• Title/Summary/Keyword: kinematically admissible velocity field

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Analysis of profile ring rolling for rings having V-groove of trapezoidal protrusion by the upper-bound elemental technique (사다리꼴 모양의 돌기나 V형 홈을 갖는 형상 환상압연에 대한 UBET 해석)

  • Hahn, Young-Ho;Yang, Dong-Yol
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.2
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    • pp.40-47
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    • 1993
  • To diversify the area of application of UBET to the analysis of ring rolling which produces rings having more complex cross-sectional configuration, an element of triangular cross-section has been introduced and the corresponding kinematically admissible velocity field has been derived while considering the material flow between neighboring elements. The theoretical perdictions in roll torque and profile formation show good agreement with the experiments. The effect of process parameters such as feed rate and taper angle of the roll groove has been discussed.

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A Study on the Forging of Internal Involute Gears with Alloy Steel (합금강을 이용한 내접 인벌류우트 기어의 단조에 관한 연구)

  • 최종웅;조해용;최재찬
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.2
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    • pp.90-98
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    • 1998
  • Forging of internal involute gears with alloy steel has been analyzed by means of upper bound method. Kinematically admissible velocity fields for forging of internal gear were proposed. It was assumed that the shape of free flow surface during forging operation is a straight line perpendicular to the plane of symmetry. Using the suggested velocity fields, forging loads and relative pressures were calculated by numerical method. Consequently forging die should be successfully designed without fracture or failure during forging operation. Experiments were carried out with the designed die and SCM415 alloy steel as billet material. The calculated loads were compared with experimental one and they are in good agreement with experimental inspections. As a result, the calculated solutions would be useful to predict the loads and the designed die is suitable for forging of internal involute spur gear with alloy steel. The forged gear is measured to be KS 4 class and its class should be improved by subsequent working such as shaving after forging operation.

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An upper-bound analysis for the guiding type forging of helical gears (헬리컬기어의 안내형 단조에 관한 상계해석)

  • Choi, J.C.;Choi, Y.;Tak, S.J.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.9
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    • pp.1364-1372
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    • 1997
  • In this paper, the forging of helical gears has been investigated. Punch is tooth-shaped as is the die insert. The punch compresses a cylindrical billet placed in a die insert. As a consequence the material of billet flows into the tooth region. The forging has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduced to represent tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, helix angle and friction factor on the forging of helical gears. Some forging experimentswere carried out with aluminum alloy to show the validity of the analysis. Good agreement was found between the predicted values of the forging load and obtained from the experimental results.

A Study on Material Characterization of Semi-Solid Materials(II) -Determination of Flow Stress For Semi-Solid Materials Using Backward Extrusion Experiment with Model Material and Upper Bound Analysis- (반용융 재료의 물성치 평가에 관한 연구(II) -모델재료의 후방압출 실험과 상계해석을 통한 반용융 재료의 유동응력식 결정-)

  • 이주영;김낙수
    • Transactions of Materials Processing
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    • v.8 no.4
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    • pp.374-383
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    • 1999
  • To determine the flow stress of semi-solid materials, a new combined method has been studied by experimental and analytic technique in the current approach. Using backward extrusion experiment and its numerical analysis, the characterization scheme of semi-solid materials according to the change of initial solid volume fraction has been proposed. Because that solid volume fraction is sensitive to temperature change, it is required to precisely control the temperature setting. Model materials can guarantee the establishment of material characterization technique from the noise due to temperature change. Thus, clay mixed with bonded abrasives was used for experiment and the change of initial solid fraction was copied out through the variation of mixing ratio. Upper bound method was adapted to increase in efficiency of the calculation in numerical analysis and new kinematically admissible velocity field was employed to improve the accuracy of numerical solution. It is thought that the material characterization scheme proposed in this study can be applied to not only semi-solid materials, but also other materials that is difficult to obtain the simple stress state.

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A study on the clamping type forging of helical gear (헬리컬기어의 구속형 단조에 관한 연구)

  • Choi, J.C.;Choi, Y.;Tak, S.J.;Cho, H.Y.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.11
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    • pp.1827-1836
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    • 1997
  • In this paper, the clamping type forging of helical gears has been investigated. Clamping type forging is an operation in which the product is constrained to extrude sideways through an orifice in the container wall. Punch is cylindrical shaped. The punch compresses a cylindrical bilet placed in a die insetr. As a consequence the material flows in a direction perpendicular to that of punch movement. The forging has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduce to re4present tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, helix angle, friction factor and initial height of billet on the forging of helical gears. Some firgiing experiments were catrried out with aluminium alloy to show the validity of the analysis. Good agreement was found between the predicted values of the forging load and obtained from the experimental results.

Design of Pipe Expanding Die by Upper Bound Analysis and Finite Element Method (상계법과 유한요소법을 이용한 확관금형 설계)

  • Cho, Yong-Il;Kim, Seung-Hwan;Qiu, Yuan-gen;Cho, Hae-Yong
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.5
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    • pp.98-104
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    • 2020
  • Pipe expansion involves various methods to enlarge the diameter of the pipes with the use of a mandrel or punch placed inside the pipe. In this study, the upper bound method was used to analyze the pipe expanding process as well as design a die. A kinematically admissible velocity field was derived for the upper bound analysis with the occurrence of pipe thinning during the expansion factored in. The analysis confirms that a semi-cone angle of the punch between 15ween pip is most advantageous for pipe expansion. The results of the upper bound analysis, which were also consistent with those of the FEM, can be useful for the design of a pipe expansion die.

An Analysis of Axisymmetric Deep Drawing by the Energy Method (에너지법에 의한 축대칭 디프드로잉의 해석)

  • 양동열;이항수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.1
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    • pp.51-61
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    • 1993
  • A systematic approach of the energy method is proposed for analysis of axisymmetric deep drawing in which the total deforming region is divided into five sections by the geometric characteristic. The corresponding solution is found through optimization of the total energy dissipation with respect to some parameters assumed in the kinematically admissible velocity field defined over each region. The sheet blank is divided into three-or five-layers to consider the bending effect. For the evaluation of frictional energy, it is assumed that the blank holding force acts on the outer rim of the flange and that the contact pressure acting on punch shoulder or die shoulder has uniform distributions, respectively. The computed results by the present method are compared with the experiment and the computed results by the elastic-plastic finite element method for the distribution of thickness strain and the relation between the punch stroke and punch load. The results for the case of multi-layers show better agreements than for the case of a single layer in load vs. stroke relation and strain distribution. It is thus shown that the multi-layer technique can be effectively employed in analyzing axisymmetric deep drawing in connection with the energy method.