• 축산식품과학과 산업
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• 제7권2호
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• pp.74-83
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• 2018

• 한국자동차공학회논문집
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• 제8권6호
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• pp.173-181
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• 2000

The stability of a structural plate is a crucial problem which causes wrinkling and buckling. In this paper, the effect of the pattern of spot-welding points in the two rectangular plate on the shear buckling load is studied with respect to the thickness, the aspect ratio of plates, the number of welding spots. Buckling coefficient of the simple plate was compared with that of two plates with various conditions to extract the effect of buckling strength. The effect of the number of welding spots are studied in two directions, longitudinal and transverse directions. The concluded that the reinforcement effect was maximized when the aspect ratio was close to 1.5 and that the effect of number of welding spots in longitudinal direction was larger than that in transverse direction.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1649-1654
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• 2004

The near field structures of an under-expanded, dual, coaxial, jets issuing from the coaxial nozzles with four different geometries are visualized by using a shadowgraph optical method. Experiments are conducted to investigate the effects of the nozzle-lip thickness, secondary stream thickness, the nozzle pressure ratio and the secondary swirl stream on the characteristics of under-expanded jets. The results show that the presence of secondary annular swirling stream causes the Mach disk to move further downstream and increases its diameter, which decreases with a decrease in the nozzle-lip thickness. The secondary stream thickness has an influence on the location of an annular shock wave.

• Corrosion Science and Technology
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• 제16권4호
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• pp.201-208
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• 2017

A finite element analysis is proposed to study the effect of specimen dimensions on lateral diffusion of hydrogen during hydrogen permeation flux measurements. The error of measurement on thick specimens because of 1D diffusion approximation may be as much as 70%. A critical condition for accurate measurements is to designate the area of hydrogen monitoring/exit surface smaller than the area of hydrogen charging/entry surface. For thin to medium thickness specimens (ratio of thickness to specimen radius of 5:10 and below), the charging surface should be maximized and the monitoring surface should be minimized. In case of relatively thick specimens (ratio of thickness to specimen radius above of 5:10), use of a hydrogen-diffusion barrier on the specimen boundaries is recommended. It would completely eliminate lateral losses of hydrogen, but cannot eliminate the deviation towards 2D diffusion near the side edges. In such a case, the charging surface should be maximized and the monitoring surface should be as closer in dimension as the charging surface. A regression analysis was carried out and an analytical relationship between the maximum measurement error and the specimen dimensions is proposed.

• 한국의류산업학회지
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• 제22권4호
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• pp.515-522
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• 2020

This study examined the effect of the blend ratio of wool and polyester fibers, yarn and fabric structural parameters to the appearance property and the formability of worsted fabrics. The mechanical properties of twenty types of manufactured worsted and PET/wool blend fabrics were measured using KES-FB and FAST systems. Garment formability increases with the thickness and cover factor as well as increases with wool content. The correlation between KES-FB and FAST system showed a relatively high correlation with an extensibility of 0.98, bending and shear rigidity 0.71; both were higher than polyester synthetic fiber. The correlation coefficient of garment formability between KES-FB and FAST systems was 0.93 and the correlation coefficient between formability and fabric extensibility was 0.8. These results were higher than those of bending and shear rigidity. This revealed that garment formability was influenced by wool content, cover factor and fabric thickness; however, wool content and fabric thickness were the most important factors for the seam pucker. The garment formability of the worsted fabrics can be predicted by fabric mechanical properties measured from KES-FB and FAST systems.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.175-187
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• 2020

The theories having been developed thus far account for higher-order variation of transverse shear strain through the depth of the beam and satisfy the stress-free boundary conditions on the top and bottom surfaces of the beam. A shear correction factor, therefore, is not required. In this paper, the effect of surface on the axial buckling and free vibration of nanobeams is studied using various refined higher-order shear deformation beam theories. Furthermore, these theories have strong similarities with Euler-Bernoulli beam theory in aspects such as equations of motion, boundary conditions, and expressions of the resultant stress. The equations of motion and boundary conditions were derived from Hamilton's principle. The resultant system of ordinary differential equations was solved analytically. The effects of the nanobeam length-to-thickness ratio, thickness, and modes on the buckling and free vibration of the nanobeams were also investigated. Finally, it was found that the buckling and free vibration behavior of a nanobeam is size-dependent and that surface effects and surface energy produce significant effects by increasing the ratio of surface area to bulk at nano-scale. The results indicated that surface effects influence the buckling and free vibration performance of nanobeams and that increasing the length-to-thickness increases the buckling and free vibration in various higher-order shear deformation beam theories. This study can assist in measuring the mechanical properties of nanobeams accurately and designing nanobeam-based devices and systems.

