• Journal of the Korean Society for Advanced Composite Structures
• /
• v.4 no.2
• /
• pp.31-38
• /
• 2013

As the Sewer Pipe is transformed by the expansion of life cycle as a result of the technology development, flexible pipe is developed by the transformed environmental conditions. To change pipe design, three phases(compaction ration - inner deflection ratio - ring stiffness) should be considered in design conditions. The input data of pipe design were provided by compaction-inner deflection ratio-ring stiffness. M oreover, The guidelines of sewerage pipes should be considered by flexible pipes design criteria.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.1 no.1
• /
• pp.189-200
• /
• 1998

본 연구에서는 얇은 마레이징강으로 제작된 천마 연소관에 브라켓이 용접되어 비행 날개를 볼트로 체결한 경우, 압력과 공력하중에 의해 브라켓 부위에 집중되는 응력의 해석기법을 정립하기 위하여 선형해석과 기하학적 비선형 해석을 수행하였다. 높은 압력에 의해 발생한 얇은 연소관의 면내 응력이 구조물의 강성을 증가시키는 응력의 강성보강효과(stress stiffening effect)를 고려한 기하학적 비선형 해석을 수행하여 선형해석 결과와 비교하였으며, 압력과 공력하중을 동시에 적용할 수 있는 복합하중시험기로 변형률을 측정하여 해석치의 정확성을 검토하였다. 얇은 연소관에 압력과 공력하중이 동시에 작용하는 경우는 응력의 강성보강효과를 고려한 기하학적 비선형 해석을 수행함으로써 보다 정확한 응력을 구할 수 있다는 결론을 얻었다.

• Tunnel and Underground Space
• /
• v.26 no.6
• /
• pp.508-515
• /
• 2016

In this study, we compared the stability of the pillars by using room and pillar mining method with the four models with different stiffness and pillar overlap ratio. The experimental models consist of two plaster models (overlap ratio 0%, 100%) and two cement models(overlap ratio 0%, 100%). The soft and hard rocks are modeled by plaster and cement models respectively. In these experiments, the model materials with strength values reflecting the calculated scaled factors not been used, so it is not a true scaled model test that reproduces in situ state in the laboratory. Experimental results show that the different overlap ratio pillars are one of the factors that can affect the stability of the mine.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2003.04a
• /
• pp.60.1-60
• /
• 2003

• 환경사랑
• /
• s.63
• /
• pp.10-11
• /
• 2012

국회 강성천 황영철 의원이 주최하고 자원순환연대가 주관하며 한국농어민신문과 당 협회가 후원한 '농수산물 스티로폴 상자 종이스티커 재질개선 간담회'가 지난 2월 29일 국회의원회관에서 열렸다. 이날 간담회에서 EPS 포장재의 재활용률을 높이고 상품의 이미지를 제고시키기 위해 종이 스티커 대신 PS(폴리스틸렌) 필름 스티커를 붙여야 한다는 데 의견이 모아졌다. 한국농어민신문이 정리한 이날 종합토론에서 개진 된 참석자들의 의견을 발췌했다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.3
• /
• pp.543-552
• /
• 1994

A series of drained plane strain compression tests was performed on dried samples of dense Toyoura sand and Silver Leighton Buzzard sand prepared by air-pluviation method to find out the deformation and strength characteristics on the value of confining pressure ${\sigma}{_3}^{\prime}({\sigma}{_3}^{\prime}=0.05{\sim}4.0kgf/cm^2)$. The axial and lateral strains measured in this apparatus ranged from $10^{-6}$ up to the failure of the specimen. So the stress-strain characteristics would be investigated from very small to very large strain levels. It was found that the change of the angle of internal friction ${\phi}^{\prime}{_{max}}=arcsin\{({\sigma}{_1}^{\prime}-{\sigma}{_3}^{\prime})/({\sigma}{_1}^{\prime}+{\sigma}{_3}^{\prime})\}_{max}$ with the change of ${\sigma}{_3}^{\prime}$ is very small when ${\sigma}{_3}^{\prime}$ is lower than higher. Furthermore, the effect of confining pressure on stiffness of sands was evaluated. It was also found that for the range of shear strain ${\gamma}$ from $10^{-6}$ to those at peak, the Rowe's stress-dilatancy relation seems to be a good approximation for air-dried Toyoura sand and Silver Leighton Buzzard sand, irrespective of the change of ${\sigma}{_3}^{\prime}$.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.4
• /
• pp.55-62
• /
• 2019

