• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.3
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• pp.251-260
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• 2001

Damage Profess of CFRP laminates under monotonic tensile test was characterized by the correlation between Acoustic Emission(AE) and Ultrasonic Test(UT). The amplitude distribution of AE signal from a specimens is an aid to the determination of the extent of the different fracture mechanism such as matrix crack, debonding, fiber pullout and fiber fracture as load is increased. In addtion, the characteristics of ultrasonic amplitude attenuation are useful lot analysis of the different type of fracture mechanism. Different orientation of carbon fiber reinforced plastic specimens were used to investigate the AE amplitude range and ultrasonic amplitude attenuation. Finally, loading-unloading tests were carried out to check Felicity effect. During the tests, ultrasonic amplitude attenuation was investigated at the same time and compared with AE parameters. The result showed that two parameters of both AE and UT could be effectively used for analysis of fracture mechanism in CFRP laminates.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.65-65
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• 2000

Microwave response of intrinsic Josephson junctions in mesa structure formed on HgI2-intercalated Bi2Sr2CaCu2O8+x single crystals was studied in a wide range of microwave frequency. With irradiation of 73${\sim}$76 GHz microwave, the supercurrent branch becomes resistive above a certain onset microwave power. At low current bias, the current-voltage characteristics show linear behavior, while at high current bias, the resistive branch splits into multiple sub-branches. The voltage spacing between neighboring sub-branches increase with the microwave power and the total number of sub-branches is almost identical to the number of intrinsic Josephson junctions in the mesa. All the experimental results suggest that each sub-branch represents a specific mode of collective motion of Josephson vortices generated by the microwave irradiation. With irradiation of microwave of microwave of frequency lower than 20 GHz, on the other hand, no branch splitting was observed and the current-voltage characteristics exhibited complex behavior at hlgh blas currents. This result can be explained in terms of incoherent motion of Josephson vortices generated by non-uniform microwave irradiation.

• Korean Journal of Ichthyology
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• v.20 no.2
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• pp.123-128
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• 2008

The foraging behavior of the beauty goby, Pterogobius zacalles, was studied at Mutu Bay, Aomori province, Japan. P. zacalles harvested invertebrates prey from benthic substrates by using two distinct foraging modes: picking substrate among boulders and sucking surface of boulder. Among others, picking substrate among boulders was primarily used foraging mode. The foraging modes of P. zacalles were followed by three stages: searching for prey, feeding and chewing. For foraging, it takes less time to suck out the surface of boulder than pick up substrate among boulders, because the resting site of P. zacalles is close to the place where they do sucking. The diets of P. zacalles primarily consisted of benthic amphipods regardless of their foraging modes. Only the difference was that they can get bigger amphipods when they did picking rather than sucking. Even though it needs more time and energy to do picking, P. zacalles was compensated by getting a high-calorie diet eventually, therefore prey size can be the determinant of their foraging modes.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.47-56
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• 2017

Aseismic designs of pile-supported wharves are commonly performed utilizing simplified dynamic analyses, such as multi-mode spectral analyses. Simplified analyses can be useful for evaluating the limit state of structures. However, several pile-supported wharves, that have been damaged during past earthquakes, have shown that soil deformation and soil-pile dynamic interaction significantly affect the entire behavior of structures. Such behavior can be captured by performing nonlinear effective stress analyses, which can properly consider the dynamic interactions among the soil-pile-structure. The present study attempts to investigate the earthquake performance of a pile-supported wharf utilizing a three-dimensional numerical method. The damaged pile-supported wharf at the Kobe Port during the Hyogo-ken Nambu earthquake (1995) is selected to verify the applicability of the numerical modeling. Analysis results showed a suitable agreement with the observations on the damaged wharf, and the significant effect of excess pore pressure development and pile-soil dynamic interaction on the seismic performance of the wharf.

• Structural Engineering and Mechanics
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• v.75 no.1
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• pp.71-86
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• 2020

This paper presents a study on the mechanical behavior of buried pipelines crossing faults using experimental and numerical methods. A self-made soil-box was used to simulate normal fault, strike-slip fault and oblique slip fault. The effects of some important parameters, including the displacement and type of fault, the buried depth and the diameter of pipe, on the deformation modes and axial strain distribution of the buried pipelines crossing faults was studied in the experiment. Furthermore, a finite element analysis (FEA) model of spring boundary was developed to investigate the performance of the buried pipelines crossing faults, and FEA results were compared with experimental results. It is found that the axial strain distribution of those buried pipelines crossing the normal fault and the oblique fault is asymmetrical along the fault plane and that of buried pipelines crossing the strike-slip fault is approximately symmetrical. Additionally, the axial peak strain appears near both sides of the fault and increases with increasing fault displacement. Moreover, the axial strain of the pipeline decreases with decreasing buried depth or increasing ratios of pipe diameter to pipe wall thickness. Compared with the normal fault and the strike-slip fault, the oblique fault is the most harmful to pipelines. Based on the accuracy of the model, the regression equations of the axial distance from the peak axial strain position of the pipeline to the fault under the effects of buried depth, pipe diameter, wall thickness and fault displacement were given.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.862-868
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• 2013

