• Title/Summary/Keyword: High Strength Steel Sheet

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A Development of Longitudinal and Transverse Springback Prediction Model Using Artificial Neural Network in Multipoint Dieless Forming of Advanced High Strength Steel (초고강도 판재 다점성형공정에서의 인공신경망을 이용한 2중 곡률 스프링백 예측모델 개발)

  • Kwak, M.J.;Park, J.W.;Park, K.T.;Kang, B.S.
    • Transactions of Materials Processing
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    • v.29 no.2
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    • pp.76-88
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    • 2020
  • The need for advanced high strength steel (AHSS) forming technology is increasing as interest in light weight and safe automobiles increases. Multipoint dieless forming (MDF) is a novel sheet metal forming technology that can create any desired longitudinal and transverse curvature in sheet metal. However, since the springback phenomenon becomes larger with high strength metal such as AHSS, predicting the required MDF to produce the exact desired curvature in two directions is more difficult. In this study, a prediction model using artificial neural network (ANN) was developed to predict the springback that occurs during AHSS forming through MDF. In order to verify the validity of model, a fit test was performed and the results were compared with the conventional regression model. The data required for training was obtained through simulation, then further random sample data was created to verify the prediction performance. The predicted results were compared with the simulation results. As a result of this comparison, it was found that the prediction of our ANN based model was more accurate than regression analysis. If a sufficient amount of data is used in training, the ANN model can play a major role in reducing the forming cost of high-strength steels.

저탄소 2상조직강의 열처리공정 조건에 따른 기계적특성 변화

  • Kim, Hun-Dong;Park, Jin-Seong;Mun, Man-Bin
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2010.05a
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    • pp.40.1-40.1
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    • 2010
  • Recently high strength steel sheets with high formability for automotive parts have been being developed to meet the demands for passenger safety and weight reduction of car body. Among these high strength steels, dual-phase steels are regarded as one of the attractive steels due to their excellent mechanical properties including high strength and ductility. However, to be successfully applied to automotive parts they should be corrosion resistant enough to satisfy the required quality of car maker. This also requires their feasibility for galvannealed production including hot dip galvanizability. In this study has been placed on understanding the effects of heat-treatment(austenizing and isothermal treatment) on the microstructures and mechanical properties of a 0.06C-0.03Si-2.0Mn high strength steel for cold forming. The microstructure and phase distribution were examined with eth aids of SEM, EBSD, TEM etc.. Through the study the production of 590MPa grade DP GA steels with good formability and galvaniability were shown to be possible.

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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.

Recent Trends of Coated Sheet Steels for Automotive use

  • Moon, Man-Been
    • Corrosion Science and Technology
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    • v.11 no.2
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    • pp.37-42
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    • 2012
  • Recent issues in the automotive industries are, improvement of fuel efficiency according to the worldwide $CO_2$ regulation, passenger safety through enhanced crashworthiness, superior design and cost reduction due to price fluctuation of raw material. To meet these demands, steelmaking companies are developing advanced high strength steel and new process technologies such as hydroforming, TWB(Tailor Welded Blank), hot stamping and so on. In addition, eco-friendly and high corrosion resistant coating technologies are getting more attention to comply with the environmental regulations. In this paper, reviews and prospects of recent coating technologies for automotive use are presented.

Recent Progress of Automotive Galvanized Steels in Korea

  • Lee, Suk-Kyu;Kim, Jong-Sang;Choo, Wung-Yong
    • Corrosion Science and Technology
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    • v.9 no.6
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    • pp.254-258
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    • 2010
  • Due to the global warming and economic crisis, automakers are currently focusing on the development of high fuel-efficiency vehicles. To accord with these requirements, steelmakers have been trying to develop advanced high-strength steels with improved automotive-related properties. In addition, galvanizing technologies have been developed to improve coating properties for AHSS (Advanced High Strength Steel) such as pre-oxidation and pre-coating, as well as roll dent prevention. In this paper, newly developed products and technologies for automotive galvanized steel sheet are reviewed.

