• Title, Summary, Keyword: Hole Flanging

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Fracture Analysis of Hole Flanging Process for High Strength Steel Sheets (고강도 열연판재의 홀 플랜정시 파단특성연구)

  • 김정운;김봉준;문영훈
    • Transactions of Materials Processing
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    • v.10 no.6
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    • pp.465-470
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    • 2001
  • Hole flanging experiments are performed on flat circular plates with a hole in the center and the flangeability and fracture behaviors of TRIP steels and ferrite-Bainite duplex steels were examined. In the hole flanging, deformation by lip and petalling occurs when plates are struck by punches of various shapes and high circumferential strains induced in the target material cause radial cracking and the subsequent rotation of the affected plate material in a number of symmetric petals. In all cases, failure of the plate was due to lip fracture that results from multiple localized neckings that take place around the hole periphery where straining is most severe and a somewhat regular pattern was observed in a fracture shape. The neck characteristics in flange formation and the transition from the lip to petal mode at which fracture occurs were compared with two materials.

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Prediction of fracture in hub-hole expansion with a defected-edge model (결함을 가지는 모델을 이용한 허브 홀 확장에서의 파단 예측)

  • Lee Jong-Sup;Huh Hoon
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.131-134
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    • 2004
  • The hub hole is usually formed with a stretch flanging process followed by a blanking process of a hole. Since the hole is made by blanking, the blanked surface is so rough that the formability in the region is rather poor. The emerging task is to identify the formability of the blanked region in the forming simulation and to relate the criterion to the real forming process by experiments. In this paper, the blanked region of a hole surface is modeled by a defected-edge finite element for stretch flanging simulation. The analysis deals with the level of defect in the blanked region in order to identify the formability in the real process. The analysis provides the formability depending on the level of defect and seeks the way to match the level of defect to that of the real surface. The approach makes the analysis possible to deal with the formability of the high strength steel and predict the fracture at the hole surface during the stretch flanging simulation.

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Hole Flangeability and Fracture Behaviors of Circular Flanges of High Strength Hot Rolled Steels (고강도 열연재의 Hole Flanging시 성형특성과 파단에 관한 연구)

  • Kim J. W.;Gong S. R.;Kim B. J.;Moon Y. H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.49-52
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    • 2000
  • The hole flanging experiments are performed on a flat circular plates with a hole in the center and the flangeability and fracture behavior of TRIP steel and ferrite-bainite duplex steel were examined. Over the ranges of conditions investigated, the flangeability of ferrite-bainite duplex steel is better than TRIP steel and the term 'hole flanging capacity' introduced in this study. Fracture behavior of TRIP steel and ferrite-bainite duplex steel was characterized by petal formation at the edge of flange. In case of crack propagation, crack tip diversion that is supposed to be responsible for flangeability occurs more severely on HSLA Steel.

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Effect of Lip Shape on the Hole Flangeability of High Strength Steel Sheets (고강도 열연재의 홀 플랜징시 립 형상이 플랜정성에 미치는 효과)

  • Kim, Jeong-Un;Kim, Bong-Jun;Mun, Yeong-Hun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.1
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    • pp.147-152
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    • 2002
  • Effect of lip shape on the hole flangeability of high strength steel sheets is investigated. Circular plates of various hole sizes are tested and the variation of lip length as well as the variation of thickness on the sectional views of the finished lip were studied. The conventional hole flanging process is limited to a certain limit hole diameter below which failure will ensue during the hole expansion. The intention of this work is to examine the effect of lip shape on the flangeability of TRIP steel and Ferrite-Bainite duplex steel and find out major parameters which can affect flanging shape of high strength hot rolled steels. Over the ranges of conditions investigated, the minimum hole diameter of F+B steel is better than TRIP steel. while, the lip-shape accuracy of TRIP steel is better than that of F+B steel. although the tensile strength and elongation of %P steel are superior than those of Ferrite-Bainite duplex steel, the flangeability is found to be not so strongly sensitive to the tensile properties but sensitive to displacement on the circumferential direction of hole edge.

Evaluation of Role Flangeability of Steel Sheet with respect to the Role Processing Condition (가공조건에 따른 강판의 구멍확장성 평가)

  • Lee, J.S.;Kim, Y.K.;Huh, H.;Kim, H.K.;Park, S.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.359-362
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    • 2006
  • In this paper, hole expanding tests are carried out in order to identify the effect of the hole process condition on the hole expanding ratio. Specimens with two different hole conditions are prepared: one is produced with punching process; and the other is reamed after punching to get smoother hole surface. The experimental results show that the facture mechanism and the hole expanding ratio are quite different with respect to the hole condition. The hole expanding ratio of a punched specimen is much smaller than that of a reamed one due to the difference of surface roughness and internal defects. For the thorough investigation of those effects, tensile tests of a specimen with a hole are performed. The fracture strain is obtained with different hole conditions and a finite element analysis of the hole flanging process carried out. The experimental results are confirmed and reevaluated by finite element analysis of the hole flanging process with ductile fracture criterion proposed.

