• 제목/요약/키워드: Expansion Process

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연성 파괴 기준을 이용한 허브 홀 확장 과정에서의 파단 예측 (Prediction of fracture in hub-hole expansion process using ductile fracture criteria)

  • 고윤기;이종섭;허훈;김홍기;박성호
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2004년도 추계학술대회논문집
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    • pp.160-163
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    • 2004
  • The hub hole in a wheel of vehicles usually formed with hole expansion process. Formability of material, especially the hole expansion ratio, is important to produce a fine hub hole. The hub hole expansion process is different from general forming process or bore expansion process in the viewpoint of forming a thick plate. In the hole expansion process of the plate with a hole, as the hole being expanded, the crack is occurred to outward direction at the boundary of a hole. Therefore, it is need to apply the fracture criterion in the hub hole expansion process. In this paper, the hub hole expansion process is simulated with commercial elasto-plastic finite element code, LS-DYNA3D considering some ductile fracture criteria. Fracture mode and hole expansion ratio is compared with respect to the fracture criteria. Analysis results demonstrate that only the effective plastic strain is not adequate to predict the fracture mode in the hub hole. And the analysis results also indicate that the ductile fracture criteria properly predict the fracture mode but hole expansion ratio is different with the result of each other because of their different characteristics.

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연성파괴기준을 이용한 허브홀 확장과정에서의 파단 예측 (Prediction of fracture in Hub-hole Expansion Process Using Ductile fracture Criteria)

  • 고윤기;이종섭;허훈;김홍기;박성호
    • 소성∙가공
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    • 제14권7호
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    • pp.601-606
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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. 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 for 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 are 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.

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

  • 고윤기;이종섭;김홍기;박성호;허훈
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2005년도 춘계학술대회 논문집
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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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팽창과정에서의 터보엑스펜더 영향에 관한 연구 (Effect of a Turbo-Expander for Regeneration in the Expansion Process)

  • 조종현;조봉수;김재실;조수용
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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    • pp.157-160
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    • 2006
  • A turbo-expander is developed for the regeneration in the expansion process. The turbo-expander operates in the partial admission and supersonic flow, and an axial-type single stage turbine is applied to the turbo-expander. Its outer diameter is 82mm and the operating gas is R134a. A 15kW reciprocating compressor is applied in this experiment and the turbo-expander is installed in the expansion process instead of the commonly using expansion valve. Two supersonic nozzles are applied for the expansion process. The high speed of R 134a after passing the supersonic nozzles gives the impulse force to the turbo-expander and some powers are generated on this process. A generator is installed at the end of the turbo-expander shaft. The generating output power from the turbo-expander is controlled by the power controller. Pressures and temperatures are measured on the lines for the performance investigation. More than 600W/(kg/sec) are generated in this experiment.

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펀치 노우즈의 곡률반경이 표면확장에 미치는 영향 (Influence of Punch Nose Radius on the Surface Expansion)

  • 민경호;비스라;황병복;장동환
    • 소성∙가공
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    • 제16권8호
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    • pp.582-589
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    • 2007
  • This paper is related to an analysis on the surface expansion in backward can extrusion process using spherical punches. It is generally known that the backward can extrusion process usually experiences severe normal pressure and heavy surface expansion. This is a reason why the backward can extrusion process is one of most difficult operations among many forging processes. Different punch nose radii have been applied to the simulation to investigate the effect of punch nose radius on the surface expansion, which is a major effort in this study. AA 2024 aluminum alloy is selected as a model material for investigation. Different frictional conditions have also been selected as a process parameter. The pressure applied on the punch has been also investigated since heavy surface expansion as well as high normal pressure on the tool usually leads to severe tribological conditions along the interface between material and tool. The simulation results are summarized in terms of surface expansion at different reduction in height, deformation patterns including strain distributions and maximum pressure exerted on the workpiece and punch, the effect of punch nose radius and the frictional condition on the surface expansion and the location and magnitude of maximum pressure exerted, respectively.

이산화탄소 사이클에서 팽창장치의 영향에 관한 수치적 연구 (Numerical Study for the Effect of Expansion Device on the Performance of the $CO_2$ Cycle)

  • 김무근;김욱중;김유진
    • 설비공학논문집
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    • 제16권1호
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    • pp.84-90
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    • 2004
  • In order to evaluate the performance of carbon dioxide cycle, a simulation model was developed to predict the steady state performance of $CO_2$ transcritical cycle. The expansion process is treated as an isenthalpic throttling process or isentropic expansion process. The mathematical model is based entirely on the basic energy conservation law and thermodynamic and transport properties of $CO_2$. A Parametric study has been conducted in order to investigate the effect of isentropic efficiency of expansion turbine and various operating conditions on the cycle performance. An optimal heat rejection pressure existed for the given evaporating temperature and outlet temperature of gas cooler.

