• Title/Summary/Keyword: High Strength Steel Sheet

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

  • Cha, C.H.;Lee, S.K.;Ko, D.C.;Kim, B.M.
    • Transactions of Materials Processing
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    • v.18 no.1
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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.

Compensation Design to Reduce Springback in Sheet Metal Forming of 1.2GPa Ultra High Strength Steel (1.2GPa급 강판 판재 성형에서 스프링백 감소를 위한 금형 보상 설계)

  • Kwon, S.H.;Lee, H.S.;Lee, Y.S.;Kim, S.W.;Jung, C.Y.;Hong, S.
    • Transactions of Materials Processing
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    • v.25 no.5
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    • pp.301-305
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    • 2016
  • The manual modification of stamping die has widely been used in order to reduce springback after sheet metal forming. When UHSS (Ultra High Strength Steel) is used in sheet metal forming, the die design considering springback compensation is more difficult because higher strength sheet has more springback. In this study, the optimization method was used in order to design die geometry considering springback compensation after forming of 1.2GPa UHSS. Die geometries were defined as design variables and the springback distance from the die surface was conducted as object function in optimization process. The optimized die geometry considering springback compensation was performed using finite element and optimization analysis. The simulation results such as thickness distribution and springback amount were compared with measured data using 3D optical measurement system (GOM ARGUS, ATOS). And the prediction of springback amount showed a good agreement within test results.

Application of Single Lap-Shear Test for Extracting Adhesive Bonding Strength of Coating Layer on Galvannealed sheet (합금화용융아연코팅강판의 코팅층 접합강도 평가를 위한 단일 겹치기이음 시험의 적용)

  • Lee, Jung-Min;Lee, Cha-Joo;Lee, Sang-Gon;Ko, Dae-Cheol;Kim, Byung-Min
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.238-243
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    • 2007
  • This paper is designed to estimate the adhesion strength of coating layer on galvannealed steel sheet using lap shear test. The single lap shear test is the most commonly used standard test for determining the strength of medium-strength and high strength bonds. The bond strength of bonded single lap joints on subjecting the substrates to loads is determined by lap shear forces in the direction of the bonded joint. In this study, specimen for adhesion strength test was made to attach coated sheet to cold rolled sheet and were heated in temperature of 180 for 20minutes. After test, detached parts of coatings on coated sheet were observed using SEM and EDX to identify substrate and complete detachment. The tested results showed that adhesive strength of coating is unrelated to anisotropy of sheet and is difficult to be extracted using conventional theory because of fine cracks of coating layers which were created during annealing process.

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Analysis of the High Formability of Automotive Steel Sheets by the Surface Texturing Effect (자동차용 강판의 표면 텍스처링 효과에 따른 고성형성 연구)

  • Yoon, Seung-Chae;Lyo, In-Woong;Cho, Min-Haeng
    • Korean Journal of Metals and Materials
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    • v.50 no.1
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    • pp.8-12
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    • 2012
  • This study aims to analyze the formability property of surface texturing processed automotive steel sheet for improving the sheet forming property. In the paper, the effect of cavities fabricated using the laser surface texturing technique on automotive high strength steel sheets was studied. The frictional behavior of the sheet drawing is a function of interface parameters such as sheet surface roughness, holding force, contact pressure, etc. For these reasons, automotive steel researchers want to optimize the surface topography of automotive steel sheets in order to enhance the formability. Therefore, this study presents the behavior of deformation of a laser surface texturing steel sheet by considering the frictional operation during the deep drawing process.

Study on the Cold Stamping Process Design Method of 1.5GPa Grade Front Side Rear Lower Member (1.5GPa급 Front Side Rear Lower Member 냉간 성형공정 설계기법 연구)

  • Nam, S.W.;Bae, G.H.
    • Transactions of Materials Processing
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    • v.30 no.5
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    • pp.236-241
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    • 2021
  • This study describes the cold stamping process design procedure to secure the formability and dimensional accuracy of the automotive structural component fabricated by 1.5GPa grade ultra-high strength steel sheet. The target product is selected as the front side rear lower member which is the most important energy absorption part in the frontal impact condition. To secure the product quality, an intermediate product shape is added while considering the low elongation and high strength characteristics of 1470Mart. The sequential optimization procedure of the intermediate product shape, the fine dimensional quality is then achieved without any crack or wrinkling. The cold stamping method with ultra-high strength steel sheets is validated by conducting the die tryout of the front side rear lower member.

