• 대한기계학회논문집A
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• 제25권4호
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• pp.602-609
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• 2001

This paper is concerned with the orthotropic problem of diaphragm-type air springs which consist of rubber linings, nylon reinforced rubber composite and bead ring. The analysis is carried out with a finite element method developed to consider the orthotropic properties, geometric nonlinearity using four-node degenerated shell element with reduced integration. Physical stabilization scheme is used to control the zeroenergy mode of the element. The analysis includes an inflation analysis and a lateral analysis of an air spring for the deformed shape and the spring load with respect to the vertical and l ateral deflection. Numerical results demonstrate the variation of the outer diameter, the fold height, the vertical force and the lateral force with respect to the inflation pressure and the lateral deflection.

• Structural Engineering and Mechanics
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• 제24권1호
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• pp.31-50
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• 2006

This paper deals with the mechanical behaviour of the thin-walled cylindrical air-spring shell (CAS) made of rubber-textile cord composite (RCC) subjected to different types of loading. An orthotropic hyperelastic constitutive model is presented which can be applied to numerical simulation for the response of biological soft tissue and of the nonlinear anisotropic hyperelastic material of the CAS used in vibroisolation of driver's seat. The parameters of strain energy function of the constitutive model are fitted to the experimental results by the nonlinear least squares method. The deformation of the inflated CAS is calculated by solving the system of five first-order ordinary differential equations with the material constitutive law and proper boundary conditions. Nonlinear hyperelastic constitutive equations of orthotropic composite material are incorporated into the finite strain analysis by finite element method (FEM). The results for the deformation analysis of the inflated CAS made of RCC are given. Numerical results of principal stretches and deformed profiles of the inflated CAS obtained by numerical deformation analysis are compared with experimental ones.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.274-279
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• 2000

This paper is concerned with the orthotropic problem of diaphragm-type air springs which consist of rubber linings, nylon reinforced rubber composite and bead ring. The analysis is carried out with a finite element method developed to consider the orthotropic properties, geometric nonlinearity using four-node degenerated shell element with reduced integration. Physical stabilization scheme is used to control the zero-energy modes of the element. An inflation analysis and a lateral deformation analysis of an air spring are carried out. Numerical analysis results demonstrate the variation of the outer diameter, the fold height, the vertical force and the lateral force.

• 한국산학기술학회논문지
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• 제17권3호
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• pp.432-437
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• 2016

본 연구는 금속 주름관, 내부 스프링, 금속마개 등으로 구성된 소형 벨로우즈 세트의 거동에 대하여 연구하였다. 벨로우즈는 자동차용 에어컨의 제어를 위한 전자기제어밸브의 핵심 부품으로써 기계적 하중과 외부 압력에 대하여 민감하고 정확하게 작동하여야 한다. 벨로우즈 설계 인자 도출을 위하여, 소형 인장시험기를 이용하여 벨로우즈 내부 스프링의 스프링 상수를 측정하고, 벨로우즈 세트의 하중-변위 선도를 측정하였다. 내부 스프링의 하중-변위 관계는 선형관계를 나타내었다. 벨로우즈 세트의 하중-변위 관계는 변위가 작을 때는 낮은 기울기를 가지고 하중이 증가하다가 이후 선형으로 증가하는 특성을 나타내었다. 실측 결과를 바탕으로 유한요소해석을 수행하여 외부 주름관의 유효 물성을 도출하고 유한요소 모델링을 확보하였다. 원통형의 형상을 고려하여 축대칭 모델을 적용하였으며, 주름관은 쉘 요소를 적용하였다. 확보한 모델을 활용하여 냉매 압력에 따른 벨로우즈의 거동에 대한 연구를 수행하였다.

