• Title, Summary, Keyword: Shrinkage

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Effect of the Thermal Shrinkage of PET Filament Yarn on the Dimensional Properties of Woven Fabric(I) -Shrinkage Characteristics of PET Drawn Yarn- (PET Filament 연신사의 물성이 직물의 수축특성에 미치는 영향(I) - 연신사의 수축특성 -)

  • 송주화;김종섭;강태진
    • Textile Science and Engineering
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    • v.36 no.12
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    • pp.902-907
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    • 1999
  • Variations in the shrinkage characteristics of PET drawn yarns were studied in terms of thermal tension and shrinkage level at different pre-heat treatment conditions in practical fabrication processes. The shrinkage of PET drawn yarn decreases with tension and heat treatment temperature applied during the preparation processes for weaving, however, the extent of shrinkage reduction depends on the history of the drawing process.

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Drying Shrinkage Characteristics of the Concrete Incorporated Shrinkage Reducing Agent According to Mixed Proportion of Concrete (콘크리트 배합조건에 따른 수축저감제의 건조수축 특성)

  • Kim, Young-Sun;Kim, Kwang-Ki;Park, Soon-Jeon;Kim, Jung-Sun
    • Journal of the Korea Institute of Building Construction
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    • v.17 no.3
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    • pp.245-252
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    • 2017
  • Recently, structures such as large retailers, outlets and warehouses have been increasing in accordance with changes in consumption patterns. Since these structures include ultra-flat slab members, they are thoroughly managed to control slab cracking by the plastic and drying shrinkage. In order to control the cracking of the slab member, a chemical crack reduction method is used. In particular, the use of the shrinkage reducing agent has been examined. However, domestic research results are limited. In this study, the shrinkage properties of concrete using shrinkage reducing agent and the drying shrinkage properties according to the mixing factors were investigated. The performance of domestic shrinkage reducing agent was appeared similar to that of overseas high-grade shrinkage reducing agent. As the shrinkage reducing agent usage increased, the drying shrinkage reduction effect increased. At the age of 100 days, the dry shrinkage rate of specimen with the shrinkage reducing agent of 1.5%was shown about half that of the specimen without the shrinkage reducing agent. The shrinkage reducing agent was gound to have no specific performance change for the use of the admixture.

POLYMERIZATION SHRINKAGE KINETICS OF SILORANE-BASED COMPOSITES (Silorane 복합레진의 중합수축의 동력학)

  • Kwon, Young-Chul;Lee, In-Bog
    • Restorative Dentistry and Endodontics
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    • v.35 no.1
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    • pp.51-58
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    • 2010
  • Dental composites have improved significantly in physical properties over the past few decades. However, polymerization shrinkage and stress is still the major drawback of composites, limiting its use to selected cases. Much effort has been made to make low shrinking composites to overcome this issue and silorane-based composites have recently been introduced into the market. The aim of this study was to measure the volumetric polymerization shrinkage kinetics of a silorane-based composite and compare it with conventional methacrylate-based composites in order to evaluate its effectiveness in reducing polymerization shrinkage. Five commercial methacrylate-based (Beautifil, Z100, Z250, Z350 and Gradia X) and a silorane-based (P90) composites were investigated. The volumetric change of the composites during light polymerization was detected continuously as buoyancy change in distilled water by means of Archemedes' principle, using a newly made volume shrinkage measurement instrument. The null hypothesis was that there were no differences in polymerization shrinkage, peak polymerization shrinkage rate and peak shrinkage time between the silorane-based composite and methacrylate-based composites. The results were as follows: 1. The shrinkage of silorane-based (P90) composites was the lowest (1.48%), and that of Beautifil composite was the highest (2.80%). There were also significant differences between brands among the methacrylate-based composites. 2. Peak polymerization shrinkage rate was the lowest in P90 (0.13%/s) and the highest in Z100 (0.34%/s). 3. The time to reach peak shrinkage rate of the silorane-based composite (P90) was longer (6.7 s) than those of the methacrylate-based composites (2.4-3.1 s). 4. Peak shrinkage rate showed a strong positive correlation with the product of polymerization shrinkage and the inverse of peak shrinkage time (R = 0.95).

An Experimental Study on The Differential Dry Shrinkage of Concrete Using Artificial Lightweight Aggregate (인공 경량골재를 사용한 콘크리트의 부등 건조수축에 관한 실험적 연구)

  • Lee, Chang-soo;Kim, Young-ook;Lin, Yan
    • Journal of the Society of Disaster Information
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    • v.6 no.1
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    • pp.78-90
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    • 2010
  • Exposure to the outside, the concrete is differential moisture distribution depending on the depth. Such a differential moisture distribution causes the differential drying shrinkage in concrete structures. This thesis is researched to compare the shrinkage of lightweight concrete depending on depth to normal concrete. It is used artificial lightweight aggregate which has 20% of pre-absorb value by lightweight concrete. When water-binder ratio is 30%, average shrinkage of lightweight concrete section decreased than normal concrete, but differential shrinkage of lightweight concrete section increased. However water-binder ratio is 40% and 50% average shrinkage and differential shrinkage of lightweight concrete section decreased than normal concrete.

