• 한국초전도학회:학술대회논문집
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• v.10
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• pp.285-288
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• 2000

The effect of the initial BSCCO 2212 grain size on the final gain size and the formation of the BSCCO 2223 was studied using a powder precursor synthesized by two-powder method. 2212 and CaCuO$_2$ tapes were prepared by dip coating and joined by pressing and then followed by the repeated thermo mechanical treatment. The samples were characterized by XRD and SEM analysis. The formation and grain size of the BSCCO 2223 depended on the initial BSCCO 2212 grain size.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.04b
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• pp.375-380
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• 1999

In order to improve the optical properties of high yield pulp, bleached chemi-thermo-mechanical pulp (BCTMP) was produced from CTMP of Betula maximowicziana Regel by two staged ozone-hydrogen peroxide bleaching. This pulp was used for the evaluation of the improvement of optical properties, chemical characteristics of lignin in fiber, and the relationship between lignin and optical properties in fiber cell wall. By hydrogen peroxide treatment, the brightness was improved, but the post color number (PC No.) was not. There was little improvement on optical properties by ozone treatment, but his could be solved by using two staged ozone-hydrogen peroxide bleaching. The hydrogen peroxide treatment did not make nay change on chemical characteristics of lignin in cell wall, but by ozone treatment, it was found that the non-aromatic conjugated structure was existed in the surface of cell wall, but this could be removed by hydrogen peroxide treatment in two staged ozone-hydrogen peroxide treatment. Therefore, the optical properties was significantly improved due to the removal of non-aromatic conjugated structure.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.3
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• pp.136-141
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• 2002

During warm and hot forging process of steels or aluminum alloys, dies are subject to early fracture, severe wear by thermo-mechanical stress. Especially, during the die-casting of aluminum alloys, the service life of dies is incredibly lowered. In this study we investigated the characteristics of TiBN films produced by PECVD. TiBN films showed very high hardness, excellent wear resistance, which could enhance the service life of die parts such as forging punch, die casting core pin successfully.

• Structural Engineering and Mechanics
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• v.22 no.5
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• pp.517-539
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• 2006

Friction problems involving rubber components are frequently encountered in industrial applications. Their treatment within the framework of numerical simulations by means of the Finite Element Method (FEM) is the main issue of this paper. Special emphasis is placed on the choice of a suitable material model and the formulation of a contact model specially designed for the particular characteristics of rubber friction. A coupled thermomechanical approach allows for consideration of the influence of temperature on the frictional behavior. The developed tools are implemented in the commercial FE code ABAQUS. They are validated taking the sliding motion of a rubber tread block as example. Such simulations are frequently encountered in tire design and development. The simulations are carried out with different formulations for the material and the frictional behavior. Comparison of the obtained results with experimental observations enables to judge the suitability of the applied formulations on a structural scale.

• Journal of the Korean Ceramic Society
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• v.43 no.9 s.292
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• pp.515-518
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• 2006

The microstructure of $ZrO_2$ toughened $Al_2O_3$ ceramics was carefully controlled so as to obtain dense and fine-grained ceramics, thereby improving the properties and reliability of the ceramics for capillary applications in semiconductor bonding technology. $Al_2O_3-ZrO_2(Y_2O_3)$ composite was produced via Ceramic Injection Molding (CIM) technology, followed by Sinter-HIP process. Room temperature strength, hardness, Young's modulus, thermal expansion coefficient and toughness were determined, as well as surface strengthening induced by the fine grained homogenous microstructure and the thermal treatment. The changes in alumina/zirconia grain size, sintering condition and HIP treatment were found to be correlated.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.3
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• pp.47-54
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• 2015