알루미늄 합금을 이용한 후방압출에 의한 캔 성형시 성형 조건이 표면확장과 접촉 압력에 미치는 영향 (Influences of Process Conditions on the Surface Expansion and Contact Pressure in Backward Can Extrusion of Al Alloys)

  • 민경호;서정민;구훈서;비스라;탁상현;이인철;황병복
    • 소성∙가공
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    • 제16권7호
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    • pp.521-529
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    • 2007
  • This paper is concerned with the analysis on the surface expansion of AA 2024 and AA 1100 aluminum alloys in backward extrusion process. Due to heavy surface expansion appeared usually in the backward can extrusion process, the tribological conditions along the interface between the material and the punch land are very severe. In the present study, the surface expansion is analyzed especially under various process conditions. The main goal of this study is to investigate the influence of degree of reduction in height, geometries of punch nose, friction and hardening characteristics of different aluminum alloys on the material flow and thus on the surface expansion on the working material. Two different materials are selected for investigation as model materials and they are AA 2024 and AA 1100 aluminum alloys. The geometrical parameters employed in analysis include punch corner radius and punch nose angle. The geometry of punch follows basically the recommendation of ICFG and some variations of punch geometry are adopted to obtain quantitative information on the effect of geometrical parameters on material flow. Extensive simulation has been conducted by applying the rigid-plastic finite element method to the backward can extrusion process under different geometrical, material, and interface conditions. The simulation results are summarized in terms of surface expansion at different reduction in height, deformation patterns including pressure distributions along the interface between workpiece and punch, comparison of surface expansion between two model materials, geometrical and interfacial parametric effects on surface expansion, and load-stroke relationships.

유한요소법을 이용한 CT 시편의 홀확장 잔류응력 및 응력확대계수 해석 (Analysis of the Residual Stress due to Cold Expansion and Stress Intensity Factor in CT specimen Using Finite Element Method)

  • 장재순;양원호;김철;고명훈;조명래
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.603-608
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    • 2001
  • Recently, cold expansion of fastener holes is commonly used in the aerospace industry to increase the fatigue endurance of airframes. Cold expansion process is used as the retardation of crack initiation in the hole. This treatment leads to an improvement of fatigue behavior due to the compressive residual stresses developed on the hole surface. The residual stress profile depends on the cold expansion ratio. In the present paper, it is shown that residual stress is redistributed due to the application of cold expansion process for CT specimen. It is further shown that residual stress increases in proportion to cold expansion ratio. It is thought that crack growth rate increases as cold expansion ratio.

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홀확장과 링압인 동시적용에 의한 피로균열지연 (Fatigue Crack Retardation by Concurrent Cold-Expansion and Ring-indentation)

  • 유진상
    • 대한기계학회논문집A
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    • 제21권2호
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    • pp.305-316
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    • 1997
  • A more efficient method for obtaining the fatigue life enhancement of a structure member with fastener holes is described. It is based on the combined process of cold-expansion and ring-indentation. Residual stresses were induced onto premachined holes using ring-indentation process near the fastener hole combined with cold-expansion. And residual stresses at the vicinity of a hole were evaluated using a fracture mechanics approach. The compressive residual stresses were larger using the combined process than is in the case of simple cold-expansion. Fatigue testing of aluminum specimens showed that the fatigue crack growth retardation emanating from a circular hole was greater for the combined process than for a simple cold-expansion alone.

치과 주조공정의 수축 및 팽창에 관한 연구 (A study of shrinkage and expansion for dental casting process)

  • 김영훈
    • 대한치과기공학회지
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    • 제42권2호
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    • pp.107-112
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    • 2020
  • Purpose: This study compares how accurately the specimen produced by the machining method and the rapid prototyping method is produced and how much dimensional error occurs with the finished casting body, and presents the results as experimental comparative data. Methods: Specimens produced using a digital processing method were cast by a conventional dental casting process, and dimensional changes of the finished casting body were measured to compare shrinkage and expansion. Results: In the control group that did not artificially induce large swelling, the dimensional error was the smallest, and the shrinkage and expansion reactions cannot be elimainated in all processes. Conclusion: The shrinkage and expansion depend on the given conditions, so if there is a change in the traditional dental casting process, it is necessary to adjust all the parameters to obtain an accurate casting body.