• 한국산업융합학회 논문집
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• 제27권3호
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• pp.519-525
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• 2024

In this paper, a study on the physical properties of mortar applying 3D Textile was conducted to compensate for the shortcomings of the existing concrete surface repair and reinforcement method. In the tests conducted to analyze the physical properties, compressive strength, flexural strength, and dynamic modulus measurement tests were conducted. As a result of the compressive strength test, as the number of surfaces to which the stereoscopic fiber was applied increased, the amount of displacement and strength reduction rate increased, and the flexural strength also increased as the number of surfaces to which the stereoscopic fiber was applied increased. In addition, it was confirmed that the use of stereoscopic fibers tended to decrease the dynamic modulus of elasticity. This result is a characteristic of the application of stereoscopic fibers, and it caused a decrease in compressive strength due to a decrease in the mortar content of the part to which the stereoscopic fib er was applied, and the high tensile force of the stereoscopic fiber is believed to have affected the increase in flexural strength.

• 한국가구학회지
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• 제17권1호
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• pp.23-32
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• 2006

This study was carried out to explore a new application of traditional Hanji and obtain fundamental properties for producing Hanji wallpaper by incorporating ceramics from wood and rice-husk as an interior building material. The results of properties determined were summarized as follows: The addition of ceramics in Hanji paper reduced its apparent density, but increased bulk density due to the ceramic particles distributed on the surface and inside the fiber of Hanji wallpapers. In particular, woodceramic particles were specifically distributed on the fiber surface, while particles of rice-husk ceramics were permeated into the inside surface of fibers. The density of rice-husk ceramics were greater than that of woodceramics. The physical properties of Hanji wallpapers, such as breaking strength, wet breaking strength, burst strength, tear index and folding endurance were deteriorated with the addition of ceramics. However, the addition of woodceramics in the Hanji wallpaper resulted in better strength in most cases than that of rice-husk ceramics, except tear strength. Therefore, an optimum addition level of woodceramics into the wallpaper was found to be 5% on the basis of intensity. The addition of ceramics also prolonged the combustion time because it lowered air permeability and brightness of the wallpaper.

• 한국표면공학회지
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• 제45권5호
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• pp.212-217
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• 2012

High strength steel sheets used for automobile outer-panels have been intensively studied for developing a lightweight automobile under a strong pressure of the requirements for enhancing the mileage and energy saving in production of automobile parts. It is known that high strength steels are susceptible to hydrogen embrittlement, The susceptibility to hydrogen embrittlement increases with increasing its strength. However, the effect of hydrogen on the fracture behavior of high strength steels, though investigated extensively, has not been fully understood. In this paper, hydrogen was charged with 590DP steels by electrochemical method and its content was measured by hydrogen determinator with the different charging conditions. It was shown that the SP energy and maximum load decreased with increasing charging time. The results of SEM-fractography investigation for the hydrogen contained samples showed that a small portion of dimples on cleavage-fractured surface were observed and the size of the dimples were decreased with increasing hydrogen charging time.

• Composites Research
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• 제16권5호
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• pp.15-20
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• 2003

본 논문에서는 표면 손상을 입은 적층판의 파괴 강도를 결함이 없는 적층판의 파괴 강도와 결함이 있는 적층판의 파괴 강도를 이용하여 예측하였다. 이를 위해 고전 적층판 이론을 적용하여 적층판의 파괴 강도식을 단순화했으며 이를 표면 손상을 입은 적층판에 적용하였다. 단순화한 적층판의 파괴 강도 이론식의 검증을 위해 Lagace와 Tsai의 논문에서 측정한 데이터를 이용하였다. 또한, 표면 손상을 입은 적층판의 파괴 강도 예측식의 검증을 위해 실험을 수행하였다. 실험을 위해 표면 결함이 없는 적층판과 표면 결함이 있는 적층판을 제작하여 실험하였으며 이 결과를 예측식과 비교하였다. 시편의 섬유 방향은 인장 방향과 같은 방향으로 제작되었으며, 예측식과 실험 결과는 잘 일치하였다. 따라서 본 논문에서 예측만 표면 결함이 있는 적층판의 파괴 강도 예측식을 이용하여 복합재료가 사용되는 구조물이 표면 손상이 되었을 때 이 구조물의 파괴 강도를 예측할 수 있을 것이다.

• 펄프종이기술
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• 제48권2호
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• pp.83-90
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• 2016

Increasing the amount of filler in paper is of high interest for paper industry while maintaining its key sheet quality properties. In this study, a MFC-GCC composite, made through a co-grinding NBSK (Northern bleached softwood kraft) pulp with a ground calcium carbonate (Intracarb 60), was used as a strength aid in paper in order to evaluate a potential cost reduction through filler increase without sacrificing paper quality. Hand-sheets were made of NBSK and/or eucalyptus pulp by using white water recirculation in a Tappi sheet former and was compared its properties without or with MFC additions at different filler levels. It was found that the MFC-GCC composite has a large surface area compared to the fiber, allowing the formation of more hydrogen bonds in the web, thus giving natural strength to the paper. Overall results are encouraging that the MFC-GCC composite allows papermaker to reduce basis weight and maintain critical sheet properties.

