• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.84-86
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• 2007

Aluminum sheets were asymmetrically cold rolled without lubrication by using different roll velocities of upper and lower rolls in order to intensify the shear deformation. During asymmetrical cold rolling of aluminum sheets, a reduction per a rolling pass, initial sheet thickness, roll diameter, roll velocity ratio were varied to investigate the effect of rolling parameters. The formation of through thickness shear texture was related to the ratio of the contact length between the roll and sample($l_c$) to the sheet thickness(d). The strain states associated with asymmetrical rolling were investigated by the finite element method (FEM) simulation. FEM results indicated that the evolution of deformation texture in a thickness layer is strongly governed by integrated values of strain rates $\dot{\varepsilon}_{13}$ and $\dot{\varepsilon}_{11}$ along the streamline in the roll gap.

• 산업기술연구
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• 제22권A호
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• pp.185-192
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• 2002

The performance of old and the new concrete construction depends upon bond strength between old and the new concrete. Current adhesive and strength measurement method ignores the effect of stress concentration from shape of specimens. Therefore, this research calculates stress concentration coefficient as the ratio of drilling depth to drilling diameter($h_s/D$), the ratio of overlay thickness to drilling diameter($h_0/D$), the ratio of steel disk thickness to drilling diameter(t/D), the ratio of overlay elastic modulus to substrate modulus($E_1/E_0$), the distance from core to corner border(L_$_{corner}$) and the distance between cores(L_$_{coic}$) vary. The finite element method is adapted to analysis The results from 'the F.E.M analysis are as follows. The stress concentration effects can be minimized when the ratio of drilling depth to drilling diameter($h_s/D$) is 0.20~0.25, the elastic modulus ratio($E_1/E_0$) is 06~1.0, and the ratio of steel disk thickness to drilling diameter(t/D) is 3.0. The overlay thickness, the distance from specimens to corner border(L_$_{corner}$), the distance between cores(L_$_{coic}$) almost do not affect to the stress concentration.

• Steel and Composite Structures
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• 제34권5호
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• pp.657-670
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• 2020

In this paper, vibration analysis of functionally graded nanoshell is studied based on the sinusoidal higher-order shear and normal deformation theory to account thickness stretching effect. To account size-dependency, Eringen nonlocal elasticity theory is used. For more accurate modeling the problem and corresponding numerical results, sinusoidal higher-order shear and normal deformation theory including out of plane normal strain is employed in this paper. The radial displacement is decomposed into three terms to show variation along the thickness direction. Governing differential equations of motion are derived using Hamilton's principle. It is assumed that the cylindrical shell is made of an arbitrary composition of metal and ceramic in which the local material properties are measured based on power law distribution. To justify trueness and necessity of this work, a comprehensive comparison with some lower order and lower dimension works and also some 3D works is presented. After presentation of comparative study, full numerical results are presented in terms of significant parameters of the problem such as small scale parameter, length to radius ratio, thickness to radius ratio, and number of modes.

• 한국산업융합학회 논문집
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• 제9권1호
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• pp.5-11
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• 2006

This study was performed to determine the effect of structural characteristics of selected wool fabrics on mechanical and thermal properties. 52 wool fabrics, including 18 plain woven fabrics and 34 twill and satin woven fabrics were used as samples woven with various weft density for the study. Several physical characteristics such as mechanical properties, keeping warmth ratio of wool fabrics were measured. Data analyses including 1) analysis of tactile and thermal comfort sensation were performed. the following were obtained from the results: The main factors affecting keeping warmth ratio were thickness and bulk density. The keeping warmth ratio of samples increased with increasing thickness and decreasing bulk density of samples. In addition, coefficient of friction of the samples increased with keeping warmth ratio of samples. The above results show that wearing sensation and comfort properties of fabrics are changed depending on the end-use, and thus, above results can be used to manufacture of fabrics for specific end-use with high comfort properties.

• 대한방사선기술학회지:방사선기술과학
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• 제2권1호
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• pp.95-99
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• 1979

When the ${\gamma}-ray$ of average energy 375KeV emitted by Ir-192 is exposed to each film through lead foil with various thickness, the film sensitivity will be different according to the thickness of lead foil and film type. The results on the study, different density and sensitive ratio appeared depending on exposed time and film type, but was made on the following common points. 1. The effect of film sensitivity by the front lead foil showed rapid increase up to the thickness of more or less 0.03mm, and the thicker lead foil was decreased more in the thickness of about $0.05{\sim}0.09mm$. 2. The effect of film sensitivity by the back lead foil was increased up to around of $0.03{\sim}0.08mm$ thickness, the maximum sensitivity was obtained in the thickness of more than $0.03{\sim}0.08mm$ without any change in the above effect. 3. The sensitivity of front lead foil was higher than that of back lead foil in thin lead foil with about 0.127mm thickness, but the sensitivity of back lead foil was higher than that of front lead foil when thickness became thicker.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.306-311
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• 2001

