• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.190-190
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• 2003

동력 전달용 구동부품에 있어서 중공 플랜지 형상의 부품은 흔히 찾아 볼 수 있으며, 이는 높은 강도를 요구하기 때문에 강도향상을 위하여 단조에 의한 제품의 성형 방법이 많이 연구되고 있다. 중공 플랜지형상을 갖는 제품의 제조 방법으로서는 중실 플랜지 형상으로 단조하여 내경부를 절삭가공하는 방법, 중실 소재를 후방압출하여 중공 플랜지형상으로 단조하는 방법, 또는 중공의 초기소재를 사용하여 중공 플랜지형상으로 단조하는 방법이 일반적이다. 본 연구에서는 Fig. 1에 나타낸 것과 같이 중공 플랜지 형상을 갖는 기계 부품의 단조방법에 대해 연구하였으며, 중공 관의 내경을 $d^1$, 외경을 $d^2$, 플랜지부의 외경을 $D^0$, 중공 관의 두께를 t, 플랜지부의 두께를 T로 정의하였다. 중공 플랜지 형상에 있어서 공정 설계의 변수는 다양하겠으나, 본 연구에서는 중공관의 외경과 내경의 형상비 $\alpha$(=$d^2$/$d^1$), 플랜지의 폭과 중공관의 두께비 $\beta$(=B/t) 및 중공관의 두께와 플랜지의 두께비 r(=T/t)의 변화에 따른 성형조건에 관해 고찰하였다. 중공 플랜지 형상의 성형방법으로 Fig. 2에 나타낸 것과 같은 $\circled1$중실소재를 이용한 후방압출단조(backward extrusion forging)방법, $\circled2$중공 소재를 이용한 엎셋(upset forging)방법, $\circled3$중공 소재를 이용한 압조법(injection forging), $\circled4$중실소재를 이용한 압조-압출(injection-extruding forging)법의 4가지의 단조 방법을 제시 하였다. 또한, 유한요소해석을 수행하여 소성유동 형태, 유효변형률, 단조하중을 검토하고. 모델재료인 납을 이용한 실험을 통하여 이를 검증하였다. 이를 바탕으로 산업 현장에서 경험에 의존하였던 공정 설계를 보다 효과적으로 개선하기 위한 단조법을 제시하고자 하였다. 또한 중실 소재를 이용한 중공 플랜지 형상의 단조 방법 중 보다 적절한 단조방법인 압조 단조에 있어서 일반적으로 사용되고 있는 SM10C에 대한 유한요소 해석을 수행하였으며, 제품의 형상비에 따라 폴딩 결함의 발생 유무를 검토하고, 폴딩 결함 없이 단조하기 위한 중공 플랜지의 형상한계 비를 제시하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.1
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• pp.92-99
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• 2003

Bevel gears are important mechanical parts to transmit power in transportation system high precision parts like bevel gears might be manufactured by closed die forging process for dimensional accuracy. Closed die forging of bevel gears offers the high quality and good mechanical properties and also leads to considerable cost saving. To determinate the proper closed-die forging process for bevel gear forms, three-dimensional finite element simulation for the progressive forging process was earned out and also the simulation results were compared with experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.55-62
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• 1994

For theoretical estimate of closed-die forging pressure, upper-bound method is applied to the involute tooth profile. In the analysis, the deformation regions have been divided into several zones. A constant frictional stress has been assumed on the contacting surfaces. Utilizing the formulated velocity fields, 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. Very close agreement was found between the predicted values of forging load and those obtained from experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.05a
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• pp.219-226
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• 1996

일반적으로 밀폐 형단조공정에서 약 10,000톤의 성형력이 필요한 직경이 540mm인 플랜지 형태의 알루미늄 7175 합금 단조품을 2,500톤 프레스에서 단조하기 위한 공정연구를 하였다. 장비의 성형력 부족을 극복하기 위하여 업셋단조와 기계가공 및 전방압출을 조합한 복합성형공정을 제안하였으며, 복합공정은 실제재료를 이용한 $\frac{1}{4}$ 축소 모델 실험과 유한 요소 해석으로 그 타당성이 판단되었고, 선정된 프레스에서 실물 크기의 플랜지 단조 가능성을 확인하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.134-138
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• 1996

A simple kinematically admissible velocity field for closed-die forging of clutch teeth is analysed which takes account of the profiled teeth chosen kinematically by approximating these as straight taper teeth. The upper bound load and the deformed configurations are predicted by the velocity field at varying punch movements considering differing frictional factors. Experiments were carried out using a model material of plasticine at room temperature where talcum powder was used as a lubricant. The theoretical predictions of the forging load and the relative pressures are found to be in reasonably good agreement with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.7
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• pp.1081-1088
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• 1997

The purpose of this work is to investigate the working limit of carbon steel and forging condition of cold forging. The fracture criteria which was proposed by Oyane and Osakada was used. Compression test, hardness study and tension test by Oyane's creteria, microstructure study by Osakada's were carried out. The results were compared with each other. It was found that working limit on compressive hydrostatic stress is increased in comparison with that of tensile stress field and can be forecasted the fracture limit of closed cold forging.

• Transactions of Materials Processing
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• v.3 no.1
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• pp.97-109
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• 1994

Closed-die forging of the spur gears with circular are fillet has been analyses by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, the tooth profile consists of the involute curve and the circular arc fillet. In the analysis, the deformation regions have been divided into eight 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, addendum modification coefficient and friction factor, on the relative forging pressure of spur gears. As the result of numerical calculations, the relative forging pressure does not change so much against the variation of module. On the other hand, the relative forging pressure increases at the final filling stage as the addendum modification coefficient increases.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.06a
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• pp.119-127
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• 2001

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.206-211
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• 1996

Closed-die forging of external spine is analysed using an upper bound elemental technique. The kinematically admissible velocity field for three-dimensional deformation in forging of the external spine with trapezoidal teeth was obtained. The upper bound to the deforming load necessary and the the deformed configurations are predicted using integration of the formulation of energy expressions which were obtained from B(upset forging method) were considerd in the present analysis and the theoretical results compared with experimental ones Experiments were carried out on plasticine as model material at room temperature where talcum powder was used as a lubricant. The present investigation revealed that the analytical method B predicts a reducet forging load and improved configuration better than method A for the forged products.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.242-247
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• 1998

The conventional closed-die forging processes had been applied to forging of the spur gears. But this type process requires high pressure. The commercial finite element analysis code ANSYS for the stress and elastic deformation of non-axisymmetric die was adopted in this study. In the non-axisymmetric die such as gear forging, maximum stresses were imposed on the tip of the gear tooth. When the stress exceeds yield strength of insert die, many approaches were attemped to prevent the die failure. Good shaped products are forged successfully. This type process could by used as an advanced technique to replace conventional hobbing process of gear.