• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.57-62
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• 2014

Using flexible bismaleimide-triazine co-polymer as a substrate, inkjet-printed Cu films were also investigated for low-cost and process feasibility of flexible electronics. After annealing at $200^{\circ}C$ for 1 h under various reducing ambient, surface color was changed to red and electrical resistivity was decreased to the level of conductor under formic acid ambient. However, its resistivity was much higher than conventional copper films due to surface crack. In order to reduce the residual film stress after annealing, additional isothermal treatment was inserted before anneal hiring the stress relaxation applied in processes of amorphous materials. As a result, no surface crack was observed and electrical resistivity of $3.4{\mu}{\Omega}cm$ was measured after annealing at $230^{\circ}C$ with stress relaxation while electrical resistivity of $7.4{\mu}{\Omega}cm$ was observed after normal annealing without relaxation. The effect of stress relaxation was also confirmed by observing surface crack after decreasing the relaxation time to 0 min.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.1101-1107
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• 2016

As an increase in the amount of RAP, there are growing interests in recycling asphalt concrete. In case of using the RAP as recycled asphalt pavement, it tends to be quality deteriorate. Therefore, the amount of RAP using is advised to be limited or has to be used with rejuvenator. In this study, asphalt mixture containing WMRA was analyzed to be used up to 50% for the sake of convenience on the process. As the results of evaluation, there was no significant difference in case of using 30% of RAP in the test of Marshall stability. However, in case of WMRA using up to 50%, it was satisfied criteria by flow value at 34.7. Further, result of toughness test was found that the crack resistance showed 55% higher than using straight asphalt when using WMRA binder up to 50%. According to the results of directly comparing crack resistance through repeated direct tensile test, it was shown that the fatigue crack resistance of WMRA pavement was increased by 263%. Therefore, it was shown that WMRA binder was effective in recycling RAP because WMRA binder could increase the percentage of RAP using up to 50%.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.316-325
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• 1986

Characteristics of fatigue crack propagation in martensite-ferrite duel phase steels have been investigated. In low .DELTA.K region, fatigue crack propagation resistance increases with increasing volume fraction of martensite, but the difference of crack propagation resistance resulted from the volume fraction decreases with increasing .DELTA.K. Also, threshold stress intensity factor range .DELTA.K$_{th}$ increases with increasing volume fraction of martensite, But fatigue crack propagation rates of dual-phase steels in terms of .DELTA.K$_{eff}$ are independent to volume fraction of martensite. These phenomena can be explained by the roughness induced crack closure due to crack deflection.n.n.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.103-109
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• 2012

Micro-cracks with a width less than 0.1 mm in precast concrete panels do not cause structural problem, but they can cause problems in long term durability and concrete surfaces aesthetic, requiring additional repair costs. In this paper, polymer cement concrete is used to increase flexural tensile strength and to prevent micro-cracks due to construction loads on LB-DECK panels. Using 5% polymer-cement ratio, the panel crack moment is increased by improving flexural tensile strength and controlling visible micro-cracks during construction stage of LB-DECK.

• Journal of the Korea Concrete Institute
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• v.27 no.4
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• pp.387-397
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• 2015

In the present study, to enhance the constructability, a composite slab system using deck plate and micro steel fiber concrete was studied. In the proposed slab system, on-situ re-bar placement is not required. Steel fibers replace the temperature reinforcement. The present study focused on the crack control at the slab top in the continuous composite slab without spliced bars. Eight continuous slabs with various parameters were tested under vertical loading. The test parameters were the amount and types of micro steel fibers, types of deck plate, and the use of top bars in the continuous slab. To evaluate the crack resistance of the slabs, crack widths were measured in the continuous slabs. The test results showed that although the top spliced bars were not used, cracking were restrained by large flexural stiffness of the composite sections.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1126_1127
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• 2009

