• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.8
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• pp.2458-2467
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• 1996

The rigid-plastic finite element analysis was performed for analysis of ofhot forging and cold sizing of a bevel gear. Two dimensional analysis was carried out to investigate the defect occurrence on vertical symmetric planes during hot forging and three dimensional analysis was to understand the filling behavior on horizontal planes during cold sizing. The involute curve of a tooth was approximated by a circle for convenience in the present analysis. In order to estimate the elastic deformation of the gear and dies during cold sizing, linear elastic finite element analysis was performed. Results of the analysis can be used to predict grain flows and strength distributions in the forged gear, and to design dies and an appropriate preform for the cold sizing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.297-298
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• 2008

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.230.1-230.1
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• 2005

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.621-627
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• 2006

Recently, micro-alloyed steels which could eliminate heat treatments after forging has been developed. These non heat-treated micro-alloyed steels have several advantages over the conventional quenched and tempered steel for cold forging. First of all, long components can be fabricated with a better dimensional accuracy since bending of long forged part after quenching treatment could be avoided. And it is possible to eliminate two energy consuming heat treatment steps, which are a spherodizing before forging and quenching/tempering after forging. Therefore, more cost effective and environment friendly process could be designed. However, there is non-uniform distribution of strain occurred across the forged part, since these non heat-treated micro-alloyed steel use strain hardening mechanism. In the present study, it was investigated how to lessen non-uniformity and increase strength together for cold forging when a baking heat treatment is applied in micro-alloyed steels. For this purpose, micro-alloyed steels developed by Se-A Besteel recently was used for the experiment.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.8
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• pp.63-72
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• 1995

Closed-die forging of spur gears with hollow cylindrical billet has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduced to represent the forging die profile. In the analysis, the deformation region has been divided into nine zones. A constant frictional stress has been assumed on the contacting surfaces. Utilizing the formulated velocity field, numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth and friction factor, on the forging of spur gears. Hardness and accuracy of forged gears are measured. The following results have been obtained: (1) It is verified that an axisymmetric deformation zone exists between root circle and center of gear through forged gears. (2) The average relative forging pressure is predominantly dependent on the number of teeth and increases near the final filling stage as the addendum modification coefficient increases. (3) Close agreement was found between the predicted values of forging load and those obtained from experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.326-329
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• 2005

Since the required strength of forged part is achieved by work hardening with the accumulation of plastic strain during the cold working, severe load can be exerted on die system. So, dies are liable to the early fracture for the non-heat treated steel forging in comparison with the conventional mild steels. Therefore, it is necessary to lower the flow stress of steels as much as possible during forging steps. Bauschinger effect can be utilized to lower flow stress during forging steps by giving the tensile prestrain on the forging billet during wire drawing step. In the present study, the prestrain effect on Bauschinger phenomenon is studied to avoid difficulties with application of non-heat treated cold forging steels in practice.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2096-2103
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• 2002

Cold ironing, as a post-forging operation of warm forged gears, needs a clear understanding of form errors due to die-elasticity and springback of component. In order to simplify the analysis of cold ironing, a single tooth instead of a whole gear component was investigated. The influence of initial surface roughness, die design, and die/workpiece interference has been examined experimentally and numerically. As a result the changes in geometrical profile, dimensions, and surface finish in a single tooth were observed. This study demonstrates that predicted dimensions can be achieved and surface finish also can be greatly improved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.10-17
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• 2003

The amount of production orders from Japanese car and construction machine industries have slightly increased in 2002, but the costs of the forged parts have decreased due to severe competitions with the other Asian countries. Most of the forging industries and some universities are making more efforts for technological researches and developments to meet the demand for higher accuracy and higher quality products, shortening of delivery time, and development of forged parts for new industrial fields. Some helical gears of which surfaces can be net-shaped have been started for commercial base production to be shipped to car industries. Some non-graphite lubricants for hot forging and some conversion coating free lubricants for cold forging have been developed to improve some environmental problems.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.160-163
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• 2005

The cute. race of CV(constant velocity) Joint is an important load-supporting automotive part, which transmits torque between the transmission gear box and driving wheel. The outer race is difficult to forge because its shape is very complicated and the required dimensional tolerances are very small. The forged CV Joint investigated in this study has six inner ball grooves requiring high operational accuracy. Therefore, the precise measurement of forged CV Joint is very important to guarantee the sound operation without noise and abnormal wear. In this study, unique in-situ measuring system designed specifically to measure the dimensional accuracy of six inner ball grooves of CV joint has been developed and implemented in shop environments. Newly developed system shows high measurement accuracy with simple operational sequence.

• Transactions of Materials Processing
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• v.17 no.1
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• pp.5-8
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• 2008

As the semi-solid forming technology has a lot of advantages compared to the die casting, squeeze casting and hot/cold forging, it has been studied actively. This paper focuses on the thixoforging of the rheological materials fabricated by the spiral mechanical stirring equipment with A356 casting aluminum alloy and A6061 wrought aluminum alloy. Formability tests of rheological materials fabricated by spiral mechanical stirring were carried out and the microstructures of forged sample were observed. After thixoforging experiment, the heat-treated conditions of forged samples are investigated to improve the mechanical properties. These results are able to suggest the possibility of commercialization for rheological materials fabricated by spiral mechanical stirring.