• Title/Summary/Keyword: Stretching Sheet

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Development of Plane Strain Punch Stretching Test (평면변형 장출실험기술의 개발)

  • 김영석;김기수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.5
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    • pp.1132-1137
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    • 1993
  • A simple simulative test was developed to evaluate stamping formability in plane strain stretching mode. The stamping formability was evaluated by limit punch height(LPH) in plane strain punch stretching test(PSST) compared to limit dome height(LDH) in hemispherical punch stretching test. PSST shows stable plane strain condition and good reproducibility with minimum scatter. Moreover LPH-value in PSST well ranks the stamping formability of various material and correlates with press performance.

The Effect of Planar Anisotropy in Plane-Stress Bore Expanding (평면 응력 Bore Expanding 에 있어서의 평면이방성 의 영향)

  • 주진원;이중홍;양동열
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.8 no.5
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    • pp.435-441
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    • 1984
  • The matrix method, as an effective FEM formulation for the analysis of rigid-plastic deformation, was applied to the bore expanding of anisotropic sheet metal. The effect of planar anisotropy on sheet metal deformation was studied for bore expanding process under the uniform radial stretching condition, and the results were compared with isotropic and normal anisotropic solutions. Experiments were carried out using a flat punch for cold-rolled sheet metal. The experimental results were compared with computations from the matrix method with the boundary conditions corresponding to actual experiment. Both in theory and experiment, it is found that the maximum thinning which results in necking occurs in the direction of the minimum R-value. The results also suggest that the matrix method is efficient for analyzing planar anisotropic sheet metal. The comparison between theory and experiment suggests that Hill's theory of planar anisotropy is somewhat exaggerated. However, the theoretical predictions are in qualitative agreement with the experimental results.

A Simplified Approach for Predicting Springback in U-Draw Bending of Sheet Metals (용접 판재의 U 드로오 벤딩에서 스프링백 예측을 위한 이론적 단순화)

  • Chang S. H;Seo D. G.
    • Transactions of Materials Processing
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    • v.13 no.8
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    • pp.678-688
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    • 2004
  • The U-draw bending operation is known as a representative test method for springback evaluation of sheet metals since the sheet in U-draw bending operation undergoes stretching, bending and unbending deformations occurred at the stamping process. In this study, a simplified approach was proposed for predicting springback and side-wall curls of tailor-welded blank in U-draw bending operations, using moment-curvature relationships derived for sheets undergoing stretching, bending and unbending deformation. Two different welded strips were adopted to compare the effects of weld-line locations on the springback. One (type A) was welded along the centerline of the strip-width and the other (type B) was welded along the centerline of the strip-length. To investigate the effect of different thickness combination on the springback, the tailor-welded strips were joined by the laser welding process and consisted of three types of thickness combinations of sheets, SCP1 0.8t * SCP1 1.2t, SCP1 0.8t * SCP1 1.6t and SCP1 0.8t * TRIP 1.0t. Some calculated results by the simplified formula were compared with experimental results.

Investigation into Low Velocity Impact Characteristics of the Stainless Steel Sheet with Thickness of 0.7 mm on the Stretching Condition using Three-Dimensional Finite Element Analysis (3 차원 유한요소해석을 이용한 스트레칭 조건에서의 두께 0.7mm 스테인레스 강판의 저속 충격 특성 분석)

  • Ahn, Dong-Gyu;Moon, Kyung-Je;Jung, Chang-Gyun;Yang, Dong-Yol
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.8
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    • pp.80-87
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    • 2008
  • This paper investigated into the impact characteristics of the stainless sheet with thickness of 0.7 mm on the stretching boundary condition through three-dimensional finite element analysis. High speed tensile tests were carried out to obtain strain-stress relationships with the effects of the strain rate. The FE analysis was performed by the ABAQUS explicit code. In order to improve an accuracy of the FE analysis, the hyper-elastic model and the damping factor were introduced. Through the comparison of the results of the FE analyses and those of the impact tests, a proper FE model was obtained. The results of the FE analyses showed that the absorption rate of energy maintains almost 82.5-83.5% irrespective of the impact energy level and the diameter of the impact head. From the results of FE analyses, variations of stress, strain, dissipation energy, strain energy density, and local deformation characteristics in the stainless sheet during the collision and the rebound of the impact head were quantitatively examined. In addition, it was shown that the fracture of the specimen occurs when the plastic strain is 0.42 and the maximum value of the plastic dissipation energy of the specimen is nearly 1.83 J.

FE Analysis for Application of Isotropic Steel Sheet on Auto-Roof Panel (등방성 강판의 자동차용 Roof Panel 부품 적용 특성 해석)

  • Han S.S.
    • Transactions of Materials Processing
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    • v.15 no.3 s.84
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    • pp.241-246
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    • 2006
  • The isotropic steel sheet was developed and started to apply on the auto-body outer panel, however the characteristics of application on auto-body were not well known. In this paper the FE analysis of outer panel of auto-body was carried out to investigate the characteristics of isotropic steel sheet. For the FE analysis of the roof panel of ULSAB body the isotropic steel sheet and the bake hardening steel sheet were used. The Isotropic steel sheet shows more deformation at punch bottom area of roof panel than the bake hardening steel sheet that is most required forming properties far outer panel to obtain the shape likability of forming parts. It is shown that the isotropic steel sheet has suitable material properties far outer panels of auto-body.

