• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.1051-1060
• /
• 2008

The use of the coal ash for surcharge material, in a view of the environmental aspect, can decrease amount of the reclamation through recycling waste materials as well as prevent a destruction of the ecosystem attributed to sand picking. In addition, it can reduce both unit cost of material and construction expenses. In this study, new construction material as alternative surcharge material using coal ash, which is by-product from thermoelectric power plant, were developed. Mixing ratios of fly ash and bottom ash derived from the coal ash in Samchunpo thermoelectric power plants were determined. Furthermore, mixing conditions depending on the ratios of the cement and gypsum used for chemical additive were determined too. Uniaxial compression strength tests were conducted at different mixing conditions and Design graph of optimum mixing ratio at each required strength for economic efficiency is indicated in this paper.

• Journal of the Korea Concrete Institute
• /
• v.12 no.1
• /
• pp.113-125
• /
• 2000

The purpose of this study was to examine the durability characteristics of controlled low strength material(flowable fill) with high volume fly ash content. Flowable fill refer to self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. The two primary advantages of flowable fill over traditional methods are its ease of placement and the elimination of settlement. Therefore, in difficult compaction areas or areas where settlement is a concern, flowable fill should be considered. The fly ash used in this study met the requirements of KS L 5405 and ASTM C 618 for Class F material. The mix proportions used for flowable fill are selected to obtain low-strength materials in the 10 to 15kgf/$\textrm{cm}^2$ range. The optimized flowable fill was consisted of 60kg f/$\textrm{m}^3$ cement content, 280kgf/$\textrm{m}^3$ fly ash content, 1400kgf/$\textrm{m}^3$ sand content, and 320kgf/$\textrm{m}^3$ water content. Subsequently, durability tests including permeability, warm water immersion, repeated wetting & drying, freezing & thawing for high volume fly ash-flowable fill are conducted. The results indicated that flowable fill has acceptable durability characteristics.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.05a
• /
• pp.127-128
• /
• 2017

Tests are conducted according to the ISO TS 16774, Part 3 standard for quality management of leakage repair materials used in cracks in underground concrete structures. These test methods are performed indirectly using a nonwoven fabric on a chalet containing leak repair materials. However, it is considered that it is appropriate to verify the resistance of the repair material, which is required to be applied directly to the cracks in the actual field and to exhibit the resistance of the flow velocity. In this study, mass change was measured by using nonwoven fabric and nonwoven fabric. As a result, both methods showed an increase in mass, which indicated that the maintenance material itself contained a large amount of water, and that the mass change occurred depending on the drying state. Also, depending on the use of nonwoven fabric, the error due to the indirect test could not be ruled out. Therefore, further verification is needed, and it is considered that the test for change of mass reduction measurement is necessary according to the drying time of other types of the same series.

• Journal of the Korean Applied Science and Technology
• /
• v.25 no.3
• /
• pp.341-346
• /
• 2008

Cellulose nanofibers from microfibril cellulose (MFC) was prepared by hydrobromic acid (HBr) treatment at different concentrations. Polyvinyl alcohol (PVA) composite films at various loading level of nanofibers were manufactured by a film casting method. The analysis of degree of polymerization (DP), crystallinity ($X_c$) and molecular weight ($M_w$) of cellulose after acid treatment was conducted. The mechanical and thermal properties of the cellulose nanofibers reinforced PVA films were characterized using tensile tests and thermogravimetric analysis (TGA). The DP and $M_w$ of MFC by HBr hydrolysis considerably decreased, but $X_c$ showed no significant change. After acid hydrolysis, the diameter of cellulose nanofibers was in the range of 100 to 200 nm. The thermal stability of the films was steadily improved with the increase of nanofiber loading. There was a significant increase in the tensile strength of PVA composite films with the increase in MFC loading. Finally, 5 wt.% nanofiber loading exhibited the highest tensile strength and thermal stability of PVA composite films.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.117-126
• /
• 2001

Tribological properties of high temperature fade were investigated by changing relative amounts of ingredients in the brake friction material. Based on a simple experimental formulation containing 10 ingredients, friction materials were tested using a pad-on-disk type friction tester. Twenty-five friction material specimens with different relative amounts of the ingredients were manufactured according to the constrained mixture design .The difference ($\Delta$${\mu}$=${\mu}$$\sub$max/. -${\mu}$$\sub$min/. ) of friction coefficients was measured to represent the high temperature fade. Results from elevated temperature tests showed that five ingredients including cashew, graphite, Sb$_2$S$_3$, ZrSiO$_4$, and Cu fibers played important roles on $\Delta$${\mu}$. In order to find relative importance on fade phenomena among these ingredients, ANOVA(analysis of variance) was performed in this investigation. Thirty-two friction material specimens by changing ${\pm}$50vol.％ of these five ingredients were tested to examine the relative importance. Results showed that cashew, graphite '||'&'||' Sb$_2$S$_3$, and cashew '||'&'||' graphite aggravated the fade behavior and Cu fibers improved on fade resistance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.10a
• /
• pp.295-298
• /
• 2005

