• International Journal of Concrete Structures and Materials
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• v.10 no.4
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• pp.513-525
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• 2016

The resistance-demand approach has emerged as an effective approach for determining the shear capacity of reinforced concrete beams. This approach is based on the fact that both the shear resistance and shear demand are correlated with flexural tensile strain from compatibility and equilibrium requirements. The basic shear strength, under a given loading is determined from the intersection of the demand and resistance curves. This paper verifies the applicability of resistance-demand procedure for predicting the shear capacity of high strength concrete beams without web reinforcement. A total of 18 beams were constructed and tested in four-point bending up to failure. The test variables included the longitudinal reinforcement ratio, the shear span to depth ratio, and the beam depth. The shear capacity of the beams was predicted using the proposed procedure and compared with the experimental values. The results of the comparison showed good prediction capability and can be useful to design practice.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.192-195
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• 2004

Recently, the development of construction materials is rapidly advancing. Especially, the rate of development of cement based construction materials is much quicker than steel or composite materials. In order to optimize the ductility and strength of cement based materials, Micro-mechanics based fiber concrete called Engineered Cement Composite (ECC) is developed and studied extensively by many researchers in the field. Due to ECC's remarkable flexural strain and strength capacities, many leading nation (i.e., US, Japan, and European countries) are currently using ECC in actual constructions. In this study, ECC with internationally competitive material capacities is manufactured using domestic materials. Then, unreinforced concrete beams are repaired using ECC with $10\%,\;20\%,\;30\%$ of concrete specimen height Using 4 point bending test, the flexural strength of repaired flexural members are determined. The results show that ECC manufactured with domestic materials can be effectively used for repairing materials.

• Journal of Power System Engineering
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• v.8 no.2
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• pp.12-17
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• 2004

In this study, to verify the reliability of the indentation for measuring welding residual stresses to get in method we compared the results of the method with those measured by the saw cutting method. Also for the same purpose we used a 4-point bending test and confirmed the reliability of indentation method. The specimens used in this experiment are made with the same conditions for hot reheater pipes and cold reheater pipes used in the electric power plant. Therefore we could know that the results of the methods showed the reliability of the method to obtain welding residual stresses.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.04a
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• pp.127-133
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• 1991

Acoustic microscopy has attracted much intrest recently as potential mondestructive evalution technique for detecting and sizing defects of surface and sub-surface. Also acoustic emission testing method has been developed for detecting microcracks which is more than 30 umm in length quintitatively on ceramics material. In the present paper, acoustic emission during the four point bending test in hot-pressed sintered Si$\_$3/N$\_$4/ specimen which was stressed bythermal shock has been measured by high sensitive sensing system. The surface and sub-surface cracks were detected by scanning acoustic microscope of 800 MHz and conventional ultrasonic testing in C-scope image. The purpose was to investigate the location and size of cracks by SAM and AE technique, whose experimental datas demontrates good agreement for detecting microcracks.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.4
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• pp.173-178
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• 1999

KS-code(KS B 0896) for nondestructive ultrasonic testing classifies the quality level by ratio of flaw size to plate thickness only. But stress distributions using verification(3 point bending test) show that location of the flaws is more important than the flaw size. So. KS-code should take the effect of flaw location for classifying the quality level of welded steel structures.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.106-123
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• 1996

This paper experimentally investigates the characteristics of Al-honeycomb sandwich panels which are considered as a promising primary strength member of weight critical large structures. Some tests on the aluminum honeycomb panels subject to 3-point bending or uniaxial compression or crushing load are carried out. Based on the test results, linear elastic response, buckling/ultimate strength and crushing/energy absorption capacity are discussed. Some guidelines for design of aluminum honeycomb panels are given.

