• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.564-573
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• 2001

The mechanical properties of short carbon/glass fiber reinforced polypropylene are experimentally measured as functions of fiber content and nozzle diameter. Also, these properties are compared with the survival rate of reinforced fibers and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber aspect ratio as well as fiber volume fraction is influenced by injection processing condition, the used materials and mold conditions such as diameter of nozzle, etc. In this study, the survival rate of fiber aspect ratio is investigated by nozzle size variations in injection/mold sides. It is found that the survival rate of glass fiber is higher that the survival rate of glass fiber is higher than that of carbon fiber. Both tensile modulus and strength of short-fiber reinforced polypropylene are improved s the fiber volume fraction and nozzle diameter are increased.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2005.11a
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• pp.81-85
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• 2005

Recently, fire resistance of high performance concrete for explosive spalling was issued as high performance concrete was vulnerable to the explosive spalling in initial fire. Therefore, in this study, an experiment about reduction effect to explosive spalling of high performance concrete is performed by adding several polymer fiber with various volume fraction, an then final fiber and volume fraction of that which reduce the explosive spalling of high performance concrete is presented. As the result of this study, the most fitted fiber volume fraction of reducing effect for explosive spalling at high performance concrete is under the 0.1%, as consider the flowability and efficiency.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.6
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• pp.255-259
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• 2002

Effect of martensite on the mechanical properties of austempered ductile cast iron was investigated after obtained the martensite by subzero treatment. Retained austenite was transformed to martensite by subzero treatment, and with decreasing subzero treatment temperature, volume fraction of martensite was increased. With increasing of the volume fraction of martensite, tensile strength was increased and elongation was decreased, ratio of increasing of strength and decreasing of elongation was higher in case of specimens with lot's of Cu contents. With increasing of the volume fraction of martensite, hardness slowly increased until only about 5% and it rapidly increased in a straight proportion when it is above 5%, while impact value was rapidly decreased until about 7% but it had a little change when it is above 7%.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.5
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• pp.233-238
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• 2012

The effect of subzero treatment on the mechanical properties of cold rolled high manganese austenitic stainless steel was investagated. ${\alpha}$'-martensite was formed by cold rolling, and it was formed with surface relief and specific direction or crossing each other. The volume fraction of martensite increased by subzero treatment, and it was increased with longer time of subzero treatment and higher temperature of subzero treatment. The hardness and strength increased by subzero treatment, while the elongation decreased. With the increase of volume fraction of martensite, the hardness and strength was increased steeply with proportional relationship, elongation was decreased slowly. The results show that the hardness and strength was strongly controlled by the volume fraction of martensite, and the elongation was affected by transformation behavior of deformation induced martensite in the initial stage of deformation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.163-170
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• 1999

Although the bulge forming technique is currently employed in commercial superplastic forming processes, the uniaxial tensile test is still the most commonly used method for the evaluation of the superplasticity of materials due to its simplicity in testing. However, the results obtained from the uniaxial tensile test can not be applied in analyzing the characteristics of the real parts formed in multi-axial stress state. In this paper, using the tensile test specimen obtained from the square cup manufactured by superplastic forming, tensile strength and elongation have been investigated according to the strain and cavity volume fraction. From the result of experiment, tensile strength and elongation are decreased according to the strain and cavity in Al-6%Cu-0.4%Zr alloy. On condition of uniaxial stress, cavity volume fraction is increased on linear according to the increasement of thickness strain. However, on condition of biaxial stress there are critical point( E t=1.5-1.6) that the slope, the ratio of cavity volume fraction and strain, have been changed. Therefore, cavity volume fraction is different with respect to stress condition, although the same strain.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.46-51
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• 2008

The effect of the addition of Co and N and subzero treatment on tensile strength and damping capacity was investigated in Fe-Cr-Mn alloy. Austenite was transformed into martensite by cold rollins increasing the degree of cold rollins led to an increase in the volume fraction of martensite. The damping capacity linearly increased with increasing volume fraction of ${\varepsilon}$ martensite in cold rolled specimens and subzero treated specimens after cold rolling. The volume fraction of ${\varepsilon}$ martensite, tensile strength and damping capacity was also increased by the addition of Co, while this treatment decreased the elongation. However, the volume fraction of ${\varepsilon}$ martensite, elongation and damping capacity were reduced by the addition of N, although the tensile strength increased. Tensile strength and damping capacity werealso increased by subzero treatment, while elongation decreased.

