• 교육시설 논문지
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• 제20권4호
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• pp.35-43
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• 2013

Some results of experimental investigation conducted to assess the effect of cement composite strength and ductility on the shear behavior and crack-damage mitigation of stud connections between existing reinforced concrete frame in school buildings and seismic strengthening elements from cyclically direct shear tests are described. The cement composite strengths include 50 for medium strength and 70 MPa for high strength. Two types of cement composites, strain-hardening cement composite (SHCC) and non-shrinkage mortar, are used for stud shear connection specimens. The special SHCCs are reinforced with hybrid 0.2% polyethylene (PE) and 1.3% polyvinyl alcohol (PVA) fibers at the volume fraction and exhibits tensile strain capacity ranging from 0.2 to 0.5%. Test result indicates that SHCC improves the seismic performance and crack-damage mitigation of stud shear connections compared with stud connections with non-shrinkage mortar. However, the performance enhancement in SHCC stud connections with transverse and longitudinal reinforcements is less notable for those without additional reinforcement.

• 한국세라믹학회지
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• 제56권2호
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• pp.130-145
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• 2019

Widespread commercialization of solid oxide fuel cells (SOFCs) is expected to be realized in various application fields with the advent of cost-effective fabrication of cells and stacks in high volumes. Cost-reduction efforts have focused on production yield, power density, operation temperature, and continuous manufacturing. In this article, we examine several issues associated with processing for SOFCs from the standpoint of the bimodal packing model, considering the external constraints imposed by rigid substrates. Optimum compositions of composite cathode materials with high volume fractions of the second phase (particles dispersed in matrix) have been analyzed using the bimodal packing model. Constrained sintering of thin electrolyte layers is also discussed in terms of bimodal packing, with emphasis on the clustering of dispersed particles during anisotropic shrinkage. Finally, the structural transition of dispersed particle clusters during constrained sintering has been correlated with the structural stability of thin-film electrolyte layers deposited on porous solid substrates.

• 한국세라믹학회지
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• 제53권2호
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• pp.246-252
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• 2016

Complex designed silica-based ceramic cores were fabricated by ceramic injection molding. Slow heating rate (0.2K/min) for debinding restrained bloating on the surface of ceramic cores. To investigate effect of sintering conditions on mechanical properties of ceramic cores, green bodies were sintered at temperatures in a range from $1150^{\circ}C$ to $1400^{\circ}C$ for various dwelling times (6 h to 48 h). Sintering above $1300^{\circ}C$ for 12 h and dwelling time over 24 h at $1200^{\circ}C$ reduce the flexural strength and increase the linear shrinkage of ceramic cores. Cristobalite, formed by high sintering temperature or long dwelling time, induces reduction of mechanical properties due to its phase transformation, which is accompanied by volume contraction and microcracking. Ceramic core sintered at $1200^{\circ}C$ for 12 h endured wax patterning and shell molding, and was manufactured successfully.

• International Journal of Concrete Structures and Materials
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• 제8권4호
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• pp.309-313
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• 2014

The volume fraction of the coarse aggregate in the conventional plastic concrete is controlled relatively low to ensure a required workability. In this paper, a new type of coarse aggregate interlocking concrete with strength ranging from C30 to C80 was prepared with scattering-filling aggregate process. The strength of concrete prepared with this method increases obviously whereas the shrinkage decreases significantly, the cement dosage in the concrete decreased 20 % at the same time. The microhardness of the ITZ between the cement paste and scattering-filling aggregate is higher than that of the original aggregate, the ITZ become narrower and tighter also. The interlocking and more even distribution of the coarse aggregate and the water absorption of the addition of extra amount of coarse aggregates contribute to the strength and performance improvement of the concrete prepared with scattering-filling aggregate process.

• Asian-Australasian Journal of Animal Sciences
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• 제19권7호
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• pp.1054-1058
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• 2006

The purpose of this study was to use pig blood plasma transglutaminase (TGase) combined with thrombin and fibrinogen as a binder, which was applied to restructured meat, and to investigate its effect on the restructured meat quality. Pig meat was obtained 10 h post mortem from a traditional market was ground using a 10 mm aperture plate. A binder admixture was added (TGase:thrombin:fibrinogen mixed as 0.5:1:20 (v/v/v) to which was added 12% of its volume of 0.25 M calcium chloride) at 0, 5, 10, 15 and 20% of meat weight. Measurements included cooking loss, shrinkage rate, shear value, total plate count, pH value, TBA value, color difference, tension strength and sensory evaluation. The results showed that ground meat containing 20% w/w of binder admixture had higher cooking loss, shrinkage rate and shear value (p<0.05). Addition of different percentages of binder admixture did not affect total plate count, pH value, TBA value, and sensory evaluation of restructured meat (p>0.05). Tension strength was increased with increased level of binder admixture. Addition up to 15% binder admixture to restructured meat showed better scores of sensory texture, flavor and total acceptability (p<0.05).