Effect of boundary layer thickness on the flow characteristics around a rectangular prism has been investigated by using a PIV(Particle Image Velocimetry) technique. Three different boundary layers(thick, medium and thin)were generated in the Atmospheric Boundary Layer Wind Tunnel at Pusan National University. The thick boundary layer having 670mm thickness was generated by using spires and roughness elements. The medium thickness of boundary layer$(\delta=270mm)$ was the natural turbulent boundary layer at the test section with fully long developing length(18m). The thin boundary layer with 36.5mm thickness was generated by on a smooth panel elevated 70cm from the wind tunnel floor. The Reynolds number based on the free stream velocity and the height of the model was $7.9{\times}10^3$. The mean velocity vector fields and turbulent kinetic energy distribution were measured and compared. The effect of boundary layer thickness is clearly observed not only in the length of separation bubble but also in the reattachment points. The thinner boundary layer thickness, the higher turbulent kinetic energy peak around the model roof. It is strongly recommended that the height ratio between model and approaching boundary layer thickness should be a major parameter.

• 에너지공학
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• 제7권2호
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• pp.180-186
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• 1998

본 연구에서는 벤토나이트 혼합액의 유동특성 등을 파악하기 위형 전단속도에 따른 점도의 변화를 측정하였으며, 박막형성에 관한 특성을 파악하기 위하여 혼합비 및 점도에 따른 박막두께를 측정하였다. 또한 건조 후 박막이 박막의 두께에 따른 오염표면에서 분리되는 특성을 조사하였으며 벤토나이트의 흡착성능에 영향을 미치는 비표면적을 측정하기 위하여 BET 방법을 이용하였다. 점도는 혼합비의 증가에 따라 감소하였으며 건조박막의 두께는 혼합비가 증가할수록 두꺼워진다. 건조박막의 분리특성은 혼합비가 5에서 10% 이내로 박막이 40에서 150$\mu\textrm{m}$가 적당하다.

• 대한가정학회지
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• 제27권1호
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• pp.1-8
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• 1989

In order to investigate the mechanical properties such as tensile, bending, shearing, thickness and weight of the wool fabrics were measured by KES-F system. Samples were classified into blend ratio, weave type, fabric count. Blend ratio was classified into two groups, which are P/W blended fabric (p=63~65%, w=35~37%) and all wool fabric. Weave type was classified into four groups, which are plain, 3 harness twill, 4harness twill, satin. Cloth count was classified into three groups, which are loose, medium, tight. Statistical analysis was performed using T-test, F-test. The results were as follows; 1. There was significant difference in the thickness, tensile, bending, shearing according to the blend ratio. 2. According the weave, there was significant difference in the bending, weight and thickness in the P/W blended fabrics. There was significant difference in the tensile, weight, thickness, bending, shearing, shearing hysterisis (2HG) in the all wool fabrics. 3. There was significant difference in the shearing properties according to the fabric count.

• Geomechanics and Engineering
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• 제19권2호
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• pp.193-199
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• 2019

A frozen fringe plays a key role in frost heave development in soils. Previous studies have focused on the physical and mechanical properties of the frozen fringe, such as overall hydraulic conductivity, water content and pore pressure. It has been proposed that the thickness of the frozen fringe controls frost heave behavior, but this effect has not been thoroughly evaluated. This study used a temperature-controllable cell to investigate the impact of frozen fringe thickness on the characteristics of frost heave. A series of laboratory tests was performed with various temperature boundary conditions and specimen heights, revealing that: (1) the amount and rate of development of frost heave are dependent on the frozen fringe thickness; (2) the thicker the frozen fringe, the thinner the resulting ice lens; and (3) care must be taken when using the frost heave ratio to characterize frost heave and evaluate frost susceptibility because the frost heave ratio is not a normalized factor but a specimen height-dependent factor.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.149-152
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• 2010

75톤급 개방형 액체로켓엔진에 장착되는 터보펌프의 초음속 충동형 터빈의 로터 전방 두께에 따른 성능 특성 변화의 시험적 연구를 수행하였다. 75톤 터빈 시험에서는 로터 두께 대 피치비가 30톤 로터 대비 각각 1.9배와 1.4배인 로터의 성능을 비교하였다. 시험 결과 로터 두께가 상대적으로 작은 로터의 설계 상사점 효율이 1.5% 상승하였고, 동일 회전수에서 최대 효율이 나타나는 압력비도 증가하였다.