• 대한토목학회논문집
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• 제35권2호
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• pp.465-470
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• 2015

에폭시 아스팔트 혼합물은 에폭시 수지와 경화제의 화학반응이 진행되어 양생시간을 거쳐 성능 발현이 이루어진다. 에폭시 아스팔트의 양생수준은 후속공정의 진행과 교통개방 및 공정계획의 수립에 절대적인 영향을 미치므로 정확한 예측모델의 개발이 중요하다. 본 연구에서는 기존 예측식에 사용되는 인자들의 화학적 의미 분석을 통하여 에폭시 수지의 농도와 경화특성을 반영하여 기존식보다 확대된 적용 범위를 갖는 양생수준 예측식을 제시하였다. 실외양생 실험과 비교 결과 상관계수가 0.971 이상으로 나타나 조성이 다른 에폭시 아스팔트 혼합물의 온도와 시간에 따른 양생수준을 예측할 수 있는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.397-402
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• 2001

Microstructural characteristics such as hydrates and porosity greatly influence the development of concrete strength. In this study, a strength estimation model for early-age concrete considerig, the microstructural characteristics was proposed, which considers the effects of both an increment of degree of hydration and capillary porosity on a strength increment. Hydration modeling and compressive strength test with curing temperature and curing ages were carried out. By comparing test results with estimated strength, it is found that the strength estimation model can estimate compressive strength of early-age concrete with curing ages and curing temperature within a margin of error.

• Advances in concrete construction
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• 제11권4호
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• pp.347-356
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• 2021

To address the limitation of the commonly used steam curing of reactive powder concrete (SC-RPC) in engineering, a preparation technology of normal curing reactive powder concrete (NC-RPC) is proposed. In this study, an experimental comparative research on the mechanical properties of NC-RPC and SC-RPC under uniaxial tension is conducted. Under the premise of giving full play to the ultra-high performance of RPC, the paper tries to explore whether normal curing can replace steam curing. The results show that various mechanical indexes of NC-RPC (e.g., tensile strength, ultimate tensile strain, elastic modulus and deformation performance) could basically reach the mechanical index values in steam curing at 28d age, some performance is even better at a longer age. So it affirms the feasibility of normal curing. In this paper, the influence of normal curing age on the tensile properties of RPC is discussed, and the relationship between each index and age is introduced in detail. Based on the experimental data, the tensile mechanism of RPC is analyzed theoretically, and two kinds of tensile constitutive models for RPC are proposed, one is curvilinear model, and another one is polygonal line model. The validity of the two models is further verified by the test results of others.

• 대한치과기공학회지
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• 제43권2호
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• pp.48-55
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• 2021

Purpose: This study aimed to analyze deformation according to post-curing of complete arch artificial teeth for temporary dentures printed with a digital light processing (DLP) printer. Methods: An edentulous model was prepared and an occlusal rim was produced. The edentulous model and occlusal rim were scanned using a model scanner. A complete denture was designed using a dental computer-aided design, and the denture base and artificial tooth were separated. Ten complete arch artificial teeth were printed using a 3D printer (DLP). Complete arch artificial teeth was classified into the following three groups: a group no post-curing (NC), a group with 10 minutes post-curing (10M), and a group with 20 minutes post-curing (20M). Specimens were scanned using a model scanner. The scanned data were overlapped with the reference data. Statistical analysis was performed using one-way ANOVA analysis of variance, Kruskal-Wallis test, and Mann-Whitney U test (α=0.05). Results: Regarding the overall deviation of complete arch artificial teeth, the NC group showed the lowest mean deviation of 111.13 ㎛ and the 20M group showed the highest mean deviation of 131.03 ㎛. There were statistically significant differences among the three groups (p<0.05). Conclusion: The complete arch artificial tooth showed deformation due to post-curing. In addition, the largest shrinkage deformation was observed at 10 minutes of post-curing, whereas the least deformation was observed at 20 minutes.

• 콘크리트학회논문집
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• 제12권6호
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• pp.35-42
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• 2000

In paper I, the relationships between compressive strength and splitting tensile strength or modulus of elasticity were proposed. In this paper, new prediction model is investigated from estimating splitting tensile strength and modulus of elasticity with curing temperature and aging without compressive strength. New prediction model is based on the model which was proposed to predict compressive strength, and splitting tensile strength and modulus of elasticity calculated by this model are compared with experimental values of paper I. To evaluate in-situ applicability of the model, strength and modulus of elasticity tested with variable temperatures are estimated by the prediction model. The prediction model reasonably estimates the strength and the modulus of elasticity of type I and V cement concretes tested in paper I and experimental results with variable temperature tested in this paper.

