• 한국초전도ㆍ저온공학회논문지
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• 제16권4호
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• pp.7-16
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• 2014

Rare-earth barium copper oxide (REBCO) coated conductor (CC) tapes have already been commercialized but still possess some issues in terms of manufacturing cost, anisotropic in-field performance, $I_c$ response to mechanical loads such as delamination, homogeneity of current transport property, and production length. Development on improving its performance properties to meet the needs in practical device applications is underway and simplification of the tape's architecture and manufacturing process are also being considered to enhance the performance-cost ratio. As compared to low temperature superconductors (LTS), high temperature superconductor (HTS) REBCO CC tapes provide a much wider range of operating temperature and a higher critical current density at 4.2 K making it more attractive in magnet and coil applications. The superior properties of the REBCO CC tapes under magnetic field have led to the development of superconducting magnets capable of producing field way above 23.5 T. In order to achieve its optimum performance, the electromechanical properties under different deformation modes and magnetic field should be evaluated for practical device design. This paper gives an overview of the effects of mechanical stress/strain on $I_c$ in HTS CC tapes due to uniaxial tension, bending deformation, transverse load, and including the electrical performance of a CC tape joint which were performed by our group at ANU in the last decade.

• Journal of Welding and Joining
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• 제15권6호
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• pp.32-40
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• 1997

Solid state diffusion bonding is the joining process performed by creep and diffusion, which is accelerated by heating below melting temperature and proper pressing, in vacuum or shielding gas atmosphere. By this process we can obtain sufficient joint which can't be expected from the fusion welding. For Ti-6Al-4V alloy, the optimum solid state diffusion bonding condition and mechanical properties of the joint were found, and micro void morphology at bond interface was observed by SEM. The results of tensile test showed sufficient joint, whose mechanical properties are similar to that of base metal. 850$^{\circ}$C, 3MPa is considered as the optimum bonding condition. Void morphology at interface is long and flat at the initial stage. As the percentage of bonded area increases, however, small and round voids are found. Variation of void shape can be explained as follows. As for the void shrinkage mechanism, at the initial stage, power law creep is the dominant, but diffusion mechanism is dominant when the percentage of bonded area is increased.

• Advances in nano research
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• 제14권2호
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• pp.117-126
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• 2023

This experimental study investigated friction stir welding (FSW) of the acrylonitrile-butadiene-styrene (ABS) T-joint in the presence of various nano-silica levels. This study aim to handle the drawbacks of the friction stir welding (FSW) of an ABS T-joint with various quantity of nanoparticles and assess the performance of nanoparticles in the welded joint. Moreover, the relationship between the nanoparticle quantity and FSW was analyzed using response surface methodology (RSM) Box-Behnken design. The input parameters were the tool rotation speed (400, 600, 800 rpm), the transverse speed (20, 30, 40 mm/min), and the nano-silica level (0.8, 1.6, 2.4 g). The tensile strength of the prepared specimens was determined by the universal testing machine. Silica nanoparticles were used to improve the mechanical properties (the tensile strength) of ABS and investigate the effect of various FSW parameters on the ABS T-joint. The results of Box-Behnken RSM revealed that sound joints with desired characteristics and efficiency are fabricated at tool rotation speed 755 rpm, transverse speed 20 mm/min, and nano-silica level 2.4 g. The scanning electron microscope (SEM) images revealed the crucial role of silica nanoparticles in reinforcing the ABS T-joint. The SEM images also indicated a decrease in the nanoparticle size by the tool rotation, leading to the filling and improvement of seams formed during FSW of the ABS T-joint.

• Advances in concrete construction
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• 제10권5호
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• pp.455-462
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• 2020

This study investigated the effect of horizontal casting joints on the mechanical properties and structural behavior of sustainable self-compacting reinforced concrete beams (SCRCB). The experimental research consisted of two stages. The first stage used four types of concrete mixtures which were produced to indicate the effects of cement replaced with cement waste at 0%, 5%, 10%, and 15% by weight of cement content on fresh concrete properties of self-compacting concrete (SCC) such as, passing ability, filling ability, and segregation resistance. In addition, mechanical properties such as compressive, tensile, and flexural strength were also studied. The second stage selected the best mixture from the first stage and studied the effect of horizontal casting joints on the structural behavior of sustainable SCRCBs. The effect of horizontal casting joints on the mechanical properties and structural behavior were at the 25%, 50%, 75%, and 100% of sample height. Load deflection, failure mode, and theoretical analysis were studied. Results indicated that the incorporation of replacement with cement waste by 5% to 10% led to economic and environmental advantages, and the results were acceptable for fresh and mechanical properties. The results indicated that delaying the time for casting the second layer and increasing the cement waste in concrete mixtures had a great effect on the mechanical properties of SCC. The ultimate load capacity of horizontal casting joints reinforced concrete beams slightly decreased compared with the control beam. The maximum deflection of casting joint beams with 75% of samples height is similar with the control beam. The experimental results of reinforced concrete beams were substantially acceptable with the theoretical results. The failure modes obtained the best forced casting joint on the structural behavior at 50% height of casting in the beam.

