• Structural Engineering and Mechanics
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• 제66권6호
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• pp.713-727
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• 2018

Thin-walled mental tubes under lateral crushing are desirable and reliable energy absorbers against impact or blast loads. However, the early formations of plastic hinges in the thin cylindrical wall limit the energy absorption performance. This study investigates the energy absorption performance of a simple, light and efficient energy absorber called the ring stiffened tube. Due to the increase of section modulus of tube wall and the restraining effect of the T-stiffener flange, key energy absorption parameters (peak crushing force, energy absorption and specific energy absorption) have been significantly improved against the empty tube. Its potential application in the offshore blast wall design has also been investigated. It is proposed to replace the blast wall endplates at the supports with the energy absorption devices that are made up of the ring stiffened tubes and springs. An analytical model based on beam vibration theory and virtual work theory, in which the boundary conditions at each support are simplified as a translational spring and a rotational spring, has been developed to evaluate the blast mitigation effect of the proposed design scheme. Finite element method has been applied to validate the analytical model. Comparisons of key design criterions such as panel deflection and energy absorption against the traditional design demonstrate the effectiveness of the proposed design in blast alleviation.

• 설비공학논문집
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• 제14권4호
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• pp.341-349
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• 2002

Heat and mass transfer characteristics of a surfactant-added LiBr-$H_2O$ solution flowing over a single horizontal tube were examined experimentally. The parameters considered were surfactant (2-ethyl-1-hexanol) concentration, solution temperature at the top of the tube and absorber pressure. Even with an amount of the surfactant below the solubility limit, heat and mass transfer performances were enhanced tremendously. The Nusselt and Sherwood numbers increased by about 70% and 340%, respectively, when 10 ppm of the surfactant was added. However, an excess amount of the surfactant in the solution did not bring a further enhancement. The absorption performance deteriorated when the non-condensable gases were extracted from the system (by a vacuum pump) since the vaporized surfactant was also extracted during the process. Therefore, it is desirable to add a sufficient amount of the surfactant (more than 10 ppm) to maintain high performance of absorption.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.774-779
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• 2007

The crash energy absorbers used in the trains normally are classified into two types. The first is the structure type, which mainly used in not only the primary structure of train but also the crash energy absorbers at the critical accidents. The second is the module type, which just absorbs the crash energy independently and attached onto the structures of the trains. The expansion tube is widely used as the module type of the crash energy absorbers, especially in the trains that have a heavy mass. Since the crash energy is absorbed by means of expanding the tube in the radial direction, the features of the expansion tube have the uniform load during the compression. As the uniform load remains in sudden impact, the expansion tube is effective to decrease acceleration of passengers when the train accident occur. The buckling instability of the expansion tubes is affected by the boundary conditions, thickness and length of tube. In this study, the effects of the length and thickness of the expansion tubes under the arbitrary load on the buckling are studied using the ABAQUS/standard and ABAQUS/explicit, a commercial finite element analysis program, and then presents the guideline to design the expansion tubes. The analysis processes to compute the buckling load consist of the linear buckling analysis and the nonlinear post-buckling analysis. To analysis the nonlinear post-buckling analysis, the geometry imperfections are introduced by applying the linear buckling modes to nonlinear post-buckling analysis.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.233-236
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• 2003

A bumper comprises a bumper face, a bumper beam for distributing the load from the impacts applied to the bumper face and reinforcing the bumper, an absorber member interposed between the bumper face and the bumper beam, and a pair of bumper stays which secure the bumper beam to the vehicle body. A conventional bumper stay structure is assembled into several stamped parts, so several processes are needed and the structure is complicated. In this study the bumper stay is applied to the tubular hydroforming which is known to have several advantages such as the reduction of the number of the process and the part weight. The thickness distribution of the tube after hydroforming and the internal energy at the event of the a compression are mainly considered to evaluate the hydro-formability and energy absorption performance.

• 설비공학논문집
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• 제14권8호
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• pp.641-647
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• 2002

Objectives of this paper are to investigate the effect of roughness of micro-hatching tubes on the absorption performance and to develop on experimental correlation of Nusselt as a function of the roughness. Three different micro-scale hatched tubes and a bare tube were tested in the present experiment. $H_{2}O/LiBr$ solution is used as working fluid. It was found that absorption performance of micro-scale hatched tubes were improved upto 2 times with an error band of ${\pm}25%$ compared with the bare tube. An experimental correlation of Nusselt was developed as a function of the roughness.

