• 제목/요약/키워드: drying defects

검색결과 73건 처리시간 0.021초

분자동역학을 이용한 다공성 물질 건조공정 멀티스케일 시뮬레이션(2부: 미시 물성) (Multi-scale simulation of drying process for porous materials using molecular dynamics (part 2: material properties))

  • 백성민;금영탁
    • 한국결정성장학회지
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    • 제15권4호
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    • pp.162-167
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    • 2005
  • 건조공정 중인 다공성 물질의 물성은 재료의 비균질성 즉 전위, 입자, 입계, 균열, 기공과 같은 미시적인 결함인자들의 영향을 받는다. 따라서 다공성 물질의 건조공정을 전산 시뮬레이션하기 위해서는 원자 스케일 해석을 통한 미시적 물성을 알아야 한다. 본 연구에서는 분자동역학 시뮬레이션을 이용하여 원자 모델을 구성하고 원자 상호간 거동을 예측하여 재료의 미시적 물성을 계산하였다. 이렇게 구한 탄성계수, 열팽창계수, 체적 열용량은 실험 및 이론에 기초한 결과들과 비교하여 검증하였다.

소나무재의 단면치수에 따른 수축률 특성 (Effect of Cross-Sectional Dimension on the Shrinkage Property of Korean Red-Pine Wood)

  • 황권환;박병수
    • Journal of the Korean Wood Science and Technology
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    • 제37권3호
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    • pp.231-238
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    • 2009
  • 우리나라에서 전통주택(한옥) 및 목조건축 문화재의 구조부재로 많이 이용되는 소나무는 천연건조가 일반적이어서 건조에 많은 시간이 소요되고 건조가 불충분하면 수축에 의한 갈라짐 및 변형 등의 결함을 일으킬 수 있다. 소나무 소시험편과 대단면 시험편을 제작하여 함수율상태에 따른 수축률변화를 검토하였다. 특정 함수율 상태에서의 체적수축률을 예측할 경우, 생재상태에서 기건상태, 기건상태에서 전건상태까지의 구간으로 나누어 적용하는 것이 정밀도가 높았다. 변재의 체적수축률은 단면크기에는 상관성이 없으며, 심재는 단면이 커질수록 체적수축률이 감소하는 것으로 나타났다.

페인트 도장공사의 색관리에 관한 연구 (A study on the color controlled of painter's work)

  • 심명섭;이현정
    • 한국건축시공학회지
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    • 제3권1호
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    • pp.107-114
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    • 2003
  • This study aims to find methods that prevents aging of buildings paint coating and that limits defects in construction. Defects in painting can occur in four stages: pure paint, during painting, after the paint coating has dried, and after some period of time has passed after coating. Paint may become bad due to precipitation of pigments, formation of membranes, and seeding during manufacturing. Therefore, it is important that the paint is well mixed and kept airtight at a cool, dark place. Indents, paint brush strokes, orange peel, separation of colors, and paint running and spreading during the paint work process can be prevented by using high quality materials and applying a high-level of construction method. After the paint coating has dried, boiling, yellowing, poor drying, poor bonding, and/or glen deficiency may occur. These are influenced by the levels of cleanness of the dried product, drying temperature and hydration. Then, when the coating has been left dried for some period of time, cracking, peeling, scaling, swelling, discoloring, and/or rusting may develop due to the ultraviolet and contaminants in the air. Since these defects occur due to inappropriate construction schedule and/or hot and humid condition, one must use weatherproof materials. Furthermore, poor paint color may be caused by contamination in the sample plate, discoloration, and/or discrepancies in colors which are due to material differences, level of glossiness, degree of dispersion, dual color property of metallic colors, precipitation of pigments, etc. One should achieve reduction in construction cost and effectiveness in paint work by limiting contaminations in the construction site and strictly observing to construction regulations.

