• 항공우주시스템공학회지
• /
• 제12권6호
• /
• pp.41-49
• /
• 2018

이번 연구에서는 복합재료 박벽보(thin-walled beam)에서 시위 방향으로 단일 셀의 비대칭성 단면을 가지는 모델을 선정하여, 단면의 형상에 대한 이론적인 동특성을 연구하였다. 이를 위해 전단 변형 효과(transverse shear effect)와 와핑 구속 효과(warping restraint effect), 보의 길이 방향으로 일정한 테이퍼비와 기하학적 단면비 등을 고려하고, 비대칭 단면의 와핑 함수 보정을 통해 수학적 모델링을 수행하였다. 그 결과에 따라, 고려한 단면의 질량 계수와 강성 계수 및 고유 진동수 등의 특성을 조사하였다. 특히, 단면의 비대칭성, 와핑 함수를 보정하지 않은 경우, 모델의 테이퍼비와 단면비 등이 고유 진동수에 미치는 영향을 비교 분석하였다.

• Journal of Mechanical Science and Technology
• /
• 제16권8호
• /
• pp.1064-1071
• /
• 2002

Stainless steel pipe of type 304 the with a wall thickness of 26.9 mm and the outer diameter 406.4 mm is welded by manual arc welding process. Mechanical properties and fracture toughness of type 304 stainless steel are investigated in the temperature ranging from room temperature to -162$^{\circ}C$ The results obtained are summarized as follows. The tensile strength noticeably increases as the temperature becomes lower while the yield strength is relatively insensitive to temperature. The Charpy impact energy and CTOD values become higher in the case that crack propagation direction is aligned to the transverse axis upon the rolling direction than longitudinal direction. The drop of fracture toughness is associated with the noticeable diminution of plastic component as temperature seduces from room temperature to -162$^{\circ}C$ .

• 한국섬유공학회:학술대회논문집
• /
• 한국섬유공학회 2003년도 봄 학술발표회 논문집
• /
• pp.339-340
• /
• 2003

섬유 고분자 물질의 물리적 성질은 물질의 화학적 구조뿐만 아니라 분자의 배향과 결정화도와 같은 내부 구조에 의해 크게 영향을 받는다. 적외선 분광법은 특정 segment의 배향과 conformation, 결정화도와 같은 내부 구조의 변화를 선택적으로 관찰할 수 있는 장점으로 인하여 섬유 고분자 물질의 연구에 널리 사용되고 있다. 특히 적외선 분광법의 한 방법인 ATR (Attenuated Total Reflection) 방법은 투과에 의한 방법으로는 관찰이 불가능한 fiber, fabric, coating, thick film과 같은 형태의 시료를 관찰 할 수 있는 특성이 있으며 무엇보다 가장 큰 장점은 시료의 Machine Direction (MD), Transverse Direction(TD), Normal Direction (ND)의 세 방향으로 필름의 3차원적 배향 분석이 가능하다는 점이다.$^{1)}$ (중략)

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
• /
• pp.211-214
• /
• 2000

Filament wound pressure vessels have been studied for the efficient design tool to consider the variation of fiber angles through-the thickness direction. Filament winding patterns were simulated from semi-geodesic fiber path equation to calculate fiber path on arbitrary surface. Finite element analyses were performed considering fiber angle variation in longitudinal and thickness directions by ABAQUS. For the finite element modeling of the pressure tank, the 3-dimensional layered solid element was utilized. From the stress results of pressure tanks, maximum stress criterion in transverse direction was applied to modify material properties for failed region. In the end of each load increment, resultant layer stresses were compared with a failure criterion and properties were reduced to 1/10 for a failed layer. Results of progressive failure analysis were compared with two experimental data.

• Journal of Welding and Joining
• /
• 제21권1호
• /
• pp.87-92
• /
• 2003

JLF-1 steel (Fe-9Cr-2W-V-Ta), reduced activation ferritic steel, is one of the promising candidate materials for fusion reactor applications. Tensile properties of JLF-1 base metal and its TIG weldments has been investigated at the room temperature, $400^{\circ}C$ and $600^{\circ}C$. The tensile strength of base metal (JLF-1) showed the level between those of weld metal and the Heat Affected Zone (HAZ). When the test temperature was increased from room temperature to high temperature ($400^{\circ}C$ and $600^{\circ}C$), both strength and ductility decreased or base metal, weld metal and the HAZ. The longitudinal specimens of base metal represented similar strength and ductility at room temperature and high temperature, compared to those of transverse specimens. Little anisotropy for the rolling direction was observed in the base metal of JLF-1 steel.

