• 한국전산구조공학회논문집
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• 제24권1호
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• pp.33-41
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• 2011

본 연구에서는 비부착형 포스트텐션 시스템의 해석에 적용할 수 있는 모델링기법을 제시하였다. 모델링은 유한요소 해석 프로그램을 이용하였으며, tube-to-tube contact 요소를 도입하여 강연선의 물리적 형상을 직접적으로 모델링하는 방법과 실제의 강연선 외에 가상의 강연선을 콘크리트에 매입하고, 두 개의 강연선을 스프링으로 연결하여 간접적으로 모델링하는 방법을 동시에 제시하고 비교하였다. 콘크리트의 인장경화 현상을 무시하였을때 두 모델링기법에서는 거의 동일한 결과를 제공하지만 콘크리트의 인장경화를 고려한 경우에는 스프링을 이용한 간접적인 모델링기법을 통해서만 결과를 얻을 수 있었으며, 결과 또한 콘크리트의 경화현상을 고려하지 않은 경우와 다소 상이하였다. 비교를 통하여 비부착형 포스트텐션 시스템의 모델링기법으로 스프링을 이용한 모델링기법을 최종적으로 선정하고 기존의 실험적 연구에서 인용한 실험결과와 해석결과를 비교, 검증하였으며 또한 파라미터 스터디를 통해서 모델링의 적절성을 확인하였다.

• 소성∙가공
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• 제11권1호
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• pp.75-83
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• 2002

Recently, the hydroforming process is widely applied to the automotive industry and rapidly spreaded to other industries. In this paper, An implicit finite element formulation for simulating axisymmetric tube hydroforming processes is performed. In order to describe normal anisotropy of the tube, Hill's non-quadratic yield function is employed. The frictional contact between die and tube and the frictionless contact between tube and fluid are considered using the mesh-normal vectors computed from the finite element mesh of the tube. The complete set of the governing relations comprising equilibrium and interfacial equations is linearized for Newton-Raphson procedure. In order to verify the validity of the developed finite element formulation, the axisymmetric tube bulge test is simulated and the simulation results are compared with experimental measurements. In a simulation of stepped circular tube hydroforming processes, an optimal hydraulic pressure curve is pursued by considering simultaneously internal pressures and axial forces.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.58-61
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• 2001

An implicit finite element formulation for axisymmetric tube hydroforming is investigated. In order to describe normal anisotropy of the tube, Hill's non-quadratic yield function is employed. The frictional contact between die and tube and frictionless contact between tube and fluid are considered using the mesh-normal vector computed from finite element mesh of the tube. In order to verify the validity of the developed finite element formulation, the axisymmetric tube bulge test is simulated and simulation results are compared with experimental measurements. In the axisymmetric tube hydroforming process, an optimal hydraulic curve is pursued by performing the simulation with various internal pressures and axial forces.

• 소성∙가공
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• 제10권6호
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• pp.478-484
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• 2001

Tube Process (TP) is a process to produce permanent magnets using a deformable tube for densification of magnet powder. This process claims that it can accomplish both densification and anisotropication in one step forming. This process is distinguished from other processes since it uses a deformable copper tube for densification of magnet powder. In this paper, simulation has been carried out for tile Tube Process in a closed die considering the compressibility of powdered material, arbitrary curved shape and deformable body contact between Nd-Fe-B magnet powder and a copper tube. Results show that the finite element analysis of the Tube Process plays an important role in the stage of preform design.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.82-85
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• 1999

Permanent magnets of Nd-Fe-B group have kept a key post in the permanent magnet market and used in various parts. Tube Process is a process to produce permanent magnets using a deformable tube for denslfication of powder magnets. Advantage claimed for this process is that it can accomplish both densification and anisotropication in one step forming. In this paper. the simulation has been carried out for a full Tube Process in a closed Qe considering the compressibility of material, arbitrary curved shape and deformable body contact between Nd-Fe-B powder magnet and copper tube. The results show that the analysis of Tube Process is applicable with great help in the stage of preform design.

