• 국제학술발표논문집
• /
• The 6th International Conference on Construction Engineering and Project Management
• /
• pp.680-681
• /
• 2015

This study develops an algorithm that automatically performs reverse engineering on three-dimensional (3D) sweeping shapes using a user's pre-defined feature templates and 3D point cloud data (PCD) of sweeping shapes. Existing methods extract 3D sweeping shapes by extracting points on a PCD cross section together with the center point in order to perform curve fitting and connect the center points. However, a drawback of existing methods is the difficulty of creating a 3D sweeping shape in which the user's preferred feature center points and parameters are applied. This study extracts shape features from cross-sectional points extracted automatically from the PCD and compared with pre-defined feature templates for similarities, thereby acquiring the most similar template cross-section. Fitting the most similar template cross-section to sweeping shape modeling makes the reverse engineering process automatic.

• 대한기계학회논문집A
• /
• 제26권2호
• /
• pp.275-282
• /
• 2002

Tensile residual stress happen by difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composite(MMC). In this study, TiNi fiber was used to solve the tensile residual stress as the reinforced material. TiNi fiber improves the tensile strength of composite by occurring compressive residual stress in matrix using shape memory effect of it. Pre-strain was added to generate compressive residual stress inside TiNi/A16061 composite. It was also evaluated the effect of compressive residual stress corresponding to pre-strains variation. AE technique was used to clarify the microscopic damage behavior at high temperature and the effect of pre-strain difference of TiNi/A16061 shape memory alloy composite.

• 한국해양공학회지
• /
• 제9권1호
• /
• pp.101-110
• /
• 1995

In SMA(Shape Memory Alloy), the degradation by fatigue is one of the most important problems to be overcome, when SMA is used for robot-actuator materials. The actuator is operated repetitively for long time and its repeating operation develops the fatigue degradation of SMA. The fatigue degradation changes the transformation temperature and deformation behavior and results in inaccurate operation and deformation which results form repeating operation is to be investigated in advance and the scheme to resolve those problems have to be made for the design of actuator. In this paper, for the improvement of the fatigue degradation by repetive movement and better control of the correct movement by the stability of martensite transformation in the development of Robots actuator, Pre-strain(0, 1.5, 5, 8%) are loaded in the specimens and fatigue testing were carried out by the method of heating and cooling in direct condition. From the results of these experiments, the effect on pre-strain which affect the transformation characteristic and fatigue degradation phenomena were correctly investigated.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
• /
• pp.31-34
• /
• 2008

Construction of buildings downtown is increasing as much as ever with a strong demand. A Top-Down Method is suitable for its advantage in minimizing its disturbance to the neighborhood. In general, the Pre-founded Column, one of the most important aspects of the Top-Down Method, has been made with an H-Shape Steel Column. However, due to its structural and economical benefits, the usage of CFT(Concrete Filled Tube) columns in the place of Pre-founded Columns is increasing. To promote their applications, we analyze the merits of CFT columns by comparing them with I-Shape columns and propose further research.

• 한국해양공학회지
• /
• 제30권6호
• /
• pp.431-439
• /
• 2016

This paper reports a numerical method for determining the resistance and self-propulsion performance of an asymmetric pre-swirl stator used as an energy saving device by cancelling a propeller's rotational energy. The present asymmetric pre-swirl stator propulsion system consists of three blades at the port and one blade at the starboard, which can effectively recover the biased rotating flow. This paper provides the design concept for the present asymmetric stator, which produces more efficient results than a conventional propeller.

• 대한지구과학교육학회지
• /
• 제11권2호
• /
• pp.107-115
• /
• 2018

지구의 모양을 아는 것은 지구과학 교육에서 중요한 성취기준이다. 이 연구의 목적은 학교 급별로 효과적인 지구의 모양 실험을 조사하여 학교 탐구실험에 도움을 주고자하는데 있다. 이를 위해 연구자는 지구의 모양을 학습하기 위한 다양한 실험 방법을 제시하고, 예비교사 26명에게 초등학교, 중 고등학교, 대학교 학생들에게 적절한 실험이 무엇인지 조사하였다. 그 결과 효과적인 지구의 모양 실험에 있어서 학교 급별로 차이가 있었다. 예비교사는 초등학생들에게는 '항구로 돌아오는 배의 돛 관찰하기 실험이 효과적일 것으로 생각하고 있었다. 그리고 중 고등학교 학생들에게는 지구의 위도에 따른 북극성 고도 비교하기 실험, 대학교 학생들에게는 지면의 높이에 따른 시야의 차이 비교하기 실험이 효과적일 것이라고 응답하였다. 예비교사는 학교 급별 효과적인 지구의 모양 실험을 선택할 때에는 실험 방법의 난이도, 추상적인 사고와 배경지식의 깊이 등이 고려되어야 한다고 생각하였다.

