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배기현(Gihyun Bae),송정한(Junghan Song),허훈(Hoon Huh),김세호(Seho Kim),박성호(Sungho Park) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Draw-bead is applied to control the material flow in sheet metal forming process and improve the product quality by providing sufficient draw-bead restraining force (DBRF). However, actual die design depends mostly on the trial-and-error method without the accurate prediction of DBRF and the normal force. Die design with the predicted value of them can be utilized effectively to reduce the cost and time. In order to construct a prediction model, process parameters, which affects significantly to DBRF and the normal force, are selected as design variables. At first, the prediction model without considering the effect of BHF is constructed using the Box-Behnken design which is the most representative DOE method. Results obtained from finite element analysis are approximated with the second order regression model. It provides the maximum value of DBRF and the normal force because the male bead fully presses down the sheet. After that, the variation of DBRF with respect to the change of BHF is approximated with the first order regression model by adopting the fractional factorial design. It provides the equation for the scale factor with respect to the change of process parameters. Using two equations, DBRF can be obtained in general sheet metal forming process. To verify the reliability of the prediction model, results obtained from the prediction model are compared with them obtained from finite element analysis.
연선공정 실험을 통한 이층연 스틸코드의 교정도 예측모델 개발
배기현(Gihyun Bae),허훈(Hoon Huh),이준우(Junwu Lee),이병호(Byungho Lee) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
This paper proposes prediction models for the quality of a double-layer steel cord. Main process parameters were first selected from experiments according to the usage of straightening devices in the stranding machine. The stranding experiments for selected process parameters were conducted based on the experimental table established by the Taguchi method. Prediction models were constructed from the regression analysis with the measured assessment items of a doublelayer steel cord. The prediction models constructed can be utilized as a design guideline effectively for the stranding process design of a double-layer steel cord.
드로우비드 저항력과 수직력의 유한요소해석 기반 예측모델
배기현(Gihyun Bae),허훈(Hoon Huh),박성호(Sungho Park) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper deals with the simulation-based prediction model to predict the restraining force and the normal force of draw-beads in sheet metal forming process. The modified DOE method is newly proposed in order to construct the prediction model for the equivalent draw-bead and the finite element analysis is utilized to calculate equivalent draw-bead forces in each design case. The reliability of the finite element analysis is verified by comparing with the experiment. To increase the accuracy of prediction models, a special technique is applied for normalizing the estimated force in each design case. Finally, the accuracy of constructed prediction models is verified by comparing the predicted result with the experimental result. It demonstrates that the simulation-based prediction model can provide accurate equivalent draw-bead forces. The constructed prediction model can not only provide the restraining and the normal force conveniently with respect to the draw-bead design for the simulation of sheet metal forming process, but also be utilized to determine the dimension of draw-beads at actual die design.
측면충돌 시 소성변형 특성을 고려한 단순 B-필라 모델의 최적설계
배기현(GiHyun Bae),송정한(JungHan Song),허훈(Hoon Huh),김세호(SeHo Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_2
This paper is concerned with the optimum design of the B-pillar assembly induced by the high-speed side impact of the vehicle. In order to simulate the deformation behavior of the B-pillar assembly, the simplified finite element model of a B-pillar and a moving deformable barrier are developed based on results of the crash analysis of the full vehicle model. In order to optimize the deformation shape of B-pillar, S-shaped deformation is targeted for guaranteeing the reduction of injury level of the passenger dummy in the crash test. Tailor welded blank is adopted in the simplified B-pillar model to control the deformation shape of B-pillar assembly. The thickness distribution of each part which constitutes the simplitied mode is initially selected as a design parameter. Important design parameters which have effects on the deformation mechanism are selected with sensitivity analysis based on the design of experiment technique. The objective function is constructed so as to minimize the weight and lead to the S-mode deformation shape. The results in this paper fully show that the design criterion of B-pillar model can be simply applied to the part design at the trial design stage for confronting the side impact test such as US-SINCAP and EURO-NCAP.
고강도 강판을 적용한 단순 측면충돌 시 센터필라의 최적설계
배기현(Gihyun Bae),허훈(Hoon Huh),송정한(Junghan Song),김세호(Seho Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_3
This paper is concerned with optimum design of a center-pi1lar assembly induced by the high-speed side impact of the vehicle using advanced high strength steels(AHSS). Nowadays steel industries promote ULSAB-AVC project for applying AHSSs as an alternative to improve crash characteristic and fuel efficiency because it is superior comparing with conventional steels in the aspect of strength. Tn order to simulate deformation behavior of the center-pillar assembly, a simplified finite element model is adopted and parts of that are subdivided employing tailor-welded blanks(TWB) in order to control the deformation shape of the center-pillar assembly. The thickness of each part which constitutes the simplified model is selected as a design parameter. Initial design is a result of thickness optimization using conventional steels and factorial design is carried out aimed at the application and configuration of AHSSs to a simplified side impact analysis because it is impossible to considering all combinations of parts. In optimization of the deformation shape of the center-pillar, S-shaped deformation is targeted to guarantee reduction of the injury level of a driver dummy in the crash test. The objective function is constructed so as to minimize the weight and lead to a S-mode deformation shape. After the optimization, the vehicle 'weight is highly reduced comparing with the case of using conventional steels. The result shows that AHSSs can be utilized effectively for the minimization of the vehicle weight and the induction of S-shaped deformation.
ULSAB-AVC모델의 경량화 및 충돌성능을 고려한 설계 가이드라인 개발
배기현(Gihyun Bae),허훈(Hoon Huh),임지호(Jiho Lim),김교성(Gyosung Kim) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
This paper deals with a method to construct a design guideline for the weight reduction and crashworthiness enhancement of an auto-body. To construct a design guideline, a crashworthiness index is newly suggested by considering the crashworthiness sensitivity based on the amount of the energy absorption, the dynamic material properties and the volume of parts. A design guideline is constructed in the side impact condition using the ULSAB-AVC model. Significant parts in the side impact condition are selected based on the amount of the energy absorption during the car crash. According to the change of the material, the thickness and the cross-sectional area of selected parts, the crashworthiness index is calculated and assessment items are measured from crash simulations. A regression analysis is performed to approximate prediction equations of assessment items according to the crashworthiness index. Prediction equations constructed can provide the quantitative crashworthiness of an auto-body without the crash simulation. Therefore, prediction equations can be utilized effectively as a design guideline for the weight reduction and the crashworthiness enhancement of an auto-body.
초기 변형률 및 변형률 속도에 따른 차체 강판의 인장/압축 경화 거동
배기현(Gihyun Bae),허훈(Hoon Huh) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
This paper investigates the effect of the pre-strain and the strain rate on the tension/compression hardening behavior of auto-body steel sheets. To conduct the tension/compression test of auto-body steel sheets, a spring-loaded clamping device was adopted to suppress buckling of specimens. Tension/compression hardening curves was obtained by correcting the friction and biaxiality due to the clamping force during tests. From the hardening curves, the hardening behavior of auto-body steel sheets was compared carefully with respect to the pre-strain and the strain rate. The Bauschinger ratio and the transient behavior in the compression state were quantitatively compared to explain effectiveness of the pre-strain and the strain rate.