엔드테이핑 처리들이 백합나무 원반의 고주파진공건조 중 건조결함 예방에 미치는 영향 (Effect of End-taping Treatments on Prevention of Drying Defects during Radio-Frequency/Vacuum Drying of Domestic Yellow Poplar Log Cross Section)

  • 이남호;;장세환;신익현
    • Journal of the Korean Wood Science and Technology
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    • 제36권6호
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    • pp.59-68
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    • 2008
  • 본 연구에서는 엔드테이핑(End-taping) 처리가 두께가 20~75 mm이고, 직경이 120~470 mm인 백합나무 원반들의 고주파진공건조중 건조결함 예방 미치는 영향에 대하여 조사하였다. Inside end-taping (Inside-ET)과 Outside end-taping (Outside-ET)의 경우 두께 33 mm, 직경 270 mm 이하 원반에서 할렬의 예방효과가 우수하게 나타났다. 직경이 30 cm 이하이고, 두께 60 mm와 두께 75 mm의 원반에서도 전처리을 통하여 경계할렬을 예방할 수 있을 것으로 기대되었다. 경계할렬의 발생위치는 0.50~0.63 diameter 지점으로서 직경에 따라서 상이하였으며, 따라서 횡단면의 부분 엔드테이핑 처리의 경계선도 원반의 직경 따라 적정하게 선정할 필요가 있는 것으로 조사되었다. 중경재의 경우 0.3 diameter 지점이 경계할렬 예방을 위한 전처리의 경계점일 가능성이 높을 것으로 해석된다. 대경재의 경우 경계할렬과 V형 크랙에 의한 손상이 매우 심하였으며, 이는 방사방향으로의 함수율 분포변이가 극심한 백합나무 고유의 재질특성에 기인한 것으로 해석된다. 따라서 대경재의 경우 원반으로 활용하는 것은 적절하지 않는 것으로 생각된다.

수입 솔로몬산(産) 미이용(미利用) 수종(樹種)의 인공건조(人工乾燥)스케쥴 개발(開發) (Development of Kiln Drying Schedule of Lesser-Known Species Imported from Solomon)

  • 정희석;심재현
    • Journal of the Korean Wood Science and Technology
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    • 제14권1호
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    • pp.45-54
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    • 1986
  • A study was conducted to determine the physical properties related to drying characteristics, the seasonal air drying curves and the kiln drying schedule for taun lumber imported and utilized. This kiln drying schedule was found by oven drying and developed by pilot testing of green lumber and partially air dried lumber. The results of this study were as follows; 1. Average green specific gravity and standard deviation of heartwood lumber were 0.60${\pm}$0.03 and those of sapwood lumber were 0.64${\pm}$0.02. 2. Radial shrinkage from green to air dry and from green to oven dry were 3.05 percent and 5.96 percent respectively, and tangential shrinkage from green to air dry and to oven dry were 5.49 percent and 8.74 percent respectively. 3. Drying time for 25mm thick green lumber (50 percent moisture content) air dried to 30 percent moisture content were 14 days in springtime. 6 days in summertime, and 12 days in autumntime, whereas for 50mm thick lumber in 36 days in springtime, 18 days in summertime, 38 days in autumntime. 4. Kiln drying schedules developed by oven drying were T8-B3 for 25mm thick lumber and T5-B2 for 50mm thick lumber. 5. Kiln drying curves of green 25mm and 50mm thick lumber were similar to those of partially air dried lumber from the level of 30 percent average moisture content. Green 25mm thick lumber (55.7 percent moisture content) was dried to 9.3 percent moisture content in 101.5 hours and green 50mm thick lumber (65.6 percent moisture content) was dried to 11.5 percent moisture content in 526 hours. 6. End checking for green 25mm thick lumber occured in 49.6 percent moisture content and reached maximum amount in 27.6 percent moisture content and closed in 15.8 percent moisture content. 7. End checking for green 50mm thick lumber and partially air dried lumber developed and reached maximum amount earlier then for 25mm thick lumber. 8. Final moisture content of surface layer for 50mm thick lumber was one half of that of core, and moisture content equalized in the lumber after nine days of room conditioning. 9. Casehardening for 50mm thick lumber was slight and was conditioned after nine days of room stroage. 10. Drying defects, such as end checking and surface checking, were not observed and the quality of dry lumber was first.

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받침의 구속과 편기를 갖는 경사지게 설치된 PSCI빔의 안전성 평가 (Safety Evaluation for PSCI-Beam by Tilt-Constructed with Constraint and Deviation of Bearings)

  • 박창호;신재인;이병주;서상길
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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    • pp.346-349
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    • 2006
  • Superstructure of reinforced concrete bridges are shortened or elongated due to creep, drying shrinkage, temperature and so on. Most of bridge superstructures are free to shortening and elongation without constraint and stresses will not be induced by creep, drying shrinkage and temperature. But if bridge superstructure are constraint due to wrong setting and functional defects of bridge bearing, very large constraint forces can be induced. In this study, PSCI-Beam by tilt-constructed with constraint and deviation of bearings are presented and the effects of time-dependent constraint stress and temperature loads are investigated.