• Progress in Superconductivity and Cryogenics
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• v.11 no.2
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• pp.29-32
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• 2009

The conduction cooling HTS SMES magnet is operated in cryogenic temperature. The insulation design at cryogenic temperature is an important element that should be established to accomplish miniaturization that is a big advantage of HTS SMES. However, the behaviors of insulators for cryogenic conditions in air or vacuum are virtually unknown. Therefore, we need active research and development of insulation concerning application of the conduction cooling HTS SMES. Specially, this paper was studied about high vacuum and cryogenic temperature breakdown and flashover discharge characteristics between cryocooler and magnet-coil. The breakdown and surface flashover discharge characteristics were experimented at cryogenic temperature and vacuum. Also, we were experimented about mechanical properties of 4-point bending test. From the results, we confirmed that about research between cryocooler and magnet-coil established basic data in the insulation design.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.1
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• pp.69-77
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• 1996

The fatigue crack initiation behavior of plasma ion nitrided SACM645 steel was investigated through the rotary bending fatigue test and residual stress measurement by XRD. It was shown by XRD and EPMA that the plasma ion nitrided surface was composed of ${\gamma}^{\prime}(Fe_4N)$phase and ${\varepsilon}(Fe_{2-3}N)$phase, and that the nitrogen atoms existed in Fe matrix in diffusion layer. The OM, SEM and Auger spectroscopy showed that the depth of compound layer, mixed compound and diffusion layer, and diffusion layer was $8{\mu}m$, $30{\mu}m$ and $300{\mu}m$, respectively. However, the microhardness test showed that the depth of hardened layer was $500{\mu}m$. The tensile strength of the ion nitrided SACM645 was lower than that of the unnitrided SACM645, and the ion nitrided specimen was fractured without plastic deformation. The nitrided SACM645 showed much poorer low cycle fatigue properties than the unnitrided one. In rotary bending fatigue, the fatigue strength of the ion nitrided SACM645 was higher than that of the unnitrided specimen, and the fatigue crack initiation sites changed by applied fatigue stress levels. The XRD result showed that the ion nitrided SACM645 has the compressive residual stress from surface to $600{\mu}m$ deep and the tensile residual stress from $600{\mu}m$ to deeper site. It is thought that crack initiation takes place at the point where the total stress of residual stress and applied stress is maximum.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.2
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• pp.49-55
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• 2016

The effects of post-annealing and temperature/humidity conditions on the interfacial adhesion energies of atomic layer deposited RuAlO diffusion barrier layer for Cu interconnects were systematically investigated. The initial interfacial adhesion energy measured by four-point bending test was $7.60J/m^2$. The interfacial adhesion energy decreased to $5.65J/m^2$ after 500 hrs at $85^{\circ}C$/85% T/H condition, while it increased to $24.05J/m^2$ after annealing at $200^{\circ}C$ for 500 hrs. The X-ray photoemission spectroscopy (XPS) analysis showed that delaminated interface was RuAlO/$SiO_2$ for as-bonded and T/H conditions, while it was Cu/RuAlO for post-annealing condition. XPS O1s peak separation results revealed that the effective generation of strong Al-O-Si bonds between $AlO_x$ and $SiO_2$ interface at optimum post-annealing conditions is responsible for enhanced interfacial adhesion energies between RuAlO/$SiO_2$ interface, which would lead to good electrical and mechanical reliabilities of atomic layer deposited RuAlO diffusion barrier for advanced Cu interconnects.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.31-37
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• 2009

Cu-Cu thermo-compression bonding process was successfully developed as functions of the $N_2+H_2$ forming gas annealing conditions before and after bonding step in order to find the low temperature bonding conditions of 3-D integrated technology where the quantitative interfacial adhesion energy was measured by 4-point bending test. While the pre-annealing with $N_2+H_2$ gas below $200^{\circ}C$ is not effective to improve the interfacial adhesion energy at bonding temperature of $300^{\circ}C$, the interfacial adhesion energy increased over 3 times due to post-annealing over $250^{\circ}C$ after bonding at $300^{\circ}C$, which is ascribed to the effective removal of native surface oxide after post-annealing treatment.