• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.207-218
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• 1997

A new blank design method is introduced to predict the blank shape and the strain distribution in the sheet metal forming process. This method deals with only one step from the final shape to the initial blank using the ideal forming theory. Based on this theory, a three-dimensional membrane finite element code has been developed to design an initial blank in the sheet metal forming process. In this paper, the designs of initial blanks for forming a cylindrical cup, a rectangular cup, and a front fender are presented as examples. Also, it compares the two shapes, the target shape with the shape which is deformed from the initial blank using the FEM analysis code. The results illustrate the information that this direct design code is useful in the preliminary design state.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.55.2-55.2
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• 2011

최근 자동차용 강판을 대체하기 위한 재료로서 알루미늄 합금에 대한 관심이 높아지고 있다. 알루미늄 합금은 철강 재료에 비해 비강도가 높으며 재활용이 용이하고 내식성이 뛰어난 활용 가치가 높은 소재이다. 하지만 기존의 강판을 알루미늄 합금으로 대체하기 위해서는 높은 경제성, 강도 및 성형성이 요구되고 있는 현실이다. 따라서 고강도 알루미늄 합금 판재를 경제적으로 제조하기 위한 제조 공정기술 및 후가공 기술의 개발이 필요하다. 본 연구에서는 기존의 쌍롤 박판주조법에 비대칭 노즐을 이용하여 높은 주조 속도를 유지하면서도 중심 편석 및 열간 균열을 완화시켜 첨가되는 용질 원소의 양을 증가시켰다. 제조한 다양한 조성을 가진 알루미늄 합금 판재의 후속 압연성, 기계적 특성 및 성형성을 평가하기 위하여 미세조직 및 집합조직을 분석하였으며 이에 따른 실용화 가능성을 평가하였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.36-39
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• 1998

To predict strain distributions and weld line movements in the forming processes of tailored blank sheets, the 2-dimensional finite element formulation is developed. The welding zone is modelled with the several, narrow finite elements. The material properties of weld elements are calculated from those of base metals, based on the experimental evaluation. To verify the finite element formulation developed, the forming process of an autobody door inner panel section is simulated. FEM predictions are compared and showed good agreements with experimental measurements.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.32-35
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• 1998

The material properties and forrnabilities of tailored blanks are evaluated by experimental tests. In the tensile test, the gradient of strength coefficients of the heat affected zone associated with the welded line width represents the quality of a welded part. In the hemispherical dome punching test, the plane strain state of the welded line is observed. In the squared cupping test, the thin side is stretched more than the thick side in the stretch mode, while both sides are similarly stretched in the draw mode. In the 2D draw test, FLCo is measured in a simple manner and the forming defects of the tailored blanks with the same thickness are found.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.125-136
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• 2012

Wrinkle and fracture are two major defects frequently found in the sheet metal forming process. In this process there are more than one design attributes to optimize and several uncontrollable factors which cannot be ignored in determining the optimal values of design variables. Therefore, attempts to reduce defects through a traditional optimization technique are often led to failures. In this research, a new design method for reducing the wrinkle and fracture under uncontrollable factors is presented by using decision-making theory. To avoid the psychological difficulties in determining the scaling constants of the multi-attribute utility function by using the ordinary lottery questions, a pair-wise comparison procedure is adapted to avoid this problem. The effectiveness of the proposed method is illustrated through a robust design of sheet metal forming process of a side member of an automotive body.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.318-321
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• 2005

The shell part is made of 2-layered blank because of functional requirements. To investigate the draw formability in this kind of part, the 2-layered sheet metal forming analysis process should be stipulated. First of all, treatment of contact with each blank must be considered to prevent the penetration on the each blank. Subsequently, applying the draw bead force is considered carefully because application of drawbead force for analysis is different with equivalent drawbead force. Formability as like crack, neck and wrinkles is estimated by FLD(Forming Limit Diagram) and thinning. A feasibility of the 2-layered sheet metal forming analysis process study is verified compare 2-layered sheet metal forming analysis with experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.402-405
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• 2005

Such press-forming process are the used machine ability and the characteristic, used material, tile accuracy of the part, condition of a process are considered the designed. In order to estimate in automotive sheet forming processes used AutoForm software. A through in simulation result comparison with experimentation result, it was possible to know that much the same estimated spring-back through a forming analysis. By making apply this to an industrial site the productivity improvement and cost reduction etc. effect able was predicted.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.228-233
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• 2002

TWB(Tailor Welded Blanks) is one of the recent techniques to reduce the weight and cost of the body members. To apply the TWB technique, we must decide the position of the welding line and the thickness of the welded blanks. Although many researchers have tried to check the formability of welded blanks, there are not so many researches from the structural point of view. In this paper, the TWB technique is applied to combine the door inner panel and the hinge face panel into one piece. The finite element structural analysis of the door assembly leads to the final design of the tailor welded door inner panel, which shows the mass reduction of 1.08kg without the sacrifice of the structural stiffness. The structural stiffness analysis includes the frame stiffness analysis, the belt line stiffness analysis, the door sagging analysis and the vibration analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.27-30
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• 2007

In order to measure the friction coefficient used in sheet metal forming analysis, a friction tester was manufactured and friction tests were performed in various forming conditions. Based on the friction coefficients measured, a mathematical friction model was constructed in terms of lubricant viscosity, blank holding force, punch velocity and sheet roughness. In addition, the effect of the number of forming parameters in the calculation of friction coefficient on the accuracy of sheet metal forming analysis was investigated by comparing the punch loads obtained from the FEM simulation, in which the friction coefficients were determined by a few parameters with the experimental measurement.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.41-48
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• 2013

Springback is a very typical dimensional discrepancy phenomenon, which occurs usually on the final stamping parts after the tool loading is removed. Variation of springback leads to amplified variations and problems during assembly of the stamped components, in turn, resulting in quality issues. The variations in the properties of the incoming material and process parameters are the main causes of springback variation. In this research, a robust design methodology which combines orthogonal array based experimental design and design space reduction skim to reduce the springback variation for advanced high strength steel parts in sheet metal forming is suggested. The concept of design space reduction is adapted in the experimental design setup to improve the quality of the obtained solution. The effectiveness of the proposed procedures is illustrated through a robust design of springback in metal forming process of a cross member of auto body.