• Journal of Hydrogen and New Energy
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• v.24 no.5
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• pp.451-460
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• 2013

In a direct coal fuel cell (DCFC) system, it is essential to identify volume fraction of coal suspended in electrolyte melt in order to control its dispersion and fluidity. This requirement is compelling especially at anode channel where hot slurry is likely to flow at low velocity. In this study, light scattering techniques were employed to measure the volume fraction for a pulverized coal suspension with relatively high absorption coefficient. The particle size, scattering angle, and volume fraction were varied to evaluate their effects on the scattering behavior as well as scattering regime. The larger coal size and smaller forward scattering angle could provide a shift to more favorable scattering regime, i.e., independent scattering, where interferences of light scattering from one particle with others are suppressed.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.712-716
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• 2003

In the present study, the gas injection system based on air-water model was designed to investigate the behavior characteristics of bubbles injected into a ladle. The parameters such as gas volume fraction and bubble rise velocity were exprementally measured in a gas-liquid flow region. To measure gas volume fraction, an electo-conductivity probe was used and bubble rise velocity was obtained by a high speed CCD camera. Gas volume fraction was symmetric to the axis of nozzle secured on the bottom of a ladle. The bubble rise velocity was calculated for two different experimental conditions. That is, gas flow conditions were following two case: 1) Q = $0.63{\times}10^{-4}$ $m^{3}/s$, 2) $1.26{\times}10^{-4}$ $m^{3}/s$. As a gas injected into the liquid ladle, the liquid-phase region is circulated by bubbles' behavior. The bubble rise velocity was influenced of the circulation flow of liquid phase. As a result, the bubble rise velocity was appeared higher middle region of ladle than near the nozzle.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.130-136
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• 2005

The effects of additional Mg content, the size and volume fraction of reinforcement phase on the mechanical properties of ceramic particle reinforced aluminium matrix composites fabricated by pressureless metal infiltration process were investigated. The hardness of $SiC_p/AC8A$ composites increased gradually with an increase in the additive Mg content, while the bending strength of $SiC_p/AC8A$ composites increased with an increase in additive Mg content up to 5%. However, this decreased when the level of additive Mg content was greater than 5% due to the formation of coarse precipitates by excessive Mg reaction and an increase in the porosity level. The hardness and strength of the composites increased with decreasing the size of SiC particle. It was found that the composites with smaller particles enhanced the interfacial bonding than those with bigger particles from fractography of the composites. The hardness of $Al_2O_{3p}/AC8A$ composites increased gradually with an increase in the volume fraction, however, the bending strength of $Al_2O_{3p}/AC8A$ composites decreased when the volume fraction of alumina particle was greater than 40% owing to the high porosity level.

• Korea-Australia Rheology Journal
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• v.13 no.1
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• pp.47-54
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• 2001

Prediction of the maximum packing volume fraction with non-spherical particles has been one of the important problems in powder technology. The sphericity of fly ash particles depending on the particle diameter was measured by means of a CCD image processing instrument. An algorithm to predict the maximum packing volume fraction with non-spherical particles is proposed. The maximum packing volume fraction is used to predict the slurry viscosity under well dispersed conditions. For this purpose, Simha's cell model is applied for concentrated slurry with wide particle size distribution. Also, Usui's model developed for aggregative slurries is applied to predict the non-Newtonian viscosity of dense fly ash - water slurry. It is certified that the maximum packing volume fraction for non-spherical particles can be successfully used to predict slurry viscosity. The pressure drop in a pipe flow is predicted by using the non-Newtonian viscosity of dense fly ash-water slurry obtained by the present model. The predicted relationship between pressure drop and flow rate results in a good agreement with the experimented data obtained for a test rig with 50 mm inner diameter tube. Base on the design procedure proposed in this study, a feasibility study of fly ash hydraulic transportation system from a coal-fired power station to a controlled deposit site is carried out to give a future prospect of inexpensive fly ash transportation technology.