• 한국소음진동공학회논문집
• /
• 제19권1호
• /
• pp.94-100
• /
• 2009

This paper proposes a novel curved shape piezoelectric unimorph using a new fabrication method. Instead of using thermal coefficient mismatch, which has been used for conventional processes for curved shape unimorphs, we used pre-stressed substrates and the room temperature adhesion process. A difference of the mechanical strains between the substrate and the piezoelectric layer makes the final manufactured unimorph get curved. Several performance tests of the proposed unimorph actuators were accomplished and the test results showed the proposed unimorph actuator got comparable actuation capability compared with conventional curved shape actuators.

• 대한기계학회논문집A
• /
• 제26권9호
• /
• pp.1787-1794
• /
• 2002

TiNi alloy fiber was used to solve the problem of the tensile residual stress as the reinforced material. TiNi alloy fiber improves the tensile strength of composite by occurring compressive residual stress in the matrix using shape memory effect. In order to generate compressive residual stress in TiNi/Al6061 shape memory alloy(SMA) composite, 1, 3 and 5% pre-strains were applied to the composite in advance. It was also evaluated the effect of compressive residual stress corresponding to the pre-strain variation and the volume fraction of TiNi alloy. AE technique was used to clarify the microscopic damage behavior at high temperature and the effect of pre-strain in TiNi/Al6061 SMA composite. The results of the microscopic damage evaluation of TiNi/Al6061 SMA composite under various pre-strain using AE technique can be divided into three stage corresponding to the AE signals. AE counts and events were useful parameters to evaluate the fracture mechanism according to the variation of pre-strain. In addition, two dimensional AE source location technique was applied for monitoring the crack initiation and propagation in composite.

• 한국산학기술학회논문지
• /
• 제16권10호
• /
• pp.6673-6678
• /
• 2015

최근 빈번히 건설되고 있는 비정형 건축물들은, 개별부재의 수직/수평적 연결방식 에서 벗어나, 외관 및 내부 구성요소들의 단면이 자유롭게 변화되는 곡선의 형태를 띠고 있다. 이러한 구조물의 안정성 평가를 위해서 고전적 방식의 유한요소 해석기법이 적용된 상용프로그램이 사용되고 있으나, 과도한 절점분할 방식 또는 유한요소망(Finite Element Mesh)의 도입으로 인하여 해석시간이 길어지고 사용성 및 해석 정밀도가 낮은 문제점을 안고 있다. 따라서 본 연구에서는, 전술된 문제점을 개선하기 위하여, 임의의 곡률을 가진 단위 부재 및 단위요소에 대한 수학적 해석모형을 활용하여 비정형구조물에 대한 구조안정성 평가를 효과적으로 수행할 수 있는 전후처리 모듈을 개발하였다. 본 연구에서 개발된 전후처리 모듈은 곡선형 부재의 곡률을 NURBS 제어점을 이용하여 제어할 수 있도록 개발되었으며, 그로 인해 상용프로그램보다 빠른 형상 모델링이 가능하였다. 또한, 자유로운 형상에 대한 시각적 확인이 가능하여 비정형 건축물의 형상과 거동양상의 현실적인 묘사가 가능하였다.

• Smart Structures and Systems
• /
• 제18권1호
• /
• pp.139-154
• /
• 2016

This paper is concerned with the dynamics of hyperelastic solids and structures. We seek for a smart control actuation that produces a desired (prescribed) displacement field in the presence of transient imposed forces. In the literature, this problem is denoted as displacement tracking, or also as shape morphing problem. One talks about shape control, when the displacements to be tracked do vanish. In the present paper, it is assumed that the control actuation is provided by imposed eigenstrains, e.g., by the electric field in piezoelectric actuators, or by thermal actuators, or via analogous physical effects, such as magneto-striction or pre-stress. Structures with a controlled eigenstrain-type actuation belong to the class of smart structures. The action of the eigenstrains can be conveniently characterized by actuation stresses. Our theoretical derivations are performed in the framework of the theory of small incremental dynamic deformations superimposed upon a statically pre-deformed configuration of a hyperelastic solid or structure. We particularly ask for a distribution of incremental actuation stresses, such that the incremental displacements follow exactly a prescribed trajectory field, despite the imposed incremental forces are present. An exact solution of this problem is presented under the assumption that the actuation stresses can be tailored freely and applied everywhere within the body. Extending a Neumann-type solution strategy, it is shown that the actuation stresses due to the distributed control eigenstrains must satisfy certain quasi-static equilibrium conditions, where auxiliary body-forces and auxiliary surface tractions are to be taken into account. The latter auxiliary loading can be directly computed from the imposed forces and from the desired displacement field to be tracked. Hence, despite the problem is a dynamic one, a straightforward computation of proper actuator distributions can be obtained in the framework of quasi-static equilibrium conditions. Necessary conditions for the functioning of this concept are presented. Particularly, it must be required that the intermediate configuration is infinitesimally superstable. Previous results of our group for the case of shape control and displacement tracking in linear elastic structures are included as special cases. The high potential of the solution is demonstrated via Finite Element computations for an irregularly shaped four-corner plate in a state of plain strain.