• Structural Engineering and Mechanics
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• 제69권6호
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• pp.627-635
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• 2019

In order to study the axial compression performance of sand-lightweight concrete-filled steel tube (SLCFST) stub columns, three circular SLCFST (C-SLCFST) stub column specimens and three SLCFST square (S-SLCFST) stub column specimens were fabricated and static monotonic axial compression performance testing was carried out, using the volume ratio between river sand and ceramic sand in sand-lightweight concrete (SLC) as a varying parameter. The stress process and failure mode of the specimens were observed, stress-strain curves were obtained and analysed for the specimens, and the ultimate bearing capacity of SLCFST stub column specimens was calculated based on unified strength theory, limit equilibrium theory and superposition theory. The results show that the outer steel tubes of SLCFST stub columns buckled outward, core SLC was crushed, and the damage to the upper parts of the S-SLCFST stub columns was more serious than for C-SLCFST stub columns. Three stages can be identified in the stress-strain curves of SLCFST stub columns: an elastic stage, an elastic-plastic stage and a plastic stage. It is suggested that AIJ-1997, CECS 159:2004 or AIJ-1997, based on superposition theory, can be used to design the ultimate bearing capacity under axial compression for C-SLCFST and S-SLCFST stub columns; for varying replacement ratios of natural river sand, the calculated stress-strain curves for SLCFST stub columns under axial compression show good fitting to the test measure curves.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.406-408
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• 2019

자동차에 사용되는 전동식 워터펌프에 적용되는 모터는 CANNED TYPE의 모터 구조이다. 모터의 구동 부품인 로터는 플라스틱 사출물의 격벽 구조 내에 위치하며, 부동액에 침수되어 있는 상태로 회전을 하게 된다. 플라스틱 사출물 격벽 구조 외부에 Stator가 위치되어 Rotor가 회전이 가능하도록 한다. Rotor의 구성은 Magnet와 Core, Shaft로 구성되며, Magnet와 Core의 경우 부품 특성상 수분 침투에 부식되는 재질이기 때문에 부품의 기밀 유지는 매우 중요하다. 차량에 장착된 상태에서는 120도의 환경조건에서 구동이 가능하여야 하며, 내부압력이 1 Bar 이상의 압력에도 누수가 없어야 한다. 본 논문에서는 이 조건을 만족하여 개발된 전동식 워터펌프의 불량을 검사하기 위하여 헬륨을 이용한 Leak 검사 자동화 시스템을 설계 및 구현하였다.

• Structural Engineering and Mechanics
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• 제83권4호
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• pp.551-561
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• 2022

In this paper, the effect of fire conditions according to ISO 834 standard on the behavior of carbon fibre-reinforced plastic (CFRP) reinforced steel beams coated with gypsum-based mortar has been investigated numerically. To study the efficiency of these beams, 3D coupled temperature-displacement finite element analyzes have been conducted. Mechanical and thermal characteristics of three different parts of composite beams, i.e., steel, CFRP plate, and fireproof coating, were considered as a function of temperature. The interaction between steel and CFRP plate has been simulated employing the adhesion model. The effect of temperature, CFRP plate reinforcement, and the fireproof coating thickness on the deformation of the beams have been analyzed. The results showed that within the first 120 min of fire exposure, increasing the thickness of the fireproof coating from 1 mm to 10 mm reduced the maximum temperature of the outer surface of the steel beam from 380℃ to 270℃. This increase in the thickness of the fireproof layer decreased the rate of growth in the temperature of the steel beam by approximately 30%. Besides excellent thermal resistance and gypsum-based mortar, the studied fireproof coating method could provide better fire resistance for steel structures and thus can be applied to building materials.