Effect of Hydration Heat Evolution on Autogenous Shrinkage of High Strength Concrete (초기수화발열이 고강도콘크리트의 자기수축특성에 미치는 영향)

  • 정해문;도변박지;하야도륭
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.95-100
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    • 2003
  • The shrinkage of high strength/high performance concrete is very important property for the good working of a structure since it very often generates early age cracking due to thermal and autogenous shrinkage. Autogenous shrinkage occurs as a result of internal moisture depletion due to hydration and temperature-induced effects. The level of autogenous shrinkage occurring due to hydration also depends on temperature history at very early age. It is necessary that effect of temperature on autogenous shrinkage is investigated since the stress generated due to autogenous shrinkage is quantified. In this study, Effect of hydration heat evolution on autogenous shrinkage of high strength concretes with W/C=25-40% was investigated.

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Effect on the Residual Stress of Cure Profiles, Fillers and Mold Constraints in an Epoxy System

  • Moon, Chang-Kwon;Nam, Ki-Woo
    • Journal of Ocean Engineering and Technology
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    • v.23 no.4
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    • pp.1-5
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    • 2009
  • A dilatometer was used to investigate the effect of cure conditions, mold types and the presence of filler in an epoxy system. These studies showed shrinkage in the cured epoxy when heating it through the glass transition temperature region. The magnitude of the shrinkage, related to stress build up in the epoxy during curing, was influenced by the processing conditions, filler presence and the nature of the mold used to contain the resin. Cure and cyclic cure at a lower temperature, prior to a post cure, decreased the magnitude of observed shrinkage. Cure shrinkage decreased with the number of cyclic cures. Post cured samples outside the mold led to less shrinkage compared with samples in the mold. Sample cured in a silicon mold represented less shrinkage than sample cured in an aluminum mold. Sample containing kaolin filler showed less shrinkage than unfilled sample.

Shrinkage of Injection Molded Part for Inorganic Additive Compositions (무기 첨가물 함량에 따른 사출성형품의 성형 수축)

  • Kim B.D.;Yoo Y.H.;Hwang B.H.;Lyu M.Y.;Kim A.S.;Park S.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.58-64
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    • 2004
  • The shrinkages of injection molded parts are different in molding operational conditions, resins and additives. The shrinkage of injection molded part for crystalline polymer, PBT (polybutylene terephthalate) has been studied for various operational conditions of injection molding and content of additives. Mica was used as a additive to PBT to examine the part shrinkage according to the mica content. The part shrinkages of mica contained PBT decreased as mica content increases. Higher injection temperature and injection pressure resulted in a lower shrinkage. As mold temperature increases the part shrinkage decreased. The part shrinkage of flow direction was less than that of the perpendicular direction to the flow for both pure and mica contained PBT. However the shrinkage difference between flow and perpendicular to flow directions decreased as mica content increased.

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The Properties of Stress Induced by Autogenous Shrinkage and Dry Shrinkage for High Strength Concrete Using Type I and Type IV Cement (보통 및 저열시멘트를 이용한 고강도 콘크리트의 자기수축응력 및 건조수축응력 특성)

  • Lee Woong-Jong;Um Tae-Sun;Lee Jong-Ryul
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.17-20
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    • 2005
  • In this study, the properties of autogenous shrinkage stress and dry shrinkage stress for high strength concrete using Type I and Type IV cement were discussed. According to experimental results, autogenous shrinkage stress of SN30(the high strength concrete using type I cement) shows values higher than SL30(the high strength concrete using type IVcement). It is observed that the total shrinkage stress of SN30 is higher than that of SL30, because the ratio of autogenous shrinkage stress of the total shrinkage stress is relatively large. Therefore, SL30 is more effective to control or minimize the cracking of the high strength concrete, compared with SN30.

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A Study On the Chemical shrinkage and Autogenous Shrinkage of High strength Concrete (고강도 콘크리트의 수화수축과 자기수축의 실험연구)

  • Heo, Woo-Young;Kim, Wha-Jung
    • Journal of the Korea Institute of Building Construction
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    • v.4 no.2
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    • pp.81-88
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    • 2004
  • The purpose of this study is to investigate the chemical shrinkage and autogenous shrinkage of high strength cement paste and silica fume and fly ash and sand to cement ratio by the method of volumetric tests, and also investigate the autogenous shrinkage of high measurement method, and compare the results of volumetric test and linear length measurement test. A series of cement paste which have W/C ratio of 25%, 35%, 45% respectively were planed to study the effect of the W/C ratio to the shrinkages, and a series of cement paste which were replaced the cement by the silica fume and fly ash with 5%, 10%, 15% as the mass of cement respectively were planed to investigate the effects of poazolana to the shrinkages. A series of mortar which have a C/S ratio of 1:1, 1:1.5, 1:2 respectively were planed to investigate the shrinkage resistant effect of aggregate.

Shrinkage analysis of reinforced concrete floors using shrinkage-adjusted elasticity modulus

  • Au, F.T.K.;Liu, C.H.;Lee, P.K.K.
    • Computers and Concrete
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    • v.4 no.6
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    • pp.437-456
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    • 2007
  • The shrinkage of large reinforced concrete floors often gives rise to cracking problems. To identify the problematic areas, shrinkage movement analysis is often carried out by finite element method with proper creep and shrinkage models using step-by-step time integration. However as the full stress history prior to the time interval considered is necessary, with the increase in the number of time intervals used, the amount of computations increases dramatically. Therefore a new method using the shrinkage-adjusted elasticity modulus (SAEM) is introduced so that analysis can be carried out using one single step. Examples are presented to demonstrate its usefulness.