• Journal of the Korean Wood Science and Technology
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• v.18 no.2
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• pp.67-78
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• 1990

This study was performed to determine the characteristics of physical and mechanical properties of domestic wood based materials; plywood, particleboard, medium density fiberboard. Main items of tested properties were panel size, moisture content, water absorption, linear expansion and thickness swelling, glue bond shear strength, bending properties(stress at proportional limit, modulus of rupture. modulus of elasticity), tensile strength, screw holding strength, and internal bond as neccessary. the results were discussed mainly with Korean Standards. The obtained conclusions are as follows; 1. Length and width of 3mm thin plywood(3-ply) and 12mm thick plywood(7-ply) were satished with KS-standard, but thicknesses of these panels were not- passed tolerance limit except one of eight makers. 2. Length and width of particleboard and medium density fiberboard were greater than the tolerance limit value of KS standard, but the thicknesses of these panels were passed this value. 3. Moisture contents of 12mm thick and 3mm thin plywood were satisfied with KS-standard except one mill made 3mm thin plywood. 4. Moisture absortion of plywood was not passed tolerance limit of KS-standard but particleboard was satisfied with this standard value. 5. Dry and wet shear strengths in glue bond of 3mm thin plywood were not reached to KS-standard, but those of 12mm thick plywood were sufficiently satisfied with KS standrad. 6. Modulus of ruptures, parallel to grain and perpendicular to grain of plywood, and particleboard and medium density fiberboard were satisfied with KS-standard. 7. Tensile strengths, parallel to grain and perpendicular to grain of plywood were satisfied with allowance stress of US product standard PS 1-74. 8. Screw holding strength of particleboard was not reached to KS standard, but internal bond was satisfied with KS standard.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.18-23
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• 2013

In this study, the effects of cryogenic treatment cycles on the residual stress and mechanical properties of 7075 aluminum alloy (Al7075) samples, in the form of a tube-shaped product with a diameter of 500 nm, were investigated. Samples were first subjected to solution treatment at $470^{\circ}C$, followed by cryogenic treatment and aging treatment. The residual stress and mechanical properties of the samples were systematically characterized. Residual stress was measured with a cutting method using strain gauges attached on the surface of the samples; in addition, tensile strength and Vickers hardness tests were performed. The detailed microstructure of the samples was investigated by transmission electron microscopy. Results showed that samples with 85 % relief in residual stress and 8% increase in tensile strength were achieved after undergoing three cycles of cryogenic treatments; this is in contrast to the samples processed by conventional solution treatment and natural aging (T4). The major reasons for the smaller residual stress and relatively high tensile strength for the samples fabricated by cryogenic treatment are the formation of very small-sized precipitates and the relaxation of residual stress during the low temperature process in uphill quenching. In addition, samples subjected to three cycles of cryogenic treatment demonstrated much lower residual stress than, and similar tensile strength compared to, those samples subjected to one cycle of cryogenic treatment or artificial aging treatment.

• Journal of the Korea Institute of Building Construction
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• v.4 no.1
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• pp.89-96
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• 2004

Porous concrete is used of various parts by advantage of porous. Example of growing of plant is possible, and dwelling of creature, and filter functions of various contaminant, and decrease of noise, and so on. This research is for porous concretes that were used by four aggregate rubble, refreshing aggregate, expanded clay, orchid stone. This research estimate that physical and mechanical characteristics of fresh concrete and hardened concrete. The purpose of this research is to make environment-friendly porous concrete. This research's conclusion is as following : 1. Porous Concrete's slump was measured 12~14cm with rubble, 12~16cm with refreshing aggregate, 11~13cm with expanded clay, 11~13cm with orchid stone. Weight of aggregate was bigger, slump price appeared by bigger thing. Because placed Porous Concrete is low viscosity and small resistance between aggregate, it estimated that have high workability. 2. Porous Concrete's unit weight was measured 1.71~1.75t/$\textrm{m}^3$ with rubble, 1.58~1.62t/$\textrm{m}^3$ with refreshing aggregate, 1.19~1.20t/$\textrm{m}^3$ with expanded clay, 0.98~1.06t/$\textrm{m}^3$ with orchid stone. Showed aspect such as weight of aggregate. 3. Porous Concrete's compressive strength was measured 76~102kgf/$\textrm{cm}^2$ with rubble, 51~60kgf/$\textrm{cm}^2$ with refreshing aggregate, 30~40kgf/$\textrm{cm}^2$ with expanded clay, 13~16kgf/$\textrm{cm}^2$ with orchid stone. 4. Tendency of tensile strength and bending strength showed generally similarly with compressive strength, but showed low value fewer than 15kgf/$\textrm{cm}^2$ Therefore, wire mesh, reinforcing rod, such as establishment of frame is considered to need in reinforcement about tensility or flexures in case receive tensility or produce product of thin absence form. It concludes by speculating on the consequences of extrapolating the results of study to remodelling the office building being already existence.

