• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1998년도 추계학술대회 논문집
• /
• pp.242-247
• /
• 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.

• 대한기계학회논문집
• /
• 제13권3호
• /
• pp.337-344
• /
• 1989

본 연구에서는 플래쉬(flash)를 가진 축대칭 리브-웨브형(rib-web type) 제품의 형단조가공을 해석하기 위한 UBET 프로그램을 개발하고 변형중의 경계 조건처리를 다르게 한 세 가지 유동모델에 대하여 소재의 유동상태와 단조하중을 계산하여 효과적인 유동모델을 제시하였다. 또한 체적은 같으나 반지름과 높이의 비가 다른 몇 가지 초기소재 형상에 대하여 변형에 따른 소재의 다이충만도 및 하중을 비교하여 적절한 초기소재의 형상을 찾고자 하였다. 본 연구에서 제시한 유동모델의 효율성을 검증하기 위하여 플라스씬(plasticine) 소재를 사용한 실험과 그 결과를 비교, 분석하였다.

• 소성∙가공
• /
• 제3권2호
• /
• pp.202-214
• /
• 1994

An upper bound elemental technique(UBET) is applied to predict the forging load and die-cavity filling for non-axisymmetric ring forging. In order to analyze the process easily, it is suggested that the finial product is divided into three different deformation regions. That is axisymmetric part in corner, lateral plane-strain part and shear deformation on boundaries between them. the place-strain and axisymmetric part are combinded by building block method. Also the total energy is computered through combination of three deformation part. Experiments have been carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.

• 대한기계학회논문집
• /
• 제18권5호
• /
• pp.1117-1125
• /
• 1994

A UBET program is developed for determining the optimum sizes of preform of a rib-web part in axisymmetric closed-die forging. The program consists of forward and backward tracing processes. In forward process, material flow, degree of die filling, and forging load are predicted. In backward tracing process, the optimum dimensions of initial billet and preform are determined from the final-shape data without flash. The above program is easy to handle input data with and is convenient to visualize the whole process of closed-die forging with. Experiments are carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.

• Journal of Advanced Marine Engineering and Technology
• /
• 제23권3호
• /
• pp.379-388
• /
• 1999

Au upper bound elemental technique(UBET) program has been developed to analyze forging load die-cavity filling and optimum kinematically admissible velocity fields for flashless forging. The simulation for flashless forgings are applied plane-strain and axisymmetric closed-die forging with rib-web type cavity. The kinematically admissible velocity fields for inverse triangular and inverse trapezoidal elements are used to analyze flashless forging,. Experiments have been carried out with pure plasticine billets at room temperature. Theoretical predictions of the forging load in plane-strain and axisymmetric forging are in good agreement with experimental results.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 춘계학술대회 논문집
• /
• pp.837-841
• /
• 1997

An upper bound elemental technique(UBET) program has been developed to analyze forging load, die-cavity filling and optimum kinematically admissible velocity fields for flashless forging. The simulation for flashless forgings are applied plane and axisymmetric closed-die forging with rib-web type cavity. The kinematically admissible velocity fields for inverse triangular and inverse trapezoidal elements, are used to analyze flashless forging. Experiments have been carried out with pure plasticine billets at room temperature. Theoretical predictions of the forging load in plane-strain and axisymmetric forging are in good agreement with experimental results.

• 한국정밀공학회지
• /
• 제12권8호
• /
• pp.63-72
• /
• 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.

• 대한기계학회논문집
• /
• 제18권9호
• /
• pp.2234-2244
• /
• 1994

A process sequence of multi-operation cold forging for actual application in industry is designed with the rigid-plastic finite element method to form a constant velocity joint housing(CVJ housing). The material flow during the CVJ housing forming is axisymmetric until the final forging process for forming of ball grooves. This study treats the deformation as an axisymmetric case. The main objective of the process sequence design is to obtain preforms which satisfy the design criteria of near-net-shape product requiring less machining after forming. The process sequence design also investigates velocity distributions, effective strain distributions and forging loads, which are useful information in the real process design.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1995년도 춘계학술대회논문집
• /
• pp.124-130
• /
• 1995

An upper-bound elemental stream function technique(UBST) is proposed for solivng forging and backward extrusion problems that are geometrically complex or need a forming simulation . And in the forging problems, this study investigates that layer of elements effects dissipation of total energy and load. The element system of UBSTuses the curve fitting property of FEM and the fluid incompressiblity of the stream function . The foumulated optimal design problems with constraints ae solved by the flixible toerance method. In the closed-die forging and backward extrusion, the result of layer of element by this study produces a lower upper-bound solution than that fo UBET and conventional layer of element . And the main advantage of UBST program is that a computer code, once written , can be used for a large variety problems by simply changing the input data.

• 대한기계학회논문집
• /
• 제14권1호
• /
• pp.1-12
• /
• 1990

본 연구에서는 자유단조용 프레서를 이용하여 돌출부가 있는 비대칭 중공형단 조 제품을 생산할 수 있도록 금형장치를 설계.제작하고, Fig.1에서 보는 바와 같이 경 사진 돌출부가 있는 비축대칭 복합단조에 UBET를 적용하여 해석하였다. 단조시편은 원주형태를 가지도록 하였다. 즉 원주형 소재가 요구되는 비축대칭 단조제품으로 변 형되는 과정에서 단조하중, 재료가 돌출부를 충만하도록 하는 유동특성, 재료가 돌출 부로 차들어가는 속도 등에 영향을 주는 인자(예:펀치 직경의 크기, 금형 상하면의 각 도)의 특성을 이론적으로 해석하고 실험으로 확인하였다.