• 소성∙가공
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• 제23권7호
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• pp.419-424
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• 2014

In order to improve efficiency, an outdoor unit using a refrigerant cooling method is designed into many air conditioner systems. The heat exchanger is composed of a Cu tube and an plate. The optimal design for the cold plate is very important because the efficiency of the heat transfer depends on the contact area between the Cu tube and the cold plate. The current study focused on the design of the cold plate to obtain a uniform contact between the Cu tube and the cold plate. Both FE(finite element) analysis and optimization were used in the design. The contact area between the tube and plate was predicted and improved by 16% through the press forming simulations. The springback after press forming was also reduced when the optimized design parameters were used. To verify the validity of the optimal cold plate design, a verification test was conducted. As a result, the performance of the heat exchanger improved by 34% when compared to benchmarked products.

• 한국압력기기공학회 논문집
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• 제7권4호
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• pp.51-56
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• 2011

Steam generator is one of the main equipments that affect safety and long term operation in nuclear power plants. Fluid flows inside and outside of the steam generator tubes and induces vibration. To prevent the vibration the tubes are supported by AVB (anti vibration bar). When the steam generator tube contact to AVB, it is damaged by the accumulation of wear and corrosion. Therefore studies are required to determine the effects of the gap between the steam generator tube and AVB. In order to obtain the stress and the displacement distributions of the steam generator tube, three dimensional finite element analyses were performed by using the commercial program ANSYS. Using the calculated the stress and the displacement distributions, the static residual strength of the steam generator tube can be evaluated. The results show that the stress and displacement of the steam generator tube increase significantly compared with the results from a zero-gap model.

• 소성∙가공
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• 제7권1호
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• pp.72-80
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• 1998

This study is concerned with the thermo-biscoplastic finite element analysis of hot tube extrusion through square dies with a mandrel. The problem is treated as a non-steady state and the ALE description is used due to abruptly turning flow at the die aperture. Since the contact heat transfer coefficient and the friction factor are required in the analysis experiments are also carried out to determine the values, In order to apply ceramics to an extrusion die the study is focussed on under-standing the characteristics of the process. The simulated results provide the useful informations such as metal flow temperature distribution stress state etc. The elastic analysis of the dies is carried out to obtain the stress state of the ceramic dies.

• Journal of Advanced Marine Engineering and Technology
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• 제34권5호
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• pp.653-660
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• 2010

선미관 베어링은 프로펠러가 회전할 시 슬립을 방지하기 위하여 충분한 간섭량을 가지고 캐스팅에 강제 압입되어야 한다. 선미관 베어링을 캐스팅에 강제 압입 시에 필요한 힘을 계산할 때 사용되어지는 공식은 업체별로 각각 다르며, 계산 시 사용되어지는 요소들의 값도 상이하다. 이에 따라 조선소에서 선미관 베어링 강제 압입력을 계산할 때에는 업체별로 제시된 공식과 재질에 따라 고려되어지는 요소들의 값을 사용하지만 간섭량은 조선소의 경험에 기반한 값을 표준으로 사용하고 있다. 본 논문은 강제 압입법에 의한 시공시에 선미관 베어링에 사용되어지는 피팅관계식을 검토하여 선미관 베어링 업체별로 제시되어지는 값을 기반으로 한 결과를 실제 값과 비교하였다. 그 결과 업체별로 제시한 식이 두께가 두꺼운 실린더 이론을 이용하였음을 알 수 있었다. 특히 J사 및 B사의 경우에는 K사와는 달리 두께가 두꺼운 실린더 이론을 근간으로 하였지만, 두께가 얇은 실린더의 경우에도 사용할 수 있도록 변형하여 사용하고 있음을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제22권2호
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• pp.133-140
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• 2018

본 연구에서는 중공형의 PHC말뚝과 강관말뚝을 합성한 중공형 콘크리트 충전 강관(HCFT)말뚝의 거동분석을 위한 수치해석 모델을 개발하였고 휨강도시험에 적용하여 모델의 타당성을 검증하였다. 개발된 비선형 유한요소해석 모델의 적정성을 파악하기 위해 실물 시험 결과와 비교하였고 이를 활용하여 HCFT말뚝에 적합한 접촉조건, PC강봉의 제원에 따른 효과, 콘크리트 두께에 따른 효과 등을 분석하였다. 소성응력분배법을 적용하여 HCFT말뚝의 휨강도 산정식을 제안하였고 시험 및 해석결과와 비교하여 활용성을 검증하였다. 본 연구의 결과는 HCFT말뚝의 최적설계 및 거동분석에 기초자료로 활용될 수 있을 것으로 판단된다.