• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.581-584
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• 2008

In this study, it is willing to present that fundamental data for proposing quantitatively shrinkage cracking evaluation method such as plat-ring type restrained test method. To examine suitable size of specimen of plat-ring type restrained test method, Evaluated concrete about restrained shrinkage crack properties of numerical analysis of 3D solid element using the MIDAS program, drying shrinkage deformation, restrained shrinkage stress, crack area and crack point with inside ring diameter of specimen in 100mm, 150mm, 200mm and high of Specimen in 30mm, 50mm after curing in condition of constant temperature and usual habit of temperature 20${\pm}$3$^{\circ}$C, humidity 60${\pm}$5%. As a result, it was available about suitable estimation with inside ring diameter of specimen in more than 150mm and high of Specimen in 50mm. Hereafter, it is considered that the study concerning environmental condition and mixing factor in plat-ring type restrained test method is need.

• Polymer(Korea)
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• v.35 no.5
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• pp.467-471
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• 2011

PET bottle is manufactured by blow molding the preform, which is molded by injection molding. The neck part of the preform of PET bottle for juice or grain-based beverage is crystallized before blowing to improve heat resistance at the entrance of the bottle. However, residual stress, developed during injection molding of preform, prevents the crystallization. In order to release the residual stress in the preform, the preform is annealed after the injection molding. If the residual stress is reduced by optimizing the injection molding conditions of preform the annealing time would be shortened. In this study, the optimum conditions for minimizing the residual stress and increasing dimensional accuracy of the injection molded preform are suggested through CAE analysis. In order to optimize the molding conditions, minimizing residual stress and shrinkage, computer simulations have been carried out with help of design of experiment scheduling. Injection temperature, initial packing pressure and filling time were selected for control parameters. Residual stress was affected by injection temperature and filling time. Shrinkage was affected by injection temperature. It was found that maximum residual stress, distribution of residual stress and shrinkage were decreased by 22%, 40% and 25%, respectively at an optimum molding condition compared with the results of previous molding condition.

• Composites Research
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• v.30 no.6
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• pp.410-415
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• 2017

This paper predicted deformation due to thermal residual stress in composites using finite element analysis. Temperature cycle, Model shape, Laminate angle, Stacking sequence, chemical shrinkage of resin, and thermal expansion are affect composite deformation. Compare the results of the analytical model with the actual model of the same shape. This paper suggests that the analytical results can be applied to actual Model.

• Magazine of the Korea Concrete Institute
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• v.14 no.3
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• pp.18-23
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• 2002

구조재료로써 콘크리트의 물리적 특성은 강재와는 달리 시간 의존적이라고 할 수 있다. 즉, 타설 후 재령이 경과함에 따라 압축강도와 탄성계수가 증가함은 물론, 콘크리트 내의 수분이 대기 상태로 증발하면서 부재가 수축하는 건조수축 및 외력의 증감없이 변형률이 증가하는 크리프 특성 등을 가지고 있다. 또한, 콘크리트는 시멘트의 수화반응에 의해 시공초기에 재료의 온도가 급격히 상승하는 발열특성도 동시에 가지고 있다. 이러한 특성들은 구조물의 설계시 무시할 수 없으며, 각 시공단계 및 완성단계의 구조물의 응력에 커다란 영향을 미치게 된다.(중략)

• Journal of the Korean Ceramic Society
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• v.38 no.2
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• pp.193-198
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• 2001

유한요소법을 이용하여 STS VOD 래들에서 내장 내화물의 재질 및 back filler의 시공 위치에 따른 열응력을 수행하였다. 불소성 내화물의 경우 높은 열전도율에 의해 가동면과 배면(back face)간의 온도구배가 소성품에 비해 감소하였으며 탄성계수도 낮아 발생되는 열응력이 2~4배 낮았다. Back filler는 dolomite 내화물의 열간 팽창을 흡수하기 위해 시공하는 것으로, 상대적으로 낮은 열전도율을 가지고 있기 때문에 back filler의 내부와 외부에 급격한 온도구배가 발생된다. 결과적으로 래들의 내부는 고온을 유지하여 내화물이 팽창이 되고, 외부는 온도가 낮아지므로 수축되어 열응력이 증가하였다.