• 한국기계가공학회지
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• 제15권3호
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• pp.44-51
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• 2016

This paper presents the characteristics of the energy absorption in an expansion tube type impact absorber that is applied to a high weight drop tester and the use of a response surface methodology to predict the impact energy absorption. In order to identify the characteristics of the energy absorption, a set of finite element analysis was conducted with Abaqus Explicit. Moreover, the ISCD-II sampling method and a first order polynomial were used to build a response surface. As a result, we demonstrated that the impact energy could be controlled by four main design variables, namely an expansion pipe's thickness, inner radius, pressing die's expansion angle and expansion ratio. Additionally, we observed the relationship between the four main design variables and the impact energy absorbing time, displacement, and maximum impact force.

• 한국가스학회지
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• 제2권4호
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• pp.47-52
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• 1998

수냉식 흡수식 냉동기에 주로 사용되고 있는 LiBr/water 흡수용액을 대체할 수 있는 신흡수 용액으로 제안된 흡수용액중 4성분계 흡수용액($LiBr+LiNO_3+LiC1+H_2O$)의 수증기 흡수성능을 수직관 흡수기를 사용하여 시험하였다. 시험변수로는 입구농도, 입구온도, 냉각수 입구온도, 용액유량을 변경하였다. 수증기 흡수특성 시험 결과 4성분계 용액이 LiBr/water용액보다 $2\%$ 높은 농도에서 대둥한 흡수력을 가짐을 알 수 있었다. 그러나 4성분계 흡수용액이 LiBr/water용액보다 $3\%$정도 용해도가 높으므로 실제 흡수식 냉동기에 적용시 LiBr용액보다 우수한 흡수능력을 가질 수 있어 소형, 공냉형 흡수식 냉동기에 적용이 가능하다.

• 한국태양에너지학회 논문집
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• 제24권3호
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• pp.27-38
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• 2004

A numerical investigation has been carried out for a solar system, which consists of all glass solar vacuum tubes Water is heated as it flows through the coaxial fluid conduit inserted in each tube. The space between the exterior of the fluid conduit and the glass tube is filled with antifreeze solution. This is to facilitate heat transfer from the solar heated absorber surface to water and to prevent the functional problems due to freezing in frigid weather conditions. A one-dimensional steady state model is fully described which will be used to develop three-dimensional model using STAR-CD. These models could be used efficiently in designing all-glass solar collector tubes with different geometrical parameters other than those considered in the present analysis. Results show good agreement when compared with other experimental data demonstrating the reliability of the present model.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.567-570
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• 2006

A numerical study has been carried out for a solar water heater which consists of double skin solar vacuum tubes. Water is heated as it flows through the coaxial fluid conduit inserted in each tube. The space between the exterior of the fluid conduit and the glass tube is tilled with antifreeze solution. This is to facilitate heat transfer from the solar heated absorber surface to water and to prevent the functional problems due to freezing in frigid weather conditions. A one-dimensional steady state model is fully described which will be used to develop three-dimensional model using STAR-CD. These models could be used efficiently in designing double skin solar collector tubes with different geometrical parameters other than those considered in the present analysis. Results show a good agreement when compared with other experimental data demonstrating the reliability of the one-dimensional model employed.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.456-462
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• 2013

Eco-friendly material applied to building would be one of the materials which is must developed for global environmental conservation and reduction of carbon dioxide. For development of eco-friendly material, a cellulose absorber has been developed with waste paper through adjustment of various mix proportions. The developed cellulose absorber has been tested for its acoustic properties such as absorption coefficient and dynamic stiffness. The absorption coefficient was evaluated by developing six samples and using impedance tube and reverberation chamber. As a result of the evaluation, 0.64(NRC) was secured in absorption coefficient and 4.7 $MN/m^3$ was indicated in dynamic stiffness. Also, for practical use of developed absorbers as inner heartwood in drywall, comparison test of sound reduction index was performed with existing glass wool absorbers and constructed drywall of gypsum board. The results have shown 55 dB(Rw) of sound reduction index in glass-wool wall and 46 dB(Rw) in cellulose.