Stiffness-gradient stretchable electronic packages of the soft PDMS/hard PDMS/FPCB structure were processed using the polydimethylsiloxane (PDMS) as the base substrate and the more stiff flexible printed circuit board (FPCB) as the island substrate. The elastic characteristics of the stretchable packages were estimated and their long-term reliabilities on stretching cycles and bending cycles were characterized. With 0.28 MPa, 1.74 MPa, and 1.85 GPa as the elastic moduli of the soft PDMS, hard PDMS, and FPCB, respectively, the effective elastic modulus of the soft PDMS/hard PDMS/FPCB package was estimated as 0.6 MPa. The resistance of the stretchable packages varied for 2.8~4.3% with stretching cycles ranging at 0~0.3 strain up to 15,000 cycles and for 0.9~1.5% with 15,000 bending cycles at a bending radius of 25 mm.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.4
• /
• pp.47-53
• /
• 2019

Stiffness-gradient stretchable electronic packages of the soft PDMS/hard PDMS/PTFE structure were processed using the polydimethylsiloxane (PDMS) as the base substrate and the more stiff polytetrafluoroethylene (PTFE) as the island substrate, and their stretchable deformation-resistance characteristics were characterized. The flip-chip joints, formed by bonding the chip bumps of 50 ㎛-diameter onto the PDMS/PTFE substrate pads, exhibited an average contact resistance of 96 mΩ. When the stretchable package of the soft PDMS/hard PDMS/PTFE structure was deformed to 30% elongation, the strain on the PTFE was restrained to 1%, resulting in a negligible resistance increase of 1% in the daisy-chain circuit formed on the PTFE island substrate. The circuit resistance increased for 1.7% after 2,500 cycles of 0~30% stretchable deformation.

• Composites Research
• /
• v.32 no.5
• /
• pp.258-264
• /
• 2019

In this paper, a progressive failure analysis method was developed using the Hashin failure criterion and crack band model. Using the failure criterion, the failure initiation was evaluated. If the failure initiation is occurred, the damage variables at each failure modes (fiber tension & compression, matrix tension & compression) was calculated according to linear softening degradation behavior and the variables are used to derive the damaged stiffness matrix. The damaged stiffness matrix is reflected to damaged material and the progressive failure analysis is continued until the damage variables to be 1 that complete failure of material. A series of processes were performed using FE commercial code ABAQUS with user defined material subroutine (UMAT). To evaluate the proposed progressive failure model, the experimental results of open hole composite laminate tests was compared with numerical result. Using digital image correlation system, the strain behavior also was compared. The proposed numerical results were coincided well with the experimental results.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.3A
• /
• pp.447-455
• /
• 2006

A general purpose of 4-node co-rotational resultant shell element is developed for the solution of nonlinear problems of reinforced concrete, steel and fiber-reinforced composite structures. The formulation of the geometrical stiffness presented here is defined on the mid-surface by using the second order kinematic relations and is efficient for analyzing thick plates and shells by incorporating bending moment and transverse shear resultant forces. The present element is free of shear locking behavior by using the ANS (Assumed Natural Strain) method such that the element performs very well as thin shells. Inelastic behaviour of concrete material is based on the plasticity with strain hardening and elasto-plastic fracture model. The plasticity of steel is based on Von-Mises Yield and Ivanov Yield criteria with strain hardening. The transverse shear stiffness of laminate composite is defined by an equilibrium approach instead of using the shear correction factor. The proposed formulation is computationally efficient and versitile for most civil engineering application and the test results showed good agreement.