• 제목/요약/키워드: DP-Steel

검색결과 111건 처리시간 0.03초

항복함수 및 경화모델에 따른 DP980 강판의 스프링백 예측 (Spring-back Prediction of DP980 Steel Sheet Using a Yield Function with a Hardening Model)

  • 김재홍;강길석;이현석;김지훈;김병민
    • 소성∙가공
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    • 제25권3호
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    • pp.189-194
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    • 2016
  • In the current study, spring-back of DP980 steel sheet was numerically evaluated for U-bending using a yield function with a hardening model. For spring-back prediction, two types of yield functions - Hill'48 and Yld2000-2d - were considered. Additionally, isotropic hardening and the Yoshida-Uemori model were used to investigate the spring-back behavior. The parameters for each model were obtained from uniaxial tension, uniaxial tension-compression, uniaxial tension-unloading and hydraulic bulging tests. The numerical simulations were performed using the commercial software, PAM-STAMP 2G. The results were compared with experimental data from a U-bending process.

Cu-Si 삽입금속을 이용한 DP강의 MIG 아크 브레이징 접합부의 미세조직과 기계적 성질 (Microstructure and Mechanical Properties of Gas Metal Arc Brazed Joint of DP Steel with Cu-Si Filler Metal)

  • 조욱제;윤태진;곽승윤;이재형;강정윤
    • Journal of Welding and Joining
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    • 제34권5호
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    • pp.70-76
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    • 2016
  • In this study, Microstructure and tensile properties in arc brazed joints of 1000MPa grade DP steel using Cu-Si insert metal were investigated. The fusion zone was composed of Cu phase which solidified a little Fe and Si. The former phase formed due to dilute the edge of base material by arc, although Fe was not solid solution in Cu at the room temperature. Cu3Si particles formed by crystallization at $1100^{\circ}C$ during faster cooling. After the tensile shear test, there are no differences between the brazed joint efficiencies. The maximum joint efficient was about 37% compared to strength of base metal. It is better than that of arc brazed joint of DP steel using Cu-Sn filler metal. Fracture position of all brazing conditions was in the fusion zone. Crack initiation occurred at three junction point which was a stress singularity point of upper sheet, lower sheet and the fusion zone. And then crack propagated across the fusion zone. The reason why the fracture occurred at fusion zone was that the hardness of fusion zone was lower than that of base material and heat affected zone. The correlation among maximum load and hardness of fusion zone and EST at fractured position was $R^2=0.9338$. Therefore, this means that hardness and EST can have great impact on maximum load.

고Si DP980강 스폿 용접 특성에 미치는 Phosphorus (P) 및 in-situ 후열처리 펄스 조건의 영향 (Effects of Phosphorus and in-situ Post-heat Pulse Conditions on Resistance Spot Weldability of High Si DP980 Steel Sheet)

  • 최두열
    • Journal of Welding and Joining
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    • 제33권6호
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    • pp.21-26
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    • 2015
  • Recently, application of UHSS(Ultra High Strength Steels) whose tensile strength is over 1000MPa to car body structure are growing due to great needs for light weighting and improved crash worthiness. However, their poor weldability is one of obstacles to expand selecting to car body. In this study, effect of Phosphorus contents on resistance spot weldability of high elongation DP980 steel whose Si content is over 1% was investigated. The cross tension strength (CTS) was decreased showing partial interface fracture as Phosphorus content increase because of solidification segregation of Phosphorus. In order to improve resistance spot weldability by modification of welding condition, in-situ post-weld heating pulse was introduced after main pulse. The optimum cooling time between main and post pulse and post-pulse current condtion were determined through FEM welding simulation and DOE tests. The CTS was increased about 1.5 time showing plug fracture. The decrease of Phosphorus segregation was found to be a major reason for weld ductility and CTS improvement.

경량콘크리트를 사용한 합성 철선트러스 데크의 푸쉬 아웃 성능 실험 (Push-out Performance Test of Composite Steel Truss Deck using Light Weight Concrete)

  • 최병정;문효진;한홍수;한권규
    • 한국강구조학회 논문집
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    • 제21권1호
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    • pp.15-26
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    • 2009
  • 본 연구의 목적은 실험을 통하여 복합 데크슬라브 시스템에 사용되는 쉬어 커넥터의 전단 성능을 연구하는 것이다. 경량콘크리트와 선조립 철선트러스를 사용하여 복합 데크슬라브를 가진 6개의 실험체를 제작하여, Push-out test를 실시하였다. 실험체는 철선트러스와 아연강판의 설치유무로 구분하여 DP, NDP, Solid의 세 가지 그룹으로 분류하였다. 전단 성능 실험을 통하여 실험체의 파괴양상, 거동, 하중-변위 관계를 분석하고, 실험값과 기존의 기준식을 비교하였고, 다음과 같은 결론을 도출하였다. 첫째, DP 및 NDP 계열의 파괴는 스터드 파괴이며, Solid계열의 파괴는 콘크리트 파괴였다. 둘째, 전단내력을 확인한 결과 NDP계열이 가장 우수한 내력을 갖는 것으로 나타났다. 셋째, 각 실험체의 스터드는 유사한 전단거동을 하였고, 스터드와 콘크리트는 항복시점까지 일체 거동을 하였다. 넷째, 다른 두 개의 기준식과 비교했을 때 ACI318-05의 기준식이 가장 근접한 스터드 전단력을 예측할 수 있는 것으로 확인되었다.

