• 제목/요약/키워드: Billet

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유한요소법을 이용한 전방압출공정의 내부결함에 관한 연구

  • 김태형;김병민;강범수;최재한
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 1992년도 춘계학술대회 논문집
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    • pp.79-83
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    • 1992
  • According to the variation of hydrostatic pressure on the central axis of deformable material, the V-shaped central bursting defect may be created on extrusion or drawing processes. The process factors whichaffect the generation of defects are die semi-angle, reduction ratio of cross-sectional area, friction factor, material properties and so on. The combination of these factors can determine the prossibility of defect creation and the shape of various round holes which have been created inside already. By the rigid plastic finite element method, this paper describes the observations of change in shape of a round hole with process conditions suchas die semi-angle, reduction ratio of cross-sectional area and friction factorat the unsteady state of axi-symmetrical extrusion process when the round hole is alreadyexisted inside the original billet, and also, the effects of process factors are investigated to prevent the possible defects.

NURBS 곡면과 면적 사상법을 이용한 T-형 압출 금형곡면의 자동생성에 관한 연구 (Investigation on the Automatic Surface Generation for Extrusion Die of T-shaped Section using NURBS Surface and Area Mapping Method)

  • 임종훈;유동진
    • 한국정밀공학회지
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    • 제20권10호
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    • pp.208-217
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    • 2003
  • In order to construct the extrusion die surface of T -shaped sections, an automatic surface construction method based on NURBS surface and area mapping method is proposed in the present work. In the present study, a center point for area mapping is determined by introducing the mapping concept based on constant area proportionality between original billet and final product. The characteristic points of inlet profile are determined using the traditional area mapping method and the root finding numerical method. The inlet and outlet profiles are precisely described with NURBS curves using the characteristic points of entry and exit sections. For the construction of NURBS surface, an interpolation method for the pre-determined two section curves has been developed to be used in the generation of interior control points and weights. To show the validity of the proposed method, automatic die surface generation is carried out for the T-shaped section and T-shaped section with rounded corners.

상계해법에 의한 원형빌렛으로부터 타원 단면을 가진제품의 압출가공의 비틀림 해석 (An Upper Bound Analysis for the Twisting Phenomenon of Extrusion of Elliptical Shapes from Round Billet)

  • 김한봉;진인태
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1998년도 춘계학술대회논문집
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    • pp.210-213
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    • 1998
  • A kinematically admissible velocity field is developed for the analysis of twisting of extruded products. The twisting of extruded product is caused by the linearly increased rotational velocity from the center on the cross-section of the workpiece at the die exit. In the analysis, the rotational velocity in angular direction is assumed by the multiplication of radial distance and angular velocity. The angular velocity is zero at the die entrance and is increased linearly by axial distance from die entrance. The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product increase with the die twisting angle and the aspect ratio of product and friction condition and reduction area and show that angular velocity increases with the decreases in die length.

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직사각재 인발 공정의 중간 금형 설계 프로그램 개발 (Development of Program for the Intermediate ie Design in the Drawing of the Rectangular Rod)

  • 김동진
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1999년도 춘계학술대회논문집
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    • pp.95-98
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    • 1999
  • In this study, a method to find the optimal intermediate die geometry for the multi-stage drawing process for the rectangular rod from a round bar is proposed and a program using the proposed method is developed. On the stage of the design of the intermediate die geometry, the virtual die was constructed using the initial billet as a inlet of the drawing die and the final product as a exit of that and the virtual die was divided by the number of pass. Divided die was transformed into the rectangular one which is the intermediate die geometry for the multi-stage rectangular drawing process. In order to verify the application of the proposed method on the real industrial product, the drawing of the rectangular rod from a round which composed two stage has been performed and simulated by the three dimensional rigid plastic finite element method.

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이동 경화를 고려한 좌굴 및 소성 불안정 유동에 관한 연구 (A Study on Buckling and plastic Instable Flow with Kinematic Hardening)

  • 황두순
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1999년도 춘계학술대회논문집
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    • pp.98-101
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    • 1999
  • The plastic instable flow phenomenon happens in practical forming process I. e. upsetting backward extrusion piercing indentation. And also it is difficult to control precisely the shape and dimensions of forming process. It is found that instabilities of the process are mainly connected with imperfection in the lubrication billet eccentricity inclined punch alignment. In view of the direct relationship between instable material flow and quality defects of the products and it is for better control of forming operation we should necessarily find out their phenomena. In this study we used the friction disturbance due to inclined punch angle and introduced the method considering kinematic hardening effect Analysis of upset forging is carried out using the rigid plastic FEM and slab method with eccentricity.

