Sharif Digital Repository

Radial forging and indentation forging processes are two processes used for sizing and/or internal profiling of tubes. In this paper, the two processes are simulated using finite element method and their results are compared with Experimental results. The purpose of this paper is to compare the pattern of residual stresses in both processes. Copyright © 2005 SAE International  

An important aspect of production of gears by precision forging process is the prediction of load required to perform the process and to design the forging die. In this research a new kinematically admissible velocity field is presented to predict the forging load by an upper bound analysis. The analysis considers the shape of tooth profile, number of teeth, and frictional conditions between the die/punch and deforming material. To verify the predicted results the 7075 aluminum alloy billets were forged at temperature of 150 to 250 °C in a precision forging die designed to produce a spur gear of 5 teeth. A good agreement was found between the two sets of results at the filling stage of the... 

Some mechanical and metallurgical properties of hollow and solid long forged products are compared. The metallurgical properties include such micro- and macro-structural characteristics as the grain size and grain flow patterns. Mechanical evaluation was performed by means of hardness testing. Some theoretical analyses were also carried out. The results indicate that the hollow or mandrel forged products possess better properties. Both the mechanical and metallurgical properties are more uniform and homogeneous through the thickness direction in such products. By contrast, in the solid forged parts, there is a gradient in the micro- and macro-structural properties from the surface to the... 

Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and for creating internal profiles in tubes. Among parameters affecting process variables, the die geometry is of fundamental importance and greatly influences variables such as forging load, stress distribution on the dies, metal flow during deformation, and surface finish of the forged product. In this paper a generalized slab method analysis of radial forging process is presented which can handle this process with curved shape dies. Results for dies with various curves are presented and it is shown that the analysis reduces to that of Lahoti and Altan [2] when the die... 

A mathematical model has been proposed for evaluation of velocity and temperature fields in hot forging operations for axisymmetric parts. The model can be applied to determine forging load, strain rate, strain and temperature distributions. In addition, the effects of temperature and strain rate on metal flow have been considered through simultaneous modelling of dynamic phase transformation within the deforming metal. Hot forging experiments have been carried out under different working conditions and the results have been compared with the predictions. A good agreement between the simulated and experimental results was found. © 2004 Elsevier Ltd. All rights reserved  

Radial forging is an open forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, as well as for creating internal profiles for tubes such as rifling the gun barrels. The radial forging of tubes is usually performed over a mandrel to create an internal profile and/or size the internal diameter; but the process can also be used without a mandrel when workpiece geometry does not allow it or the internal surface quality is not critical. In some industrial applications, it may not be possible to use a mandrel inside the tubular workpiece, e.g., due to geometrical limitations of the workpiece. In this study, finite element modelling is applied to model the... 

In this work, a neural network model is used to calculate flow stress of deforming metal as a function of temperature, strain and strain rate. Then, with the aid of this model and employing a finite element analysis, flow behavior of material and the temperature variations in hot upsetting process are predicted. To examine the model, hot nonisothermal forging of a low carbon steel is performed while force-displacement behavior during hot deformation is recorded. A good agreement is observed between the predicted data and the measured results. © 2006 Elsevier B.V. All rights reserved  

In this work, a comprehensive study of radial forging process is presented through 2-D axisymmetric and 3-D finite element simulations while considering internal tube profile. The tube used in this investigation has four internal helical grooves along its length. The material is modeled with the elastic-plastic behavior, and sliding-sticking friction model is utilized to model the die-workpiece and mandrel-workpiece contacts. The numerical results in the 2-D case are compared with available experimental data. Residual stresses in the forged product, stress concentration around the grooves, pressure distribution on the hammers and mandrel and maximum forging load are studied. The effects of... 

Precision forging is a suitable process to produce spur gears due to its advantages such as reduction in machining time and production cost. The homogeneity in microstructure and mechanical properties of precision forging products can highly affect the performance of the gears during their service. In this research the effect of precision forging temperature on homogeneity of microstructure and hardness of forged gears of low carbon steel is studied. The microstructure and hardness map of the gears forged at a temperature range of 750-1150 °C revealed that the forging temperature of 950 °C is an optimum temperature to produce a spur five teeth gear with minimum inhomogeneity in the... 

Radial forging is an open die forging process used for reducing the diameter of shafts, tubes and axels. In the present research, a new velocity field was developed to analyze the radial forging process by the upper bound method. The forging load was predicted by minimizing the deformation power with regards to the location of neutral plane. The accuracy of the model was verified by comparing the predicted forging loads with experimental results published by the previous researcher. A good agreement was found between the two sets of results. © 2007 Elsevier B.V. All rights reserved  

In this study, the artificial neural network (ANN) and the Taguchi method are employed to optimize the radial force and strain inhomogeneity in radial forging process. The finite element analysis of the process verified by the microhardness test (to confirm the predicted strain distribution) and the experimental forging load published by the previous researcher are used to predict the strain distribution in the final product and the radial force. At first, a combination of process parameters are selected by orthogonal array for numerical experimenting by Taguchi method and then simulated by FEM. Then the optimum conditions are predicted via the Taguchi method. After that, by using the FEM... 

