• Proceedings of the KWS Conference
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• 2009.11a
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• pp.57-57
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• 2009

산업의 고도화에 따른 구조물의 사용 환경이 열악해지고 최근 에너지저감과 환경문제 개선을 위한 경화의 요구에 따라 뛰어난 내식성 및 우수한 고비강도 특성을 갖고 있는 타이타늄 및 타이타늄합금의 활용에 대한 연구가 많은 주목을 받고 있다. 이에 따라 타이타늄 신합금의 개발뿐만 아니라 기존에 개발되어 비교적 보편적으로 적용되고 있는 타이타늄 부품의 제조 및 성형기술에 대한 수요도 급증하고 있다. 특히, 기기 및 부품 제조를 위한 용접/접합기술도 매우 중요한 요소기술로 자리메김하고 있다. 타이타늄은 산소, 수소 등의 침입형 원소와의 친화력이 강한 활성이 큰 금속으로 용접시 고온에 노출되면 급격히 산화 및 취화 등의 문제를 발생한다. 따라서 타이타늄의 용접시에는 $426^{\circ}C$이상의 온도에서는 대기로부터 용접부가 차단되도록 하는 쉴딩기술이 매우 중요하다. 타이타늄의 용접은 일반적으로 아크용접, 전자빔 용접, 레이저 용접 및 확산접합 등이 적용되고 있으나 용접입열 조정이 용이하고 아크 안정성이 높고 용접부의 기계적 특성이 우수한 GTA 용접이 작업성을 고려하여 가장 많이 적용되고 있다. 본 연구에서는 미국용접학회(AWS)의 타이타늄 용접가이드를 분석 및 소개하였고, 1t 이하의 박판 CP Ti를 대상으로 GTAW 용접부 미세조직 및 기계적 특성을 분석하였다. 이때, 용접 비드폭 제어 및 펄스 용접기술을 통하여 박판 타이타늄의 최적 GTAW 공정변수 제어기술을 분석하였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.87-90
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• 2005

The drawbead is used to control the material flow into the die and increase the forming quality during the binder wrap process and the stamping process in the sheet metal forming. Drawbead restraining force (DBRF) is controlled by geometrical parameters and influenced by process parameters such as friction coefficient and blank thickness. In order to inspect the effect of process parameters, parameter studies are performed with the variation of parameters using finite element model of drawbead which is utilized reliably for the calculation of the drawbead restraining force. Drawbead analysis is carried out with 2-D plane-strain element and 3-D shell element. After the verification of the accuracy of the drawbead model with 3-D shell element, it is utilized to the prediction and the investigation of the effect of process parameters. The result of parameter studies can be utilized to the die design in the tryout stage.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.93-97
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• 1997

Since the modified membrane element has the same external appearance as the ordinary membrane element, it is not able to apply the thickness variation of sheet metal in the blank holder to the contact treatment and the equally distributed blank holding force should be inevitably imposed on sheet metal along the periphery regardless of the contact status. But sheet metal does not contact with the blank holder at the periphery, nor the blank holding force is distributed uniformly along the boundary. To impose the blank holding force properly, the scheme is improved so that the blank holding force at each node imposed on sheet metal is dependent on the calculated thickness derivation and a state of equilibrium with the total blank holding force. The validity of the improved scheme is demonstrated with the simulation of cylindrical and rectangular cup deep drawing.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.379-382
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• 2007

The MEMS (Micro Electro Mechanical Systems) process is used in a micro/nano pattern manufacturing method. This method is based on the lithography technology. But the MEMS process has some problems such as complicated process, long processing time and high production costs. Many researchers are doing research in substitute manufacturing method to work out a solution to these problems. In this paper, we apply a dieless incremental forming technology to a substitute method of MEMS process. This dieless forming technology is using in the commercial scale sheet forming such as a prototype of automobile sheet parts. 5-axes CNC (Computerized Numeric Control) method are applied in this system to get a micro-scale dieless forming results. These 5-axes system are composed of precision AC servo motor stages (4-axes) and PZT actuator (1-axis). A PZT actuator is used in a precision actuating axis because it can be operated in the nano scale stroke resolution. This micro dieless incremental forming system has the advantage of minimization in manipulating distance and working space. As equipment and tools become smaller in size, minute inertia force and high natural frequency can be obtained. Therefore, high precision forming performance can be obtained. This allows the factory to quickly provide the customer with goods because the manufacturing system and process are reduced. To construct this micro manufacturing system, many technologies are necessary such as high stiffness frame, high precision actuating part, structural analysis, high precision tools and system control. To achieve the optimal forming quality, the micro dieless forming system is designed and made with high stiffness characteristic.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.122-128
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• 2004

In order to make a doubly-curved sheet metal effectively, a sheet metal forming process has been developed by adopting the flexibility of the incremental forming process and the principle of bending deformation which causes slight deformation in thickness. The developed process is an unconstrained forming process with no holder. For this study, the experimental equipment is set up with the roll set which consists of two pairs of support rolls and one center roll. In the experiments using aluminum sheets, it is found that the curvature of the formed sheet metal is determined by controlling the distance between supporting rolls in pairs and the forming depth of the center roll and it also depends on the thickness of the sheet metal. In order to check the effect of process parameters on the generation of sheet metal curvatures in this process, the orthogonal array is adopted. From the experimental results, among the process parameters, the distance between supporting rolls in pairs along the direction of one principal radius of curvature as well as the forming depth and the thickness of the material is shown to influence the generation of curvature in the same direction significantly. That is, the other distance between supporting rolls in pairs which are not located in the same direction of one principal radius of curvature, does not have an significant effect on the generation of the curvature in that direction. It mainly affects the generation of curvature in its own direction with the forming depth and the thickness of the material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.08a
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• pp.53-57
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• 2003

In order to make a doubly curved sheet metal effectively, a sheet metal farming process has been developed by adopting the flexibility of the incremental forming process and the principle of bending deformation which causes slight deformation to thickness. The developed process is an unconstrained forming process with no holder. For this study, the experimental equipment is set up with the roll set which consists of two pairs of support rolls and one center roll. In the experiments using aluminum sheets, it is found that the curvature of the formed sheet metal is determined by controlling the distance between supporting rolls in pairs and the forming depth of the center roll and it also depends on the thickness of the sheet metal. In order to check the effect of process parameters on the generation of sheet metal curvatures in this process, the orthogonal array is adopted. From the experimental results, among the process parameters, the distance between supporting rolls in pairs along the same direction of one principle radius of curvature as well as the forming depth and the thickness of the material is shown to influence the generation of curvature in the same direction significantly. That is, the other distance between supporting rolls in pairs which are not located in the same direction of one principle radius of curvature, does not have an significant effect on the generation of the curvature in that direction. It just affects the generation of curvature in its own direction mainly with the forming depth and the thickness of the material.