• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.354-359
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• 2001

A flexible rotor was smoothly passed through its bending critical speed, which is supported by AFB. Then, maximum magnitude of the rotor vibration at the middle point was 25${\mu}$m. The test rig was largely consisted of air turbine, multi-leaf type air foil bearing and flexible rotor and its bending critical speed was 32,600 rpm. And the balancing system and method for field balancing of the flexible rotor were developd successfully.

• Journal of the Korean Society of Safety
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• v.12 no.2
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• pp.27-36
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• 1997

This paper evaluates the static and fatigue bending strengths of CFRP (carbon fiber reinforced plastic) laminates subjected to hygrothermals. The specimens which had different stacking composition, orthotropic and quasi-isotropic laminated plates, were prepared for this experiment. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages, and the 3-point fatigue bending test is carried out by using the impacted laminates to investigate the influence of hygrothermals on the effect on the residual bending fatigue strength of CFRP laminates.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1135-1144
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• 2023

In this paper, bending strength and permeability tests were conducted on concrete permeable blocks manufactured by recycling industrial by-products of oyster shell and blast furnace slag to measure and compare bending strength and permeability coefficient, and present experimental research results. To this end, a total of 54 specimens with a size of 200x200x60mm for surface layer and base layer were manufactured, and bending strength and permeability test were carried ourt accoridng to KS F 4419. Eighteen types of mixing designs were implemented by varying the mixing and replacement rates of oyster shells and blast furnace slag. As a result of the experiment, the higher the mixing ratio of oyster shell, the lower the bending strength and the permeability coefficient. Thereafter, a total of three permeable blocks with dimensions of 200x200x60mm were manufactured and subjected to bending strength and permeability tests according to KS F 4419. As a result of the test, the bending strength satisfies the standard of KS F 4419, and the permeability coefficient is 12 times higher than the standard of KS F 4419. It seems that the proper mixing of oyster shells and blast furnace slag increases the amount of air, and further research on durability and economic feasibility of materials used to manufacture permeable blocks is required.

• Journal of the Korean Ceramic Society
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• v.27 no.2
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• pp.161-168
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• 1990

To evaluate the corrosion behavior of reaction bonded silicon carbides, corrosion test was studied for various corrosive environments. Corrosion test for reaction bonded silicon carbides was conducted at 900$^{\circ}C$ under four different gas atmospehres ; air, So2-air, Cl2-O2-Ar, Cl2-N2 and investigated these samples using weight loss, bending strength, XRD, optical micrographs and EDS respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.8 no.2
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• pp.39-50
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• 1984

The plane bending corrosion fatigue test was performed on the welded zone between SM58 steel plate and SM41 steel plate jointed with submerged arc welding in the air and in the natural sea water with various conditions. The main results obtained from the test are summarized as follows: 1) The welded zone of the steel plates has the lowest impact strength and the highest electrode potential, but the hardness was mediate of SM58 base and SM41 base. 2) The cathodic protection of the welded zone was also effective for the plane bending corrosion fatigue, and the optimum protection potential of the welded zone was -1,000 mV SCE. 3) The corrosion fatigue strength under the various stress conditions of the steel plate could be estimated and also the require safety factors on the design could be obtained from the plane bending fatigue limit diagram.

• Journal of the Korean Society of Safety
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• v.16 no.2
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• pp.44-50
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• 2001

The rotated bending fatigue test was conducted in air md in 3.5% NaCl salt solution to investigate the fatigue fracture behaviour of raw material and F.E.M dual phase steel made from raw material(SS41) by a suitable heat treatment. This study has compared the initial microcrack creation of material by tensile test with that by fatigue test. And the rotated bending test of cantilever type under the condition of 3.5% NaCl salt solution and air has investigated the corrosion fatigue fracture behaviour with the variation of stress concentration factor determined by each of notch shapes. The initial microcrack have been developed in fragile grainboundary with general corrosion occurring in raw material : in the pits built up by corrosion in F.E.M. dual phase steel because pits bring out stress concentration. It is small that the degree of decrease in corrosion fatigue life for F.E.M. dual phase steel compared with raw material because the notch sensitivity of F.E.M. dual phase steel is lower than raw material in reason of characteristics with two-phase construction.

• Journal of Biomedical Engineering Research
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• v.36 no.2
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• pp.37-42
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• 2015

In this paper, we propose a wrist rehabilitation training device using pneumatic inflation and deflation of air cells. By alternating inflation and deflation of upper and lower air cells, the device makes the flexional and extensional movement for wrist rehabilitation. With the angular displacement sensor, it measures the flexion-extension angle of the wrist during the training and the bending angle is used for the automatic control of the device. Using the sensor output, the regression equation was obtained to measure the bending angle of the wrist from a wrist rehabilitation training device. The measurement error of the device was evaluated by comparing the measurement output with the angle from the photograph. The measurement error of wrist bending angle between the sensor and photo was $3.2^{\circ}$ in average. With additional test and improvement, the pneumatic wrist rehabilitation training device might be used for rehabilitation training.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.65-66
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• 2023

Recently, the importance of improving air quality has been greatly highlighted due to environmental problems such as indoor air pollution, and efforts are being made to improve indoor air quality not only in Korea but also around the world. In this situation, this study aims to study the physical properties of cement boards using pearlite with excellent physical adsorption performance due to micropores in materials, expanded graphite that is widely used as a flame retardant to prevent heat transfer in the event of a fire. The experimental items are bending fracture load and impact resistance. The bending destruction load at the fiber mixing rates 1, 2, 3, and 4 (%) did not meet the standard 140N, but the bending destruction load at 5% was 168.2N, and the impact resistance of the fiber mixing rates 1 and 2 (%) could not be measured due to cracks and damage, and the impact resistance at 3, 4, and 5 (%).

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.32-38
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• 1998

This paper is to investigate of microhardness, adhesive strength, tensile strength, and fatigue strength of ceramic sprayed steel. Rotary bending fatigue tests have been conducted at room temperature in air and 3% NaCl solution using specimens of carbon steel(S45C) with sprayed coating layers of Ni-4.5% Al(under coating) and $TiO_2$ (top coating). The microhardness has been improved at $800^{\circ}C$ heat treatment and 150mm spraying distance. Tensile strength of the sprayed steel is dependent on the substrate strength. The fatigue strength of the sprayed steel is larger than that of substrate due to blasting and constraint surface of plastic deformation effect. In low stress level, the corrosion fatigue strength of the sprayed steel were lower than that of fatigue strength in air by corrosion.

• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.7-12
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• 2015

CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.