• 소성∙가공
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• 제17권2호
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• pp.130-134
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• 2008

Resource and energy saving is a very important practice for the future as well as for today. Weight saving of structural parts, which are formed by extrusion, plays a key role in manufacturing field. The cross-sections of extruded parts with industrial aluminum are constant in the axial direction by conventional extrusion method. Especially, these aluminum parts used and manufactured in the car industry need other processes to vary the cross-section in the axial direction. However, applications of these parts are often limited by high cost. If the cross-section of the parts is variable by only extrusion with newly developed method, the application of extruded aluminum parts will actually increase. Therefore, a new CNC extruder that can control the section area of a car part was invented for the first time in the nation. Using the extrusion machine, the experiment was performed to validate its workability during the variable section extrusion process. Also, numerical analysis was carried out to investigate the flow mode with different speeds of main ram and various pocket shapes of a die-set in the variable section extrusion process.

• 대한토목학회논문집
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• 제30권6A호
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• pp.581-590
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• 2010

본 연구는 곡선배치 텐던을 갖는 변단면 PSC의 전단을 고려한 층상화 단면해석기술을 소개한다. 곡선배치 텐던의 전단평형을 고려하기 위해서, 각 층상화 단면에서 전단응력을 직접 산출 할 수 있는 새로운 방법과 각 층상화 단면의 변형률 산정시 기존의 반복법보다 수렴 속도가 효율적인 시스템인식기법을 적용하였다. 제안기법은 변단면 PSC보의 정재하실험 결과와 비교분석 되었으며, 추정된 구조응답과 실험결과가 잘 일치하고 있다. 또한, 동일 조건에서 변단면 PSC보와 균등단면 PSC보의 거동특성이 비교분석되었다. 분석결과을 살펴보면, 휨강성은 변단면과 균등단면이 동일하지만, 전단강성은 변단면이 균등단면 보다 크다. 더욱이, 변단면의 자중이 균등단면보다 크지만 변단면의 최대처짐이 균등단면 보다 작다.

• 한국CDE학회논문집
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• 제14권4호
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• pp.234-241
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• 2009

The use of aluminum parts in automobile structuraI applications has increased in an effort to reduce the weight of cars and hence improve fuel economy. But Aluminum bar, I-beam and channels need other processes to vary the cross section in the axial direction. Thus, applications of these parts are limited by high cost. If the cross section of the part is variable by using only extrusion, application of extruded bar, I-beam and channels will increase in the Aluminum industries. In this paper, we propose the variable-shape extrusion process which can control the thickness of Aluminum bar. And we can calculate the speed of center ram by varying the cross section in the extrusion to control the thickness of Aluminum bar.

• Structural Engineering and Mechanics
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• 제68권6호
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• pp.713-720
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• 2018

In this paper a new numerical method to determine the elastic curve of the simply supported beams of variable cross-section is demonstrated. In general case it needs to solve linear or small nonlinear second order differential equations with prescribed boundary conditions. For numerical solution the initial values of the slope and the deflection of the end cross-section of the beam is necessary. For obtaining the initial values a lively procedure is developed: it is a special application of the shooting method because boundary value problems can be transformed into initial value problems. As a result of these transformations the initial values of the differential equations are obtained with high accuracy. Procedure is applied for calculating of elastic curve of a simply supported beam of variable cross-section. Results of these numerical procedures, analytical solution of the linearized version and finite element method are compared. It is proved that the suggested procedure yields technically accurate results.