• Composites Research
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• v.27 no.4
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• pp.174-181
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• 2014

This study describes viscoelasticity analysis of carbon-fiber reinforced polymer matrix composite material. One of the most important problem during high temperature molding process is residual stress. Residual stress can cause warpage and cracks which can lead to serious defects of the final product. For the difference in thermal expansion coefficient and change of resin property during curing, it is difficult to predict the final deformed shape of carbon-fiber reinforced polymer matrix composite. The consideration of chemical shrinkage can reduce the prediction errors. For this reason, this study includes the viscoelasticity and chemical shrinkage effects in FE analysis by creating subroutines in ABAQUS. Analysis results are compared with other researches to verify the validity of the subroutine developed, and several stacking sequences are introduced to compare tested results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.281-286
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• 1993

Projection TV에는 시각 품질을 최종적으로 표시하는 디스플레이 소자인 비구면플라스틱 렌즈를 적용하고 있으나 전량 일본에서 완제품으로 공급 받고 있다. 플라스틱 비구면 렌즈를 성형하기 위해서는 사출 공정에 대한 철저한 이해 와 폴리머의 광탄성 거동에 대한 개념이 핵심이라고 말할 수 있다. 복굴절성 실험은 폴리머의 유변학적 거동을 파악 하는데있어 가장 유용한 실험중의 하나이다. 본 글에서는 이와 관련된 사항인 복굴절성, 잔류 응력 형성 메카니즘, 밀도이완 작용의 상관관계와 비구면 렌즈의 성형 조건 및 공정에대해 기술 하였고, 또한 측정된 수지데이타를 이용 상용 S/W를 사용하여 유동, 냉각, 보압 ( 압축) 및 수축 해석을 실시 하여 각 stage에서 경험한 온도 와 압력의 이력에따라 변화하는 열 응력에 기인한 잔류 응력 계산 Pg을 개발 상용 S/W 와 비교 검증 하였다.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.289-294
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• 2011

The installation of joint is to prevent random cracking due to drying shrinkage stress of concrete slab. However contraction joint spacing is empirically implemented into slab constructions without detail calculation based on quantitative criteria. In this study, shrinkage strain of concrete due to concrete shrinkage stress was measured to suggest joint spacing based on the study results. The test environmental conditions were applied temperature of $15^{\circ}C$ and relative humidity of 60%. The design compressive strength used was 30 MPa and 40 MPa, which are currently used in concrete slab designs. The drying shrinkage test result was applied to drying shrinkage models (ACI 209R, CEB MC 90, B3, GL 2000 and Sakata). The results showed that the most appropriate model was ACI 209R model. Based on the research findings, quantitative contraction joint spacing locations were calculated.

• Magazine of the Korea Concrete Institute
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• v.2 no.1
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• pp.109-119
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• 1990

This study was accomplished to investigate the characteristics of hardening shrinkage and initial creep of epoxy resin concrete depending on the presence of filler. According to the test results, the hardening shrinkage was increased with increment of sLOrage temperature, and the ef¬feel of tempemture on the hardening shrinkage of epoxy resin concrete with 6% filler was more Significant than that of epoxy resin concrete without filler. Also, the initial creep strain was increased with loading times, stress--strength ratio and elastic strain, and the values for opoxy resin concrete with 6 % filler are higher than that for eposy resin concrete without filler.

• Polymer(Korea)
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• v.28 no.1
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• pp.67-76
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• 2004

The effects of drawing temperature and draw down ratio on thermal properties, crystallinity and orientation of poly(trimethylene terephthalate)/poly(ethylene terephthalate) (PTT/PET) 100/0 ,90/10, and 80/20 blends have been investigated. The crystallinity and glass transition temperature increased while cold crystallization temperature and cold enthalpy decreased due to the development of orientation and stress induced crystallization by the cord drawing. Introducing PET to PTT decreased the crystallinity of PTT. However, it enhanced the orientation of PTT/PET blends drawn at below the glass transition temperature of PET. This lead to the increase of tensile modulus and tensile strength of PTT/PET blends. The shrinkage increased with increasing orientation, which might be minimized by the development of crystalline morphology of PTT in the course of cold drawing.