the rolling force and the amount of the flash were investigated. The obtained data were analyzed by Analysis of Variance (ANOVA), and the contributory factors of the shape rolling process were identified. The results revealed that all of the considered factors affected the rolling load, but only the initial sheet's width and thickness were the factors with impact on the volume of the flash as the second objective. The required process load decreased by increasing the number of the rolling steps, but the rolling load increased by increasing other factors. Furthermore, increasing the thickness and width of the initial sheet increased the flash volume.

The geometric optimization of orthopedic screws can considerably increase their orthopedic efficiency. Due to the high geometric parameters of orthopedic screws, a finite element simulation is an effective tool for analyzing and forecasting the effect of the parameters on the load-bearing capacity of different types of screws and bones. Thus, in the present study, the tensile strength of a typical cortical titanium screw was investigated by the finite element method, and experimental tests confirmed the obtained results. The behavior of the screw in the tensile test was discussed in terms of stress, force, and displacement. The maximum force results show a 14% difference between simulation and experimental works in tensile type loading. Moreover, it was suggested that the trend of force curves in both the experimental test and numerical simulation shows high similarity, and FEM predicts the process with acceptable accuracy. Furthermore, it was concluded that the stress values are higher while moving toward the top surface of the bone.

Equal channel angular pressing (ECAP) is one of the most appealing severe plastic deformation (SPD) methods. The proposed equal channel multi angular pressing (ECMAP) process enhances the efficiency of traditional ECAP technique with decreasing the process time. In this study, a complete investigation was done by the design of experiment (DOE) by compound Taguchi-Grey technique. FEM was applied by ABAQUS software in order to achieve responses of proposed Taguchi tests. Die geometrical parameters together with an important process parameter were selected as input factors and strain characteristics and also, required process load were selected as responses. The relationships between responses and input factors were obtained by regression analysis. Then, an analysis of variance (ANOVA) was used to determine the influence of each input factor on responses. ANOVA analysis revealed that FC with contribution percentage of 87.21% has the most influential factor on RPL. Furthermore, it was inferred that among input factors, with contribution percentage of 94.57% has the most effect on the PEEQ. Finally, a multi objective optimization study was done by grey relational analysis. It was concluded that among all input factors, die channel angle, friction coefficient (FC), and die corner angle with contribution percentages of 42.30%, 26.08% and 14.84% are the first, second and third most influential factors on objectives, respectively.

Friction is one of the important factors influencing metal forming processes e.g. forging. Besides considering a set of basic principles, efficient lubrication is the best way to control friction and wear. One way to evaluate the effect of lubricants on the friction in forming processes, is ring compression test. By using calibration curves in the forging process, friction coefficient is calculated. In this paper, the effects of nano- particles solution including copper oxide and alumina within paraffin and oil-10 as the base lubricants on the Coulomb friction model has been studied. In order to obtain the optimal design of experiments Taguchi method has been used and considering the number of investigating factors, L8 orthogonal array selected. After carrying out all suggested tests and using calibration curves for Al7xxx, Coulomb friction coefficients for different lubricants have been obtained. Weight percentage of nano-particles and the type of both base lubricant and nano-particles additives, considered as input variables, and the Coulomb friction coefficient selected as objective variable. Through variance analysis the effectiveness of each input variable on the objective evaluated and values of the input parameters to minimize friction coefficient by Taguchi signal-to-noise method were extracted. The results show that the greatest impact belongs to weight percentage of nanoparticles with a share of 62.15 percent on the friction coefficient and increasing the weight percentage of nanoparticles lead to increasing the friction coefficient. Also, the best combination to minimize friction coefficient is 0.8% solution of alumina nanoparticles with oil 10 as base lubricant.

Equal channel angular pressing (ECAP) is one of the most efficient techniques among severe plastic deformation (SPD) methods that enhance the mechanical properties of polycrystalline metals by refining subjected grains. In this article, equal channel multi angular pressing (ECMAP) process as one of the effective ECAP methods on production of ultra-fine grained (UFG) Al5754 strips studied. Route C considered as a multi pressing route and grey relational analysis used as the optimization method. Geometrical parameters were taken as input variables and strain inhomogeneity index, equivalent plastic strain and required process load were taken as the objectives. The suggested tests by full factorial method simulated by FEM. Finite element simulations were done by ABAQUS commercial software and obtained results validated by analytical methods and experimental tests. Then considering all input and output parameters, optimization was done and optimum values of input parameters were elicited. Also, the effectiveness of each parameter on the objective parameters obtained. It is concluded that, among geometrical parameters of route C, die channel angle (ϕ_2) and die corner angle (ψ_1) has the maximum and minimum effectiveness respectively.