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Numerical analysis on tensile properties of composite hybrid bonded/bolted joints with flanging

  • Cheng, Xiaoquan;Zhang, Jie;Zhang, Jikui;Liu, Peng;Cheng, Yujia;Xu, Yahong
    • Steel and Composite Structures
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    • v.26 no.3
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    • pp.265-272
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    • 2018
  • A detailed study was carried out on the tensile properties of the single-lap joint of a steel panel bolted/bonded to a composite laminate with a flanging. Finite element model (FEM) was established to predict the strength and to analyze the damage propagation of the hybrid joints by ABAQUS/Standard, which especially adopted cohesive elements to simulate the interface between the laminate and adhesive. The strength and failure mode predicted by FEM were in good agreement with the experimental results. In addition, three influence factors including adhesive thickness, bolt preload and bolt-hole clearance were studied. The results show that the three parameters have effect on the first drop load of the load-displacement curve, but the effect of bolt-hole clearance is the largest. The bolt-hole clearance should be avoided for hybrid joints.

1-Piece Typed Lower Control Arm Using High Strength Hot Rolled Steel Sheet (고강도 열연 강판 적용 단판형 로어암)

  • Kim, D.;Oh, S.T.;Yoon, C.;Han, D.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.228-229
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    • 2007
  • As one way of weight saving of the vehicle, 1-piece typed lower control arm has been developed using high strength hot rolled steel sheet. In order to overcome the edge splitting problem during edge flanging or burring process, HER (hole expansion ratio) value of steel sheet was primarily considered. The strength grade of steel sheet and the shape were optimized utilizing Taguchi method.

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Development of the technique for prediction of the hub-hole crack with the punching effect (펀칭 효과를 고려한 허브홀의 파단 예측기법 개발)

  • Lee J. S.;Ko Y. K.;Huh H.;Kim H. K.;Park S. H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.362-365
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    • 2005
  • The hub hole is usually formed with a flanging process followed by a blanking process of a ]tole. Since the hole is made by blanking, the blanked surface is so rough that the formability in the region is rather poor. The emerging task is to identify the formability of the blanked region in the forming simulation and to relate the criterion to the real forming process by experiments. In this paper, hole expansion tests are carried out with respect to various hole conditions to verify the hole condition effect on the hole expansion ratio. The hole of specimens is made by machining or punching. In the case of punching, two different punching clearances are used for making the hole. From the results of test, fracture mechanism of the hole expansion is explained.

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Study on Deformation Characteristics of Hole Expansion Test and Its Applicability (구멍확장시험의 변형특성 및 활용성 연구)

  • Han, S.S.;Lee, H.Y.
    • Transactions of Materials Processing
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    • v.28 no.3
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    • pp.154-158
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    • 2019
  • The hole expansion tests using conical punch, flat punch or hemispherical punch are widely used for stretch flangeability verification of HSS. In this study, we investigate the strain distribution on the shear edges of the hole expansion test using grid marking and a projector. A small crack at the edge is distributed, resulting in a large gap between the HER and the crack strain. The strain distribution at the edges is irregular due to anisotropy of sheet metal. While an edge perpendicular to the rolling direction indicate a lower strain level compared to an edge parallel to the rolling direction, edge cracks occur at the edge perpendicular to the rolling direction. To predict the manifestation of edge cracks in FE analysis, the result of the hole expansion test with a crack strain measurement may well be a better tool than FLD. In this case, the level of strain and the direction of the edge relative to the rolling direction should be well considered.

Prediction of fracture in hub-hole expansion process using new ductile fracture criterion (새로운 연성파괴기준을 이용한 허브홀 확장과정에서의 파단 예측)

  • Ko Y. K.;Lee J. S.;Kim H. K.;Park S. H.;Huh H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.163-166
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    • 2005
  • A hole expansion process is an important process in producing a hub-hole in a wheel disc of a vehicle. In this process, the main parameter is the formability of a material that is expressed as the hole expansion ratio. The hub-hole expansion process is different from conventional forming processes or hole flanging processes from the view-point of its deformation mode and forming of a thick plate. In the process, a crack is occurred in the upper edge of a hole as the hole is expanded. Since prediction of the forming limit by hole expansion experiment needs tremendous time and effort, an appropriate fracture criterion has to be developed fur finite element analysis to define forming limit of the material. In this paper, the hole expansion process of a hub-hole is studied by finite element analysis with ABAQUS/standard considering several ductile fracture criteria. The fracture mode and hole expansion ratio is compared with respect to the various fracture criteria. These criteria do not predict its fracture mode or hole expansion ratio adequately and show deviation from experimental results of hole expansion. A modified ductile fracture criterion is newly proposed to consider the deformation characteristics of a material accurately in a hole expansion process. A fracture propagation analysis at the hub-hole edge is also performed for high accuracy of prediction using the new fracture criterion proposed.

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