• Journal of the Korean Institute of Rural Architecture
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• v.21 no.4
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• pp.45-52
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• 2019

Chemical grouting method is mainly used for construction of dams and reservoirs, stabilization and reinforcement of slopes, reinforcement of soft grounds such as embankments, dredging and landfills, the order of earthquake response method, and the reinforcement of structures. Recently, it is widely applied in construction sites such as highways, airfields, high-speed railways, subsea facilities, port construction works, tunnels, and subway works. As such, the demand for grouting continues to increase. The development of the grouting method was focused on increasing the strength of the ground, and the development of the chemical additives, the injection device, and the stirring device were mainly performed. But ordinary portland cement used for grouting is a product that consumes natural resources such as limestone, generates a large amount of greenhouse gases, consumes a large amount of energy sources, and it is time to develop products and new methods to replace them. In this study, Ordinary Portland Cement and New Grouting Binder (circulating fluidized bed boiler fly and blast furnace slag) were compared and analyzed by the following test. Homo-gel strength and homo-gel time, water quality analysis of the water used and soil contamination process tests of homo-gel samples were performed. In the case of NGB, when Using water is used as the reservoir water, the strength measured smaller than that of the other water. However, it shows about 2.5 times greater than the homo-gel compressive strength applied to OPC (7-day, reservoir water), so there is no problem with water quality when applied.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.70-76
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• 2015

It should be noted that the use of the lathe scrap for making fiber reinforced cementitious composites(FRCCs) raised friendly environmental effect as well as economy because the lathe scrap is a by-product of steel manufactures and is occurred when lathe and milling works of them are conducted to process steel manufactures. Thus, the purpose of this research is to investigate the effect of measurements of lathe scrap on the characteristics of FRCCs. For this purpose, various lathe scraps were collected from processing plants of metal, and then these were processed 10mm, 20mm, and 40mm in lengths for 2mm and 4mm in widths, respectively. FRCCs containing lathe scraps were made according to their widths and lengths, and then characteristics such as the workability, compressive strength, and flexural strength of those were evaluated. As a result, it was observed from the test results that the optimum measurements of the lathe scrap for manufacturing FRCCs was 2mm in width and 40mm in length.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.2
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• pp.201-212
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• 2002

This study investigated the shear bond strengths between abrasion-resistant denture teeth and composite resins according to surface treatments. Denture teeth for this study were Trubyte IPN teeth(Dentsply Inc., USA) with interpenetrating polymer network and Endura Posterio (Shofu Inc. Japan) of composite resin teeth, and restorative composite resins were Clearfil FII (Kuraray, Japan) of the self-cured composite resin and Z100(3M Dental Product, USA) of the light-cured composite resin. Five different surface treatments were evaluated: (1) $50{\mu}m\;A1_2O_3$ sandblasting: (2) #100 carbide paper; (3) chloroform; (4) retentive holes; and (5) no treatment. After surface treatments, denture teeth were examined by scanning electron microscopy(SEM), and the maximum shear bond strengths between abrasion-resistant denture teeth and composite resins were measured using Instron. The results were as follows; 1. IPN teeth treated with sandblasting had the highest shear bond strength, and Endura treated with sandblasting and carbide paper had significantly greater shear bond strength than with any other surface treatment. 2. Regardless or composite resins, the shear bond strength on Endura was greater than on IPN teeth. 3. Regardless of denture teeth, the shear bond strength of Clearfil FII was greater han of Z100. 4. In appearance of SEM, IPN teeth treated with sandblasting showed generalized roughness on the all of surface, however, carbide paper treatment resulted in partly rough. Endura treated with sandblasting and carbide paper showed similar surface characteristics. Wetting denture teeth surface with chloroform removed the debris and created a particle-free and smooth surface.

