• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.585-595
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• 2008

Process design of multi-stage forging for a bolt with nonaxisymmetric washer cam has been studied by using finite element method. For shape complexity of the bolt, it is impossible to manufacture in a single stage forging. To design multi-stage forging for the bolt the forging load and fiber flow of each step have been analyzed by using commercial finite element code DEFORM-3D. Simulated results have been compared with experimental ones. Multi-stage forging process has been designed with four stages. The workpiece should be eccentric shape until third forging stage. And then bolt head and washer of eccentrical shape is created in last stage. As a results, It was predicted that shape of product would be good and effective strain would be uniformly distributed in the product. Also, it was predicted whether defects would exist or not by reviewing the fiber flow.

• Journal of Drive and Control
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• v.19 no.4
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• pp.10-18
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• 2022

Air-drop hammer press and counterblow hammer press are widely used power-drop forging hammersemploying different forging blow mechanisms. It is important and necessary to analyze mechanical vibrations of these two different hammers in their forging processes in order to develop high performance forging hammers. In this study, these two forging hammers were mathematically modelled as mass-spring-damper systems. For these two different types of forging hammers, the forging efficiency and mechanical vibrations due to hammer forging blow were theoretically analyzed and compared. The force transmitted to the ground was also determined and compared. Especially, effects of mass ratio and restitution coefficient on forging efficiency were investigated.

• Transactions of Materials Processing
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• v.8 no.4
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• pp.384-392
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• 1999

In metal forming, there are problems with recurrent geometric characteristics without explicitly prescibed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. In this paper, as a practical application of the proposed method, the precision cold forging of a helical gear has been simulated by a three-dimensional rigid-plastic finite element method and compared with the experiment. The application of recurrent boundary conditions to helical gear forging analysis is proved to be effective and valid. the elastic stress analysis of the die for helical gear forging has been calculated by using the nodal force at the final stage obtained from the rigid-plastic finite element analysis. In order to obtain more precise gear products, the elastic analysis of the die after release of punch and the elastic spring-back analysis of product after ejection have been performed, and the final dimension of the computational product has been in good agreement with that of the experimental product.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.96-103
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• 2011

Rotor grip is used as a component of rotor system in unmanned helicopter. Instead of usual machining, hot forging process has been considered to improve its proof stress against repeated loading conditions and crash in the farm-field. Die design and forming analysis have been performed according to the conditions such as billet volume, flash, cavity filling, and the distribution of damage during the forming by using FE analysis. In the results of analysis, the possibility of structural failure in the model has not been found because its maximum effective stress is much lower than yield strength of the titanium alloy. In the forging die design, flash has been allowed because of low production in the industrial field. Preform design was studied by using FE-analysis, and its optimal dimension was obtained in the hot forging of rotor grip with titanium alloy.

• Transactions of Materials Processing
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• v.30 no.1
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• pp.35-42
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• 2021

Magnesium alloys are used in electronic devices such as laptops due to their lightweight features as well as vibration absorption and electromagnetic shielding properties. However, the precision of electronics is limited by the large number of small and precise ribs, the cost-effective manufacture of which requires appropriate technology. Plate forging is an efficient manufacturing process that can address these challenges. In this study, plate forging of magnesium alloys was investigated specifically for the fabrication of laptop cover. The plate forging process with back-pressure was used for near-net shape formation. Finite element analysis was used to select appropriate variables for back-pressure formation to generate ribs of various sizes and shapes without defects. The reliability of the analysis was verified to manufacture the prototype. The effect of back-pressure can be verified via fabrication of prototypes as well as structure and forming analysis based on finite element method. The process design factor of back-pressure increases formability without defects of under-filling and flow-through. Moreover, the tensile strength was maintained even after high temperature plate forging at 370 ℃, and the elongation was improved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.369-372
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• 2006

Monolithic forging of cask is required continuously. Body-base monolithic forging of cask has advantage of an economical manufacturing process and better reliability for nuclear applications. Through the finite element analysis and parametric study of design variables, those are die angle, groove length and flange thickness, the optimal dimensions of preform and die sets are determined in order to develop a suitable forging process for body-base monolithic forging. To verify the result of finite element analysis, the physical model of 1/30 scale of actual product using plasticine was carried out. The result of this experiment, deformed shapes were very similar to the finite element analysis. As a result of this work, the special piercing method was developed using blank material consisting of a flange, groove and squared part.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.4
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• pp.26-37
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• 1994

A kinematically admissible velocity field for the numerical analysis of closed-die forging process of spur gear is proposed. The velocity field is divided into three regions of deformation. In the analysis, the involute curve is approximated to be straight line and the upper-bound method is used to calculate energy dissipation rate. A constant frictional frictional factor has been assumed on the contacting surfaces. The effects of root diameter, number of teeth, and friction factor are determined on the relative forging pressure. The frictionless relative pressure is independent of root diameter for the same number of teeth, but increases with the number of teeth on a given root diameter. In the presence of friction, the relative forging presure increasing root diameter at the start of forging, but decreases with increasing root diameter in the processing of forging.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.47-50
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• 2003

Hot-forging Process and die design was made for a large-scale compressor wheel of Ti-6Al-4V alloy with 2-D FE analysis. The design integrated the geometry-controlled approach and dynamic materials modelling(DMM). In order to obtain the processing contour map of Ti-6Al-4V alloy based on DMM, compression tests were carried out in the temperature range of 915$^{\circ}C$ to 1015$^{\circ}C$ and the strain range of 10$\^$-3/s$\^$-1/ to 10s$\^$-1/. In the die design of the compressor wheel using the rigid-plastic FE analysis, 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 Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.88-91
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• 2003

The forging of Al 6061 has been studied by using finite element analysis and real forging experiment to find out the effect of strain rate and strain on the final forged product. It seems to be well known that the mechanical properties depend on the microstructures of forged products. The hot deformation of Al alleys including Al 6061 has been researched quite a long period on the various aspects. However, the forging of Al alloys seem to have few information, especially the recrystallization, recovery and grain growth. To elucidate the process variables to control those microstuctual aspects the specially designed model was used for finite element simulation and forging experiments, in which the variation of strain and strain rate could be obtained. The effect of strain md strain rate has been related with the microstructures of forging stocks.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1211-1219
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• 1995

An upper bound elemental technique (UBET) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flash and flashless forgings. The simulation for flash and flashless forgings are applied axisy mmetric and plane-strain closed-die forging with rib-web type cavity. Inverse triangular and inverse trapezoidal elements are used to analyze flashless forging. The analysis is described for merit of flashless precision forging. Experiments have been carried out with pure plasticine billets at room temperature. Theoretical predictions of the forging load and the flow pattern are in good agreement with experimental results.