• Advances in nano research
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• 제12권2호
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• pp.117-137
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• 2022

Effect of thickness stretching on free vibration, bending and buckling behavior of carbon nanotubes reinforced composite (CNTRC) laminated nanoplates rested on new variable elastic foundation is investigated in this paper using a developed four-unknown quasi-3D higher-order shear deformation theory (HSDT). The key feature of this theoretical formulation is that, in addition to considering the thickness stretching effect, the number of unknowns of the displacement field is reduced to four, and which is more than five in the other models. Two new forms of CNTs reinforcement distribution are proposed and analyzed based on cosine functions. By considering the higher-order nonlocal strain gradient theory, microstructure and length scale influences are included. Variational method is developed to derive the governing equation and Galerkin method is employed to derive an analytical solution of governing equilibrium equations. Two-dimensional variable Winkler elastic foundation is suggested in this study for the first time. A parametric study is executed to determine the impact of the reinforcement patterns, nonlocal parameter, length scale parameter, side-t-thickness ratio and aspect ratio, elastic foundation and various boundary conditions on bending, buckling and free vibration responses of the CNTRC plate.

• 한국가스학회지
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• 제15권6호
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• pp.14-19
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• 2011

원주 방향의 두께가 불균일한 해저배관에 대한 건전성을 검토하기 위하여 수압에 의한 소성붕괴 저항성을 평가하였다. 본 연구에서는 해저배관에 부가되는 주하중을 수압으로 설정하여 4, 8, 12 및 16%의 두께편차율을 갖는 API 5L X65와 API 5L X80 배관의 소성붕괴압력 변화에 미치는 영향을 유한요소해석을 통하여 평가하였다. 두께 편차율이 증가하면 소성붕괴압력이 감소하며 두께편차율이 동일하면 직경대 두께비가 증가함에 따라 소성붕괴 압력은 감소한다.

• Steel and Composite Structures
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• 제36권2호
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• pp.187-196
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• 2020

Double skin composite wall system owns several structural merits in terms of high load-carrying capacity, large axial stiffness, and favorable ductility. A recently proposed form of truss connector was used to bond the steel plates to the concrete core to achieve good composite action. The structural behavior of rectangular high walls under compression and T-shaped high walls under eccentric compression has been investigated by the authors. Furthermore, the influences of the truss spacings, the wall width, and the faceplate thickness have been previously studied by the authors on short walls under uniform compression. This paper experimentally investigated the effect of width-to-thickness ratio on the compressive behavior of short walls. Compressive tests were conducted on three short specimens with different width-to-thickness ratios. Based on the test results, it is found that the composite wall shows high compressive resistance and good ductility. The walls fail by local buckling of steel plates and crushing of concrete core. It is also observed that width-to-thickness ratio has great influence on the compressive resistance, initial stiffness, and strain distribution across the section. Finally, the test results are compared with the predictions by modern codes.

• 대한기계학회논문집
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• 제14권1호
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• pp.214-224
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• 1990

본 연구에서는 현 저자의 이전의 연구를 확장하여 균일한 열유속을 갖는 2상 기체-고체입자 위 방정식에서 축 방향의 열전달은 반경 방향의 열전달보다 작아 무시 하였으며, 복사 열전달은 기체와 입자 사이의 온도 차이가 적어 무시하였다. 방정식 중 $F_{px}$ 와 $F_{pr}$ 은 2상 사이의 상호작용에 의한 단위부피당 축방향과 반경방향 의 저항력이며, 수직관의 열전달 특성을 부하도와 상대 입자 크기 $d_{p}$/D를 변화시 켜 가면서 조사하는 것이다.다.