• 한국농공학회지
• /
• 제11권3호
• /
• pp.1707-1718
• /
• 1969

The purpose of this experiment is to determine the relations between numbers, arrangements and pumping rates of wells. In this experiment, well pipes were vertically set up in an artificial water-bearing sand layer of homogeneous quality. Wells were arranged in different ways and their number was varied in order to observe the variation of pumping rates. Sands were filled in a square tank, $183cm{\times}91.5cm{\times}91.5cm$ so as to secure a water-bearing layer. Water was constantly supplied from a supply tank located at an end of the tank. The number of well pipes was varied from one to four. Well pipes were connected by a horizontal header pipes were connected by a horizontal header pipe located above them and one pump was used. Pumping rates were measured, when they were arranged in longitudinal and lateral directions, They were also arranged in a square and triangle. The main results thus obtained are presented as follows: (1) When well pipes are laid out in a longitudinal line, i. e., in a flow direction, the ratios of pumping rates of one-pipe well and wells 2-, 3- and 4- pipe t, are 1.903, 2.506 and 2.66, respectively. (2) When well pipes are laid out in a lateral line, i.e., in a perpendicular direction to flow, the same ratios as (1) are 1.912, 2.527 and 2.88. (3) When four pipes are laid out in a square and three pipes are laid out in a triangle, pumping rates are deereased, Comparing with the cases when pipes are laid out in a straight line.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2005년도 추계학술대회 논문집
• /
• pp.283-286
• /
• 2005

When subjected to severe shear deformation by ECAP, microstructure of Al2024 becomes nanocrystalline grained texture material. To measure the strength of that, small punch (SP) testing method was adopted as a substitute for the conventional uniaxial tensile testing because the size of material processed by ECAP were limited to $\varphi12mm$ in transverse direction. SP tests were performed with specimens in longitudinal and transverse directions of Al 2024 ECAP metal. For comparing the strength values with those assessed by SP tests, uniaxial tensile tests were also conducted with specimens in longitudinal direction. Failure surfaces of the tested SP specimens showed that failure mode was shear deformation and Al 2024 ECAP metal has an anisotropy in strength. Thus, conventional equations proposed for assessing the strength characteristics were improper to assess those of Al2024 ECAP metal. In this paper a way of assessing the strength of Al 2024 ECAP metal was proposed and was proven to be effective.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1993년도 학술발표집 지반진동 영향평가
• /
• pp.55-72
• /
• 1993

동다짐은 무거운 다짐추를 고공에서 낙하시켜 낙하시 지반에 가하는 충격을 이용하여 지반을 개량하는 공법으로서, 시공시 발생하는 진동에 의하여 주변 구조물매 피해가 유발될 수도 있다. 본 연구는 쓰레기 매립지반에서 동다짐을 시공할시 수행된 진동 측정자료들을 분석하였으며 그 결과 다음과 같은 사실들을 확인할 수 있었다. \circled1 동다짐시 발생하는 진동의 입자속도는 Longitudinal, vertical, Transversal 방향순으로 그 크기가 크며, 체감을 또한 Lcugitudinal, Vertical, Transversal 방향순으로 큰 것으로 나타났다. \circled2동다짐시 발생하는 진동의 탁훨 진동수는 7-9 Hz내외이다. \circled3구조물에 인접한 동다짐은 다짐추의 낙하고를 저하시켜 충격에너지를 감소시켰으며, 이를 이용하여 구조물께 대한 피해를 애방할 수 있었다. \circled4사무기기는 켜놓은 상태가 꺼놓은 상태보다 진동에 대하여 약하므로 사무기기에 대한 진동피해를 줄이기 위하여는 비 업무시간을 이용하여 사무실에 10m까지 인접하여 동다짐을 실시할 수 있었다.

• Steel and Composite Structures
• /
• 제27권4호
• /
• pp.525-536
• /
• 2018

This paper focuses on the application of the first-order shear deformation theory (FSDT) to thermo-elastic static problems of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) cylindrical pressure vessels. A symmetric displacement field is considered as unknown function along the longitudinal direction, whereas a linear distribution is assumed along the thickness direction. The cylindrical pressure vessels are subjected to an inner and outer pressure under a temperature increase. Different patterns of reinforcement are applied as distribution of CNTs. The effective material properties of FG-CNTRC cylindrical pressure vessels are measured based on the rule of mixture, whereas the governing equations of the problem are here derived through the principle of virtual works. A large parametric investigation studies the effect of some significant parameters, such as the pattern and volume fraction of CNTs, on the longitudinal distribution of deformation, strain and stress components, as useful tool for practical engineering applications.

• Wind and Structures
• /
• 제13권3호
• /
• pp.275-292
• /
• 2010

Wind tunnel experiments were conducted to investigate the wind characteristics in the mountainous valley terrain with 4 simplified valley models and a 1:500 scale model of an existing valley terrain in the simulated atmospheric neutral boundary layer model. Measurements were focused on the mean wind flow and longitudinal turbulence intensity. The relationship between hillside slopes and the velocity speed-up effect were studied. By comparing the preliminary results obtained from the simplified valley model tests and the existing terrain model test, some fundamental information was obtained. The measured results indicate that it is inappropriate to describe the mean wind velocity profiles by a power law using the same roughness exponent along the span wise direction in the mountainous valley terrain. The speed-up effect and the significant change in wind direction of the mean flow were observed, which provide the information necessary for determining the design wind speed such as for a long-span bridge across the valley. The longitudinal turbulence intensity near the ground level is reduced due to the speed-up effect of the valley terrain. However, the local topographic features of a more complicated valley terrain may cause significant perturbation to the general wind field characteristics in the valley.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2008년도 춘계학술대회 논문집
• /
• pp.400-403
• /
• 2008

