• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2000년도 추계학술대회 논문집
• /
• pp.37-41
• /
• 2000

Extruded Profiles of Aluminum alloys have been widely used as parts and frames in mechanical and construction structures. Nowadays, mechanical processing of extruded Al alloy profiles is often employed for various industrial applications. Especially, the bending process is more and more applied and the process is greatly influenced by the distributed mechanical properties in the extruded profiles. Due to large reduction of area or extrusion ratio in ordinary production of extruded profiles, anisotropy is naturally induced by large severe deformation during the extrusion process. Therefore, the anisotropy properties play a great role in the bending process, as a post processing of extruded profiles and errors will be involved when the extruded profiles are treated as isotropic material, ignoring the induced anisotropy in the thin-walled extruded product. In the present work, the anisotropic material change is simulated, as a simplified method, employing Barlats six-component yield criterion in the rigid-plastic finite element method. Finite element computations are carried out for extrusion of a thin-walled part.

• 대한기계학회논문집A
• /
• 제31권3호
• /
• pp.388-394
• /
• 2007

Many engineering problems require the calculation of effective material properties of a structure which is composed of repeated micro-structures. The homogenization method has been used to calculate the effective (homogenized) properties of composites and several homogenization procedures for different physical fields have been introduced. This research describes the modified homogenization technique for magnetostatic problems. Assuming that the material is periodically repeated, its effective permeability can be prescribed by calculating the homogenized magnetic reluctivity using the finite element analysis of the micro unit cell. Validity of the suggested method is confirmed by comparing the results by the energy based method as well as the widely known homogenization method.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1996년도 추계학술대회 논문집
• /
• pp.195-198
• /
• 1996

In conducting systems based on LB films, TCNQ derivatives have been extensively studied as electron acceptor molecules. We have investigated the optical, electrical, and magnetic properties of Viologen-(TCNQ￣)$_2$LB films. In UV/visible absorption measurements, we have observed TCNQ￣ peak at 380 nm and dimer peak at 620 nm. The electron spin resonance measurements infer that Viologen-(TCNQ￣)$_2$LB film exhibits anisotropic properly. In other words, the LB film shows angular dependence. Iodine doping affects the degree of charge transfer and the conductivity of the films. The UV/visible absorption spectra of the LB film doped with I$_2$show peaks at near 400~430 nm and there is no dimer absorption peak. The in-plane electrical conductivity of the undoped film is approximately 4.2$\times$10$^{-6}$ S/cm.

• Structural Engineering and Mechanics
• /
• 제4권5호
• /
• pp.469-484
• /
• 1996

Green's functions are obtained in exact closed-forms for the elastic fields in bi-material elastic solids with slipping interface and differing transversely isotropic properties induced by concentrated point and ring force vectors. For the concentrated point force vector, the Green functions are expressed in terms of elementary harmonic functions. For the concentrated ring force vector, the Green functions are expressed in terms of the complete elliptic integral. Numerical results are presented to illustrate the effect of anisotropic bi-material properties on the transmission of normal contact stress and the discontinuity of lateral displacements at the slipping interface. The closed-form Green's functions are systematically presented in matrix forms which can be easily implemented in numerical schemes such as boundary element methods to solve elastic problems in computational mechanics.

• Journal of Magnetics
• /
• 제7권4호
• /
• pp.127-131
• /
• 2002

HDDR characteristics and magnetic properties of $Nd_{15}{(Fe_{1-x}Co_{x})}_{77}B_{8}$(x=0-0.6) alloys were investigated. The effect of applying magnetic field during the recombination step on the anisotropic nature of the HDDR-treated material was also examined. The $Nd_{15}{(Fe_{1-x}Co_{x})}_{77}B_{8}$ phase in the Nd-Fe-B alloys with high Co-substitution alloy had remarkably enhanced phase stability. The $Nd_{15}{(Fe_{1-x}Co_{x})}_{77}B_{8}$(x=0-0.6) alloys with high Co-substitution could be HDDR-treated successfully by only using high pressure hydrogen. However, these alloys had no appreciable coercivity. The poor coercivity of the HDDR-treated $Nd_{15}{(Fe_{1-x}Co_{x})}_{77}B_{8}$(x=0-0.6) alloys with high Co-substitution was attributed to the $Nd{(Fe,Co)}_2$ phase in the alloys. The magnetic filed applied during the recombination step had little effect on the anisotropic nature of the HDDR-treated powder.