• 콘크리트학회논문집
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• 제14권2호
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• pp.137-147
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• 2002

콘크리트의 강도를 예측하기 위하여 널리 사용되어 온 성숙도 모델은 양생온도와 재령을 이용하여 콘크리트 강도를 비교적 정확하게 평가할 수 있다. 그러나 수화생성물의 특성과 미세구조의 공극 분포와 같이 강도 발현과 관련이 있는 물리량을 고려하지는 못한다. 따라서, 본 연구에서는 강도에 대한 이러한 인자들의 영향정도를 규명하기 위해서 수화모델 및 모세관 공극률 계산방법을 정립하였고, 실험 변수로 재령과 양생 온도를 고려하여 다양한 물/시멘트비를 갖는 콘크리트의 압축강도실험을 수행하였다. 실험결과를 분석하여 수화도와 모세관 공극률과 같은 미세구조특성을 고려한 강도예측모델을 제안하였다. 실제 실험값과 모델식에 의한 강도 예측값을 비교하여 잘 일치하는 결과를 얻었다. 결론적으로, 본 연구에서 제안한 강도예측모델은 양생온도와 재령에 따른 초기재령 콘크리트의 압축강도를 일정오차 내에서 예측할 수 있다고 판단된다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.184-191
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• 1996

In curing Process of tire, Contact and slip occurs between green tire and curing bladder. The curing process is a critical step in the manufacture of tires. In this investigation, curing bladder shaping is examined using a finite element method. Specifically, a finite element model between the inner part of green tire and the outer part of curing bladder is generated using contact element and curing bladder is generated using incompressible element, The experimental tensile tests are used to get the material properties of bladder rubber on practical conditions. Numerical analyses are performed on two different bladder types, different overall outer diameters of curing bladder and different heights of curing bladder.

• 한국산학기술학회논문지
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• 제15권11호
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• pp.6464-6471
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• 2014

웨이퍼 단위의 렌즈를 성형 시 일반적으로 UV경화 방식을 사용한다. 이 경우 발생될 수 있는 문제점은 크게. 경화후 이형과정에서 성형 렌즈의 금형 고착문제, 경화 공정 중 발생하는 소재의 수축 현상으로 렌즈간의 형상 오차 발생 및 웨이퍼 단위의 변형, 위치별 렌즈 형상 편차 발생, 웨이퍼 양면의 렌즈 형상 및 센터 정렬 오차 등이다. 이중 UV경화 과정에 직접적인 영향을 받는 것은 형상 오차 및 변형으로 그 요인은 UV 조사 균일성, UV 강도에 대한 경화도, UV 경화 소재의 수축 특성이다. 따라서 소재에 대한 경화 모델링 수립 및 경화 반응에 따른 수축율과 물성 변화에 대한 이론정립이 필요하다. 또한 이러한 모델링을 해석에 구현할 수 있는 해석 툴 개발이 필요하다. 본 연구에서는 Comsol을 이용하여 수립된 모델링을 반영하고 이를 통하여 웨이퍼 단위 렌즈의 성형 공정에 대한 해석 기법을 제안하였다. 이를 통해 7.2mm에 대한 누적 공차값을 실제 성형 공정 후 결과($0.149{\mu}m$)과 비교하여 제안한 해석 방법에 의한 결과($0.215{\mu}m$)을 비교, 검증을 수행하였으며 이를 통하여 UV경화 공정 후 변형에 대한 해석 가능성을 확인하였다.

• Korea-Australia Rheology Journal
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• 제12권1호
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• pp.77-81
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• 2000

Rheological behavior of thermoset/thermoplastic blends of epoxy/polyethersulphone (PES) was monitored during curing of the epoxy resin. During the isothermal curing of the mixture, a fluctuation in viscosity just before the abrupt viscosity increase was observed. This fluctuation is found to be due to the phase separation of PES from the matrix epoxy resin during the curing. The experimentally observed viscosity fluctuation is simulated with a simple two phase suspension model in terms of the increase in domain size. The viscosity profiles obtained experimentally at different isothermal curing temperatures are in good agreement with the predictions from the simple model taking into account the viscosity change due to the growth of PES domain and the network formation of the epoxy matrix.

• 대한기계학회논문집A
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• 제21권3호
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• pp.378-384
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• 1997

In curing process of tire, contact and slip occurs between green tire and curing bladder. The curing process is a critical step in the manufacture of tires. In this investigation, curing bladder shaping is examined using a finite element method. Specifically, a finite element model between the inner part of green tire and the outer part of curing bladder is generated using contact element and curing bladder is generated using incompressible element. Numerical analysis are performed on two different bladder types, different overall outer diameters of curing bladder and different heights of curing bladder. Numerical results show that contact pressure is increased by using toroidal type of curing bladder, increasing overall diameter and increasing height of curing bladder. To obtain natural equilibrium carcass line, there is a requirement in increasing contact pressure of the section between side and bead.