• Journal of Welding and Joining
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• v.5 no.3
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• pp.46-52
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• 1987

The mechanism of transverse shrinkage for the butt joint weldig of plates is investigated in this paper. It was certified that the compressive plastic strain due to thermal expansion of materials during heating play an important role on the transverse shrinkage. It was also pointed out that the transverse shrinkage has to be treated with the samples of which the shapes are as close to real shapes of welded materials as possible, because the distribution of temperature and relative rigidity of materials during welding have great influence on the transverse shrinkage. The formulas for the calculation of transverse shrinkage were presented and the experiments were carried out in order to verify the formulas. the main results are as follows; 1. For the bead-on-plate welding, the transverse shrinkage in the begining parts of welding is the smallest, the end parts is next and the transverse shrinkage of mid section is the largest. 2. In bead-on-plate welding, the equations presented in this paper concerning transverse shrinkage coincide fairly well with the experimental values generally. 3. Transverse shrinkage increases generally as specific heat input per unit thickness increaes.

• Journal of Adhesion and Interface
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• v.5 no.3
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• pp.10-17
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• 2004

We investigated the effect of stabilization processing parameters on the thermal shrinkage, thermal stability and microstructure of rayon fabrics stabilized under various conditions such as heating rate, stabilization temperature, atmosphere gas, and chemical treatment. The presence and absence of phosphoric acid treatment and the heating rate have most importantly influenced the thermal shrinkage and the weight change of rayon fabrics. Especially, the phosphoric acid treatment decreases the reduction of thickness, length, and weight of the fabrics by about 80%, 20%, and 26%, respectively, in comparison with the untreated counterparts, showing the protective effectiveness of the thermal shrinkage involved. The thermal stability of stabilized rayon fabrics is also affected by all the processing conditions used: stabilization temperature, phosphoric acid treatment, atmosphere gas, and heating rate. In addition, the surface and diameter of the stabilized fiber significantly depend on the treatment of phosphoric acid prior to stabilization process.

• Journal of Industrial Technology
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• v.25 no.B
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• pp.73-80
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• 2005

Durability of concrete structures is seriously compromised by cracking at early-age concretes, particularly in high-strength or high-performance concrete structures. Since early-age cracking is influenced by various factors that affect the hydration process, early-age shrinkage and stress/strain development, the behavior at early-age is highly complex and no rational methodologies for its control have yet been established. Concrete structures often present volumetrical changes particularly due to thermal and moisture related shrinkages. Volumetric instability is detrimental to the performance and durability of concrete structures because structural elements are usually restrained. These restrained shrinkages develope tensile stresses which often results in cracking in combination with the low fracture resistance of concrete. Early-age defects in high-performance concrete due to thermal and autogenous deformation shorten the life cycle of concrete structures. Thus, it is necessary to examine the behavior of early-age concrete at the stages of design and construction. The purpose of this study was to propose a shrinkage models of VES-LMC (very-early strength latex-modified concrete) at early-age considering thermal deformation and autogenous shrinkage.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.251-256
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• 2001

Shrinkage during the curing and drying of concrete is unavoidable and results in many cracks. Shrinkage strips reduce effectively shrinkage stresses and minimize shrinkage cracks by being left open for a certain time during construction allow a significant part of the shrinkage to occur without inducing stresses. This study verifies the effectiveness of shrinkage strips and provides the guide for construction of such strips.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.827-832
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• 2001

Shrinkage during the curing and drying of concrete is unavoidable and results in many cracks. Shrinkage strips reduce effectively shrinkage stresses and minimize shrinkage cracks by being left open for a certain time during construction to allow a significant part of the shrinkage to occur without inducing stresses. This study verifies the effectiveness of shrinkage strips and provides the guide for construction of such strips.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3602-3609
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• 2015

HPFRCC is characterized by a very low water-to-binder ratio which induce extremely large autogenous shrinkage at early age. The restriction of such autogenous shrinkage through the use of forms and reinforcing bars will increase substantially the risk of excessive residual stresses and shrinkage cracking. The exact understanding of the shrinkage behavior and studies on solutions to reduce shrinkage should be imperatively undertaken for further application of HPFRCC to real structures. Therefore, this paper investigated the mechanical properties of HPFRCC with respect to the eventual introduction of expansive admixture(EA) and shrinkage reducing agent (SRA) in the mixture. Autogenous shrinkage test was conducted considering the coefficient of thermal expansion (CTE) measured at early age so as to examine the effects of EA and SRA on the autogenous shrinkage behavior of HPFRCC.

