• Title/Summary/Keyword: AHSS

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Design of Drawbeads for Advanced High Strength Steel Sheet Forming (초고강도 강판 성형용 드로비드 설계)

  • Kim, B.G.;Jeong, J.Y.;Kim, D.J.;Kim, G.S.;Keum, Y.T.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.420-423
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    • 2009
  • In this study, the guideline for designing the drawbeads used in the stamping dies for advanced high strength steel (AHSS) sheets is investigated. In the drawbead drawing test, the drawbead forces for verifying the equivalent drawbead model(EDM) and the sheet strains for finding marginal strains from $FLC_0$ are measured. In the finite element analysis (FEA), the bending allowance, R/t, is obtained. Based on the forming and bending allowances obtained, the design guideline of the drawbead for determining height and width, which depends on the restraining force and the forming allowance, is prepared by using EDM.

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Impact Performance Evaluation of Advanced High-strength Steel Sheets Based on Combined Continuum-Fracture Mechanics (복합 연속체-파괴 역학에 기초한 초고강도강의 충격 특성 평가)

  • Ma, N.;Park, T.;Kim, D.;Seok, D.;Kim, Chong-Min;Chung, K.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.231-234
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    • 2009
  • Based on combined continuum-fracture mechanics, fracture criterion was utilized to predict impact performance of advanced high-strength steel sheets: 340R and TWIP940. The macro-crack propagation behavior at high stress triaxiality was characterized by V-notch tests while deformation behavior at high strain rate was characterized by simple tension tests with various cross head speeds. The characterized mechanical properties were incorporated into the FE program ABAQUS/Explicit to simulate the charpy impact tests, which showed good agreement with experiments.

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Strength Estimation Model of Resistance Spot Welding in 780MPa Steel Sheet Using Simulation for High Efficiency Car Bodies (시뮬레이션을 이용한 고효율 차체용 780MPa급 강판의 저항 점 용접 강도 예측 모델 개발)

  • Son, Chang-Seok;Park, Young-Whan
    • Journal of Power System Engineering
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    • v.19 no.2
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    • pp.70-77
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    • 2015
  • Nowadays, car manufacturers applied many high strength steels such AHSS or UHSS to car bodies for weight lightening. Therefore, a variety of applied steel sheet to car bodies increased and the needs of simulation to evaluate weldability also increased in order to reduce the cost and time. In this study, resistance spot welding simulations for DP 780 Steel with 1.0 and 1.4 mm thickness were conducted with respect to lobe curve. 2 regression models to estimate tensile shear strength were suggested and they were second order polynomial regression model and optimized second order regression model. The performance of these models was evaluated in terms of the coefficient of determinant and average error rate.

Developing Trends of Hot-roiled High Strength Steel Sheets for Automotive Chassis (자동차 샤시용 고강도 열연강판 개발 동향)

  • Jo, Yeol-Rae;Kim, Seong-Gyu
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.05a
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    • pp.341-348
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    • 2004
  • Recently deveoped HSS of POSCO and commerciallizing activities were introduced. 590DP, 590FB, 780TRIP. In this year, another three type of hot rolled AHSS will be developed and try to commerciallize with auto makers. 780FB, 780DP and 980CP. We have future plan to develope ultra high strength steels 980TR, 1170CP.

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Effect of Strain Rate on the Anisotropic Deformation Behavior of Advanced High Strength Steel Sheets (변형률속도에 따른 고강도 강판의 이방성 변화에 관한 연구)

  • Huh, J.;Huh, H.;Lee, C.S.
    • Transactions of Materials Processing
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    • v.20 no.8
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    • pp.595-600
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    • 2011
  • This paper investigates the effect of strain rate on the anisotropic deformation behavior of advanced high strength steel sheets. Uniaxial tensile tests were carried out on TRIP590 and DP780 steel sheets at strain rates ranging from 0.001/sec to 100/sec to determine yield stresses and r-values at various loading angles from the reference rolling direction. R-values were determined by the digital image correlation technique. Hill48 and Yld2000-2d yield functions were tested for their capability to describe the plastic deformation anisotropy of the materials. Initial yield loci were constructed using the Yld2000-2d yield function, which adequately described the anisotropic behavior of the materials. The shape of the initial yield loci was found to change with different strain rate, and the anisotropic behavior decreased with increasing strain rate.

