• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 추계학술대회 논문집
• /
• pp.993-996
• /
• 2005

This paper is concerned with transfer process on hot forging of bearing hub. Workers on hot forging have difficulty in working by high temperature and weight workpiece. And In conventional got forging of bearing hub, the material wasted to the flash accounts approximately 10% of the original workpiece. It is need manufacture automation and reduce the cost of forged products. Surface treatment of die and lubricant are investigated from experiment and FE-simulation for analysis of forming simulation. In order to hot forging process design considered flash thickness and blocker geometry and initial temperature of die and billet. This transfer process gave comparatively good results compared with actual products.

• 한국정밀공학회지
• /
• 제15권9호
• /
• pp.75-81
• /
• 1998

Simulations of warm and hot forming processes need reliable expressions of flow stress at high temperatures. To get flow stress of the materials usually tension, compression and torsion tests are conducted. In this study, hot compression tests were adopted to get flow stress of medium carbon steel. Experiments have been conducted under both isothermal, near constant strain rate in the temperature ranges 650～100$0^{\circ}C$. Phase transformation takes place by temperature changes for steels in hot and warm forging stage. So Constitutive equation are formulated as the function of strain, strain rate and temperature for isothermal conditions and phase transformation.

• 한국주조공학회지
• /
• 제17권5호
• /
• pp.494-501
• /
• 1997

In order to manufacture large rod preforms of 2014 Al alloy with a good mechanical property by spray forming method, it was spray-formed at a droplet temperature of $715^{\circ}C$, a droplet flight distance of 400mm, and a spraying angle of $35^{\circ}$. The rod preforms were extruded at $397^{\circ}C$ with the die temperature of $420^{\circ}C$ under the hot extrusion ratio 21:1 and T6 heat treatment was performed. The 2014 Al alloys cast by hot top process were also extruded and heat-treated at the same condition as a reference material. Microstructural observation and tensile test were carried out to investigate the effects of extrusion on microstructure and mechanical property of spray-formed Al alloy. Spray-formed Al alloys had many porosities due to inappropriate process conditions such as long droplet flight distance and low droplet temperature but have fine equiaxed grain. These porosities were reduced with decreasing in grain size by hot extrusion. Ultimate tensile strength and yield strength of spray formed-extruded 2014 Al alloy were inferior to those of the normal cast-extruded 2014 Al alloy, but elongations were superior. The control of porosity was important to get spray formed preform with a good mechanical property.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2012년도 춘계학술대회 논문집
• /
• pp.941-942
• /
• 2012

• 한국산업융합학회 논문집
• /
• 제21권6호
• /
• pp.419-427
• /
• 2018

In case high strength steels are applied for press-formed automotive parts, it is very difficult to secure forming accuracy due to large springback compared to moderate strength steels. In this study, a repetitive step-wise forming analyses based on secant method was proposed as the die design method for mandrel(bending tool) for the 2-axis bending equipments. A bending die with circular mandrel was designed for the DP780 blow motor case of which diameter and thickness are 70.8mm and 2.0mm respectively. Forming tests were performed to verify the validity of established die design and the results were compared with that of conventional HGI(Hot galvanized iron steel) blow motor case. For additional improvement in forming accuracy, an elliptical mandrel was proposed and its validity was verified using forming analyses based on secant method.

• 대한기계학회논문집A
• /
• 제36권3호
• /
• pp.319-324
• /
• 2012

이산화탄소에 대한 규제가 강화되면서 환경 보호를 위하여 차량의 경량화를 요구하고 있다. 이를 위하여 다른 재질, 두께 및 강도를 갖는 소재를 맞춤 블랭크로 제조하여 활용하는 TWB 기술과 오스테나이트 변태온도 이상으로 승온, 스탬핑 ��칭하는 핫스탬핑용 보론강을 이용한 열간 성형 기술을 접목함으로써 경량화 및 고안전성을 확보할 수 있다. 따라서 본 연구에서는 레이저 용접된 보론 강판의 열처리 온도를 달리하여 다이��칭 조건에 따른 기계적 특성을 조사하였다. 레이저 용접한 보론 강판을 다이 ��칭한 후 인장 시험한 결과, 최대인장강도 1454 MPa, 연신율은 6 %로 나타났으며, 이것은 용접하지 않은 모재 열처리재 인장강도, 1522 MPa의 95.5 %이다. 이 값은 핫스탬핑용 보론강 용접재의 실용적인 데이터로 활용될 수 있을 것이다.