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Study on the Granulation Behavior of TiO2-PVA Composite Powders Prepared Via Spray Drying Technique

  • Avcioglu, Celal;Ozkal, Burak
    • 한국세라믹학회지
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    • 제56권5호
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    • pp.443-452
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    • 2019
  • In this study, TiO2-polyvinyl alcohol (PVA) composite granules were prepared via spray drying technique. To investigate the effects of solid content and binder/powder ratio in the slurry on the granulation behavior of TiO2 powders, the feed compositions were designed to vary over a wide range. The morphology, actual densities, and average granule size and size distribution of the TiO2-PVA composite granules were characterized by using scanning electron microscopy technique, a gas pycnometer, and an image analyzing program (Image-J), respectively. The results indicate that solid content and the amount of PVA in the feedstock slurry are the dominant factors determining the granule morphology, size, and size distribution of TiO2-PVA composite. Moreover, it was observed that increasing the solid content and the amount of PVA in the slurry improved the granulation process and reduced the granule defects. For the preparation of spherical TiO2-PVA composite granules with the minimum amount of non-granulated powders, the optimized composition of the feedstock slurry was found to be 35 wt.% solid and 3 wt.% PVA.

자가골 이식에서 이식골편의 처리방법에 따른 골형성능력 비교 (Comparison of osteogenic efficacy depending on implant preparation in autograft)

  • 이종일;송하나;김남수;최인혁
    • 대한수의학회지
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    • 제47권1호
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    • pp.117-125
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    • 2007
  • Bone graft had been investigated previously to restore bone defects in orthopedics. The purpose of this study was to investigate the efficacy on new bone formation in bone autografts by treatment of implants. Cortical bone autografts were transplanted to midshaft of diaphyseal fibulae of 9 rabbits which were divided in 3 groups according to the treatment method of implants. Cortical bone implants for graft were treated with 3 different methods; freezing, freeze-drying, defat-freezing. Autografts were achieved by cross-transplantation method to bilateral fibulae of the presented rabbits after implant treatment procedures. The grafted regions of fibulae of all groups had been radiographed biweekly for 16 weeks to observe new bone formation and union between donor and recipient bone in the grafted region. Bone alkaline phosphatase (BALP) in all groups was evaluated biweekly till the end of the experiment to determine osteoblast activities. Unions of the experimental grafted regions were observed at 83% (5 of 6 cases) of freezing, 17% (1 of 6 cases) of freeze-drying and 67% (4 of 6 cases) of defat-freezing autografts, respectively. BALP was increased over 100% after 2 weeks of graft procedures in all union cases (all cases in freezing group and in defat-freezing group, and 1 of 3 in freeze-drying group, respectively), then gradually decreased from 4 th week of graft to 16 th week. In non-union cases, there is no significant variation in BALP value until the end of experiment. It is speculated that defat-freezing method of treatments of implants is more safe to preserve the osteogenic ability in autograft than freeze-drying method.

토끼 동종골이식에서 이식골편의 동결법, 동결건조법, 탈지 후 동결법 처리에 따른 신생골 형성능력 비교 (Comparison of osteoinductive efficacy of freezing, freeze-drying and defat-freezing implant preparation for allograft in rabbit)

  • 이종일;송하나;김남수;최인혁
    • 대한수의학회지
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    • 제47권2호
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    • pp.219-228
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    • 2007
  • Bone allograft had been increased the need because autogenous bone graft is associated with donor site morbidity and is restricted in quantity. The bone allograft implants have to prepare properly for increasing osteoinductive ability and decreasing immune responses before providing to graft. The purpose of this study was to investigate the efficacy on new bone formation in bone allografts by treatment of implants. Cortical bone allografts were transplanted to experimental defects on midshaft of diaphyseal fibulae in 15 rabbits, which were divided to 3 experimental groups according to the preparation methods-freezing, freeze-drying, defat-freezing. The grafted regions of fibulae of all groups had been radiographed biweekly for 16 weeks to observe new bone formation and union between implant and recipient bone. Bone Alkaline Phosphatase (BALP) in all groups was evaluated biweekly till the end of the experiment to determine osteoblast activities. Unions between implant and recipient bone were observed at 30% (3 of 10 cases) of freezing, 50% (5 of 10 cases) of freeze-drying and 80% (8 of 10 cases) of defat-freezing. BALP was increased over 100% from before graft at 2 weeks of graft procedures in all union cases of freezing and defat-freezing group, then gradually decreased till 16th week. In non-union cases, there is no significant variation in BALP value. Defat-freezing method for allograft implants might be more effective for osteoinductive efficacy of implants than freezing and freeze-drying method.

