• 대한기계학회논문집A
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• 제38권4호
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• pp.363-370
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• 2014

본 연구에서는 NURBS(Non-Uniform Rational B-spline)를 이용한 형상최적화 방법을 제안한다. 대부분 NURBS 기반 형상 최적화 방법은 NURBS의 제어점 위치 좌표 값만을 설계변수로 택하고 있다. 이러한 경우, 형상최적화 과정에서 종종 제어점들이 서로 가까워져 메쉬 품질을 악화시키고 수렴이 되지 않는 등의 문제를 야기시킨다. 본 연구에서는 형상최적화에서 NURBS 제어점의 좌표뿐 아니라 가중치를 추가적으로 설계 변수로 고려하여 세밀한 형상 변화를 가능하게 하고, 제어점 위치 좌표 최적화 과정과 제어점 가중치 최적화 과정을 분리하여 단계적으로 효율적인 형상 최적화를 수행하였다. 제안한 형상최적화 방법을 예제에 적용하여 제안된 방법의 효율성을 검증하였다.

• 한국CDE학회논문집
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• 제12권1호
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• pp.27-38
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• 2007

This paper describes a multiresidual approximation method for scattered volumetric data modeling. The approximation method employs a volumetric NURBS or VNURBS as a data interpolating function and proposes two multiresidual methods as a data modeling algorithm. One is called as the residual series method that constructs a sequence of VNURBS functions and their algebraic summation produces the desired approximation. The other is the residual merging method that merges all the VNURBS functions mentioned above into one equivalent function. The first one is designed to construct wavelet-type multiresolution models and also to achieve more accurate approximation. And the second is focused on its improvement of computational performance with the save fitting accuracy for more practical applications. The performance results of numerical examples demonstrate the usefulness of VNURBS approximation and the effectiveness of multiresidual methods. In addition, several graphical examples suggest that the VNURBS approximation is applicable to various applications such as surface modeling and fitting problems.

• 전기의세계
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• 제18권6호
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• pp.33-45
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• 1969

The purpose of this paper is design the most important part of sequential control systems, that is, command-treatment part, from the signal-transformation point of view. An orderly procedure is developed by which for sequential control systems the experimental design method can be reduced to the rational design method. Important in this procedure are: 1. To make total block diagram of sequential control systems by determining input and output signals of command-treatment part. 2. To partition over-all block diagram by observing each output signal. 3. To design concretely minimum block diagram by using the operational block diagram. By applying the method for partitioning the circuit to the design, the design method for sequential control systems is organized and done rationally without the aid of experiece.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.339-342
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• 2003

This paper newly proposes a mesh regularization method for the enhancement of the efficiency in sheet metal forming analysis. The regularization method searches for distorted elements with appropriate searching criteria and constructs patches including the elements to be modified. Each patch is then extended to a three-dimensional surface in order to obtain the information of the continuous coordinates. In constructing the surface enclosing each patch, NURBS(Non-Uniform Rational B-Spline) surface is employed to describe a three-dimensional free surface. On the basis of the constructed surface, each node is properly arranged to form unit elements as close as to a square. The analysis results with the proposed method are compared to the results from the direct forming analysis without mesh regularization in order to confirm the validity of the method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.831-836
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• 1994

This paper presents rational modeling and analysis method for complex structures with various structural joints. For modeling of structural joint, a general modeling technique is newly proposed by flexibility influence coefficient and inverse of flexibility matrix and static reduction concept which is applied to the retained DOFs(degrees of freedom) of detailed finite element model of struction joints. By this method,joint model with contact surface. which can not be reduced by the general reduction theory such as Guyan reduction theory ,can be reduced effectively. And in this method, the nonlinearity of the contact surface can be linearized within a proper range and the boundary effects of joint region can be excluded. Using the proposed method, screwed joint,glued joint and bolted joint are analyzed. And the effectiveness of the proposed method is verified by experiments.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.920-924
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• 2002

This paper presents the reverse design of a cam mechanism using NURBS(Nonuniform Rational B-spline curve). Cam is very difficult to make the accurate shape on the design and the manufacture. Because the cam shape is commonly made in order to move in special functions. The reverse design can be used to check accuracy between the designed data and the manufactured data of the cam shape and also reproduce the cam without the design data. The reverse design procedures consist of motion analysis and curve fitting. The motion analysis is used the central difference method and the relative velocity method to find the displacement and velocity. The curve fitting is used NURBS to develope the whole curve. The central difference method is derived in the 3 dimensional space.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1995년도 가을 학술발표회 논문집
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• pp.211-216
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• 1995

In recent years, Natm has been successfully applied to difficult ground conditions with the use of soil-perservention methods which promote face stability and restrict excessive ground movement. When the tunnle excavation od made through difficult ground like highly weathered rock, the umbrella arch method is often adopted which pre-reinforceas tunnel crown periphery using a stiff shell-shaped structure. The umbrella arch method was originally developed in Itali, and has recently been confirmed its effectiveness in Korea as well. However, no in depth study on the umbrella arch method has been conducted ans as a result no rational analysis/design method is available at present. Therefore this study was undertaken with the aim of identifying the basic reinforcing mechanism and satablishing both qualitative and quantiative relationships between various design parameters and ground movements.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.295-302
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• 2002

This paper introduces a method to determine strut-tie models in reinforced concrete (RC) structures using the evolutionary structural optimization (ESO). Even though strut-tie models are broadly adapted in design of reinforced concrete members subjected to shear and torsion, conventional methods can hardly give correct models in RC members subjected to complex loadings and geometry conditions. In this paper, the basic idea of the ESO method is used to determine more rational strut-tie models. Since an optimum topology of structures, finally obtained by the ESO method, usually represents a truss-like structure, the ESO method can effectively be used in finding the best strut-tie model in RC structures. Several example structures are provided to demonstrate the capability of the proposed method in finding the best strut-tie model of each RC structure and to verify its efficiency in application to real design problems.

• 소성∙가공
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• 제12권4호
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• pp.401-407
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• 2003

This paper newly proposes a mesh regularization method for the enhancement of the efficiency in sheet metal forming analysis. The regularization method searches for distorted elements with appropriate searching criteria and constructs patches including the elements to be modified. Each patch is then extended to a three-dimensional surface in order to obtain the information of the continuous coordinates. In constructing the surface enclosing each patch, NURBS(Non-Uniform Rational B-Spline) surface is employed to describe a three-dimensional free surface. On the basis of the constructed surface, each node is properly arranged to form unit elements as close as to a square. The state variables calculated from its original mesh geometry are mapped into the new mesh geometry for the next stage or incremental step of a forming analysis. The analysis results with the proposed method are compared to the results from the direct forming analysis without mesh regularization in order to confirm the validity of the method.

• Interaction and multiscale mechanics
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• 제3권1호
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• pp.1-22
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• 2010

In this paper one introduces a method of multiscale modelling called collection of dynamical systems with dimensional reduction. The method is suggested to be an appropriate approach to theoretical modelling of phenomena in mechanics of materials having in mind especially dynamics of processes. Within this method one formalizes scale of averaging of processes during modelling. To this end a collection of dynamical systems is distinguished within an elementary dynamical system. One introduces a dimensional reduction procedure which is designed to be a method of transition between various scales. In order to consider continuum models as obtained by means of the dimensional reduction one introduces continuum with finite-dimensional fields. Owing to geometrical elements associated with the elementary dynamical system we can formalize scale of averaging within continuum mechanics approach. In general presented here approach is viewed as a continuation of the rational mechanics.