• 한국농공학회논문집
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• 제50권5호
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• pp.51-60
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• 2008

This study is to relate the bond characteristics of CFRP rebar in high strength concrete incorporated with silica fume(SF) and metakaolin(MK). An direct bond test were performed to evaluate the effect of SF and MK on bond properties of high-strength concrete and CFRP rebar. The high strength concrete mix included four SF and MK mixes with 0%, 5%, 10% and 15%. Results of bond performance experiment in relation to pullout vs slip behavior of FRP rebar and high strength showed better performance of SF than MK. Also, the results showed the improved bond strength as replacement ratio of SF and MK increased. The relative bond strength in which $1.3{\sim}3.2$ of estimated values were obtained.

• Asian-Australasian Journal of Animal Sciences
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• 제15권6호
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• pp.859-865
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• 2002

The aim of this research was to clarify the direct effects of a hot environment on ruminal motility in sheep fed twice a day. In the first experiment, in order to equalize variable factors excluding the ambient temperature between the thermoneutral environment ($23^{\circ}C$, relative humidity 80%) and the hot environment ($32^{\circ}C$, relative humidity 80%), sheep were fed equal amounts of the same quality feed twice a day. The sheep were allowed free access to water for the duration of the two one-hour feeding periods (10:00 am-11:00 am, 5:00 pm-6:00 pm). On the fourth day after exposure to the hot environment, the frequency and strength of ruminal contractions were continuously recorded between 9:30 am and 11:00 pm. Prior to the exposure to a hot environment the frequency and strength of ruminal contractions were recorded in a thermoneutral environment during the period 9:30 am-11:00 pm. In the second experiment, in order to maintain the stomach content of the sheep at equal levels in both environments, the sheep were fed equal amounts of the same quality feed twice a day. Following the completion of the two one-hour feeding periods, a fixed amount of warm water was infused into the rumen. Rumen motility was then recorded during the same period as for the first experiment (9:30 am-11:00 pm). In the first experiment, when the frequency of ruminal contractions prior to (24, 24 frequency/15 min), during (48, 47 frequency/min) and after (22, 19 frequency/min) both the morning and afternoon feeding in a hot environment was compared with the values from the thermoneutral environment (20, 22; 50, 50; 21, 20 frequency/min), there was found to be no difference. However, the strength of ruminal contractions after morning and afternoon feeding (3.7, 3.1 mm Hg) in the hot environment decreased significantly in comparison with the thermoneutral environment (4.3, 3.8 mm Hg). In the second experiment, the frequency of ruminal contractions in the hot environment was not significantly different from that in the thermoneutral environment. The strength of ruminal contractions after ruminal infusion of warm water in the hot environment (morning: 4.6, afternoon: 4.5 mm Hg) was significantly lower than that in the thermoneutral environment (morning: 5.6, afternoon: 5.0 mm Hg). The results suggest that a hot environment acts directly on the strength of ruminal contractions in sheep fed twice a day rather than on the frequency.

• 한국의상디자인학회지
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• 제15권2호
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• pp.57-64
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• 2013

As the clothing materials have been more functional and advanced, the cotton fabrics for dress shirts or blouses have been more qualified and the sewability for high degree of completion has been required. This study aims to identify the seam strength depending on the change of stitch density of fine cotton fabrics by fabric and thread and so the general seam performance of fine cotton fabrics by analyzing the seam efficiency and breaking mode of seams. For an experiment, 3 kinds of fine cotton fabrics and 2 kinds of threads were selected and the sample was made by changing the stitch density by four steps. Then, the seam strength was measured. Next, the seam efficiency and breaking mode of seams were analyzed on the basis of the results of seam strength measurement. The results are as follows: All fabrics showed the similar tendency in seam strength. The seam strength is related to the tensile strength and thread strength, it increased only to a certain stitch density. When the stitch density exceeded a certain level, fabrics were destroyed or threads were cut. Then, the seam strength didn't increase. Furthermore, the more the seam strength increased, the more the seam efficiency increased. For increasing the maximum stitch density, it was required to use the fabrics and threads which had similar properties, in other words, the high thread strength for the high tensile strength and the low thread strength for the high tensile strength.

• Computers and Concrete
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• 제12권5호
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• pp.717-737
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• 2013

In this study, experiment and numerical analysis were conducted to identify the heat transfer characteristics and behavior of high-strength concrete upon a fire. The numerical analysis was employed to forecast the characteristics and properties of the high-strength concrete upon a fire, which can not be accomplished through a fire test due to the specific conditions and restrictions associated with the test. The result of the numerical analysis was compared with that of the test to verify the reliability of the analysis. In the numerical analysis of the heat transfer characteristics and behavior of 80 and 100 MPa high-strength concrete upon a fire, the commercial software of ABAQUS(V.6.8) was used. It was observed from the experiment that the contraction of the concrete with fiber-cocktail was mitigated by 25~55 % compared with that without fiber-cocktail because the fiber controlled the heat transfer of the concrete and thus improved the fire-resistance performance of the column.