For the effective manufacture of doubly curved metal plates, a line array roll set (LARS) process is proposed. The suggested process utilizes a pair of upper and lower symmetric roll assemblies. In the process, the initial plate is progressed into the final shape in a stepwise or pathwise manner according to the basic principle of the incremental forming process. The deformation proceeds simultaneously in the longitudinal and transverse directions. Moreover, there is a close correlation between the deformation in the longitudinal direction and that in the transverse direction of the plates. Therefore, the finally formed shape in the incremental forming process is strongly dependent upon process conditions, such as the forming path and the forming increment. The manufacturing of arbitrary doubly curved plates with various curvatures is not an easy task because of such complicated behaviors of the plate; thus, the forming schedules for the desired shape should be carefully and accurately designed. In this study, several experiments with the LARS system were carried out for the fundamental investigation on process design for manufacturing of doubly curved plates.

• 한국정밀공학회지
• /
• 제16권11호
• /
• pp.191-196
• /
• 1999

This stability of a plate structure is very crucial problem which results in wrinkle and bucking. In this study, the effect of the pattern of spot-welding points of the two rectangular plates on the compressive buckling load is studied with respect to the thickness, aspect ratio of plates, number of welding spots. buckling coefficient of the plate not welded was compared with that of two plates with various thickness to extract the effect of thickness. The effect of number of welding spots are studied in tow directions, longitudinal and transverse directions. The conclusions obtained were that the reinforcement effect was maximized when the aspect ratio was close to 1.25 and that the effect of number of welding spots in transverse direction was large than that in longitudinal direction.

• 대한토목학회논문집
• /
• 제11권1호
• /
• pp.29-36
• /
• 1991

장섬유 강화 마그네슘 복합제(FP/ZE41A)의 피로 균열 성장 거동에 대한 열처리 효과를 규명한 것으로 TEM관측에 의해 알루미나 섬유와 마그네슘 복합 매트릭스간의 상호 접변을 완화시키기 위하여 풀림을 실시하였다. 피로 균열 성장 방향에 수직한 섬유와 평행한 섬유들에 대한 피로 균열 성장 거동에 관한 실험을 실시 한 바, 피로 균열 성장 방향에 수직한 시험편의 경우 열처리를 실시한 시험편은 잔류 응력을 제거시키지 않은 시험편에 비해 피로 균열 성장에 대한 더 많은 저항성을 갖고 있음을 알수 있었다. 그러나, 이에 반해 피로 균열 성장 방향에 평행한 시험편의 경우는 잔류 응력을 제거시키지 않은 시험편 이 열처리를 실시한 시험편에 비해 더 많은 피로 균열 성장 저항성을 내포하고 있다는 피로 균열 성장 거동에 대한 차이점을 발견할 수 있었다. 피로 파괴 표면에 대한 연성 파열과 섬유 박리를 SEM관찰한 결과 열처리는 피로균열 성장 거동에서 지적된 바와 같이 섬유와 매트릭스 상호면의 강도를 약화시킨다는 것을 알 수 있었다.

• 한국터널지하공간학회 논문집
• /
• 제21권6호
• /
• pp.825-835
• /
• 2019

터널 설계 시 조사를 통하여 지반을 여러 개의 등급으로 분류한 후 지보패턴표에 따라 해당 지보시스템을 적용하게 된다. 그러나 암반 등급을 기준으로 한 단순한 패턴 적용방식은 암반 등급 경계부에서 발생하는 종방향 응력 전이를 고려하지 못한다. 본 연구는 NATM 터널의 종방향 암반 등급 변화부에서 응력 변화를 추정하기 위한 3차원 수치해석을 실시하였으며 Influence Line (영향선) 및 Trend Line (경향선)을 이용하여 하중전이 영향권을 파악하고자 하였다. 연구 결과 터널 굴착방향으로 암반 등급이 하향 변화하면 등급변화 경계를 중심으로 강성이 약한 암반에서 강성이 큰 암반 방향으로 0.35~0.7D 범위에서 응력 전이가 발생하며 이를 고려하여 암반 등급의 종방향 하향 변화부에서는 연구결과의 0.35~0.7D 영향권을 감안하여 안전측으로 1.0D 정도의 하향패턴을 추가 적용하는 것이 필요하다.

• 한국강구조학회 논문집
• /
• 제9권4호통권33호
• /
• pp.515-521
• /
• 1997

마그네슘 금속 복합재의 열처리 및 섬유 강화재 방향에 따른 효과를 파악하기 위하여 인장강도 및 피로해석이 연구되었다. TEM 관측에 따라 시편은 섬유 강화재와 마그네슘 복합기지 사이의 시효 열처리된 변형된 계면이다. 인장실험 결과로부터 시효 처리된 시편의 극한 인장강도는 주조상태의 시편보다 시효 처리시 화학반응에 의한 섬유 강화재-기지간의 접합강도 약화로 감소하였다. 피로균열 거동실험은 균열거동 방향이 섬유 강화재 방향과 수직인 시편과 균열거동 방향이 섬유 강화재 방향과 평행한 시편을 실험하였다. 피로균열 거동해석을 비교해보면 섬유 강화재와 하중방향이 수직인 시효처리된 시편의 경우가 주조상태의 시편보다 피로균열 거동에 더 크게 저항하였다. 반대로 섬유 강화재 방향에 평행한 주조상태의 시편은 섬유 강화재 방향에 평행한 시효처리된 시편보다 피로 균열거동에 더 크게 저항함을 알 수 있었다.