• 한국레이저가공학회지
• /
• 제9권1호
• /
• pp.25-29
• /
• 2006

This study aimed to investigate the change of mechanical properties with the rolling direction and shielding condition during laser welding of AZ31 magnesium alloy. AZ31 magnesium alloy sheets of 1mm thickness were welded using a continuous wave Nd:YAG laser with and without Ar shielding gas. The effect of Ar shielding gas and rolling direction on the mechanical properties were investigated using Vickers hardness, transverse-weld tensile. Porosity in the weld metals was investigated using an optical microscope. The experimental results showed that mechanical properties of AZ31 magnesium alloy laser welds were upgraded compared to those of base metal. Mechanical properties of AZ31 magnesium alloy laser welds were not substantially changed when Ar shielding gas was supplied.

• 한국초전도ㆍ저온공학회논문지
• /
• 제1권1호
• /
• pp.38-41
• /
• 1999

Strands composing multistage superconducting cables for AC power applications have twisted structure in each stage for lower AC loss and higher stability. So, when transport currents flow in a cable, each strand is exposed to longitudinal and azimuthal magnetic fields produced by transport current flowing in strand itself and Iongitudinal and transverse magnetic fields by transport current flowing in twisted cable. In this paper. we study the influence on self field lesses generated in second stage superconducting cable for different twist direction of filaments in a strand considering twist of strands in cables.

• 한국섬유공학회:학술대회논문집
• /
• 한국섬유공학회 2003년도 가을 학술발표회 논문집
• /
• pp.199-200
• /
• 2003

PEN (Polyethylene 2,6-dicarboxyl naphthalate)은 PET와 화학적 구조가 유사한 polyester 이다. PEN은 PET 의 benzene ring 대신 naphthalene ring이 있는 구조로서 rigid 한 구조를 바탕으로 PET 보다 훨씬 우수한 기계적 물성과 기체 차단성 및 전기 절연성을 가지고 있기 때문에, 현재 PEN에 대해서는 많은 연구가 진행되었고, 상업용으로도 생산되고 있다. 현재까지 진행된 PEN에 대한 연구 중 X-ray를 이용한 배향 거동에 대한 연구보고는 많았으나, 아직까지 FTIR-ATR 을 통해서 시료의 Machine Direction (MD), Transverse Direction (TD), Normal Direction (ND)의 세 방향으로 필름의 3차원적 분자 배향의 거동에 대한 연구보고는 없다. (중략)

• The Korean Journal of Ceramics
• /
• 제1권4호
• /
• pp.197-203
• /
• 1995

Nearly fully dense PZT samples both with tetragonal and with morphotropic phase boundary compositions were prepared by the conventional powder processing and sintering. A micro-indentation technique was used to evaluate the dependence of fracture toughness on remanent polarization, crack length and the direction of crack propagation. The result shows that the toughness increases with the remanent polarization along the poling direction and decreases in the transverse direction. The dependence of toughness on the remanent polarization is neither symmetric nor linear but rather shown to be saturated quickly with the increase in remanent polariztion. R-curve behaviors are observed in both poled and unpoled samples. Sequential SEM and XRD studies on annealed, poled, ground, fractured and etched samples show that domain switching is evident as a viable toughening mechanism but might depend upon the rate of crack propagation. Grain bridging is also observed as one of the active toughening mechanisms.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.73-75
• /
• 2005

이 논문에서는 전기강판의 자계 특성을 측정하기 위하여 이방향 자계인가형 싱글 시트 테스터가 개발되어졌다. 이 개발된 시스템은 자속밀도와 자계세기를 B-coil과 H-coil로 측정할 수 있다. B-coil은 rolling direction과 transverse direction에 대하여 각각 1-turn 감겨져 있으며 H-coil은 200-turn 각각 감겨져있다. 실험을 통하여 이 시스템은 방향성 전기 강판의 경우 rolling direction에 대하여 1.8 [T]까지 측정되어질 수 있다.