• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.2038-2043
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• 2009

This study investigates elastic lateral-torsional buckling(LTB) of T-beams subjected to pure bending using finite element analysis(FEA). The results from the FEA are compared with those from the current American Institute of Steel Council(AISC) Load and Resistance Factor Design(LRFD) Specifications. The comparison indicates that AISC-LRFD provide unsafe values for T-beam subjected to pure bending. Therefore, a new design equation are presented using results from the FEA. The new equation could be easily used to calculate the elastic lateral-torsional buckling moment resistance of T-beam for beam design and to expand the new equation for developing LTB equations of T-beam subjected to general loading conditions such as a concentrated load, distributed load, or a seres of concentrated load.

• Steel and Composite Structures
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• v.9 no.4
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• pp.349-366
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• 2009

The composite slim beam has become popular throughout Europe in recent years and has also been used on some projects in China. With its steel section encased in a concrete slab, the steel-concrete composite slim beam can provide the floor construction with minimum depth and high fire resistance. However, the design method of the T-shape steel-concrete composite beam is no longer applicable to the composite slim beam with deep deck for its special construction, of which the present design models are not available but mainly depend on experiences. The elevation of the flexural stiffness and bending capacity of composite slim beams with deep deck is rather complicated, because the influences of many factors should be taken into account, such as the variable section dimensions, development of cracks and non-linear characteristics of concrete, etc. In this paper, experimental investigations have been conducted into the flexural behavior of two specimens of simply supported composite slim beam with deep deck. The emphases were laid on the bonding force on the interface between steel beam and concrete, the stress distribution of beam section, the flexural stiffness and bending capacity of the composite beams. Based on the experimental results, the reduction factor of equivalent stress distribution in concrete flange is suggested, and the calculation method of flexural stiffness and bending capacity of simply supported slim beams are proposed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.190-195
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• 2021

Typical Mn-SnO₂/Ag/Mn-SnO₂ tri-layer films were prepared on a PET substrate by RF/DC magnetron sputtering method at room temperature. Based on EMP simulation, the thicknesses of the top and bottom Mn-doped SnO₂ layers were kept at 40 nm and the Ag layer was maintained at 13 nm for continuous electrical conduction. The experimentally measured optical transmittances at 550 nm wavelength were ranged from 82.9 to 88.1 % and sheet resistances were varied from 5.9 to 6.9 Ω/☐. The highest value of figure of merit, ϕ_TC was 48.1 × 10^-3 Ω^-1. Based on bending test under 4 and 5 mm of inner and outer curvature radius condition, tri-layer film resistance varies only by approximately 1.5 % after 10,000 bending cycles, showing excellent mechanical flexibility.

• Journal of the Korean Wood Science and Technology
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• v.51 no.4
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• pp.253-269
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• 2023

Oriented strand board (OSB) distributed in Korea was collected, and its mechanical properties were investigated according to the International Organization for Standardization (ISO), Japanese Industrial Standards, and Korean Design Standard. Ten types of OSBs were collected, including six types for walls and others for floors. The thickness swelling, moisture content, and density of each product satisfied the ISO standards. All products showed lower formaldehyde emission values than those of the SE0 grade. The internal bonding strengths of all products, except products B, H, and I, met the ISO standards. However, products A, B, C, F, and H did not satisfy the thickness swelling standard of the load-bearing OSB for use in dry conditions. Products D and G showed heavy duty load-bearing OSB for use in humid conditions in terms of internal bonding and bending strength after boiling. In the nail head pull-through force and lateral nail resistance tests, all products met the standards. In terms of the structural bending performance (four points), the six types of OSBs for walls satisfied the standard for bending strength and modulus of elasticity. All the products for flooring met the standard for bending strength but, except for product G, the products did not meet the standard for modulus of elasticity. Although the results of this study cannot represent the performance of all imported OSBs, considering the above results, the water resistance performance of seven types of OSB products did not meet the standard, and 10 types of products did not match the labeling grades.

• Journal of Korean Neurosurgical Society
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• v.37 no.3
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• pp.217-222
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• 2005

Objective: To achieve optimal fit of implant, it is necessary to bend the implant during spine surgery. Bending procedure may decrease stiffness of plate especially made of titanium and stainless steel. Typically titanium suffers adverse effects including early crack propagation when it is bent. We investigate whether 6 degree bending of titanium plates would decrease the stiffness after full cyclic loading by comparing with non-bending titanium plates group. Methods: Authors experimented 40 titanium alloy plates of 57mm in length, manufactured by 5 different companies. Total 40 plates were divided into two groups (20 bent plates for experimental group and 20 non-bent plates for control group). Twenty plates of experimental group were bent to 6 degree with 3-point bending technique and verified with image analyzer. Using the electron microscope, we sought for a initial crack before and after 3-point bending. Mechanical testing by means of 6000 cyclic axial-compression loading of 35N in compression with moment arm of 35mm-1.1 Nm was conducted on each plate and followed by the electron microscopic examination to detect crack or fissure on plates. Results: The stiffness was decreased after 6000 cyclic loading, but there was no statistically significant difference in stiffness between experimental and control group. There was no evidence of change in grain structure on the electron microscopic magnification. Conclusion: The titanium cervical plates can be bent to 6 degree without any crack or weakness of plate. We also assume that minimal bending may increase the resistance to fatigue fracture in cervical flexion-extension movement.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.3
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• pp.29-38
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• 2020