• Transactions of Materials Processing
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• v.30 no.6
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• pp.291-300
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• 2021

Currently, starting with electric vehicles, the application of ultra-high-strength steel sheets and light metals has expanded to improve mileage by reducing vehicle weight. At a time when internal combustion engine vehicles are rapidly changing to electric vehicles, the application of ultra-high-strength steel is expanding to satisfy both weight reductions and the performance safety of the chassis parts. There is an urgent need to improve the quality of parts without defects. It is particularly difficult to estimate the part formability through the finite element method (FEM) in the burring operation, so product design has been based on the hole expansion ratio (HER) and experience. In this study, design of experiment (DOE), analysis of variance (ANOVA), and regression analysis were combined to optimize the formability by adjusting the process variables affecting the burring formability of ultra-high-strength steel parts. The optimal variables were derived by analyzing the influence of variables and the correlation between the variables through FE analysis. Finally, the optimized process parameters were verified by comparing experiment with simulation. As for the main influence of each process variable, the initial hole diameter of the piercing process and the shape height of the preforming process had the greatest effects on burring formability, while the effect of a lower round of punching in the burring process was the least. Moreover, as the diameter of the initial hole increased, the thickness reduction rate in the burring part decreased, and the final burring height increased as the shape height during preforming increased.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.469-475
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• 2010

In this study, the interfacial bond strength of a squeeze infiltrated $Al_{18}B_{4}O_{33}$/AS52 Mg composite was investigated by using a finite element method. Three types of Mg composites with volume fractions of 15, 25 and 35% were fabricated. Three-dimensional models of the composite were developed by using a unit cell model in order to determine the effective elastic modulus of the metal matrix composite and the interfacial bond strength between the whisker and magnesium matrix. After modeling, numerical results were compared with the experimental tensile test results of $Al_{18}B_{4}O_{33}$/AS52 Mg composites. The results showed that the effective modulus of the composite strongly depended on the interfacial strength between the matrix and reinforcement. Based on the numerical and experimental findings, it was found that the strong interfacial bond was achieved by the interfacial reaction product of 30 nm thick MgO, which led to an improvement in the mechanical properties of the $Al_{18}B_{4}O_{33}$/AS52 Mg composites.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.27-35
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• 2015

Laser welding sector in the automotive industry has been widely recognized as one of the most important bonding processes, such as parts welding. Efforts to improve productivity and weld quality have been progressing steadily. In addition, laser welding is suitable for welding process that can produce high-quality welds suitable for flexible production and small quantity batch productions. In order to ensure the rigidity of the material, high strength material are applied to more than 1 GPa class body parts and automotive bumper beams. However, not only the situation is that the trend of domestic research, but also development is based on product molding considering freedom of shape where reinforcement is applied to meet the safety regulations and high-speed crash performance, despite the use of high strength materials. The tendency for heat-affected zone (HAZ) softening phenomenon common in areas of laser welded high tensile steel welding confirmed the occurrence of weld softening effect according to the process parameters. Based on this, range of process parameters could be selected for ensuring weld quality.

• Journal of the Korea Institute of Building Construction
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• v.9 no.2
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• pp.77-83
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• 2009

In this study, a test has been carried out to solve the problem with ground granulated blast-furnace slag, low early strength & lack of supply and to find out a way to use as concrete admixture of the ultrafine blaine air cooling slag which is all disposed as the by product of air cooling slag and its test was conducted to the replacement rate of ultrafine blaine air cooling slag & mixing condition of every concrete admixtures by type for the purpose of obtaining later a basic data for practical use of the cement that used ultrafine blaine air cooling slag by conducting comparative analysis. If ultrafine-blaine air cooling slag is used to the concrete following the results, a high efficiency water reducing agent won't be needed much for flow acquisition due to a high increase in flow, and the stripping time of concrete form will be shortened thanks to the acquisition of early strength, And though, it has the problems with long term strength which is similar or a little lower than the 3 types of ground granulated blast-furnace slag, it's still applicable as the substitute materials for 3 types of ground granulated blast-furnace slag at 10, 15% replacement rate of ultrafine-blaine air cooling slag, at which it shows higher activation index than 3 types of ground granulated blast-furnace slag.