태양전지모듈에 물리적 하중이 가해지면 전면유리의 연신율에 따라 모듈이 휘어지게 되고 이에 따라 내부에 열 봉합되어 있는 태양전지에 미세한 균열이 발생한다. 이 균열이 태양전지모듈의 단락전류 및 개방전압의 출력을 떨어뜨리는데 이는 균열로 인한 저항성분의 증가로 인한 것이다. 모듈내의 특정한 셀에서 미세균열(Micro-crack)의 발생은 출력의 저하, 셀 출력 Mismatch로 인한 모듈 내의 Hot-Spot발생, 균열로 인한 저항성분으로서의 열 발생과 같은 전체 태양전지모듈의 내구성을 저하시키는 요소로 작용한다. 본 연구에서는 결정질 태양전지 모듈의 출력에 영향을 미치는 요소 가운데 기계적 스트레스에 의한 미세균열(Micro-crack)이 전기적 출력에 미치는 영향에 대해 본 논문에서 알아보고자 한다.

• Journal of Soil and Groundwater Environment
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• v.6 no.1
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• pp.53-62
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• 2001

Effects of surface defect on thermal stability and stress crack resistance of high density polyethylene geomembranes in environmental conditions were examined by comparing the mechanical properties, chemical resistance and failure times of geomembranes between defective cases under different temperatures. Artificial surface defects were added to the surface of geomembranes by scratch apparatus designed specially. The number of surface defects was increased with the smaller size of scratch induced particles, and the more scratch addition numbers at the shear rate of scratch induced mechanism, 100mm/min. The tensile strength were decreased but the tensile strain was increased with the above conditions. In chemical resistance of defective geomembranes, the tensile strength were decreased but the tensile strain was increased with the longer immersion period and the higher temperature under the same scratch induced conditions. Finally, failure times of defective geomembranes by ESCR test were shifted to the shorter time ranges by increasing temperatures.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.101-113
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• 2006

Generally, asphalt binder modifier increases the viscosity at high temperature as well as at mixing and paving temperature, so that higher temperature is required to produce the hot-mix asphalt. Otherwise, wax is able to improve workability by means of decreasing the viscosity of asphalt binder. In this study, the effect of PE wax used to modify the asphalt binder was evaluated in laboratory. The properties of PE wax modified binder were compared with those of SBS and Crumb Rubber Modified binders. The results showed that wax type I has an effect on strengthening rut resistance as well as improving workability. However, wax type I weaken crack resistance due to making binder harder at intermediate temperature. The results also showed that wax type II has an effect on improving workability and on strengthening crack resistance due to making binder softer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.3
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• pp.377-385
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• 2018

Super-speed vacuum tube system, where the air resistance is minimized to obtain high speed of the vehicle, is considered to be a viable alternative transportation system. Air-tightness is one of the most important design requirements of the system, because the internal pressure of the system needs to be maintained significantly lower than the atmospheric pressure. This study performed an experimental test, where a series of concrete tube specimens were applied by external loads to induce cracks and the effective air-permeability of the cracked tube structures were measured. The test results indicates that the information on the length and the width of the load-induced cracks are not enough to anticipate the system air-tightness, whereas the load-induced displacement has higher correlation with the systems air-tightness. Based on these results, a direction of future research for effect of the load-induced cracks on the system air-tightness is suggested.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.117-126
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• 1994

APAL (Aramid Patched ALuminum alloy) was manufactured, which was a material that was consisting of a A12024-T3 aluminum alloy plate bonded to single-side of it with aramid/epoxy laminates. The aramid/epoxy laminates were bonded to it in condition of 1, 2 ply and fiber orientation of .+-.45, 0.deg./90.deg. Fatigue crack propagation tests were performed at stress ratio R-0.2, 0.5 with Al 2024-T3, APAL 45-1P, APAL 0/90-1P, APAL 45-2P, APAL 0/90-2P specimens to examine behavior of retardation in fatigue crack propagation. All the APAL specimens showed superior fatigue crack resistance. Number of cycle spended for crack to propagate from $a_{M}$=37 to $a_{M}$=65 mm in case of APAL 0/90-2P specimen was half that of Al 2024-T3 specimen. Fatigue crack propagation rate of APAL 0/90 specimens were retarded more compared to APAL 45 specimens and the amounts of retardation at R=0.5 were larger than that at R=0.2. It was found that the retardation in fatigue crack propagation was caused by intact fibers in the wake of crack.ack.