• 한국생산제조학회지
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• 제21권2호
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• pp.290-296
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• 2012

Cold-rolled carbon steel sheets are commonly used in railroad car or commercial vehicles such as the automobile. These are mainly fabricated by spot welding which is a kind of electric resistance welding. But fatigue strength of spot welding joint is lower than that of base metal due to high stress concentration at nugget edge of the spot welded part. And fatigue strength of them is especially influenced by not only geometrical and mechanical factors but also welding conditions of the spot welded joint. So for fatigue design of gas welded joints such as TS-type joints, it is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of spot welded joints. And also, the influence of the geometrical parameters of spot welded joints on stress distribution and fatigue strength must be evaluated. And analysis approach for fatigue test using design of experiment are evaluated optimum factor in TS-type welded joint and geometrical parameters of materials. Using these results, that factors applied to fundamental information for automation of fatigue design.

• 한국레이저가공학회지
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• 제13권3호
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• pp.19-26
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• 2010

In this study, fundamental experiment was conducted with various strength of UHSS (Ultra High Strength Steel) by $CO_2$ laser. And then, butt and lap joint laser welding with boron alloyed steel and Al-Si coated boron alloy steel have been done by changing laser beam feature, existence of gap and existence of coating layer to know welding characteristics of those materials. As a result, in case of fundamental experiment with various strength steel, hardening was found in the weld metal of all tested materials and softening was found at the heat affected zone of SGAFC 1180. In case of laser butt welding of UHSS, mechanical properties was improved by using small laser beam diameter and Al-Si coating layer caused fracture of weld metal. In case of laser lap welding of UHSS, Al-Si coating layer resulted in formation of intermetallic compound at the fusion boundary where fracture occurred. Al-Si coating layer caused lowering mechanical properties of weld metal.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.132-140
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• 1999

This paper suggests a monitoring method for the pulsed laser spot welding of the thin metal sheets using a point IR(InfraRed) sensor. A new criterion was introduced and the experimental results guaranteed the efficiency. The ideal radiation feature was derived from the mathematical model and was simulated. The radiation feature is robust to withstand the change of measuring condition and can be used to detect the absorbed laser energy. In an experiment, the radiation feature was examined for the differect laser energy. The pulse width and the laser power was variated and the radiation feature was examined. In the other experiment, the relationship between the weld strength and radiation feature was examined. Artificial Neural Network(ANN) was employed to find out the relationship. The correlation coefficient between the real strength and the estimated strength is high as 0.94 and the mean square error is low as 0.64 kgf learned parts. Another group of the welds was used to appraise the learning efficiency. The correlation coefficient between the measured and the estimated weld strength is high as 0.91.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.717-722
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• 2002

The results of an experiment on the water purification of the porous concrete and its influence on the compressive strength are reported in this paper. Two different sizes of coarse aggregate of 5-10, and 10-20mm, and three absolute volume ratios of paste to aggregate of 30, 40 and 50 percent for a given size of aggregate were used. For the compressive strength, the concrete with the aggregate size of 5-10mm showed much higher strength than that with the aggregate size of 10-20mm. But, the compressive strength is higher when the ratio of paste to aggregate is smaller. In the water purification experiment, the amount of attached an organism on the porous concrete surface indirectly is examined by measuring the consumption of the Dissolved Oxygen (DO). The ability of the water purification is evaluated by the removal amount of the Total Phosphorus(T-P) and Total Nitrogen(T-N). The ability of the removal of the T-N and T-P in the test water is superior to a porous concrete with a smaller size of aggregate and a higher void content. These results are owing to a large specific surface area of the specimen. As a result, porous concrete using by-products has sufficient performance of water purification.

• 한국정밀공학회지
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• 제28권10호
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• pp.1204-1209
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• 2011

In this study, fatigue life is evaluated by comparing with lighter car body through the experiment on SPR joints. An experimental activity on sheet metal samples of Aluminum 5J32 and Steel SPRC440 has been conducted to achieve better understanding of the process. In addition, SPR joint used less than the existing Spot Welding improves joint strength and fatigue life is evaluated by using SPR and adhesive joining Hybrid. Joining(bonding) strength and fatigue life on SPR and Hybrid (SPR + adhesive) are evaluated throughout the experiment. With joining strength than 20 % of the aluminum material, dissimilar materials has improved over 2 times as large as the strength In case of dissimilar materials, the fatigue life of aluminum is increased by 1.6 to 2.5 times as large as the life.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.161-168
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• 2015

This article aims to apply a friction stir spot welding for producing a lap joint of AA1100 aluminum alloy and SGACD zinc coated steel. The experiment was designed by MINITAB and then investigated the relation among the friction spot joint parameters. The experimental results are as follows. The friction spot joining could successively produce the lap joint of AA1100 aluminum alloy and SGACD zinc coated steel. Interaction between the rotate speed, the hold time and the tool insert speed affected to vary the tensile shear strength of the lap joint. The prediction of the optimized welding parameters that indicated the tensile shear strength of 1966 N was the rotated speed of 4000 rpm, the pin hold time of 6 sec, the pin insert rate of 6 mm/min with the S/N ratio of 66.56 that was higher than that of the total mean S/N ratio. The practical experiment of the predicted welding parameters indicated the tensile shear strength of 2165 N and had the S/N ratio of 66.70 that was higher than the predicted tensile shear strength.