• 한국기계가공학회지
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• 제15권3호
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• pp.130-134
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• 2016

Due to the need for advanced technologies in the automotive industry, the demand for lighter and safer vehicles has increased. Even though various nonferrous metals, like Aluminum, Magnesium and also Carbon Fiber Reinforced Plastic (CFRP), have been implemented in the automotive industry, a lot of technical research and development is still focused on ferrous metals. In particular, the market volume of High Strength Steel (HSS) parts and Ultra High Strength Steel (UHSS) by hot press forming parts has expanded significantly in all countries' automotive industries. A new tool steel, High Thermal-Conductivity Tool Steel (HTCS), for stamping punches and dies has been developed and introduced by Rovalma Company (Spain), and it is able to support better productivity and quality during hot press forming. The HTCS punches and dies could help to reduce cycle time due to their high thermal conductivity, one of the major factors in hot press forming operation. In this study, test dies were manufactured in order to verify the high thermal conductivity of HTCS material compared to SKD6. In addition, thermal deformation was inspected after the heating and cooling process of hot press forming. After heating and cooling, the test dies were measured by a 3D scanner and compared with the original geometry. The results showed that the thermal deformation and distortion were very small even though the cooling time was reduced by 2 seconds.

• 한국생산제조학회지
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• 제22권3호
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• pp.388-393
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• 2013

Carbon fiber reinforced plastic (CFRP) has many desirable qualities, including being lightweight and very strong. These characteristics have led to its use in applications ranging from small consumer products to vehicles. Circular and square CFRP members were fabricated using 8ply unidirectional prepreg sheets stacked at different angles ($[+15^{\circ}/-15^{\circ}]_4$, $[+45^{\circ}/-45^{\circ}]_4$ and $[90]_8$, where $0^{\circ}$ coincides with the axis of the member). Based on the collapse characteristics of a CFRP circular member, the collapse characteristics and energy absorption capability were analyzed. Impact collapse tests were carried out for each section member. In this study, the impact energies at crossheads speeds of 5.52 m/s, 5.14 m/s and 4.57 m/s were 611.52 J, 529.2 J and 419.44 J (circular member) 2.16 m/s, 1.85 m/s and 1.67 m/s are 372.4 J, 274.4 J and 223.44 J (square member). The purpose is to experimentally examine the absorption behavior and evaluation the strength in relation to changes in the stacking configuration when the CFRP circular members with different stacking configurations were exposed to various impact velocities. In addition, the dynamic characteristics were considered.

• Korea-Australia Rheology Journal
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• 제19권4호
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• pp.183-190
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• 2007

Injection molding is one of the most common operations in polymer processing. Good quality products are usually obtained and major post-processing treatment is not required. However, residual stresses which exist in plastic parts affect the final shape and mechanical properties after ejection. Residual stresses are caused by polymer melt flow, pressure distribution, non-uniform temperature field, and density distribution. Residual stresses are predicted in this study by numerical methods using commercially available softwares, $Hypermesh^{TM},\;Moldflow^{TM}\;and\;ABAQUS^{TM}$. Cavity filling, packing, and cooling stages are simulated to predict residual stress field right after ejection by assuming an isotropic elastic solid. Thermo-viscoelastic stress analysis is carried out to predict deformation and residual stress distribution after annealing of the part. Residual stresses are measured by the hole drilling method because the automotive part selected in this study has a complex shape. Residual stress distribution predicted by the thermal stress analysis is compared with the measurement results obtained by the hole drilling method. The molded specimen has residual stress distribution in tension, compression, and tension from the surface to the center of the part. Viscoelastic deformation of the part is predicted during annealing and the deformed geometry is compared with that measured by a three dimensional scanner. The viscoelastic stress analysis with a thermal cycle will enable us to predict long term behavior of the injection molded polymeric parts.