• 한국정밀공학회지
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• 제29권3호
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• pp.313-318
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• 2012

Application of composite structures on naval ships strongly depends on the mechanical strength and collapse behavior of the T-joints of the whole structure. Because of the weight advantages over single skin composite and bolt fastening joining, three types of T-joints using both honeycomb sandwich composite and adhesive bonding were suggested to determine the effect of T-joint configuration. It was found that joining with a urethane foam block and overlaminates using the secondary co-bonding technique improves T-joint strength.

• 대한기계학회논문집A
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• 제31권6호
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• pp.694-700
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• 2007

Recently, a new cellular metal, WBK(Wire woven Bulk Kagome) has been introduced. WBK is fabricated by assembling metal wires in six directions into a Kagome-like truss structure and by brazing it at all the crossings. Wires as the raw material are easy to handle and to attain high strength with minimum defect. And the strength and energy absorption are superior to previous cellular metals. Therefore, WBK seems to be promising once the fabrication process for mass production is developed. In this paper, an upper bound solution for the mechanical properties of the bulk WBK under compression is presented. In order to simulate uniform behavior of WBK consisted of perfectly uniform cells, a unit cell of WBK with periodic boundary conditions is analyzed by the finite element method. In comparison with experimental test results, it is found that the solution provides a good approximation of the mechanical properties of bulk WBK cellular metals except for Young's modulus. And also, the brazing joint size does not have any significant effect on the properties with an exception of an idealized thin joint.

• 한국의류산업학회지
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• 제3권1호
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• pp.20-24
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• 2001

The primary objective of this study was to empirically explore the mechanical properties of marketing Korean fabrics by using KES-FB system and estimate the sewability of Korean clothes by the mechanical properties. From the empirical research, it was found that Korean fabrics for spring and summer has been transformed easier and less flexible by shearing Korean fabrics for autumn and winter. Also, it was found that there is a significant difference in the hand value as tensile, surface and compression. It was found that Korean fabrics for spring and summer has a stiffness and elastic properties of matter and Korean fabrics for autumn and winter has a bulky and abundant elasticity. Finally, it was found that Korean fabrics for autumn and summer in the joint of account of the mechanical properties. Also, the difficulties of process has been expected by sewability like seam-pucker, over feed, sewing and steam-press.

• 대한기계학회논문집
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• 제12권3호
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• pp.426-439
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• 1988

본 연구에서는 유한요소모델과 실험적 모우드 해석 방법을 조합하여 완전한 모우드를 측정하지 못한 상태에서도 구조물 연결부의 강성계수와 감쇠계수를 구하는 방법론을 검토하고 실제 계에 적용하여 보고자 한다.

• 소음진동
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• 제4권2호
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• pp.155-161
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• 1994

The dynamic behavior of a complex mechanical structure can be identified by dividing the structure into a series of smaller structure, called sub- structure and by studying the dynamic characteristics of these components. Generally, the dynamic characteristics of mechanical structure are strongly affected by the properties of joint parameters. In this paper, to identify the dynamic characteristics of mechanical structure, and experimental identification method in which directrly measured frequency response function(FRF) is used is considered. The method does not use the procedure of complex matrix calculation but use that of real matrix calculation. To confirm this method, computer simulation is performed by using frequency response function mixed with noise, and the experimental study is performed about the simple structure. The dynamic characteristics of joint parameters and identified more accurately than in using the prcedure of complex matrix calculation.

• 대한기계학회논문집
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• 제19권8호
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• pp.1869-1875
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• 1995

The adhesively bonded tubular single lap joint shows a nonlinear relationship between the applied torque and the resulting displacement under the static-torsional loading, which is induced from the nonlinear properties of the adhesive. However the torque transmission capability in the case of the dynamic-torsional loading is much less than that in the case of the static-torsional loading, the stress level of the adhesive is usually in the region of the linear stress and strain relation and the stress distributions of the joint can be obtained by the linear analysis. In this paper, a failure model for the adhesively bonded tubular single lap joint under the torsional fatigue loading was developed with respect to the adhesive thickness that was a critical factor in predicting the static torque transional-cyclic loadings was proposed.