• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.206-211
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• 1996

Closed-die forging of external spine is analysed using an upper bound elemental technique. The kinematically admissible velocity field for three-dimensional deformation in forging of the external spine with trapezoidal teeth was obtained. The upper bound to the deforming load necessary and the the deformed configurations are predicted using integration of the formulation of energy expressions which were obtained from B(upset forging method) were considerd in the present analysis and the theoretical results compared with experimental ones Experiments were carried out on plasticine as model material at room temperature where talcum powder was used as a lubricant. The present investigation revealed that the analytical method B predicts a reducet forging load and improved configuration better than method A for the forged products.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 추계학술대회논문집
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• pp.37-47
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• 1995

Forging of trapezoidal spline, serration and square spline with solid cylindrical billets and hollow one has been investigated by means of upper bound method. Kinematically admissible velocity fields for forging of splines have been proposed in this study. The half pitch of splines has been divided into deformation regons. The neutral surface is introduced into forging of splines with flat punch and, for each step, it is assumed as a circle with its radius rn upper bound solutions obtained obtained by proposed kinematically admissible velocity fields are useful to predict the loads for forging of splines.

• 한국기계가공학회지
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• 제19권5호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.598-603
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• 2001

For metal forming analysis, upper-bound solution is practical method because the solution is overestimated. It is limited to determine stresses on tools by using upper-bound solution. In this study, new scheme to calculate stresses on tools based on upper bound solution is proposed. To verify the proposed scheme, plane strain drawing has been considered. The stresses on tools obtained by the proposed scheme are compared with results of rigid plastic FEM. And the stresses on tools have been determined by the proposed scheme in the forging within plane strain deformation.

• 동력기계공학회지
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• 제4권3호
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• pp.72-80
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• 2000

In order to design a stable robust controller, nominal model, and the upper bound about the uncertainty which is the error of the model are needed. The problem to estimate the nominal model of controlled system and the upper bound of uncertainty at the same time is called robust identification. When the nominal model of controlled system and the upper bound of uncertainty in relation to robust identification are given, the evaluation of the validity of the model and the upper bound makes it possible to distinguish whether there is a model which explains observation data including disturbance among the model set. This paper suggests a method to identity the uncertainty which removes disturbance and expounds observation data by giving a probable postulation and plural data set to disturbance. It also examines the suggested method through a numerical computation simulation and validates its effectiveness.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2690-2692
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• 2000

In order to design a stable robust controller, nominal model, and the upper bound about the uncertainty which is the error of the model are needed. The problem to estimate the nominal model of controlled system and the upper bound of uncertainty at the same time is called robust identifcation. When the nominal model of controlled system and the upper bound of uncertainty in relation to robust identifcation are given, the evaluation of the validity of the model and the upper bound makes it possible to distinguish whether there is a model which explains observation data including disturbance among the model set. This paper suggests a method to identify the uncertainty which removes disturbance and expounds observation data by giving a probable postulation and plural data set to disturbance. It also examines the suggested method through a numerical computation simulation and validates its effectiveness.

• 대한토목학회논문집
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• 제12권1호
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• pp.187-196
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• 1992

본 연구에서는 편심 하중을 받는 기초의 지지력을 극한해석 상계법을 이용하여 산정하였다. 편심 하중이 작용하는 기초의 지지력을 산정하는 기존의 해석방법으로는 극한평형법을 이용한 Meyerhof 방법과 Saran 방법 등이 있으나, 극한해석법을 이용하여 해석하는 경우는 없다. 이에 본 연구에서는 극한해석 상계법을 이용하여 편심하중이 작용하는 기초의 지지력을 산정하였다. 극한해석 상계법으로 해석하는 경우, 적용하는 파괴메카니즘에 따라 그 결과가 달라지므로, 본 연구에서는 기존의 파괴메카니즘을 속도장 조건에 맞게 변형시킨 후, 극한해석 상계법을 적용하여 그 결과들을 상호 비교하였다. 그리고, 편심하중을 받는 기초 구조물의 지지력에 영향을 미치는 요소들을 연구하기 위하여 흙의 내부마찰각, 기초 바닥면의 마찰각, 편심량, 그리고 상재하중 등을 변화시켜 각 요소들이 기초의 지지력에 미치는 영향을 연구하였다.

• 한국지반공학회논문집
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• 제20권7호
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• pp.207-215
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• 2004

본 연구는 보강사면에 상계이론를 적용하여 실제 한계상태에 가까운 신뢰성이 높은 해석방법을 개발하는데 목적이 있으며 상계해석의 유한요소공식화를 전개하는데 있어 거시적인 관점으로부터 비등방성이면서 균질한 재료에 대한 수치해석의 기본 개념은 얻을 수 있다. 보강토는 뒷채움한 성토와 보강재 경계면의 상호작용으로 보강토의 강도가 보강재의 재료적 특성에 의존하고 있기 때문에 흙의 역학적 특성과 보강토의 전체 거동은 보강재의 기하학적인 배열과 상대적인 면적에 의해서 조절할 수 있다. 따라서, 상계이론은 보강사면의 한계상태 거동을 효과적으로 산정할 수 있어 국부적으로 발생하는 소성파괴를 예측할 수 있다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1249-1253
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• 2005

This paper presents a method to model the path loss characteristics in microwave urban line-of-sight (LOS) propagation. We propose new upper- and lower-bound models for the LOS path loss using fuzzy linear regression (FLR). The spread of upper- and lower-bound of FLR depends on max and min value of a sample path loss data while the conventional upper- and lower-bound models, the spread of the bound intervals are fixed and do not depend on the sample path loss data. Comparison of our models to conventional upper- and lower-bound models indicate that improvements in accuracy over the conventional models are achieved.

• 제어로봇시스템학회논문지
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• 제9권9호
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• pp.664-668
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• 2003

A new sliding mode control method based on the lower bound of control gain is presented. Although the magnitube of the proposed control input is larger than that of the conventional control input using both lower and upper bounds, the positive-negative exchanging chattering is reduced and reaching mode is shorter. Because the proposed scheme needs only the lower bound of control gain, it is applicable to the system whose upper bound of control gain is doubtful to determine such as the control gain depends on the system states. It is proved that the proposed control method guarantees the sliding condition. The analysis of differences between the conventional method and the proposed method is given. The validity of the proposed control strategy is shown through a 2nd-order nonlinear system example.