The mechanics of woven fabric-based laminated composites is complex. Then, many researchers have studied woven fabric CFRP materials but fracture resistance behaviors for composites have not been still standardized. It also shows the different behavior according to load and fiber direction. Therefore, there is a need to consider fracture resistance behavior in conformity with load and fiber direction at designing structure using woven CFRP materials. In this study, therefore, the tensile strength and resistance for plain-weave CFRP composite materials were investigated under various different angle condition(load to fiber angle: $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$). Tensile strength and fracture toughness tests were carried out under mode I transverse crack opening load by using compact tension specimens.

• Journal of Surface Science and Engineering
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• v.41 no.6
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• pp.335-340
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• 2008

Cutting performance and wear behavior were studied with the diamond micro-blade of Cu/Sn bond materials containing various amount of lubricant materials such as graphite and $MoS_2$. Measurement of instantaneous electric power consumption for cutting glass workpiece at the constant velocity was conducted and proposed as a method to assess cutting efficiency. The energy consumption of micro-blade for glass cutting decreased with the content of graphite and $MoS_2$ while wear amount of blade in volume increased with the amount of lubricant addition during the dicing test. It is because that hardness, flexural strength, and fracture toughness ($K_{IC}$) reduced with the amount of lubricant addition. Blades with $MoS_2$ additive showed higher mechanical properties than those with graphite additives when the same amount of the lubricant additive in wt.% was added. Due to the lower density of graphite than $MoS_2$, higher volume fraction of graphite could result in stronger effect on lowering electric power consumption by reducing the friction between blade and work piece however increasing wear rate due to the reduction in strength and fracture toughness. Adhesive wearing mode of micro blade could be remarkably improved by the addition of graphite as well as $MoS_2$.

• Composites Research
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• v.16 no.3
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• pp.1-8
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• 2003

Densification occurs by the inelastic flow of the matrix materials during the consolidation processes at high temperature for MMCs, and the results depend on many process conditions such as applied pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites since material failure may occur by either the applied conditions or microstructural parameters through the processes, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.521-526
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• 2014

In this study, closed-cell aluminum foam with an initial crack was investigated to produce an axial load-time graph. Using the 10-kN Landmarks of MTS Corporation, a 15-mm/min velocity of mode I shape was applied to the aluminum foam specimen using the displacement control method. ABAQUS 6.10 simulation was used to model and analyze the identical model in three dimensions under conditions identical to those of the experiment. The energy release rate was calculated on the basis of an axial load-displacement graph obtained from the experiment and a transient image of the crack length, and then an FE model was analyzed on the basis of this fracture energy condition. The relation between load and displacement was discussed; it was found that the aluminum foam deformed somewhat less than the adhesive layer owing to the difference in elastic modulus.

• Journal of Fashion Business
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• v.7 no.4
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• pp.121-128
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• 2003

A new textile material, poly(trimethylene terephthalate) polymer, has been introduced to the textile industry. The structure of PTT is similar to the PET, while the tensile deformation and subsequent recovery property is better than that of PET. In this study, the physical and mechanical properties of textile woven fabrics made of PTT, PET, and nylon 6 yarns as the filling yarn were determined using the Kawabata Evaluation System (KES), including tensile, bending, shearing, compression, and surface related parameters. On top of these measurements, the subjective ratings by evaluators were performed on the fabric samples. From the examination of the stress-strain behavior of the yarn specimens focused on the recovery mode, it was evident that the PTT specimen developed lower stress at 3% elongation. The subsequent recovery curve showed that the PTT has less stress-decay rate than the other specimens, implying that the recovery behavior of the PTT is recommendable for the end-uses including stretchable textile materials, sports wears, etc. The KES bending rigidity(B) value of the PTT sample fabric was lower than that of the PET sample fabric. Subjective evaluation of the fabric samples by the evaluators on the descriptive word pair "soft - not soft" showed similar tendency with the KES B determination of the fabric samples.