• 대한기계학회논문집
• /
• 제14권1호
• /
• pp.23-36
• /
• 1990

본 연구에서는 Iosipescu의 전단 시험법을 사용하여 직접 측정한 응력 프린지 치(ｆ$_{LT}$ )와 Sampson의 응력-광법칙에 의하여 구한 ｆ$_{LT}$ 와 서로 비교하여 Sampson의 응력-광법칙이 ｆ$_{LT}$ 를 간접적으로 측정하는데 사용할 수 있는가를 확 인한다. 그리고 직교 이방성 재료를 광탄성 실험에 의하여 해석하는 경우에 필요한 기본물성치와 응력 프린지치 관계를 구하여 이 관계가 상온과 고온에서도 성립하는가 를 확인하고 또 직접 물성치를 측정하는 대신에 각 물성치에 대응되는 응력 프린지치 에 의하여 물성치를 구하는 방법을 개발하는데 이 연구의 목적을 둔다.

• 한국정밀공학회지
• /
• 제25권11호
• /
• pp.95-99
• /
• 2008

Applications of composite materials in various engineering fields have been extended significantly. For being useful composite materials, we could modify the rigidity and strength characteristics of composite material according to structures and material direction. In this study, CFRP, which has been widely used in space leisure and general structural applications due to the weight, elasticity coefficient, high fatigue strength and lower thermal transformation ect, was selected. As the CFRP is an anisotropic material whose mechanical properties change with its stacking sequence or angle, special attention was given to the effects of the fiber orientation angle on the bending characteristics of CFRP fiat and CFEP square members. It's different on the each result of strength and rigidity of CFRP flat and CFRP square members.

• 한국전산구조공학회논문집
• /
• 제27권6호
• /
• pp.625-633
• /
• 2014

본 논문에서는 액화천연가스 운송을 위해 사용되는 맴브레인형 Mark III 화물창 시스템의 주요 구조물인, 방열 판 구조물의 파손 강도 평가를 수행한 내용을 다루고 있다. Mark III 방열 판 구조물을 복합적층 구조물로 고려하였으며 상용화된 범용 유한요소 프로그램인 MSC사의 PATRAN과 MARC를 사용하여 Mark III 방열 판 구조물의 유한요소 모델을 개발하였다. 특히, 액화천연가스 화물의 특성으로 인해 Mark III 방열 판 구조물이 접하는 상온에서 극저온에 이르는 광범위한 온도 분포에 따른 재료 물성치 변화를 유한요소 모델에 포함하였다. 이 유한요소 모델을 기반으로 파손 강도 평가 절차가 확립되었으며, 이 때 Mark III 방열 판 구조물의 파손 발생 여부를 판단하기 위해 Hashin, Hill, Hoffman, maximum stress, 그리고 Tsai-Wu와 같은 이방성 파손 기준들을 사용하였다. Mark III 방열 판 구조물의 전반적인 구조적 거동을 이해하였으며 이후 초기 파손 영역에서 강도 평가를 수행하여 파손이 발생되었을 때의 위치와 하중 등을 알 수 있었다.

• Smart Structures and Systems
• /
• 제2권3호
• /
• pp.237-251
• /
• 2006

Piezoelectric sensors have many applications in geotechnical engineering, especially in characterizing soils through measurement of wave velocities. Since mechanical properties of a material are closely associated with wave velocities, piezoelectric sensors provide a reliable and non-destructive method for the determination of soil properties. This paper presents results of recent research on measuring stiffness of a wide range of soils such as clay, sand, and gravel, characterizing anisotropic properties of soil induced by external loading, measuring stiffness of base and subgrade materials in the pavement, determining soil properties in a centrifuge model during the flight of a centrifuge, and understanding wave propagation in granular materials under micro-gravity environment using this technique.

• 한국기계가공학회지
• /
• 제17권5호
• /
• pp.143-148
• /
• 2018

3D printing has been expanding beyond the bio/nano field to the automobile and aviation industries. 3D-printing technology has to overcome real problems to have economic value compared to its unlimited usability. Typically, the difference in mechanical strength along the lamination direction requires sufficient research to ensure reliability. In this paper, we study the anisotropic properties of ABS based on the stacking method of FDM 3D printing. Specifically, the mechanical properties of ABS material are determined through a tensile test and 3-point bending test, and the in-plane orthotropic properties are ascertained.