• Korean Journal of Materials Research
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• v.13 no.2
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• pp.74-80
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• 2003

The effects of risering design and alloying element on the formation of defects such as external depression, primary and secondary shrinkage cavities in ductile cast iron were investigated. Two types of risering design for the cylindrically step-wise specimen, No. 1(progressive solidification) and No. 2(directional solidification) risering designs, were prepared and six different alloy compositions were casted. In the No. 1 risering design, external depression or primary shrinkage cavities due to liquid contraction were observed in all the specimens from SG 10 to SG 60. The defects caused by liquid contraction seemed to be more affected by risering design than alloying elements. The secondary shrinkage cavities were also observed in all the specimens but a swollen surface was not observed in all the castings. The primary shrinkage cavities were located right under the top surface or connected to the top surface, and were characterized by smooth surfaces. On the other hand, the secondary shrinkage cavities were positioned in the thermal center of the specimen steps 3 and 4, and characterized by rough surfaces. In the No. 2 risering design, no external depression or primary shrinkage cavities due to liquid contraction were observed in all the specimens from SG 10 to SG 60. However, the secondary shrinkage cavities were formed in the thermal center of specimens SG 40, 50 and 60. Like the No. 1 risering design, a swollen surface was not observed in all the castings.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.569-570
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• 2009

An improvement of the test method is proposed to more accurately measure early-age autogenous shrinkage in concrete particularly within first 24 hours after casting. Experiments were conducted considering existing and improved method. In improved method, hydration temperature was artificially controlled to prevent thermal deformations. Test results indicate that the autogenous shrinkage calculated by existing approach is underestimated which might be due to the wrong assumption of considering the thermal dilation coefficient to be constant (equal to 10 ${\times}$ $10^{-6}/^{\circ}C$) at early-age. We recommend that the proposed method should be adopted to better assess precise value of autogenous shrinkage or an appropriate method of determining the time-evolution of thermal dilation coefficient be considered.

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.117-122
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• 2008

Quality control of the concrete pavement in the early stage of curing is very important because it has a conclusive effect on its life span. Therefore, examining and analyzing the initial behavior of concrete pavement must precede an alternative to control its initial behavior. There are largely two influential factors for the initial behavior of concrete pavement. One is the drying shrinkage, and the other is the heat generated by hydration and thermal change inside the pavement depending on the change in the atmospheric temperature. Thus, the coefficient of thermal expansion and drying shrinkage can be regarded as very important influential factors for the initial behavior of the concrete. It has been a general practice up until now to measure the coefficient of thermal expansion from completely cured concrete. This practice has an inherent limitation in that it does not give us the coefficient of thermal expansion at the initial stage of curing. Additionally, it has been difficult to obtain the measurement of drying shrinkage due to the time constraint. This research examined and analyzed the early drying shrinkage of the concrete and measurements of the thermal expansion coefficients to formulate a plan to control its initial behavior. Additionally, data values for the variables of influence were collected to develop a prediction model for the initial behavior of the concrete pavement and the verification of the proposed model. In this research, thermal expansion coefficients of the concrete in the initial stage of curing ranged between $8.9{\sim}10.8{\times}10^{-6}/^{\circ}C$ Furthermore, the effects of the size and depth of the concrete on the drying shrinkage were analyzed and confirmed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.493-496
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• 2008

The risk of transverse cracking in concrete decks of composite bridges is affected by many factors related to the bridge design, materials, and construction. Among others, the thermal and shrinkage stresses are the most important factors that affect the transverse cracking in early-age concrete decks. The thermal stress at the concrete deck is mainly affected by both ambient temperature and solar radiation. The shrinkage stress at the general strength concrete deck is mainly affected by drying shrinkage and the high strength concrete deck is mainly affected by autogeneous shrinkage. Three-dimensional finite element models of composite bridges were made to investigate the stress due to thermal and shrinkage stress.