• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.983-989
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• 2017

This paper presents the bearing strength for laminates in advanced composite materials in bolted joints. Bolted single lap joint tests were experimentally investigated with respect to stabilized and unstabilized lap joints. Stabilized bolted single lap joints refer to joints with out-of-plane rotational constraints. Unstabilized bolted single lap joints refer to joints with absence of out-of-plane deflection constraints. The bearing strength values of laminates in the bolted joint showed that the percentages of ply angle for 0, 45, -45, and 90 degrees were not affected. The bearing strength value in the unstabilized bolted joint was smaller than the bearing strength value in the stabilized bolted joint because of the influence of the out-of-plane behavior. The composite material studied in this paper is a carbon/epoxy unidirectional (UD) tape prepreg cured at $177^{\circ}C(350^{\circ}F)$. In the laminate reference system, the standard angles of 0, 45, -45, and 90 degrees were used for ply orientation within the laminate. A total of 112 bolted single lap joint tests were conducted on specimens from eight distinct laminates. The ASTM-D-5961M standards were adhered to for the stabilized and unstabilized bolted single lap joint tests.

• Journal of Korean Society of Steel Construction
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• v.26 no.1
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• pp.43-53
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• 2014

A single plate connection(SPC) consists of a plate welded to the columns and bolts connected to the beam web. The SPC is widely used for a simple shear connection of steel structure because it is easy-to-fabricated, easy-to-installed and economical. The conventional SPC is used for 2 to 12 bolts in a single vertical row. It is designed to limit the plate thickness by bolt diameter to obtain flexible and ductile connections. The design strength for eccentric shear shall be the lesser of the shear strength of bolts or bearing strength of plate and when the design strength is decided by edge distance failure, the results can be very conservative. Although the research on special solution for 'weak-plate/strong-bolt' model with 2 to 4 bolts has been conducted by L. S. Muir, and W. A. Thonton, 2004, study on generalized design procedures did not conduct. This study proposed design procedure for evaluation of the design strength of eccentric shear bolt groups on a single plate connection based on the actual edge distance and the direction of bolt reaction forces by using elastic vector method(EVM) and instantaneous center of rotation method(ICM).

• Composites Research
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• v.21 no.4
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• pp.15-21
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• 2008

Interfacial shear strength between epoxy and carbon fiber was analyzed utilizing a hemi-spherical microbond specimens adhered onto single carbon fiber. The hemi-spherical microbond specimen showed high regression coefficient and small standard deviation in the measurement of interfacial strength as compared with a droplet and an inverse hemi-spherical one. This seemed to be caused by the reduced meniscus effects and the reduced stress concentration In the region contacting with a pin-hole loading device. Finite element analysis showed that the stress distributions along the fiber/matrix interface in the hemi-spherical specimen had a stable shear stress distribution along the interface without any stress mode change. The experimental data was also different according to the kinds of loading device such as the microvise-tip and the pin-holed plate.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2001.11a
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• pp.124-129
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• 2001

점 용접부는 응력상태가 복잡하고, 피로균열은 판 두께, 너겟 직경, 용접 타점수, 부하 방식 등의 역학적인 인자와 재질, 화학성분, 표면 상태 등의 재료적인 인자, 그리고 용접전류, 가압력, 통전 시간등의 용접적인 인자의 영향을 동시에 받으며 3차원적으로 성장하므로 균열 성장 모드는 항상 혼합보드이고 균열이 박판 내면에서 발생. 성장하므로 검출이 곤란하여 균열 성장의 해석 및 예측이 어렵다/sup 1)/. 따라서 비접촉, 실시간, Whole-field, 레이저 파장 단위까지 측정이 가능하여 기존의 방법들의 문제점을 극복할 수 있고, 반도체와 같은 소형의 제품뿐만 아니라 기존에 측정하지 못했던 초고온, 대형 구조물의 변형도 정확하게 측정을 할 수 있는 ESPI법을 이용하여 일반가전 제품, 자동차 건축용에 많이 사용되고 있는 아연도금강판(SGCC)을 선택하여 단일 용접조건으로 점용접의 피치를 변화시켜 시험편을 제작하고 면외변위를 다각도로 측정하여 그 가능성을 검증하고자 한다.(중략)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.204-211
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• 2007

Experiments were conducted to investigate the failure and strengths of carbon composite-to-aluminum single-lap bonded joints with 5 different bonding lengths. Joint specimens were fabricated to have secondary bonding of laminate and aluminum with a film type adhesive, FM73m. Tested joints have the bonding strengths between the values of aluminum-to-aluminum joints and composite-to-composite joints. In the joints with bonding length-to-width ratio smaller than 1, the strength decreases as the bonding length increases. In the joints with the ratio larger than 1, however, the strength converges to a constant value. Final failure mode of all the specimens was delamination. To use the maximum strength of the adhesive, it is important to design the joint to have strong resistance to delamination.