Heat and mass transfer of a second grade magnetohydrodynamic fluid over a convectively heated stretching sheet

  • Das, Kalidas;Sharma, Ram Prakash;Sarkar, Amit
    • Journal of Computational Design and Engineering
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    • v.3 no.4
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    • pp.330-336
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    • 2016
  • The present work is concerned with heat and mass transfer of an electrically conducting second grade MHD fluid past a semi-infinite stretching sheet with convective surface heat flux. The analysis accounts for thermophoresis and thermal radiation. A similarity transformations is used to reduce the governing equations into a dimensionless form. The local similarity equations are derived and solved using Nachtsheim-Swigert shooting iteration technique together with Runge-Kutta sixth order integration scheme. Results for various flow characteristics are presented through graphs and tables delineating the effect of various parameters characterizing the flow. Our analysis explores that the rate of heat transfer enhances with increasing the values of the surface convection parameter. Also the fluid velocity and temperature in the boundary layer region rise significantly for increasing the values of thermal radiation parameter.

Press Formabilities of Aluminum Sheets for Autobody Application (차체용 알루미늄 판재의 프레스 성형성)

  • Kim, Y.S.;Kim, K.S.;Kwon, N.C.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.2 no.1
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    • pp.73-83
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    • 1994
  • Press formabilities of aluminum sheets for automobile body were investigated. Plane strain stretching test (called RIST-PSST), cupping test and U bending test were performed to assess the press formability of aluminum sheets respectively. The results showed that aluminum sheets are generally inferior to cold-rolled steel sheet of deep drawing quality (CSP3N) in press formability. The limiting punch height (LPH) and limiting plane strain (FLCo) of aluminum sheets are 50%-70% level compared to that of CSP3N. Moreover, the limiting drawing ratios(LDR) of aluminum sheets are ranged between 1.95 and 2.1. The poor press formability of aluminum sheets is responsible for low values of total elongation and plastic anisotropy parameter in tensile characteristic. The shape fixability of aluminum sheets evaluated in U bending test is very poor due to its low elastic modulus compared to CSP3N.

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Effect of Shot Blasting Treatment on the Formability of Thin High Strength Steels (고강도 강판의 성형성에 미치는 Shot Blasting 가공 조건의 영향)

  • Park, K.C.;Kim, J.I.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.05a
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    • pp.341-344
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    • 2008
  • In order to study the effect of shot blasting condition on the formability of thin high strength steels, specimens were made by changing line speed of a commercial shot blasting plant with maintaining constant impeller condition. Surface roughness of prepared specimens was multiplied by lowering line speed or increasing density of shot impact. Formability was reduced as increasing shot impact. The elongation and stretching formability of shot blasted sheet were decreased by about 10% compared to original sheet. More significant decrease in bending formability was observed after shot blasting. This might be due to the concentrated impact near the surface where major strain occurs during bending process.

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Experimental Study on the Forming Limit Curve of Aluminum Alloy Sheets using Digital Image Correlation (디지털 이미지 상관관계를 이용한 알루미늄 합금 판재의 성형한계도 평가)

  • Kim, Yongbae;Park, Jungsoo;Song, Junghan
    • Journal of Institute of Convergence Technology
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    • v.5 no.1
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    • pp.7-12
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    • 2015
  • Sheet metal formability can be defined as the ability of metal to deform without necking or fracture into desired shape. Every sheet metal can be deformed without failure only up to a certain limit, which is normally known as forming limit curve(FLC). In this paper, the dome stretching tests and tensile tests have been performed to obtain forming limit curve of aluminum alloy. During the experiment, failure strain is measured using digital image correlation(DIC) method. DIC method is a whole-field measurement technique that acquires surface displacements and strains from images information which characterized a random speckle as intensity grey levels. Recently years, this DIC method is being developed and used increasingly in various research. DIC results demonstrated the usefulness and ability to determine a strain.

Elastic-Plastic Finite Element Analysis of Sheet Metal Forming Processes(II) - Analysis of Metal Forming Processes with Contact Condition - (탄소성 유한요소법에 의한 박판성형 공정의 해석 II - 접촉 조건을 가지는 박판성형 공정의 해석 -)

  • 심현보;정완진;양동열
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1129-1137
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    • 1990
  • Based on the formulation which incorporates large deformation and anisotropy, an elastic-plastic finite element code is developed with membrane element to include the contact treatment. For the analysis of the general sheet metal forming process with contact condition, the treatment of contact is considered by employing the successive skew coordinate system. Three kinds of sheet metal forming processes with contact conditions are analyzed; stretching of a square diaphragm with a hemispherical punch, deep drawing of a circular cup and deep drawing of a square cup. Then the computational results are compared with the experiment. The computed loads and the distribution of the thickness strain are in good agreement with the experiment for all cases. However, the computational results of the thickness strain show the effect of bending can not be ignored in the deep drawing process whereas the effect of bending is negligible in stretching.