태양에너지를 이용한 유용목재의 건조 (Seasoning of Commercial Wood Using Solar Energy)

  • 정희석;이형우;이남호;이상봉
    • Journal of the Korean Wood Science and Technology
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    • 제16권4호
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    • pp.10-39
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    • 1988
  • This study investigated the temperatures and relative humidities in the semi-greenhouse type solar dryer with a black rock-bed heat storage and without heat storage and outdoor temperature and relative humidity at 9 a.m. and 2 p.m.. A comparison was made of the drying rates, final moisture contents, moisture content distributions, casehardening stresses, drying defects, volumetric shrinkage of dried lumber for solar- and air-drying from the green condition of mixtures of Douglas-fir, lauan, taun, oak and sycamore 25mm- and 50 mm-thick lumber during the same period for four seasons, and heat efficiencies for solar dryer with and without the heat storage for saving of heat energy and the cost of lumber drying using the solar energy. The results from this study were summarized as follows: I. The mean weekly temperatures in the solar dryers were 3 to $6^{\circ}C$ at 9 a.m. and 9 to $13^{\circ}C$ at 2 p.m. higher than mean outdoor temperature during all the drying period. 2. The mean weekly relative humidities in the solar dryers were about 1 to 19% at 9 a.m. higher than the outdoor relative humidity. and the difference between indoor and outdoor relative humidity in the morning was greater than in the afternoon. 3. The temperatures and relative humidities in the solar dryer with and without the heat storage were nearly same. 4. The overall solar insolation during the spring months was highest and then was greater in the order of summer, atumm, and winter month. S. The initial rate of solar drying was more rapid than that of air drying. As moisture content decreased, solar drying rate became more rapid than that of air drying. The rates of solar drying with and without heat storage were nearly same. The drying rate of Douglas-fir was fastest and then faster in the order of sycamore, lauan, taun and oak. and the faster drying rate of species, the smaller differences of drying rates between thicknesses of lumber. The drying rates were fastest in the summer and slowest in the winter. The rates of solar drying during the spring were more slowly in the early stage and faster in the later stage than those during the autumn. 6. The final moisture contents were above 15% for 25mm-thick air dried and about 10% for solar dried lumber, but the mean final MCs for 50mm-thick lumber were much higher than those of thin lumber. The differences of final MC between upper and lower course of pile for solar drying were greater than those of pile for air drying. The differences of moisture content between the shell and the core of air dried lumbers were greater than those of solar dried lumber, smallest in the drying during summer and greatest in the drying during winter among seasons. 7. Casehardening stresses of 25mm- and 50mm-thick dried lumber were slight, casehardening stress of solar dried lumber was severer than that of air dried lumber and was similar between solar dried lumber with and without heat storage, Casehardening stresses of lumber dried during spring were slightest and then slighter in the order of summer, autumn, and winter. Casehardening stresses of Douglas -fir, sycamore and lauan were slight, comparing with those of taun and oak. 8. Maximum initial checks of 25mm-thick lumber occurred above and below fiber saturation point and those of 50mm-thick lumber occurred in the higher moisture content than thin lumber. As the moisture content decreased, most of checks were closed and didn't show distinct difference of the degree of checks among drying methods. The degree of checks were very slight in case of Douglas-fir and lauan, and severe in case of taun and oak. The degree of checks for 50mm-thick lumber were severer than those for 25mm-thick lumber. 9. The degree of warpage showed severe in case of oak and sycamore lumber, but no warping was found in case of Douglas-fir, lauan and taun. 10. The volumetric shrinkages of taun and oak were large and medium in case of Douglas-fir, lauan and sycamore. 11. Heat efficiencies of solar dryer with heat storage were 6.9% during spring, 7.7% during summer, 12.1% during autumn and 4.1% during winter season. Heat efficiency of solar dryer with heat storage was slightly greater than that of without heat storage. As moisture content of lumber decreased, heat efficiency decreased.

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