In this study, effects of kneading treatment on the properties of hardwood bleached kraft pulp (HwBKP), softwood bleached kraft pulp (SwBKP) and hardwood bleached chemi-thermo-mechanical pulp (HwBCTMP) were elucidated with a laboratory two-shaft kneader. Kneading treatment was performed at 30% (w/w) of pulp concentration and the number of passes through the kneader was adjusted from 0 to 10 passes. Then, changes in properties of pulp fibers were evaluated. It was found that fiber characteristics were influenced by kneading treatment. Fiber length was decreased with kneading while other morphological properties such as fiber width, curl and kink became increased as the number of passes through the kneader increased from 0 to 5 passes. The magnitude of changes in the morphological properties of softwood chemical pulp was the largest, followed by hardwood chemical pulp. The morphological properties of HwBCTMP were little influenced by kneading treatment. Swelling of fiber measured by WRV was increased with kneading except of HwBCTMP.

• Resources Recycling
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• v.23 no.4
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• pp.30-36
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• 2014

300,000 tons of waste tires are annually being produced with development of the automotive industry in Korea. Landfill and incineration treatment system are causing the economic problem through secondary environmental pollution and waste. Therefore, as one of the ways to take advantage of this, Thermo-Plastic Vulcanized (TPV) composite was prepared by the ground waste tire and plastic powders. The waste tire powder was gained by mechanical fracturing through crushers. The waste tire powder was ground by a shear crushing method and a 2-stage disk mill method instead of cutting crushing one. The waste tire powder of 50 mesh was mixed with Polypropylene(PP) in various proportions. TPVs were prepared by an extrusion, and tensile and impact tests were performed. In addition, the same experiments were repeated in 40, 80, 140 mesh conditions in order to observe size effect of waste tire powders.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.135-140
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• 2004

Wear mechanisms may be briefly classified by mechanical, chemical and thermal wear. A plane strain finite element method is used with a new material stress and temperature fields to simulate orthogonal machining with continuous chip formation. Deformation of the workpiece material is healed as elastic-viscoplastic with isotropic strain hardening and the numerical solution accounts for coupling between plastic deformation and the temperature field, including treatment of temperature-dependent material properties. Effect of the uncertainty in the constitutive model on the distributions of strait stress and temperature around the shear zone are presented, and the model is validated by comparing average values of the predicted stress, strain, and temperature at the shear zone with experimental results.

• Laser Solutions
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• v.9 no.1
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• pp.9-16
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• 2006

Glass is one of brittle materials. Generally, brittle material is weak for tensile stress but strong for compression stress. Laser breaking of glass used this brittle characteristics. Laser breaking of glass was simulated to optimize breaking condition by using commercial FEM code MARC which is applicable to thermo-mechanical coupling analysis. Various shapes of heat sources were applied to the analysis and the distance between heating and cooling source were varied for each simulation. The shapes of heat sources were circle, single and double ellipse and the distance was varied from 0mm to 30mm. Moving heat sources were designed on the basis of experimental condition. As a result, double elliptic shape of heat source was the most suitable among them in laser breaking of glass. And it should be useful to determine optimal condition of laser breaking for glass.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.2
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• pp.75-81
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• 2015

Effects of B and Cu additions on the microstructure and mechanical properties of high-strength bainitic steels were investigated in this study. Six kinds of high-strength bainitic steels with different B and Cu contents were fabricated by thermo-mechanical control process composed of controlled rolling and accelerated cooling. The microstructures of the steels were analyzed using optical and transmission microscopy, and the tensile and impact tests were conducted on them in order to investigate the correlation of microstructure with mechanical properties. Depending on the addition of B and Cu, various low-temperature transformation products such as GB (granular bainite), DUB (degenerated upper bainite), LB (lower bainite), and LM (lath martensite) were formed in the steels. The addition of B and Cu increased the yield and tensile strengths because of improved hardenability and solid solution strengthening, but decreased the ductility and low-temperature toughness. The steels containing both B and Cu had a very high strength above 1.0 GPa, but showed a worse low-temperature toughness of higher DBTT (ductile-to-brittle transition temperature) and lower absorbed energy. On the other hand, the steels having GB and DUB showed a good combination of tensile and impact properties in terms of strength, ductility, yield ratio, absorbed energy, and DBTT.