• 한국산학기술학회논문지
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• 제20권11호
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• pp.217-223
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• 2019

복합 형상 부품 제작 및 제작 공정의 일체화 장점으로 3D 프린팅 기술의 적용 분야가 확대되고 있으며, 지속적인 연구 개발에 의해 다양한 기술방안들이 등장하고 있다. 대표적인 기술로는 파우더 형태의 소재 위에 레이저를 조사함으로써 원하는 영역을 소결 및 적층 제작하는 방식의 SLS 기술이 있으며, 고성능의 엔지니어링 플라스틱을 활용하여 실제 사용할 수 있는 부품을 제작하는 사례가 늘어나고 있다. 본 연구에서는 활용도가 높은 고분자 소재인 폴리아미드 12 소재 및 글라스 비드가 보강된 폴리아미드 12 소재를 대상으로 인장시편을 제작하여 시편 제작 방향 및 인장 시험 온도에 따른 특성 결과를 비교 분석하였다. 시편 제작방향은 작업 평면 기준으로 0°, 45°, 90° 로 구분하였으며, 인장시험온도는 -25℃, 25℃, 60℃로 조건을 구분하였다. 시험 결과로부터 제작 방향이 90°에 가까울수록 두 소재 모두 탄성률의 미세한 감소를 보였으며, 인장강도는 PA12보다 글라스 비드 보강 PA12가 제작방향에 대한 의존성을 명확하게 보였다. 또한 시험 온도 증가에 따라 탄성률 및 인장강도의 저하를 확인할 수 있었다.

• 농업과학연구
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• 제42권4호
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• pp.423-429
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• 2015

This study was conducted to evaluate the effects of reduced nitrogen (N) and potassium (K) fertigation as additional fertilizer on tomato yield and nutrient contents in excessively nutrients-accumulated soil. Shoot and root dry weights (DW), dry matter rate for shoot, root and fruit and number of fruit in both AF50 and AF100 (50 and 100% levels of additional fertilizer) treatments were increased in comparison with those in AF0 (0% level of additional fertilizer) treatment. In case of nutrient uptake by tomato, nitrogen, phosphorous (P) and potassium contents in all tomato parts (leaf, stem, root and fruit) in AF50 and AF100 treatment were lower than those in AF0 treatment. On the contrary, soluble sugar and starch contents in all tomato parts in AF50 and AF100 were higher than those in AF0 treatment. There were differences between AF0 and AF50 or AF100 in tomato growth, yield, nutrient level and contents of soluble sugar and starch. In contrast, the level and initiation point of fertigation did not significantly affect the parameters. Based on our results, the application of properly reduced level of additional fertilizer is possible to maintain the productivity of tomato and alleviate the nutrient accumulation in plastic film house soils.

• 복식
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• 제37권
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• pp.163-180
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• 1998

In western clothing, woman's body was port-rayed sexually as the distinction of sex was appeared, and the parts of body contain some kind of symbol of sex. Woman's body was diversly accentuated according to the divers ideal beauty concepts pursuits in the different periods. Today, in a Post-industrial Society whose social structure is very divers and complicated, the interpretation of woman's body reveals so various as the complex social structure. The purpose of this study is to comprehend the various interpretations of woman's body in the contemporary clothing. The concrete purposes of this study is as follows. First, this study is to define the concept of natural body and built body by differentiating the parts of body and searching for the sexual symbols accentuated in the western clothing. Second this study aims to review, the histori-cal process of prejudged distinction of sex in the western clothing, and to analyse the con-temporary sociocultural which forced to change this prejudged distinction of sex. Third, on the bases of this analses, this study also aims to present various interpretation on divers aspects of woman's body portrayed in the contemporary clothing. The interpretation of woman's body in the contemporary clothing were as follow. First, it is a body interpreted as a natural and neutral body which is based not so much on prejudged division of sex as on the expression of the body structure. And, it is a decomposed and recomposed body which is based on plastic principles. This body is portrayed by a layer-ing and wrapping which interrogated such traditional symbols of western clothing as collar, sleeve or trousers, skirt, etc. Second, it is a sexually symbolized body. This body is display-ed by exposure or sexual accentuation in the clothing. To conclude, a body interpreted in the contemporary clothing is no more a body accentuated by division of sex, but a body which per-mits indefinite hypotheses and interpretations under synthetic imagination.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.457-460
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• 2000

Injection molding is the most widely used process for the industrial forming of plastic articles. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation·orientation and infection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of welding parts in injection-molded products is assessed. And the effects of fiber content and injection mold shapes on the fiber orientation in case of fiber reinforced polymeric composites are studied. experimentally.