• 펄프종이기술
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• 제48권3호
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• pp.91-98
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• 2016

Linerboards have been produced by recycling recovered paper such as old corrugated containers(OCC). Usually linerboards produced during summer season show weak strength compared with those of produced during winter. In order to cope with the weak strength of linerboards produced during summer, and to confirm uniform quality, it is important to understand the seasonal effect on strength properties. Effect of pulping temperature of the OCC for linearboard production was investigated by controlling pulping temperatures at $18^{\circ}C$ and $51^{\circ}C$. Low pulping temperature ($18^{\circ}C$) caused more generation of fines in stock. Consequently retention and drainage of linerboard defibrated at high pulping temperature ($51^{\circ}C$) were better than those of $18^{\circ}C$. Strength properties of handsheet at low pulping temperature were higher than those of high pulping temperature and it could be confirmed that low pulping temperature during winter is one reason of seasonal variation of recycled linerboard strength. It is considered that surface modification of OCC fibers by harsh pulping action during winter caused increase of paper strength.

• KCI Concrete Journal
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• 제13권2호
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• pp.10-18
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• 2001

The spectral analysis of surface waves (SASW) method, which is an in-situ seismic technique, has mainly been developed and used for many years to determine the stiffness profile of layered media (such as asphalt concrete and layered soils) in an infinite half-space. This paper presents a modified experimental technique for nondestructive evaluation of in-place cement mortar compressive strength in single-layer concrete slabs of rather a finite thickness through a correlation to surface wave velocity. This correlation can be used in the quality control of early age cement mortar structures and in evaluating the integrity of structural members where the infinite half space condition is not met. In the proposed SASW field test, the surface of the structural members is subjected to an impact, using a 12 mm steel ball, to generate surface wave energy at various frequencies. Two accelerometer receivers detect the energy transmitted through the medium. By digitizing the analog receiver outputs, and recording the signals for spectral analysis, surface wave velocities can be identified. Modifications to the SASW method includes the reduction of boundary reflections as adopted on the surface waves before the point where the reflected compression waves reach the receivers. In this study, the correlation between the surface wave velocity and the compressive strength of cement mortar is developed using one 36"x36"x4"(91.44$\times$91.44$\times$91.44 cm) cement mortar slab of 2,000 psi (140 kgf/$\textrm{cm}^2$) and two 36"x36"x4"(91.44$\times$91.44$\times$91.44 cm) cement mortar slabs of 3,000 psi (210 kgf/$\textrm{cm}^2$).

• 펄프종이기술
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• 제47권4호
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• pp.76-80
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• 2015

In filler loaded paper, the size of the filler affects its strength, optical and surface properties. As the size of the filler increases, tensile strength and bulk usually increases, opacity decreases, and smoothness becomes worse. Pre-flocculation of GCC (grounded calcium carbonate) makes large diameter flocs at aqueous medium that consists of multiple GCC particles, but they collapse to 2-dimensional shape in dried paper and makes low bulk paper. The hybrid calcium carbonate (HCC) that was made by in-situ $CaCO_3$ formation between GCC in aqueous medium made high bulk paper without harming tensile strength, bulk, opacity, and smoothness. The GCC that has equivalent size as HCC failed to make high opacity and smoothness as much as HCC.

• 한국도로학회논문집
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• 제3권3호
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• pp.135-146
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• 2001

기존의 교면포장공법의 근본적인 문제점으로 인해 새로운 교면포장 공법이 점차 부각되고 있는 실정이며, 새로운 교면포장 공법으로 연구되고 있는 것이 라텍스 개질 콘크리트를 이용하는 것이다. 따라서, 본 연구에서는 신설 콘크리트 교량 교면포장으로 덧씌우기된 LMC의 강도발현 특성과 덧씌우기 될 때의 기존콘크리트와의 부착특성을 파악하고자 하였다. 이런 연구를 위해 라텍스 혼입률에 따른 라텍스 개질 콘크리트의 압축강도와 휨강도, 그리고 기존콘크리트와의 부착강도를 측정하였다. 본 연구결과 라텍스 혼입량 증가로 폴리머 입자들의 볼베어링 작용, 연행된 공기 및 라텍스 안에 있는 계면활성제의 분산작용에 의하여 LMC의 작업성과 휨강도를 증가시킨다는 사실을 파악 할 수 있었고, LMC와 기존 콘크리트 슬래브와의 부착강도는 크게 증진함을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제27권1호
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• pp.54-63
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• 2023

본 논문에서는 부식된 철근과 콘크리트 계면의 부착강도-슬립거동에 있어 부식수준 및 균열폭의 영향에 대한 연구를 수행하였다. 기존의 연구는 주로 부식수준에 따른 부착강도 저하에 초점을 맞추고 있으나 부식에 의한 콘크리트 표면 균열폭에 따른 부착강도 저하에 관한 연구는 매우 적다. 따라서 본 연구에서는 부식된 철근과 콘크리트 접합부의 부착강도, 슬립 거동 및 철근의 질량손실 등을 평가하고 균열폭 대비 접합성능을 확인하기 인발시험을 실시하였다. 그 결과로 표면 균열폭에 따른 접착강도 저하의 경향성이 부식수준에 따른 경향성보다 균등하게 나타났다. 따라서 부식수준에 비해 콘크리트 표면 균열 발생 여부가 부착강도-슬립거동 관계의 성능저하를 판단하기에 적합한 것으로 판단된다.