• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1166-1180
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• 1990

The study is concerned with the two-dimensional thermo-viscoplastic finite element analysis for radial forging as an incremental forging process. The deformation and temperature distribution of the workpiece during radial forging are studied. The analysis of deformation and the analysis of heat transfer are carried out for simple upsetting of cylinder by decoupling the above two analyses. A method of treatment for heat transfer through the contact region between the die and the workpiece is suggested, in which remeshing of the die elements is not necessary. Radial forging of a mild steel cylinder at the elevated temperature is subjected to the decoupled finite element analysis as well as to the experiment. The computed results in deformation, load and temperature distribution are found to be in good agreement with the experimental observations. As an example of viscoplastic decoupled analysis of hot radial forging, forging of a square section into a circular section is treated. The stresses, strains, strain rates and temperature distribution are computed by superposing material properties as the workpiece is rotated and forged incrementally. It was been thus shown that proposed method of analysis can be effectively applied to the hot radial forging processes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1243-1250
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• 2003

In the present study, hot forging process for a lower arm connector of an automobile was investigated. An FEM code, DEFORM-3D, was used to analyze the process and the process parameters, such as temperature, strain and strain rate, were obtained. The microstructure of the connector was predicted by applying the Sellars and Yada microstructure evolution models to the process parameters. The method of microstructure prediction used in the present study seems to be effective for the quality assurance of a forged automotive product.

• Transactions of Materials Processing
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• v.9 no.5
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• pp.533-538
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• 2000

This study has been carried out to develop a CRT die using hot forging. The conventional CRT die made by casting has defects such as void and inclusion. These defects of the cast die make micro-spots on the surface of the CRT which affect the quality of the final product. So, a hot forging process is developed to avoid these defects of CRT die by the model material test and the rigid-plastic FEM. Firstly, model material tests are carried out with plasticine billets in order to investigate the material flow pattern in the die cavity and to get the reasonable initial values for designing the preform in the FE simulation. And then a finite element analysis has been performed to Predict the preform and the forging load of a CRT die. We also suggest an integrated die-set which combines two die-sets into one die-set to save manufacturing time and cost in case of similar die-size.

• Journal of Powder Materials
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• v.4 no.4
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• pp.258-267
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• 1997

The powder forging process is an attractive manufacturing route for bevel gears. It offers beneficial material utilization and the minimization of finishing operations over that of conventional hot forging. The paper describes the process conditions for the powder forging of bevel gear, for example, powder alloy design, preform design, deformation of sintered preform, forging processes. The characteristics of prototype gear are investigated with microstructure, the density distribution, surface roughness of tooth, bending strength test of tooth, etc. The results of the bending strength test may prove the mechanical properties of powder forged gear.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.120-123
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• 1999

The precision cold forging process for steering yoke of automobile has been analysed by using rigid-plastic finite element analysis code DEFORM-3D Also the experiment has been performed through the optimized process. Until now steering yoke has been largely manufactured by hot forging or welding of forged head and shaft parts because of technical difficulty. the study has shown successful results of the precision cold forging through the proper selection of the process.

• Transactions of Materials Processing
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• v.18 no.4
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• pp.354-360
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• 2009

Hot-forging process and die design were made for a large-scale compressor wheel of Ti-6Al-4V alloy by using the results of 2-D FEM simulation. The design integrated the geometry-controlled approach and the processing contour map based on the dynamic materials model and the flow stability criteria. In order to obtain the processing contour map of Ti-6Al-4V alloy, compression tests were carried out in the temperature range of $915^{\circ}C$ to $1015^{\circ}C$ and the strain rate range of $10^{-3}s^{-1}$ to $10s^{-1}$. In the die design of the compressor wheel using the rigid-plastic FEM simulation, forging dimensional accuracy, the capacity of the forging machine and defect-free forging were considered as main design factors. The microstructure of hot forged wheel using the designed die showed a typical alpha-beta structure without forging-defects.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.627-632
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• 2001

Nimonic 80A superalloy with high-temperature strength and high corrosion-resistance is used in jet engine for aircraft, gas turbine for power plant and marine diesel engine, etc. To develop the manufacturing process of exhaust valve for large diesel engine using Nimonic 80A, various mechanical tests, such as hot compression, microstructure and hardness test have been performed. This results effectively used to set the reasonable forging conditions while hot forging of Nimonic 80A superalloy. Open die and closed die forging experiments are carried out from ESR ingot and finally get a good shaped exhaust valve product.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.4
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• pp.76-82
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• 2008

Alloy 718 nozzle component was manufactured by hot forging and electron beam welding process. In this process, 718 billets produced in domestic company were used and evaluated. Before performing industrial scale hot forging, small size hot compression tests were carried out under various process conditions and then microstructural evaluations were analyzed. Using the results, FEM simulations were performed in order to optimize the hot working process. After hot working, forged work-pieces were machined and welded by electron beam. Final nozzle components were heat treated and their microstructure and mechanical properties were investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.11-16
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• 1997

In this study, the finite element analysis of AA6061 wheel forging processes over hot working range is performed and a thermo-viscoplasticity theory applicable to hot forging is applied for simulation. Aluminum alloy has frequently been utilized to manufacture automobile and aircraft parts due to its various advantages such as lightness, good forgeability, and wear resistance. Several forging conditions are applied to the simulation, such as die speeds, rib thicknesses, and depth of die cavity. The effectiveness of the simulation results is summarized in terms of metal flow, strain distributions, temperature distributions, forging load, which are essential to over all process design.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.3 s.168
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• pp.21-28
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• 2005

In the hot forging process lubricant influences on frictional condition only, but in the warm forging process it influence on the formability such as dimensional accuracy, filling state and frictional condition and it is important to estimate a lubricating characteristic of lubricants in the warm forging. In this paper, in order to evaluate the formability of billet in warm forging process according to the lubricant and lubricating method, lubricant and lubricating test have been performed using oil-based and water-based lubricant which were widely used in the hot and warm forging processes. The surface roughness of initial billet was measured to evaluate the influence on the formability of billet and the forming load and dimensional accuracy were compared and evaluated. From the experimental results, it can be known that water-based lubricants are more excellent than oil-based lubricants for warm forging of complex shape like a bevel gear. Also, in this study characteristics of deformation have been investigated according to surface treatment of initial billet.