A Study on the Retained Austenite and Tensile Properties of TRIP Type High Strength Steel Sheet with Cu (Cu 함유 TRIP형 고장력 강판의 잔류오스테나이트 및 인장특성에 관한 연구)

  • Kang, C.Y.;Kim, H.J.;Kim, H.G.;Sung, J.H.;Moon, W.J.
    • Journal of the Korean Society for Heat Treatment
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    • v.12 no.3
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    • pp.231-239
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    • 1999
  • Volume fraction and morphology of retained austenite, tensile properties of TRIP type high strength steel sheet with Fe-C-Si-Mn-Cu chemical composition have been investigated. The retained austenite of granular, bar and film type existing in specimen was obtained after intercritical annealing and austempering. The granular type retained austenite increased with increase of intercritical annealing and austempering temperature. With increase of intercritical annealing temperature, retained austenite and carbon contents increased. Maximum contents of retained austenite was obtained by austempering at $400^{\circ}C$. The maximum tensile strength was obtained by austempering at $450^{\circ}C$ and maximum elongation was obtained at $400^{\circ}C$. T.S${\times}$E.L value increased with increase of retained austenite contents due to the elongation strongly controlled by contents of retained austenite, but tensile strength was affected with various factors such as bainitic structure etc.

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Dynamic Tensile Characteristics of the High Strength Steel Sheet for an Auto-body (차체용 고장력 강판의 동적 인장 특성 평가)

  • Kim, Seok-Bong;Huh, Hoon;Shin, Chirl-Soo;Kim, Hyo-Kun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.171-176
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    • 2007
  • An important challenging issue in the automotive industry is the light-weight, safe design and enhancement of crash response of an auto-body structures. These objectives lead to increasing adoption of high strength steel sheet for inner and outer auto-body members. This paper evaluates the dynamic tensile characteristics of high strength steel sheets, HS45R, TRIP60, DP60 and DP100, along the rolling direction and transverse direction. Static tensile tests were carried out at the strain rate of 0.003/sec using the static tensile machine (Instron 5583). Dynamic tensile tests were carried out at the range of strain rate from 0.1/sec to 200/sec using a high speed material testing machine developed. The tensile tests acquire stress-strain relation and strain rate sensitivity of each material. The experimental results show two important aspects for high strength steels: the flow stress increases as strain rate increases; the strain hardening decreases as the tensile stress increases. The experiments also produce interesting results that the elongation does not decrease even when the strain rate increases.

Fatugue Chacrateristics of Spot Welding between High Strength Steel and Galvanized Steel Sheet (II) (高張力 鋼板과 亞鉛鍍金 鋼板間의 疲勞特性 II)

  • 서창민;강성수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.2
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    • pp.229-235
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    • 1989
  • The influence of monogalvanized layer to fatigue strength of two different mating metal specimens (HS*GA, HS*GAB) of high strength steels(HS) and of monogalvanized steel sheets(GA, GAB) were investigated under tensile-shear repeated load, and hardness test. Some of the results are; (1) The main cause of crack initiation and growth at high load range is plastic bending hinge. (2) In low load range, the cracks initiated near the nugget front where the hardness variation is steep.

Characteristic of Mechanical Clinching for Al5052 to High-Strength Steels (Al5052 합금소재와 고장력강판의 이종재료 클린칭 접합특성)

  • Lee, Chan-Joo;Lee, Sang-Kon;Lee, Seon-Bong;Kim, Byung-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.8
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    • pp.997-1006
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    • 2010
  • For manufacturing modern cars, so-called multi-materials, such as aluminum alloy with high-strength steels, are used. For obtaining such materials, a new joining method is required to achieve the multi-material design. Mechanical clinching is one of joining methods used to join the dissimilar materials. The objective of this study is to investigate the characteristics of mechanical clinching of Al5052 alloy to high-strength steels (SPFC440, 590, 780). Using FE-analysis and clinching experiment, the joinability of Al5052 alloy to high-strength steel is evaluated by geometrical shape of mechanical clinched joint, such as neck-thickness and undercut. Further, the joint strength is evaluated by performing a single-lap shear test. The upper high-strength steel SPFC780 was not clinched because of the necking of the upper sheet. The joint strength increased with increasing strength of the upper sheet. For the lower high-strength steel sheet, the joinability and joint strength decreased with increasing strength of the lower sheet.