An Evaluation of the Weldability Characteristics on the 4 Lap Spot Welded Joint of Structural Steel Sheets in Automobile (자동차용 강판의 4겹 다층 점용접물의 용접특성 평가)

  • Kim, Hoi-Hyun;Kim, Seong-Su;Baek, Seung-Se;Kwon, Il-Hyun;Yang, Seong-Mo;Yu, Hyo-Sun
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.314-318
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    • 2004
  • This research is conducted to investigate weldability characteristics with various welding conditions on the 4 lap spot welded joint of structural steel sheets in automobile. The relationship between the tensile-shear strength and the indentation depth has been investigated to evaluate the weldability and the optimum welding conditions. The welding current and the welding time have a greatly affect to the tensile-shear strength compared to the electrode force. It was found that the indentation depth has a relatively close relationship with the expulsion occurrence. The optimum welding conditions were proposed for the 4 lap spot welded joint.

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Development of High Strength Steel Body by Hot Stamping (핫스탬핑에 의한 고강도 차체 부품 개발)

  • Lee, D.H.;Kim, T.J.;Lim, J.D.;Lim, H.J.
    • Transactions of Materials Processing
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    • v.18 no.4
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    • pp.304-309
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    • 2009
  • Quenchable boron steel is a new type of high strength steel to reduce the weight of automobiles and maintain the safety conditions. Quenchable blanks can be hot-stamped and hardened in a water-cooled tool to achieve high strength. In this paper, new alloy for hot stamping is designed based on requirement of mechanical properties and two types of surface coating are investigated in viewpoints of oxidization and exfoliation. An automotive part of center pillar is manufactured by hot-stamping using Al-Si coated sheet. The performance of developed part is compared by static compression test and side impact crash test.

Development of 590MPa Grade Galvannealed TRIP Steel Sheets containing Low Silicon Contents for High Strength and Formability (차량구조용 고강도 고성형성 590MPa급 Si 저감형 변태유기소성 합금화 용융아연 도금강판의 개발)

  • Chi, Kwang-Sub;Kim, Yong-Hee;Kim, Byoung-Il
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.6
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    • pp.141-147
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    • 2008
  • Hot-dip galvannealed sheet (GA) with high strength of 590MPa grade in tensile strength, has developed for automotive applications. However, for a successful application, the microstructure and galvannealing behavior of galvannealed TRIP steel sheets must be strictly controlled. High silicon contents steel has problems with weld-ability, zinc coating and reduction of retained austenite volume fraction after galvannealing process. The main purpose of this study is to solve the problem as indicated above.

Experimental study on RC beams externally bonded by CFRP sheets with and without end self-locking

  • Chaoyang Zhou;Yanan Yu;Chengfeng Zhou;Xuejun He;Yi Wang
    • Steel and Composite Structures
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    • v.48 no.5
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    • pp.599-610
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    • 2023
  • To avoid debonding failure, a novel type of hybrid anchorage (HA) is proposed in this study that uses a slotted plate to lock the ends of the fiber-reinforced polymer (FRP) sheet in addition to the usual bonding over the substrate of the strengthened member. An experimental investigation was performed on three groups of RC beams, which differed from one another in either concrete strength or steel reinforcement ratio. The test results indicate that the end self-locking of the CFRP sheet can improve the failure ductility, ultimate capacity of the beams and its utilization ratio. Although intermediate debonding occurred in all the strengthened beams, it was not a fatal mode of failure for the three specimens with end anchorage. Among them, FRP rupture occurred in the beam with higher concrete strength and lower steel reinforcement ratio, whereas the other two failed by concrete crushing. The beam strengthened by HA obtained a relatively high percentage of increase in ultimate capacity when the rebar ratio or concrete strength decreased. The expressions in the literature were inspected to calculate the critical loads at intermediate debonding, FRP rupturing and concrete crushing after debonding for the strengthened beam. Then, the necessity of further research is addressed.

A Study on the Application of High Manganese Austenitic Steel Sheet to Automobile Parts (고망간 오스테나이트계 강판의 자동차 부품 적용성 연구)

  • Jung, Y.I.;Chae, S.H.;Kim, S.Y.;Hong, S.H.;Lim, J.D.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.393-396
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    • 2009
  • The mechanical properties, press formability and texture of a TWIP steel were investigated. This steel combines both high strength and high ductility due to so called TWIP effect which are related to the microstructural changes. The formation of twins during deformation leads to an increase of its mechanical properties. In this study, the texture and mechanical properties evolutions of a TWIP steel subjected to tensile tests and press trials at room temperature were investigated in relation to the feasibility of the application to automotive body parts.

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