This paper is concerned with the precision material property measurement of a micro metal thin foil that is used in MEMS technology. Since these MEMS components require great precision and accuracy, evaluation of reliability such as the lift cycle endurance test, impact test, and residual stress test is necessary for these components. However, in practice, real reliability tests are not easy to perform due to consideration of various factors. Rather than actual testing, it would be much easier to evaluate the reliability of components by the analytical approach. Although the analytical method is utilized by software tools, it is obviously necessary to acquire fundamental properties of materials through real test methods. In this paper, the oriented mechanical properties of aluminum thin foil are measured by nano scale material property measurement system.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.15 no.2
• /
• pp.31-39
• /
• 2019

Cracked component analysis is needed for structural integrity analysis under seismic loading. Under large amplitude cyclic loading conditions, the change in material properties can be complex, depending on the magnitude of plastic strain. Therefore the cracked component analysis under cyclic loading should consider appropriate cyclic hardening model. This study introduces a procedure for determining an appropriate cyclic hardening model for cracked component analysis. The test material was nuclear-grade TP316 stainless steel. The material cyclic hardening was simulated using the Chaboche combined hardening model. The kinematic hardening model was determined from standard tensile test to cover the high and wide strain range. The isotropic hardening model was determined by simulating C(T) test under cyclic loading using ABAQUS debonding analysis. The suitability of the material hardening model was verified by comparing load-displacement curves of cyclic C(T) tests under different load ratios.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.6 no.3
• /
• pp.177-184
• /
• 2002

The most tunnel damage such as cracks or leakage which exist in tunnel lining commonly, is caused by the cavities where exist behind the tunnel lining, through the tunnel safety inspections. These cavities were analysed to affect a stability of a running-tunnel seriously. This study is on the development of the controlled low-strength and flowable filling material which is able to apply to the cavity behind the tunnel lining. The major materials of backfilling developed are a crushed sand and a stone-dust which exists as a cake-state and is a by-product obtained in the producting process of aggregate. It is conformed with the design standard to the physical characteristics of backfilling. The backfilling material developed is designed to reduce the fair amount of cement. According to the designed compound ratio, it is carried out the laboratory tests such as a compressive strength and a chemical analyses and is applied to dilapidated old tunnel for an application assessment.

• The Journal of Advanced Prosthodontics
• /
• v.8 no.4
• /
• pp.267-274
• /
• 2016

PURPOSE. This study aimed to evaluate the effect of surface treatments on bond strength of indirect composite material (Tescera Indirect Composite System) to monolithic zirconia (inCoris TZI). MATERIALS AND METHODS. Partially stabilized monolithic zirconia blocks were cut into with 2.0 mm thickness. Sintered zirconia specimens were divided into different surface treatment groups: no treatment (control), sandblasting, glaze layer & hydrofluoric acid application, and sandblasting + glaze layer & hydrofluoric acid application. The indirect composite material was applied to the surface of the monolithic zirconia specimens. Shear bond strength value of each specimen was evaluated after thermocycling. The fractured surface of each specimen was examined with a stereomicroscope and a scanning electron microscope to assess the failure types. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey LSD tests (${\alpha}$=.05). RESULTS. Bond strength was significantly lower in untreated specimens than in sandblasted specimens (P<.05). No difference between the glaze layer and hydrofluoric acid application treated groups were observed. However, bond strength for these groups were significantly higher as compared with the other two groups (P<.05). CONCLUSION. Combined use of glaze layer & hydrofluoric acid application and silanization are reliable for strong and durable bonding between indirect composite material and monolithic zirconia.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.11 no.1 s.22
• /
• pp.29-37
• /
• 2005

The design and development if Resonant-type Magnetometer(RM) using isotropic magnetic with high permeability is described in this paper. At first, the relationship between the inductance L if the coil winding on a magnetic material and the permeability u(H) appearing in the magnetic material with isotropic and high permeability is defined as a background theory. Then the circuit if RM, which is to obtain the values if L as the change qf frequency is implemented using simple Schmitt Trigger Circuit Through the swinging tests, which is to evaluate the measurement ability if RM, the measurement possibility for the component of earth field was confined.