• 대한기계학회논문집
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• 제18권3호
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• pp.768-776
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• 1994

This paper describes computer-aided forging design for rib/web shaped parts. In manufacturing a part by means of forging process, the first step is to design the forging. This is done by modifying the given machined part geometry according to the requirements of the forging process. Traditionally, this is done by experienced forging designers using empirical forging design guidelines. Generally, it would be neither possible nor practical to develop a system which encompasses the design of all types of forgings. Accordingly, forging design can be simplified by considering critical two dimensional cross sections of the machined part geometry. This system is composed of three modules(process variable decision module, forging design module and redesign module) and each module is carried out in regular sequence. In the process variable decision module, first of all, the undercut is checked and modified, and then deep recesses and holes difficult to forge are eliminated. Also parting line, forging plane, forging plan view area, forging weight and maximum size(maximum height or width)are determined. In the forging design module, the magnitude of various allowances, draft angle, minimum web thickness, corner and fillet radius are determined and then geometry modification is performed. Finally, since the design rules and databases used in this system are based on parameters of the forging geometry, such as the trimmed forging plan area, forging weight, forging maxmum size, plausible estimates need to be made for these parameters. Therefore, in the re-design module, the design process is iterated until a satisfactory forging is obtained.

• Design & Manufacturing
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• 제6권2호
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• pp.54-58
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• 2012

A counter shaft gear is an important part in the transmission system of vehicle. Its shape is relatively complicated and should meets high strength. Traditionally it has been manufactured as follows; the counter shaft gear has consisted of a clutch and helical body with teeth which are forged and machined for teeth respectively and then attached by frictional welding. In this study, a new hot forging process was proposed and designed so that the counter shaft gear is formed as one body without divide it into two parts. Furthermore, the precision forging process has been developed for the clutch teeth without additional grinding.

• Design & Manufacturing
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• 제6권2호
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• pp.6-11
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• 2012

A counter shaft gear is an important part in the transmission system of vehicle. Its shape is relatively complicated and should meets high strength. Traditionally the counter shaft gear has been manufactured as follows; a spline body is firstly machined for teeth and then attached to the main gear body by frictional welding, and finally is finished by grinding. Therefore it is necessary to develop a new manufacturing technology eliminating both frictional welding and grinding processes. In this study, a new hot forging process was proposed and designed so that the spline body with teeth and main gear body are formed as one body. Finite element simulations and experimental works were peformed for design of forging processes to get the quality final precision-forged product. Consequently the most suitable blocker process could be obtained.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송∙미디어공학회 2017년도 하계학술대회
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• pp.63-65
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• 2017

본 논문에서는 동영상의 조작 시 발생하는 High Efficiency Video Codec (HEVC) 부호화 패턴의 변화를 감지하여 동영상의 조작 여부를 검출하는 기법에 대하여 소개한다. 동영상의 일부가 삭제되고 재 압축될 경우, 삭제 이후 여러가지 부호화 정보의 패턴 변화가 발생하게 됨을 특징정보로 하여 기계학습 기반의 분류 알고리즘을 이용해 조작유무를 검출한다. 실험 결과, 제안한 방식이 동영상 조작 검출을 효과적으로 수행하는 것을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.377-380
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• 2000

The dimensional accuracy of the cold forged part is depended on the elastic characteristics of the die. To obtain the high stiffness of the prestressed die, the first stress ring of the tungsten carbide material is considered. For the design, Lam 's equation is used. The design of the prestressed die has been compared with the conventional that. For the comparison, the FE-analysis using ANSYS has been performed. The results indicate that the prestressed die with the high stiffness can be obtained by the using the high stiffness material as the first stress ring.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.381-385
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• 2006

This research introduces easy tool manufacturing method regarding tool manufacturing procedure. In the conventional method, wire cutting machining and lapping operation of corner and render region were performed after shrink-fitting to ensure the accuracy of gear profile. But lapping operation is very difficult due to corner and render is located deep inside of die. In this research, wire cutting operation was performed after $1^{st}$ ring was shrink-fitted to ease lapping operation and increase the accuracy of corner radius. Before $2^{nd}$ ring fitting, lapping was completed. Elastic deformation amount due to $2^{nd}$ ring fitting and cold forging was calculated through finite element analysis and wire cutting specification was offset in that amount. Comparison of gear dimension between analysis and forged part ensures the validity of new manufacturing methods.

• 한국기계가공학회지
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• 제7권4호
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• pp.56-61
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• 2008

Cropping metal materials is widely used for feeding processes of various forming method, such as forging, extrusion, drawing, and upsetting. However, cropping has many weak points, which are material loss in part of cutting, chip creation, and much use of lubrication oil, etc. In this study, instead of cropping, a novel process is proposed to cut metal materials, especially stainless steel bar which is known very difficult to crop. Results of FE-analysis will be shown to verify the proposed method comparing with those of the conventional cropping process. Also, fitting products were successfully forged using the fabricated billet by the proposed process.

• Asian review of World Histories
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• 제2권1호
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• pp.1-16
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• 2014

This paper examines the historical relationship between the Little Ice Age and the Anthropocene, which has not yet been studied. The Little Ice Age is the coldest multi-century period in the Holocene. The reforestation of huge farmlands, abandoned due to pandemics in the Americas, aggravated the cooling weather of the Little Ice Age. It was in the long and severe cold of the Little Ice Age that the transition from renewable energy to non-renewable energy was completed in Britain in the latter part of the eighteenth century, and when the pattern of linear growth in greenhouse gas concentrations was forged in the ecosystems of the Earth. The Little Ice Age forced humans to depend on fossil fuels while the advent of warmer and more stable climate in the Holocene enabled them to start agriculture in an energy revolution 11,000 years ago, thus making the coming of the Anthropocene possible.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.277-280
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• 2005

A shape optimization is applied to achieve a design objective in three-dimensional forging processes. In multi-stage forging processes, among the important design aspects, the die shape fur preforming is regarded as the design variable since it influences the forged part relatively higher than the others. The rigid-plastic finite element method and the sensitivity method are employed and formulated to solve a formulated optimization problem. An approximation scheme is also used for the direction search during the optimization. The upset forging of a square box is selected as a test example in order to demonstrate and verify the optimization process of this study. After the optimization, the optimized shape of the die yields a finial product of desire shape.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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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.