• 한국세라믹학회지
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• 제32권12호
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• pp.1337-1348
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• 1995

TZP/SUS- and ZT/SUS-functionally gradient materials (FGM) were fabricated by pressureless sintering in Ar-atmosphere. The sintering defects such as warping, frustrum formation, splitting and cracking which originated from shrinkage and sintering behaviors of metal and ceramics different from each other could be controlled by the adjustment with respect to the particle size and phase type of zirconia. The residual stresses generated on the metal and ceramic regions in FGM were characterized with X-ray diffraction method, and relaxed as the thickness and number of compositional gradient layer were increased. The residual stress states in TZP/SUS-FGM have irregular patterns by means of the different sintering behavior and cracking at ceramic-monolith. While in ZT/SUS-FGM, compressive stress is induced on ceramic-monolith by the volume expansion of monoclinic ZrO2 at phase transformation. Also, compressive stress is induced on metal-monolith by the constraint of warping which may be created to the metal direction by the difference of coefficient of thermal expansions. As a consequence, it has been verified that the residual stress generated on FGM is dominantly influenced by the thickness and number of compositional gradient layer, and the sintering defects and residual stress can be controlled by the constraint of the difference of shrinkage and sintering behaviors of each component.

• Journal of Welding and Joining
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• 제18권5호
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• pp.84-89
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• 2000

Friction welding of titanium and aluminium is numerically modeled by the axisymmetric thermal elastic-plastic analysis. In titanium/aluminium friction welding, heat transfers into the titanium substrate to a distance of z=10(mm) on the side of the bondline and into the whole region of the aluminium substrate having the large thermal conductivity. Adjacent to the bondline, $^{\sigma}r\;and\;^{\sigma\theta}$ are tensile in the substrate whose thermal shrinkage is large, and are compressive in the substrate whose thermal shrinkage is small. $\sigma_z$ along the radial direction is large tensile at the periphery of the component. Plastic strain occurs only close to the bondline in the aluminium substrate. In the components of plastic strain, $\varepsilon^p_r\;and\;\varepsilon^p_{\theta}$ have positive values and $\varepsilon^p_r$ has large negative value. However, $\varepsilon^p_r$ is produced not because of the severity of the mechanical restraint condition, but on purpose to satisfy the condition of the volume constant. A plastic work is proposed as a measure to evaluate the mechanical severity. The plastic work is larger in the aluminium substrate than that in the titanium substrate. The mechanical condition is severer in the aluminium substrate.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권5호
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• pp.223-230
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• 2006

The reliability of imprint patterns molded by stamps for industrial application of nanoimprint lithography (NIL), is an important issue. Usually, defects can be produced by incomplete filling of negative patterns and the shrinkage phenomenon of polymers in conventional NIL. In this paper, the patterns that undergo a varied temperature or varied pressure period during the thermal NIL process have been investigated, with the goal of resolving the shrinkage and defective filling problems of polymers. The effects on the formation of polymer patterns in several profiles of imprint processes are also studied. Consequently, it is observed that more precise patterns are formed by the varied temperature (VT-NIL) or varied pressure (VP-NIL). The NIL (VT-NIL or VP-NIL) process has a free space compensation effect on the polymers in stamp cavities. From the results of the experiments, the polymer's filling capability can be improved. The VT-NIL is merged with the VP-NIL for the better filling property. The patterns that have been imprinted in the merged NIL are compared with the results of conventional NIL. In this study, the improvement in the reliability for results of thermal NIL has been achieved.

• Advances in nano research
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• 제3권4호
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• pp.225-242
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• 2015

The current investigation aims to study performance of geopolymer mortar reinforced with Multiwalled carbon nanotubes upon exposure to $200^{\circ}C$ to $1000^{\circ}C$ for 2 hrs. MWCNTs are doped into slag Geopolymer mortar matrices in the ratio of 0.0 to 0.4, % by weight of binder. Mortar composed of calcium aluminosilicate to sand (1:2), however, binder composed of 50% air cooled slag and 50% water cooled slag. Various water / binder ratios in the range of 0.114-0.129 used depending on the added MWCNT, while 6 wt., % sodium hydroxide used as an alkali activator. Results illustrate reduction in mechanical strength with temperature except specimens containing 0.1 and 0.2% MWCNT at $200^{\circ}C$, while further increase in temperature leads to decrease in strength values of the resulting geopolymer mortar. Also, decrease in firing shrinkage with MWCNT up to 0.1% at all firing temperatures up to $500^{\circ}C$ is observed, however the shrinkage values increase with temperature up to $500^{\circ}C$. Further increase on the firing temperature up to $1000^{\circ}C$ results in an increase in the volume due to expansion.

• Journal of Welding and Joining
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• 제31권6호
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• pp.37-43
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• 2013

This study targets to make clear the connection between MS (Martensite start) point and welding shrinkage. We approved that a Martensite-transformed weldment may not yield state under low MS point, but also admitted the limitation of numerical calculation by inherent strain approach or thermal strain approach. Therefore, new thermal strain formulae during cooling stages were made. As a thermal strain is obtained by integrating thermal extension coefficient, a constant of integration should be decided. In our suggested formulae, the origin was based on totally remained austenite, and added strain from volume changes in Martensite transformation was based on totally transformed ferrite. Through the suggested methodology, It is verified that an MS point under a critical temperature can let weld shrinkage relax and the critical value can be obtained. For supporting this process, 15 weld-consumables were made, were tested by fillet type and were measured. As a result, a positive correlation between MS point and level of weld-distortion was obtained, but it was rather weak.