• Transactions of Materials Processing
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• v.23 no.5
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• pp.297-302
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• 2014

The current paper introduces work that was conducted during the development of a stamping die for a reinforce center pillar made from high strength steel. In the current study, the Bauschinger effect on the springback analysis was studied by comparing simulation results with real panels, which are currently in production. For a complicated part shape, quantitative measurements of the deformed shape are not easy in general to obtain. An adjustment procedure of the shape data for some chosen sections has been suggested to improve the accuracy of the quantitative measurements. The results show that the kinematic hardening model provides more accurate results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.465-468
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• 2008

In this paper, ABAQUS, one of the implicit finite element codes, is used to analyze the U-channel Draw benchmark problem of NUMISHEET 2005. Forming and springback stages have been done consecutively to compare their results with the experimental ones. The main measures for comparing are the side wall curl and angle. The result by numerical analysis are shown generally to be correspondent with the experimental results that the max. error is confined under about 10%.

• Design & Manufacturing
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• v.6 no.1
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• pp.63-66
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• 2012

In the manufacturing of a LCD TV bottom chassis, the distortion after forming should be suppressed below pre-defined amount to avoid contact with electric components. Finite element analysis procedure of forming and springback of a LCD TV bottom chassis is developed to investigate the distortion behaviour. It is shown that after the first forming large distortion occur due to uneven metal flow induced by various embossings. In the second forming, distortion is decreased by introducing bead that absorbs the excessive metal flow. It is proved that analysis method could describe these behaviour effectively. The developed analysis method can be used to find the proper location and shape of bead more quickly and effectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.192-198
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• 2005

In this paper, a systematic attempt for estimating geometric dimensions of cold forgings is made by finite element method and a practical approach is presented. In the approach, the forging process is simulated by a rigid-plastic finite element method under the assumption that the die is rigid. With the information obtained from the forging simulation, die structural analysis and springback analysis of the material are carried out. In the springback analysis, both mechanical load and thermal load are considered. The mechanical load Is applied by unloading the forming load elastically and the thermal load is by cooling the increased temperature due to the plastic work to the room temperature. All the results are added to predict the final dimensions of the cold forged product. The predicted dimensions are compared with the experiments. The comparison has revealed that predicted results are acceptable in the application sense.

• Journal of Korean Society for Quality Management
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• v.36 no.4
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• pp.29-36
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• 2008

최근 자동차 경량화를 위한 부단한 노력이 진행되고 있다. 이 목적에서, HSS (high strength steel)는 전통적인 연강 (mild steel)의 대안으로 널리 사용되고 있다. 본 연구의 목적은 판금의 형단조에 있어서의 공구와 공정설계를 위하여 HSS의 스프링백(springback)을 정확히 예측하기 위한 성공적인 방법론을 추구하고자 함이다. 연구를 위하여 먼저 스프링백의 개념과 그의 측정치들을 설명했으며 U-draw bending 시험을 수행하였다. 시험 결과 및 선정된 파라메터들 중심의 수행평가기준에 근거하여, 주어진 파라메터 조합들을 중심으로 유한요소 해석을 수행하였다. 직교배열을 통하여 스프링백에 대한 인자 효과들을 포괄적으로 분석하였으며 최적 인자 조합들을 도출하였다. 이 과정에서 직교배열상의 한 조합 전체의 데이터가 가용하지 않는 문제가 수반되었으며, 반복적으로 signal-to-noise 비(ratio)를 개선해가는 기법을 적용하여 해결하였다.

• Transactions of Materials Processing
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• v.15 no.2 s.83
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• pp.164-171
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• 2006

The die development of the high-strength steel sheet is very different with that of the common steel sheet. Especially, the springback problem of the high-strength steel is serious in the stamping process. This paper showed the optimized die development of the high-strength steel sheet which was based on the experimental measured and simulated springback auto panel stamping process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.1 s.232
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• pp.156-162
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• 2005

Stouts are frequently used throughout the human body, but the most critical areas are in coronary arteries. They open pathways in vessels and supply blood directly to the heart muscle. To simulate behavior of expansion for the coronary stent by balloon, the commercial finite element code LS-DYNA and ANSYS were used in the analysis. The explicit method is used to analyze the expansion of the stent and the implicit method is performed to simulate the springback that developed in a stent after the balloon pressure has been removed. Finally the experimental results for the expansion of the PS153 stents were compared with the FEM results. The springback was measured with the stents subjected to no external pressure to which stents are subjected in vivo. The simulated results were in good agreement with experimental results. Standard mechanical characteristics such as stress, plastic strains, and springback can be derived from the numerical results. These data can be used to determine maximum expansion diameter without fracture and expansion pressure considering elastic recoil.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.06a
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• pp.83-94
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• 1998

An analysis system for sheet metal forming has been developed to improve the design and tryout process by predicting the deformation behaviour more precisely. This analysis system consists of forming analysis, springback analysis and post processor modules. The more accurate prediction of stress history can be achived due to the improved contact algorithm. Successive simulation of several processes can be carried out conveniently without interrupt by the improved data management of the developed system. The error of data transfer between forming analysis and springback analysis is minimized using the proper shell element. Several benchmark test results and practical results are presented to show the effectiveness and reliability of this program.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.89-92
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• 2007

The metallic bipolar plate in PEMFC is widely used for automotive driving because of its advantages, i) high strength, ii) high chemical stability, iii) low gas permeability and iv) applicability to mass production. Especially, the metallic bipolar plate which is manufactured with the sheet metal stamping process can be applied in automotive PEMFC with less volume and weight because of its thin thickness but the formability and springback problems arise in real manufacturing process. The assessment for formability and springback of metallic bipolar plate should be performed before making stamping die sets. In this work, the methodology for determining the allowable draft angle of flow passage is introduced by using finite element analysis. In analysis results, as the draft angle of flow passage increase, the major strain and thinning is increase with exponential function. The allowable draft angle without fracture is presented by fitting the results. Additionally, the staking results with manufactured metallic bipolar plates by stamping process is presented.

• Transactions of Materials Processing
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• v.18 no.3
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• pp.236-244
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• 2009

In response to growing environmental and collision-safety concerns, the automotive industry has gradually used high-strength and ultla-high-strength steels to reduce the weight of automobiles. In order to overcome inherent process disadvantages of these materials such as poor formability and high springback at room temperature, hot forming has recently been developed and adopted to produce some important structural parts in automobiles. This method enables manufacturing of components with complex geometric shapes with minimal springback. In addition, a quenching process may enhance the material strength by more than two times. This paper investigates mechanical and forming characteristics of high-strength boron-alloyed steel with hot forming, in terms of hardness, microstructure, residual stress, and springback. In order to compare with experimental results, a finite element analysis of hot forming process coupled with phase transformation and heat transfer was carried out using DEFORM-3D V6.1 and also, to predict high temperature mechanical properties and flow curves for different phases, a material properties modeler, JMatPro was used.