• 대한기계학회논문집A
• /
• 제37권4호
• /
• pp.547-554
• /
• 2013

천연가스 자동차에 장착되는 연료저장용기는 크게 두부, 실린더부 그리고 바닥부로 나뉜다. 실린더부와 바닥부에 관한 연구는 이미 충분히 수행되었으나, 두부 성형에 관한 연구 및 설계자료는 전무한 실정이며, 현재 현장 작업자들의 경험이나 시행착오에 의해 제작되고 있다. 본 연구에서는 천연가스 저장용기의 두부 성형 공정인 열간스피닝 공정 분석을 위하여 회전체 소성가공에 적합한 ALE method를 적용하여 유한요소해석을 수행하였다. 성형인자들(이송거리, 성형시간, 소재의 온도, 회전속도)이 성형롤러의 하중 및 두부의 좌굴에 미치는 영향을 분석하고, 이를 토대로 저장용기의 두부성형 가능성을 검토하였다. 또한 성형해석 결과로 제조된 저장용기 두부의 안전성을 평가하기 위하여 파열압력에 대한 용기의 구조해석 및 실험을 수행하였다.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 춘계학술대회 논문집
• /
• pp.198-201
• /
• 2004

Aluminum alloys have high potential for weight reduction in automotive and other applications. But aluminum alloys have relatively low tubular hydroformability which can be enhanced by conducting the hydroforming at elevated temperatures. Hot working processes are commonly used in bulk forming such as forging and rolling, but still is rare in sheet metal forming like hydroforming. In this study hydroforming test at elevated temperatures is performed by special designed induction heating system to investigate the hydroformability of aluminum alloys. The high temperature formability characteristrics are obtained by 1?fitting forming test and circular bulging test and the effects of the process parameters such as feeding amount, internal pressure and temperatures on the tubular forming limits are mainly investigated.

• 소성∙가공
• /
• 제8권2호
• /
• pp.188-199
• /
• 1999

Semi-Solid Forming Process(Thixoforming, Rheocasting) is a novel forming process which has some advantages compared with conventional die casting, squeeze casting and hot/cold forging. In this study. Thixoforming process was selected as analysis processing in terms of billet handling and easiness of automation process. The Thixoforming process consists of reheating process of billet, billet handling, filling inot the die cavity and solidification of SSM part. In filling process, two rheology models which were Newtonian and Non-Nettonian model (Ostwald-deWaele)were verified with experimental results. The Ostwald-deWaele model shows the good agreement to the real flow and filling phenomena in die cavity. To give a boost the economical efficiency of Thixoforming process and to ensure the good forming result, reheating device coupled die set was proposed and the initial billet temperature for system that was found from experimental resluts. This study presents an overview of application of numerical analysis for simulation of semi-solid metal forming process to reduce the lead time for development of manufacturing part in industrial field.

• 소성∙가공
• /
• 제19권2호
• /
• pp.127-131
• /
• 2010

Carbon-epoxy prepreg has been introduced in the forming of the upper and lower swash plates that control the pitch of rotor blade of unmanned helicopter because of its lightweight. Taguchi experimental method has been used by introducing the variables such as arrangement angle, laminated number and forming temperature, in order to obtain the proper forming method by using prepreg satisfying the required strength of the swash plate. In the evaluation of structural safety for the swash plates, three kinds of models are considered by using FE-analysis. In comparison of the hot forged products with Al6061-T6 and the formed products with prepreg, it was found that ultimate tensile strength of the products with prepreg is three times higher than that of the Al6061-T6, and the weight reduction of 68.5g can be achieved by using prepreg swash plates.