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상계해법에의한 원형빌렛으로부터 S형 단며의 압출가공의 비틀림 해석 (An Upper Bound Analysis for the Twisting Phenomenon of Extrusion of S shape from Round Billet)

  • 진인태
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1997년도 춘계학술대회논문집
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    • pp.130-135
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    • 1997
  • A kinematically admissible velocity field is developed for the analysis of twisting of extruded products. The twisting of extruded product is caused by the linearly increased rotational velocity from the center on the cross-section of the workpiece at the die exit. In the analysis, the rotational velocity in angular direction is assumed by the multiplication of radial distance and angular velocity. The angular velocity is zero at the die entrance and is increased linearly by longitudinal distance from die entrance. The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product changes with the aspect ratio of product and increases with the decreases in die length and in eccentricity of gravity center of the cross-section of workpiece at die entrance from that of the cross-section at the die exit.

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헬리컬기어 블랭크 열간단조의 유한요소해석 (Finite-Element Analysis of a Helical-Gear Blank Hot-Forging)

  • 안승우;박종진
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1995년도 제2회 단조심포지엄 단조기술의 진보
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    • pp.180-187
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    • 1995
  • Helical gears are machined from blanks, which are usually prepared by forging cylindrical billets at high temperatures through buster, blocker and finisher processes. As dimensions of the blank are closer to those of the machined part, machining cost can be more reduced. Therefore, there are a lot of efforts being made to optimize the forging processes in order to produce near-net shaped blanks. In the present investigation, a rigid viscoplastic finite element technique was used to analyze a helical gear blank hot forging processes and deformation, strain and temperature distributions, forging load variations during forging were obtained. In the paper, it is discussed how these results can be utilized to optimize die design, billet dimensions and press usage.

원형빌렛으로부터 타원단면 및 S단면 가진제품의 압출가공의 DEFORM-3DTM에 의 한 비틀림 해석 비교 (A Comparision of the Twisting of Extrusion of Elliptical Shape with that of S shape from Round Billet by DEFORM-3DTM Software)

  • 김진훈;김한봉;진인태
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1997년도 춘계학술대회논문집
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    • pp.136-139
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    • 1997
  • Applications of commercial software DEFORM-3DTM for 3-D simulation in extrusion process are developed for the analysis of twisting of extruded products. Because the elliptical shape has at least one line symmetry, the twisting is not occured during the extrusion. But, the results of extrusion simulation of the elliptical shape show that the twisted boundary of the die surface makes the material inside die surface rotate with the constant angular velocity. Otherwise, the simulation results of the S shaped product show that the twisting can be occured by the only 180$^{\circ}$rotation symmetry of S shape without no line symmetry and show that the angular velocity increases by the only 180$^{\circ}$rotation symmetry without no twisted die surface between on the die entrance section and on the die exit section. The results of the analysis show that the angular velocity of the extruded product changes with die length and friction condition.

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로터리 스웨이징 공정의 성형성 연구 (The Forming Characteristic of Rotary Swaging Process)

  • 임성주;윤덕재;나경환
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1997년도 춘계학술대회논문집
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    • pp.273-280
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    • 1997
  • Rotary swaging is a process for reducing the cross-sectional area or changing the shape of bar, tube or wires by repeated radial blows with one or more parirs of opposed dies. The present study is concerned with investigation the effect of process parameters upon product quality(hardness, roughness, precision of dimension). To enhance the product quality, experimental works are carried out for some process parameters such as forming speed, billet shape, lubrication, reduction of area and ratio of t/D. Rod shift formed by RSM25 under cold conditions has good surface quality, hardness and precision of dimension. The recommendable process conditions are suggested for solid and tubular products.

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재가열 공정과 유도 가열의 FEM 해석 (Reheating Process and FEM Analysis of Inductive Heating)

  • 손영익
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1999년도 춘계학술대회논문집
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    • pp.195-198
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    • 1999
  • For the thixoforming process beside an existing solidus-liquidus interval, the reheating conditions to obtain the globular microstructure are very important. It relies on the control of globular microstructure of semi-solid alloys that contain non-dendritic particles. To obtain the globular microstructure in cross section of billet, the optimal design of the induction coil is necessary. Therefore, in this paper the optimal coil design to minimize electromagnetic end effect will be proposed. The results of coil design were also applied to the reheating process to obtain a fine globular microstructure. Finally, reheating data base of aluminum alloys for thixoforming and FEM model for induction heating based on the optimal coil design have been proposed.

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