980MPa급 초고장력 강판의 자동차 프런트 사이드 멤버 부품 성형에 관한 연구 (A Study on the Forming of Automotive Front Side Member Part with Ultra High Strength Steel of DP980)

  • 차승훈;이상곤;고대철;김병민
    • 소성∙가공
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    • 제18권1호
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    • pp.39-44
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    • 2009
  • This paper is concerned with forming technology of an automotive front side member part with ultra high strength steel sheet of DP980. The forming technology considered in this paper is the draw & form type, which installs the upper pad and lower pad to produce the complicated shape of ultra high strength steel sheet. In order to produce sound product, comparison between form type and draw & form type and between draw type and draw & form type are investigated by FE-analysis. FE-analysis is carried out with commercial sheet metal forming analysis S/W, DYNAFORM. It was shown from FE-analysis that the draw & form type satisfied the required specifications such as the dimensional accuracy and soundness of automotive front side member part. The effectiveness of the analytical result was verified by the experiment. From this investigation, the draw & form type is proved to be able to supply useful forming technology in forming ultra high strength steel.

고강도 DP강과 TRIP강의 표면 수소 주입량에 따른 수소취성평가 (The Change of Microstructures According to the Charging Amounts of Hydrogen in High Strength DP Steels and TRIP Steel)

  • 박재우;이철치;강계명
    • 한국표면공학회:학술대회논문집
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    • 한국표면공학회 2012년도 춘계학술발표회 논문집
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    • pp.252-253
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    • 2012
  • 음극전기분해법을 이용하여 고강도 DP강과 TRIP강에 수소를 강제 주입시켜, 시험편 내 수소량을 정량적으로 분석하였고, 표면하 미소경도분포 측정과 소형펀치시험 및 파단면 관찰을 통하여 수소주입량에 따른 고강도 박강판재의 수소침투 및 수소취화거동을 평가하고자 하였다. DP강은 강도가 클수록 높은 수소량으로 조사되었고, TRIP강은 DP강에 비해 주입된 수소량이 적은 것으로 조사되었다. 또한 미소경도분포 및 소형펀치시험에서도 DP강은 TRIP강에 비해 수소취성에 민감성이 높은 것으로 평가되었다.

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마찰교반용접(FSW) 된 알루미늄 합금(AA6111-T4, AA5083-H18) 및 DP강 판재의 인장 실험시 파단 현상 해석 (Analysis of Failure Phenomena in Uni-axial Tension Tests of Friction Stir Welded AA6111-T4, AA5083-H18 and DP-Steel)

  • 박상준;엄기문;마닝;안강환;정경환;;;;정관수
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2007년도 춘계학술대회 논문집
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    • pp.258-261
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    • 2007
  • Failure phenomena in uni-axial tension test were experimentally and numerically investigated for AA6111-T4, AA5083-H18 and DP-Steel, which were friction-stir welded with the same and different thicknesses. Forming limit diagram(FLD) was measured using hemispherical dome stretching tests for base materials and also predicted by Hill's bifurcation and M-K theories for welded areas. Finite element simulations well predicted hardening behaviors, failure locations as well as failure patterns for the uni-axial tension tests especially utilizing very fine meshes and FLD along with stress softening.

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DP780이 적용된 자동차용 계단형 사이드실의 성형공정 연구 (A Study on the Forming Process of Stair Type Side Sill for Automobile using DP780)

  • 서창희;신효동;정윤철;박춘달;임용희;김영석
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2009년도 추계학술대회 논문집
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    • pp.301-306
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    • 2009
  • High strength steels are widely used for lightweight automobile parts and the control of springback is very important in sheet metal forming. The object of this study is to develop the forming process for stair type side sill made of high strength steel, DP780. Stair type side sill with local formed area and geometry change area can improve stiffness and design freedom but there are a few studies for forming process. The forming technology considered in this paper is form type process, which have many advantages for farming of high strength steel compared with draw type process. Finite element analysis is carried out to predict formability and springback. It is shown that angle calibration of die is essential for reducing springback, and local forming involving bead is effective to control springback also. The effectiveness of local forming and angle calibration is verified by experimental.

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Investigation of Galling In Forming Galvanized Steel Sheet

  • Altan, Taylan;Kardes, Nimet;Kim, Hyunok
    • Corrosion Science and Technology
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    • 제10권1호
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    • pp.1-5
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    • 2011
  • The major purpose of the present study is to evaluate the performance of various galvanized (GI) or galvannealed (GA) mild steels and AHSS in stamping applications. Finite Element Analysis (FEA) of selected stamping operations was conducted to estimate the critical pressure boundary conditions that exist in practice. Using this information, laboratory tribotests, e.g. Twist Compression (TCT), Deep Drawing (DDT) and Strip Drawing (SDT) Tests, were developed to evaluate the performance of selected lubricants and die materials/coatings in forming galvanized steels of interest. The sheet materials investigated included mild steels and AHSS (e.g. DP600 GI/GA, DP780 GI/GA, TRIP780 GA and DP980 GI/GA). Experimental results showed that galvanized material resulted in more galling, while galvannealed material showed more powdering and flaking. The surface roughness and chemical composition of galvanized sheet materials affected the severity of galling under the same testing conditions, i.e. lubricants and die materials/coatings. The results of this study helped to determine the critical interface pressure that initiates lubricant failure and galling in stamping selected galvanized sheet materials. Thus, to prevent or postpone the critical interface conditions, the results of this study can be used to select the optimum combination of galvanized sheet, die material, die coating and lubricant for forming structural automotive components.