• Journal of the Korean Society of Costume
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• v.57 no.3 s.112
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• pp.53-62
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• 2007

The purpose of this study was to investigate mechanical and comfort performances of the material for the improved working uniform for a volunteer fire brigade member, to get basic data for its evaluation and to help its material and design development. The results were as follows; The material of the newly developed working uniform was thinner and lighter than the material of the current used working uniform. It had better breathability, air permeability and heat transmission rate than the current one. It also had superior anti-flammability In all mechanical properties(tensile, bending, shearing, compression and surface properties), it showed better performances than the current one. It elongated and bended easier and more in both warp and weft directions. The elastic recovery and shape stability after elongation were also higher. The recovery and resistance to shearing and the resiliency and recovery after compression were also better than the current one. It was more flexible, softer and smoother in primary hand value, and was more suitable for the material for winter suit which needs softness and fullness in total hand value. The material of the improved working uniform showed lower thermal insulation value and higher evaporative resistance value compared to the material of the currently used working uniform from the sweating thermal manikin test. It was shown that the physical performances and the hand value of the textile material used in the newly developed working uniform for a volunteer fiber brigade member was improved compared to the one used in the currently used working uniform.

• Composites Research
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• v.32 no.6
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• pp.403-407
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• 2019

Long-fiber-reinforced composites have the advantages of cost-competitiveness and high degree of freedom of molding compared to continuous-fiber-reinforced composites. On the other hand, it is difficult to ensure uniform characteristics due to the randomly distributed fiber orientation incurred from the process of manufacturing intermediate materials. In this study, the effect of the directionality of LFPS (Long Fiber Prepreg Sheet) materials on the mechanical properties was analyzed. The eddy current measurement method was used to analyze fiber orientations, and tensile and compression tests on LFPS materials were performed according to ASTM standards. In addition, the test results and theoretical values of LFPS materials were verified using the ROM (rule-of-mixtures) theory. These results confirmed the effect of fiber orientation on mechanical properties of discontinuous-fiber-reinforced composites.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1281-1293
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• 2013

A sophisticated finite element model is illustrated to analyze the behavior of Prefabricated Parallel Wire Strand(PPWS) sockets for main cables of suspension bridges. An orthotropic model is proposed for the casting material by considering both effects of individual wires and a casting alloy, and the contact between surfaces of a socket and a casting alloy is idealized by using the Coulomb friction and the surface-based contact model. The proposed FE model is verified by comparing the strain distributions obtained from the tensile test and FE analysis. The mechanical behavior of a socket is investigated with respect to the variation of the frictional coefficient. The result shows that the friction between surfaces significantly diminishes the stress concentration of a socket and a casting alloy, and the normal stress from the design equation represents the averaged value of the upper and lower quartiles in the distribution of contact stresses between a socket and a casting alloy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.670-677
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• 2006

Vacuum interrupters are used in various switch-gear components such as circuit breakers, distribution switches, contactors. The electrodes of a vacuum interrupter are manufactured of sinter-forged Cu-Cr material for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain-rate at the given velocity, the dynamic material property of the sinter-forged Cu-Cr alloy is important to design the vacuum interrupter reliably and to identify the impact characteristics of a vacuum interrupter accurately. This paper is concerned with the dynamic material properties of sinter-forged Cu-Cr alloy for various strain rates. The amount of chrome is varied from 10 wt% to 30 wt% in order to investigate the influence of the chrome content on the dynamic material property. The high speed tensile test machine is utilized in order to identify the dynamic property of the Cu-Cr alloy at the intermediate strain-rate and the split Hopkinson pressure bar is used at the high strain-rate. Experimental results from both the quasi-static and the high strain-rate up to the 5000/sec are interpolated with respect to the amount of chrome in order to construct the Johnson-Cook and the modified Johnson-Cook model as the constitutive relation that should be applied to numerical simulation of the impact behavior of electrodes.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.3
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• pp.133-141
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• 2017

This article described the development of transparent antimicrobial oxo-biodegradable (AOB) film with the function of enhanced freshness of food by employing oxo-biodegradable masterbatch (MB) and antimicrobial MB together with organic metal salt, organic acid, or unsaturated fatty acid. Antibacterial test of the AOB film with the different contents of the antimicrobial MB resulted in the significant freshness extension of plum. Tensile strength and elongation rate of the AOB films before UV treatment were similar to those of polyethylene films used as control. The reduced mechanical properties of AOB film after UV treatment (340 nm) suggested that the AOB film could be degraded by oxo biodegradation. The developed AOB films can effectively prevent decomposition of food by providing antibacterial function and preserving freshness.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.4
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• pp.270-277
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• 1997