• Composites Research
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• v.20 no.5
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• pp.34-42
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• 2007

Strength and failure of adhesively bonded carbon composite-to-aluminum single-lap joints were studied by experiment. The main objective of this study is to investigate the effect of various parameters such as curing pressure for bonding, overlap lengths, and adherend thickness on the failure loads and modes of the bonded Joints with dissimilar materials. Experimental results show that the bonding pressure for composite-to-aluminum dissimilar materials should be 4 atm at the lowest. Failure load of the joints increases as the overlap length increases, but the strength (failure load divided by bonded area) decreases rapidly after the overlap width-to-length ratio is greater than 1. When the adherend thickness increase to double, bonding strength increase $12{\sim}55%$. Major failure mode of the joints is the delamination in the composite laminate and the location of delamination goes deeper into the laminates as the bonding pressure and overlap length increase.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.11
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• pp.46-54
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• 1998

A planar Bi-Sb multijunction thermal converter, which is consisted of a linear or bifilar thin film NiCr-heater and a thin film Bi-Sb thermopile, has been fabricated, and its ac-dc transfer characteristics were examined in a frequency range from 10 Hz to 10 KHz. In order to increase the thermal sensitivity and to decrease the ac-dc transfer error of a thermal converter, the heater and the hot junctions of a thermopile were prepared on a Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$-diaphragm which acts as a thermal isolation layer, and the cold junctions on the Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$-thin film supported with the silicon rim which functions as a heat sink. The respective thermal sensitivities in air and in a vacuum of the converter with a built-in bifilar heater were about 14.0 ㎷/㎽ and 54.0 ㎷/㎽, and the ac-dc voltage and the current transfer difference ranges in air were about $\pm$0.60 ppm and $\pm$0.11 ppm, respectively, indicating that the ac-dc transfer accuracy of the converter are much higher than that of a commercial 3-dimensional multijunction thermal converter. However, the output thermoelectric voltage fluctuation of the converter was rather high.

• Journal of Korean Society of Steel Construction
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• v.25 no.5
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• pp.569-578
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• 2013

In a super-tall building construction, thick and large-sized embed plates are usually used to connect mega structural steel members to RC core wall or columns by welding a gusset plate on the face of the embed plate with T-shape. A large amount of heat input accumulated by weld passes causes the plates to expand or deform. In addition, the temperature of concrete around the plates also could be increased. Consequently, cracks and spalls occur on the concrete surface. In this study, the effect of weld heat on embed plates and 80MPa high strength concrete is investigated by considering weld position (2G and 3G position), edge distance, concrete curing time, etc. Measured temperature of the embed plates was compared with the transient thermal analysis results. Finally, push-out tests were performed to verify and compare the shear studs capacity of the embed plate with design requirement. Test result shows that the shear capacity of the plate is reduced by 14%-19% due to the weld heat effect and increased as the concrete curing time is longer.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.154-162
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• 1998

A planar Bi-Sb multijunction thermal converter with high thermal sensitivity and small ac-dc transfer error has been fabricated by preparing the bifilar thin film Pt-heater and the hot junctions of thin film Bi-Sb thermopile on the $Si_{3}N_{4}/SiO_{2}/Si_{3}N_{4}$-diaphragm, which functions as a thermal isolation layer, and the cold junctions on the dielectric membrane supported with the Si-substrate, which acts as a heat sink, and its ac-dc transfer characteristics were investigated with the fast reversed dc method. The respective thermal sensitivities of the converter with single bifilar heater were about 10.1 mV/mW and 14.8 mV/mW in the air and vacuum, and those of the converter with dual bifilar heater were about 5.1 mV/mW and 7.6 mV/mW, and about 5.3 mV/mW and 7.8 mV/mW in the air and vacuum for the inputs of inside and outside heaters, indicating that the thermal sensitivities in the vacuum, where there is rarely thermal loss caused by gas, are higher than those in the air. The ac-dc voltage and current transfer difference ranges of the converter with single bifilar heater were about ${\pm}1.80\;ppm$ and ${\pm}0.58\;ppm$, and those of the converter with dual bifilar heater were about ${\pm}0.63\;ppm$ and ${\pm}0.25\;ppm$, and about ${\pm}0.53\;ppm$ and ${\pm}0.27\;ppm$, respectively, for the inputs of inside and outside heaters, in the frequency range below 10 kHz and in the air.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.735-741
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• 2016

Increasing the total length of waveguide-below-cutoff array(WBCA) as it is used to the duct in order to enhance shielding effectiveness, the design could cause higher cost, higher levels of difficulties in construction and the interruption a flow velocity. The multi-layered WBCA can compensate for this problem, which can be designed by crossing each waveguide layer. By conducting simulations from 2-layer to 8-layer structure, it can be observed that the shielding effectiveness increases from 52 dB to 75 dB. Comparing with the original WBCA in a shape of mono layer rectangular, our proposed waveguide becomes similar with the original value as the number of crossing layer increases. In addition, the analysis with the flow of fluid in the duct installed multi-layered WBCA are required. We demonstrate this analysis by doing the flow of fluid simulation, and concluded that the multi-layered WBCA has loss of flow of fluid less than unit rectangular WBCA.