• Tribology and Lubricants
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• 제40권1호
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• pp.17-23
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• 2024

This study analyzes the thermal effects on the performance of an air foil thrust bearing (AFTB) using COMSOL Multiphysics to approximate actual bearing behavior under real conditions. An AFTB is a sliding-thrust bearing that uses air as a lubricant to support the axial load. The AFTB consists of top and bump foils and supports the rotating disk through the hydrodynamic pressure generated by the wedge effect from the inclined surface of the top foil and the elastic deformation of the bump foils, similar to a spring. The use of air as a lubricant has some advantages such as low friction loss and less heat generation, enabling air bearings to be widely used in high-speed rotating systems. However, even in AFTB, the effects of energy loss due to viscosity at high speeds, interface frictional heat, and thermal deformation of the foil caused by temperature increase cannot be ignored. Foil deformation derived from the thermal effect influences the minimum decay in film thickness and enhances the film pressure. For these reasons, performance analyses of isothermal AFTBs have shown few discrepancies with real bearing behavior. To account for this phenomenon, a thermal-fluid-structure analysis is conducted to describe the combined mechanics. Results show that the load capacity under the thermal effect is slightly higher than that obtained from isothermal analysis. In addition, the push and pull effects on the top foil and bump foil-free edges can be simulated. The differences between the isothermal and thermal behaviors are discussed.

• Journal of the Korean Wood Science and Technology
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• 제16권4호
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• pp.10-39
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• 1988

This study investigated the temperatures and relative humidities in the semi-greenhouse type solar dryer with a black rock-bed heat storage and without heat storage and outdoor temperature and relative humidity at 9 a.m. and 2 p.m.. A comparison was made of the drying rates, final moisture contents, moisture content distributions, casehardening stresses, drying defects, volumetric shrinkage of dried lumber for solar- and air-drying from the green condition of mixtures of Douglas-fir, lauan, taun, oak and sycamore 25mm- and 50 mm-thick lumber during the same period for four seasons, and heat efficiencies for solar dryer with and without the heat storage for saving of heat energy and the cost of lumber drying using the solar energy. The results from this study were summarized as follows: I. The mean weekly temperatures in the solar dryers were 3 to $6^{\circ}C$ at 9 a.m. and 9 to $13^{\circ}C$ at 2 p.m. higher than mean outdoor temperature during all the drying period. 2. The mean weekly relative humidities in the solar dryers were about 1 to 19% at 9 a.m. higher than the outdoor relative humidity. and the difference between indoor and outdoor relative humidity in the morning was greater than in the afternoon. 3. The temperatures and relative humidities in the solar dryer with and without the heat storage were nearly same. 4. The overall solar insolation during the spring months was highest and then was greater in the order of summer, atumm, and winter month. S. The initial rate of solar drying was more rapid than that of air drying. As moisture content decreased, solar drying rate became more rapid than that of air drying. The rates of solar drying with and without heat storage were nearly same. The drying rate of Douglas-fir was fastest and then faster in the order of sycamore, lauan, taun and oak. and the faster drying rate of species, the smaller differences of drying rates between thicknesses of lumber. The drying rates were fastest in the summer and slowest in the winter. The rates of solar drying during the spring were more slowly in the early stage and faster in the later stage than those during the autumn. 6. The final moisture contents were above 15% for 25mm-thick air dried and about 10% for solar dried lumber, but the mean final MCs for 50mm-thick lumber were much higher than those of thin lumber. The differences of final MC between upper and lower course of pile for solar drying were greater than those of pile for air drying. The differences of moisture content between the shell and the core of air dried lumbers were greater than those of solar dried lumber, smallest in the drying during summer and greatest in the drying during winter among seasons. 7. Casehardening stresses of 25mm- and 50mm-thick dried lumber were slight, casehardening stress of solar dried lumber was severer than that of air dried lumber and was similar between solar dried lumber with and without heat storage, Casehardening stresses of lumber dried during spring were slightest and then slighter in the order of summer, autumn, and winter. Casehardening stresses of Douglas -fir, sycamore and lauan were slight, comparing with those of taun and oak. 8. Maximum initial checks of 25mm-thick lumber occurred above and below fiber saturation point and those of 50mm-thick lumber occurred in the higher moisture content than thin lumber. As the moisture content decreased, most of checks were closed and didn't show distinct difference of the degree of checks among drying methods. The degree of checks were very slight in case of Douglas-fir and lauan, and severe in case of taun and oak. The degree of checks for 50mm-thick lumber were severer than those for 25mm-thick lumber. 9. The degree of warpage showed severe in case of oak and sycamore lumber, but no warping was found in case of Douglas-fir, lauan and taun. 10. The volumetric shrinkages of taun and oak were large and medium in case of Douglas-fir, lauan and sycamore. 11. Heat efficiencies of solar dryer with heat storage were 6.9% during spring, 7.7% during summer, 12.1% during autumn and 4.1% during winter season. Heat efficiency of solar dryer with heat storage was slightly greater than that of without heat storage. As moisture content of lumber decreased, heat efficiency decreased.