In this study, multi-directional forging (MDF) as a severe plastic deformation method, annealing, and compression test at different strain rates are applied on pure aluminum. One of the main observations is when the number of MDF passes is increased, the hardness is risen. The most noticeable reduction in hardness occurs when the MDFed samples are annealed at 350 and 450 °C. Moreover, increasing the number of MDF passes and the strain rate of the compression test cause the increase in the yield stress of the samples. If the MDFed samples are non-annealed or if they are annealed at a maximum temperature of 250 °C, the effect of an increase in the number of passes on the yield stress is more... 

Radial forging is an open forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and creating internal profiles for tubes such as rifling of gun barrels. Usually a mandrel is used inside a tubular workpiece to create internal profile and/or size the internal diameter, but the process can also be performed without a mandrel when workpiece geometry does not allow utilizing it or the internal surface quality is not critical. Moreover, in stepped shafts and tubes, often there is a fillet connecting two different sections. If it is possible to produce that fillet during the forging process, the process could be more cost effective. So, in this paper, four... 

In this study, a hybrid model is presented to predict the dislocation density and strength evolution of the rheoforged non-dendritic A356 alloy during multi-directional forging. Regarding the characteristics of non-dendritic A356 alloy, combination of Shear Lag and Nes models is used for the eutectic structure, and Nes model is used for the α-Al globular phase. The aspect ratio variations of Si particles in eutectic structure during 3 passes of multi-directional forging do not change the model predictions, significantly. Model predictions on shear stress are in good agreement with experimental results of shear punch test  

A hybrid algorithm based on the finite element method, Monte Carlo model, and Hall-Petch relationship is utilized to predict the mechanical properties of the rods after cold forging at different degrees of deformations and heat treatments at different temperatures and times. The results show that the flow stress and hardness of the rods after forging and those of the forged rods after the heat treatments are decreased from their center to surface. However, with increasing the temperature and time of the heat treatment the flow stress and hardness are decreased, their effects are not considerable. In addition, the distribution of the mechanical properties of the forged rods after the heat... 

The effect of cooling rate after hot deformation on the microstructure and mechanical properties of a commercial microalloyed forging steel (30MSV6 grade) was investigated using the hot compression test. Hot compression test was performed at 1150 and 925 °C followed by air cooling at different rates. Final microstructures and mechanical properties were evaluated by optical microscopy and shear punch test (SPT), respectively. The results indicated that by increasing the cooling rate, the as-received ferritic-pearlitic microstructure changes to the acicular ferrite, bainite or martensite. It is shown that both yield and ultimate strength increase but the ductility decreases significantly. At a... 

Radial forging is an open die forging process used for reducing diameter of shafts, tubes, stepped shafts and axels, and creating the internal profiles for tubes such as rifling the gun barrels. In the present research, a new model based on calculating the deformation work was developed to find an upper bound limit for the deformation load in the case of radial forging of rods and tubes. Also, the model was used to assess the effects of the process parameters. The accuracy of the model was tested by comparing the predicted results with those achieved from the experiment at work of Uhlig [Investigation of the motions and the forces in radial swaging. Doctoral Dissertation, Technical... 

Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and for creating internal profiles in tubes. In this study, the effect of the workpiece rotation (the circumferential feed) on the strain and residual stress distribution in the inner surface of the tube in the cold radial forging process is investigated using nonlinear three dimensional finite element modeling. To verify the model, the predicted radial forging load is compared with the published experimental data which shows a good agreement. It is shown that for achieving a more favorable residual stress distribution in the workpiece inner surface, the rotation angle... 

It is known that the thermomechanical processing is one of the most important techniques for improving quality and mechanical properties of microalloyed steels. In this paper, the main parameters of hot forging (preheat temperature, strain and post-forging cooling rate) on the primary austenite grain size of vanadium microalloyed steel (30MSV6) were studied. From this investigation, it was found that increasing preheat temperature from 1150 °C to 1300 °C will result in a decrease in grain size number. Furthermore, it has shown that as the strain increases, the austenite grain size number increases, as is evident for the two cooling rates of 2.5 °C/s and 1.5 °C/s for primary austenite.... 

In the present study, a mathematical model has been developed to evaluate temperature and strain fields as well as dynamic and static microstructural changes during the nonisothermal forging process. To do so, a finite element analysis and a microstructural model based on Bergstrom's model have been coupled for predicting temperature history, velocity and strain fields as well as phase transformations within the metal during and after hot forging. To verify the results of the model, theoretical predictions for loadstroke behavior and austenite grain size have been compared with experimental results for two grades of steel