Process Design of Seat Rail in Automobile by the Advanced High Strength Steel of DP780 (DP780 초고장력 강판을 이용한 자동차용 시트레일의 성형공정 설계)

  • Ko, D.C.;An, J.H.;Jang, M.J.;Bae, J.H.;Kim, C.H.;Kim, B.M.
    • Transactions of Materials Processing
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    • v.17 no.3
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    • pp.197-202
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    • 2008
  • The control of springback is very important in sheet metal forming since springback affects the dimensional inaccuracy of product. The object of this study is to design the manufacturing process for the improvement of the performance of seat rail by DP780. The influence of process variables such as bend angle and pad force on the springback has been firstly investigated through the comparison between the results of FE-analysis and trial out for initial design based on designer's experience. The process variables of the initial design have been modified in order to improve the dimensional accuracy of seat rail from the prediction of springback by FE-analysis. It was shown from experiment that the improved design satisfied the required specifications such as the dimensional accuracy and the strength of seat rail.

Application Technology of high strength hot-rolled steels for automotive lightweight chassis parts (고강도 열연강판의 경량 자동차 샤시부품 개발)

  • Kim J. C.;Kwon T. W.;Jeon J. H.;Son K. S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.10a
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    • pp.43-45
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    • 2005
  • For application of advanced high strength hot-rolled steels (i.e. DP590, DP780) to automotive lightweight chassis parts, various technologies from design to forming test, optimization of welding condition and investigation of coating properties were tried. The target part of this study was automotive rear sub frame and we could make $16.8\%$ weight reduction by reducing the material thickness and optimizing the design. In addition, the formability and weldability of the newly developed AHSS, DP780, were evaluated.

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Prediction of Deformation Mechanism and Fracture for an Auto-Part with Advanced High Strength Steel using Solid Element and Damage Theory (연속체요소 및 손상이론을 이용한 고강도강 차량부품의 변형기구와 파단 예측)

  • Kwak, J.H.;Yoon, S.J.;Kim, S.H.;Park, J.K.;Han, H.G.
    • Transactions of Materials Processing
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    • v.26 no.5
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    • pp.293-299
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    • 2017
  • In this paper, finite element stamping analysis was carried out for the front lower arm to examine the applicability of solid element with damage theory to predict shear fracture phenomena induced by sheared edge as well as deformation mechanisms. Mechanical properties related to deformation and damage theory were determined from tensile test. Shear fracture was predicted by normalized Cockcroft-Latham model with initial imposition of the damage value along the sheared edge. Simulation results illustrated that the analysis with solid element and damage theory predicted edge profile, strain distribution, and forming load more accurately than the analysis with shell element. Simulation with solid element can also predict the shear fracture more exactly comparing to analysis with shell element and forming limit curve.

Evaluation of Forming Limits of Automotive Muti-phase Steel Sheets (자동차용 다상복합조직강판의 성형한계 평가)

  • Lee, S.Y.;Jeong, J.Y.;Park, S.H.;Kim, S.;Keum, Y.T.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.195-198
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    • 2009
  • In this study, in order to get the forming limit of AHSS sheet in the negative minor strain region, the shapes of die corner and drawbead are redesigned by employing the Taguchi's design of experiment method and the FEM forming simulation. With the redesigned FLD tool, the forming limit tests of automotive multi-phase(Dual Phase and Complex Phase) steel sheets which induce the normal fractures on the blank are performed.

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Study on the Springback Reduction of Automotive Advanced High Strength Steel Panel (자동차 초고강도 강판 패널의 스프링백 저감에 관한 연구)

  • Kim, B.G.;Lee, I.S.;Keum, Y.T.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.191-194
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    • 2009
  • Very big springback in advanced high strength steel(AHSS) sheets invokes undesired shape defects, which can be eliminated by the tool surface correction method or the forming process control method. Since the springback reduction by controlling the forming process is limited, in this study, the die correction method which finds die correction from the relationship between die design variable and springback is introduced to achieve springback reduction and is applied to the automotive side rail to reduce the springback of 75.8% within the assembly limit of 1 mm.

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