• 한국지반신소재학회논문집
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• 제15권4호
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• pp.89-96
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• 2016

인천 ${\bigcirc}{\bigcirc}$지역의 연약지반에 시공된 변단면 연약지반보강기초(Variable cross-section soft ground reinforced foundation)의 연직압축거동을 분석하였다. 변단면 연약지반보강기초는 원지반과 고화재를 혼합교반하여 형성되는 고형체의 높은 강성과 강도를 이용하여 상부구조물로부터 유발되는 연약하중을 효과적으로 저항하기 위하여 시공된다. 변단면 연약지반보강기초는 군말뚝 형식으로 시공이 되는데, 정확한 연직거동을 알기 위하여 1개소의 기초에 대한 연직재하시험을 수행하였다. 변단면 연약지반보강기초의 거동을 일반적인 깊은 기초의 거동과 비교하기 위하여 유사한 천층지반조건에 시공된 PHC 파일의 재하시험 결과와 비교하여 재하하중에 따른 침하량 및 하중전이 거동특성을 분석하였다. 연직재하시험결과를 비교분석하였다. 변단면 연약지반보강기초는 제한된 범위의 연직하중에 대하여 천층에서도 효율적으로 저항하는 것으로 분석되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.858-863
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• 2003

In the practical engineering fields, the horizontally curved beams are frequently erected as the major/minor structural components. The effects of both variable curvature and variable cross-section on structural behavior are very important and therefore these effects should be included in structural analyses. From this viewpoint, this paper deals with the free vibrations of horizontally curved beams with variable curvature and variable cross-section. In this study, the parabola as the curvilinear shape and stepped beam as the variable cross-section are considered. The ordinary differential equation governing free vibrations of such beams are derived. For calculating the natural frequencies, the governing equations are solved by numerical methods. The Runge-Kutta and Determinant search Methods are used for integrating the differential equations and for calculating the natural frequencies, respectively. With regard to numerical results, the relationships between frequency parameters and various beam parameters are presented in the forms of Table and Figures.

• 한국자동차공학회논문집
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• 제8권1호
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• pp.135-147
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• 2000

Section design of vehicle structure has been developed by two methods. One is the section property method which uses section property as a design variable. This method shows the tendency of an optimum section approximately. The other method is the section shape method which utilizes geometric parameter of section as a design variable. Practical solutions are obtained by this method. However, it is very expensive for large-scale problems due to the large number of geometric parameters. These two methods are compared through several sample problems. The finite element method is used for the structural and sensitivity analyses. The results are analyzed based on the number of function evaluations, the quality of cost function, the complexity of programing, and etc. The applications of both methods are also discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.643-644
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• 2009

• 한국강구조학회 논문집
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• 제16권1호통권68호
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• pp.81-89
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• 2004

구조물과 같은 아치의 진동해석은 많은 산업분야에서 다양하게 적용되기 때문에 공학적 문제에 중요한 주제이다. 특히 변화하는 단면형상을 가지는 아치는 질량이나 강도를 최적화 하거나 특별한 구조물이나 요구조건들을 만족하기 위해서 폭넓게 사용되어 진다. 최근에는 일반화 미분구적법(GDQM)이나 미분변환법(DTM)은 각각 Shu와 Zou에 의해서 제안이 되었다. 연구에서는 변화하는 단면형상을 가지는 아치의 진동해석이 일반화 미분구적법과 미분변환법을 적용하였다. 변화하는 단면형상을 가지는 아치에 대하여 지배방정식이 유도되어졌으며, 미분변환과 일반화 미분구적법의 개념이 간단히 소개되었다. 변화하는 단면형상을 가지는 아치의 무차원화된 고유진동수가 다양한 경계조건에 대해서 구해졌으며, 이러한 방법들에 의해서 얻어지는 결과들은 선행연구와 비교 되어졌다. 일반화 미분구적법과 미분변환법은 변화하는 단면형상을 가지는 아치의 진동문제를 해석함에 있어서 빠른 수렴, 정확도, 효율성, 유효성을 보인다.

• 한국해양공학회지
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• 제24권1호
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• pp.34-38
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• 2010

An analytical solution procedure for the dynamic response of beams with variable properties is developed by using an asymptotic solution and the Green's function. This asymptotic closed form solution is derived for the transverse vibration of beams under the assumption of slowly varying properties, such as mass, cross-section, tension etc., along the beam length. However, this solution is still found to be very accurate even in the case of large variation, such as step change in cross-section, mass, and tension. Therefore, this derived asymptotic closed form solution and the Green's function can be easily applied to find dynamic responses for various kind of beam vibration problems.