• 대한기관식도과학회:학술대회논문집
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• 대한기관식도과학회 1982년도 제16차 학술대회연제순서 및 초록
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• pp.8.1-8
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• 1982

기도 이물은 이비인후와 영역에서 중요한 위치를 차지하고 있는 질환으로서, 타 질환에 비하여 그리 드문 것은 아니며 지금까지 국내외에서 많은 보고가 있어왔다. 기도 이물은 때로는 순식간에 생명을 위협하거나 중증의 합병증을 초래하기도 하며, 이물의 종류와 형태도 다양할 뿐 아니라 그 개재부위도 달라서 이물적출은 항상 낙관을 불허하는 것으로 수술적 방법을 요할때도 있다. 저자들은 최근에, 이물이 자연 객출된 1예와 기관지경술로 성공한 4예 및 외과적 수술로 제거한 2 예를 경험하였기에 문헌적 고찰과 함께 보고하는 바이다.

• 한국잠사곤충학회지
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• 제35권1호
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• pp.21-27
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• 1993

용천뽕 급상후에 위조억제에 의한 사료가치향상을 목적으로 수원(1989, 1992년)과 춘천(1990년)에서 위조억제자료인 한냉사를 잠좌에 피복하여 가지뽕치기로 누에 사육한 결과는 다음과 같다. 1. 무피복방치상태에서 용천뽕의 뽕잎 수분감모율은 최초 3시간 내에는 개량뽕보다 뚜렷이 많았으며, 용천뽕의 뽕잎위에 한냉사를 피복한 경우에는 6시간내의 수분감모율은 무피복구 보다 건조한냉사구는 7%, 흡수한냉사구는 7~26% 정도 낮았다. 2. 기상환경이 건조한 춘잠기에 용천뽕을 급잠후 한냉사피복사육을 한결과 수견량이 개량뽕 무피복사육보다 7%, 용천뽕 무피복사육보다 9% 증수되었으며, 견층비율이 큰 차이 없는 등의 우수한 효과를 나타내었다. 3. 우리나라의 예년 기상환경보다 약간 다습한 환경에서는 용천뽕 급상 한냉사 피복사육은 용천뽕 무피복사육보다는 사육성적이 다소 우수하지만 개량뽕 무피복사육에는 미치지 못하여 뽕품종 고유의 엽질차를 극복하지 못하였다. 더우기 비오는 빈도가 잦은 환경에서는 한냉사피복사육 효과는 없었다. 4. 한냉사의 종류에 따른 피복효과는 공시한 300호(두께 24.0x10-2mm, 21.5mesh)보다 100호(두께 42.0x10-2mm, 15.2mesh)가 다소 우수하였다.

• 한국잠사곤충학회지
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• 제32권2호
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• pp.94-100
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• 1990

우리나라의 대표적인 내동성뽕품종인 용천뽕의 엽질을 규명하고 그 이용효율증진을 위하여 뽕잎을 분석하는 한편 1987년과 1988년에 잠박육과 조상육으로 사율시험을 수행하여 다음과 같은 결론을 얻었다. 1. 4-5령은 용천뽕으로 사육한 때의 수견량은 개량뽕 대비 춘잠기에 5%, 추잠기에 10% 떨어졌으나 견층비율과 생사량비율은 개량뽕과 같거나 약간 높았으며 춘잠기의 생사량은 개량뽕과 대등하고 추잠기에는 75 정도 낮았다. 2. 4령기에만 용천뽕으로 사육한 때의 사율시험은 거의 개량뽕과 같았다. 3. 4령기간과 5령전기를 용천뽕으로 사육하면 수견량은 개량뽕의 95%, 생사량은 97-98% 수준에까지 향상되었다. 4. 용천뽕은 전실소, 조단백질이 개량뽕보다 적은 반면 전탄수화물 조분 조지방 함량이 많았으며 무기물 중에는 인산과 붕소가 많고 망간 함량은 적었다. 5. 용천뽕의 엽면적중은 1.57g/dcm2, 잎두께는 113$\mu$으로 개량뽕보다 가볍고 얇었으며 방치 3시간 후의 수분감모율은 41.3%로 갸량뽕보다 4.6% 많었다.