Plastic anisotropy is one of important factors which determine the drawability of a steel sheet. It has been mainly measured by mechanical tensile test. From the ultrasonic velocities propagating along the relative directions to the rolling direction, CODF(crystallite orientation distribution function) can be measured and ODC's(orientation distribution coefficients) has some correlations with the plastic anisotropy. In this study the correlations between the plastic anisotropy and ODC's of the cold rolled steel sheet were measured. From the results of ultrasonic velocity measurements the average normal anisotropy, $\bar{\gamma}$ and the average planar anisotropy, ${\Delta}r$ could be predicted within the accuracy of ${\pm}0.082$ and ${\pm}0.096$, respectively. Acoustic resonance method was applied to measure the ultrasonic velocities and EMAT's were used for generating and detecting the ultrasonic waves.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.1
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• pp.41-46
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• 2012

As the development of MEMS/NEMS structure and application technology the demand for an assessment of the mechanical properties have increased. The mechanical properties are mainly evaluated by using tensile test or ultrasonic wave measurement. However, the new technology have been developed such as nano-indentation, guided wave method because they have a limitation in case of a thin plate and thin film. In the study, the guided wave velocities are measured by electromagnetic-acoustic transducer(EMAT), the material properties of thin metallic foils are obtained using optimization process of the theoretical and experimental group velocity of guided wave. The Young's modulus obtained by the optimization process(201.6 GPa), nano-indentation(207.0 GPa) and literature value(203.7 GPa) of a $50{\mu}m$ thick nickel thin plate shows good agreement within 3%.

• Computers and Concrete
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• v.14 no.3
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• pp.299-313
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• 2014

Effects of polypropylene (PP) fibers, steel fibers (SF) and hybrid on the properties of highstrength fiber reinforced self-consolidating concrete (HSFR-SCC) under different volume contents are investigated in this study. Comprehensive laboratory tests were conducted in order to evaluate both fresh and hardened properties of HSFR-SCC. Test results indicated that the fiber types and fiber contents greatly influenced concrete workability but it is possible to achieve self consolidating properties while adding the fiber types in concrete mixtures. Compressive strength, dynamic modulus of elasticity, and rigidity of concrete were affected by the addition as well as volume fraction of PP fibers. However, the properties of concrete were improved by the incorporation of SF. Splitting tensile and flexural strengths of concrete became increasingly less influenced by the inclusion of PP fibers and increasingly more influenced by the addition of SF. Besides, the inclusion of PP fibers resulted in the better efficiency in the improvement of toughness than SF. Furthermore, the inclusion of fibers did not have significant effect on the durability of the concrete. Results of electrical resistivity, chloride ion penetration and ultrasonic pulse velocity tests confirmed that HSFR-SCC had enough endurance against deterioration, lower chloride ion penetrability and minimum reinforcement corrosion rate.

• Advances in materials Research
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• v.7 no.1
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• pp.45-72
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• 2018

In the present study, a special attention has been paid to the effects regarding the use of different superplasticizers in different dosages. To do so, 36 mixes of normal and self-compacting concrete with two water/binder ratios of 0.35 and 0.45, four different types of superplasticizer including melamine-formaldehyde, naphthalene-formaldehyde, carboxylic-ether and poly-carboxylate, four different superplasticizer/cement ratios of 0.4%, 0.8%, 1.2% and 1.6% and two silica fume/cement ratios of 0% and 10% have been cast. Moreover, the initial and final setting time of the pastes have been tested. For self-compacting mixes, flow time, slump flow, V-funnel, J-ring and L-box tests have been carried out as well as testing the compressive strength and rupture modulus. For normal concrete mixes,slump test has been conducted to assess the workability of the mix and then for each mix, the compressive strength and rupture modulus have been determined. The results indicate that in addition to the important role of superplasticizer type and dosage on fresh state properties of concrete, these parameters as well as the use of silica fume could affect the hardened state properties of the mixes. For instance, the mixes whose superplasticizer were poly-carboxylic-ether based showed better compressive and tensile strength than other mixes. Besides, the air contents showed robust dependency to the type of the superplasticizer. However, the use of silica fume decreased the air contents of the mixes.

• Advances in concrete construction
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• v.9 no.2
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• pp.207-215
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• 2020

This paper describes the experimental studies carried out to determine the properties of fresh and hardened concrete with Recycled Plastic Waste (RPW) as a partial replacement material for fine aggregates. In the experimental study, RPW was used for replacing river sand and manufactured sand (M sand) aggregates in concrete. The replacement level of fine aggregates was ranging from 5% to 20% by volume with an increment of 5%. M40 grade of concrete with water cement ratio of 0.40 was used in this study. Two different types of RPW were used, and they are (i) un-activated RPW and (ii) activated RPW. The activated RPW was obtained by alkali activation of un-activated RPW using NaOH solution. The hardened properties of the concrete determined were dry density, compressive strength, split tensile strength, flexural strength and ultrasonic pulse velocity (UPV). The properties of the concrete with river sand, M sand, activated RPW and un-activated RPW were compared and inferences were drawn. The effect of activation using NaOH solution was investigated using FT-IR study. The micro structural examination of hardened concrete was carried out using Scanning Electron Microscopy (SEM). The test results show that the strength of concrete with activated RPW was more than that of un-activated RPW. From the results, it is evident that it is feasible to use 5% un-activated RPW and 15% activated RPW as fine aggregates for making concrete without affecting the strength properties.