Since some warm-mix asphalt (WMA) concretes were known to show poorer rut resistance than the hot-mix asphalt (HMA) concretes, many studies were performed in efforts of improving its performance at high temperature. The reason is assumed to be due to the moisture remaining in aggregates dried at lower temperature. Therefore, not only the rut resistance, the crack resistance of WMA concrete was also in question. In this study, fatigue life of WMA concrete was evaluated in comparison with HMA using 3-point bending (3PB) beam test. The asphalt mixtures were prepared based on Korean mix-design guide using a 13 mm dense-graded aggregate and 6 binders; two HMA binders and four WMA binders. By 3PB fatigue test, normal (unmodified) and polymer-modified WMA concretes were evaluated in comparison with normal and polymer-modified HMA concretes at a low temperature (-5℃). The results showed that most of WMA concretes showed longer fatigue lives than HMA concretes, even though the same PG binders were used for HMA and WMA. This result indicates that the WMA concretes have stronger resistance against fatigue cracking than HMA at the low temperature, and this result is in contrast to the high-temperature performance test.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.105-112
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• 2021

In the case of harbor structures, it is important to understand the characteristics of structures that are subjected to repeated loads as they are structures that receive repetitive loads such as wave pressure as well as static loads. In this study, the lateral resistance according to the pile embeded depth of the block breakwater reinforced with piles by cyclic lateral loads was obtained through an model experiment. As the depth of embedment of the pile increased, the lateral resistance showed a tendency to increase. As the load was repeated, the gradient of the lateral resistance gradually appeared to be gentle. The bending moment of the rear pile was larger than that of the front pile. The bending moment of piles in the ground was similar to that when the pile head was free in the cohesionless of Broms (1964).

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.93-99
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• 2016

In this paper, we investigated the mechanical and electrical reliability of silver nanowire (AgNW) films. In particular, the durability and reliability of AgNW films were studied when the AgNW film was subjected to the bending deformation under current flow. The electrical durability of AgNW was evaluated by observing changes in heat generation and current density occurring in AgNW through voltage and current tests. The AgNW film showed a constant resistance change up to a bending radius of 2 mm and 200,000 cycles in the bending fatigue tests. The over-coating layer has an effect of improving the durability of the AgNW film. In the case of AgNW with the over-coating layer, heat was uniformly dissipated on the surface of AgNW film, whereas in the case of AgNW film without the over-coating layer, heat was generated locally. In the bending test under the current flow, the current density of the AgNW film was continuously decreased up to 52.4%. During bending, the AgNW was deformed due to mechanical deformation such as tensile, bending and sliding of the AgNW, consequently contact resistance of the AgNW was increased, leading to a electrical breakdown of AgNW by Joule heating. It was found that the application of the over-coating layer can improve the electrical and mechanical reliability of the AgNW film.

• Korean Journal of Materials Research
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• v.12 no.2
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• pp.135-139
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• 2002

Carbon powders (CP) and carbon fiber (CF) were introduced info glass fiber reinforced plastics (FRP) composites to obtain fracture detection function. The composites were evaluated through the relation between a load-displacement curve and an electrical resistance change curve in three point bending test. CP containing FRP (CP-FRP) has a sensitivity of electrical resistance change at much lower load level than CF containing FRP (CF-FRP). In loading-unloading tests, CP-FRP showed a large amount of residual electrical resistance which enables the estimation of loading hysteresis.

• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.413-419
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• 1997

The specimens which were prepared from cokes with additions of 0~25 wt% B4C were sintered in Ar atmosphere at 220$0^{\circ}C$. The effects of B4C content on graphitization and oxidation resistance of cokes were investigated. B4C accelerates the graphitization of cokes and at 220$0^{\circ}C$ the degree of graphitization increased from 0.33 which is the value of pure carbon to 0.56, which increased bluk density and porosity. Especially bending strength increased as th graphitization temperature increased. Oxidation resistance property was greatly improved when B4C was added more than 10wt% at 80$0^{\circ}C$ and when B4C was added more than 20wt% at 100$0^{\circ}C$. This was because that the thin layer of B2O3 glass phase on the surface of the composite could be identified to increase the oxidation resistance.