• Korean Journal of Materials Research
• /
• v.33 no.11
• /
• pp.482-490
• /
• 2023

The purpose of this study was to analyze microstructural changes and evaluate the mechanical properties of TWIP steel subjected to variations in heat treatment, in order to identify optimal process conditions for enhancing the performance of TWIP steel. For this purpose, a homogenization heat treatment was conducted at 1,200 ℃ for 2 h, followed by hot rolling at temperature exceeding 1,100 ℃ and cold rolling. Annealing heat treatment is achieved using a muffle furnace in the range of 600 ℃ to 1,000 ℃. The microstructure characterization was performed with an optical microscope and X-ray diffraction. Mechanical properties are evaluated using micro Vickers hardness, tensile test, and ECO index (UTS × Elongation). The specimens annealed at 900 ℃ and 1,000 ℃ experienced a significant decrease in hardness and strength due to decarburization. Consequently, the decarburization phenomenon is closely related to the heat treatment process and mechanical properties of TWIP steel, and the effect of the microstructure change during annealing heat treatment.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.3
• /
• pp.11-18
• /
• 2009

• Journal of Mechanical Science and Technology
• /
• v.17 no.7
• /
• pp.1104-1110
• /
• 2003

The present study investigates the hemorheological characteristics of blood flow with applying vibration to a non-aggregating red blood cell suspension. In order to obtain the non-aggregating RBC suspension, blood samples were treated with vibration at a specified condition, which viscosities were taken before and after the treatment, respectively. The viscosity of the blood samples after treatment was higher than before treatment. These treated blood samples were forced to flow through a capillary tube that was vibrated perpendicularly to the direction of the flow. The experimental results showed that vibration caused a reduction of the flow resistance of the non-aggregated blood. The reduction of the flow resistance was strongly dependent on both frequency and amplitude of vibration. These results show potential in treating various diseases in the microcirculation associated with blood cell aggregation.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.24 no.7
• /
• pp.987-994
• /
• 2000

Cotton fabrics were finished with mixture of BTCA and silicone by pad-dry-cure process to achieve better mechanical properties than those of finished with BTCA alone. The changes of mechanical properties o( finished cotton fabrics were measured with by the KES-FB System and the hand values were calculated from the data of mechanical properties. With the durable press finish with BTCA tensile, bending, shear and compression properties increased. In hand values, Stiffness Crispness and Anti-Drape Stiffness increased, and Fullness & Softness decreased. Whereas silicone treatment reduced bending and shear properties and improved tensile and compressional resilience. Thus, Stiffness Crispness and Anti-Drape Stiffness decreased, and Fullness & Softness increased. These results indicated that BTCA treatment restricts fiber/yarn mobility in the fabric structure due to crosslinking, but silicone treatment reduces inter-fiber and inter-yarn frictional forces. Therefore, finish with mixture of BTCA and silicone provided cotton fabrics with a lower Stiffness, Crispness and Anti-Drape Stiffness and a higher Fullness & Softnesss than finish with BTCA alone.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.11
• /
• pp.83-92
• /
• 1998

In this paper, an experimental study has been carried out to develop an aluminum forged piston which has good mechanical properties. Through the experiment, the cavity filling, microstructure and mechanical properties of the final product are investigated with respect to chosen process parameters, which are die shape, heat-treatment condition and preform shape. The mechanical properties of the forged piston are compared with these of the cast piston. As the results, an appropriate die-shape is obtained to produce a perfect piston. The suitable heat-treatment condition and preform-shape are found to good hardness and minute microstructure in the forged piston. And we could obtain the mechanical properties(tensile strength, elongation and hardness) of the forged piston are superior to these of the cast piston.

• Journal of Hydrogen and New Energy
• /
• v.33 no.5
• /
• pp.566-573
• /
• 2022

In this study, the mechanical properties of the polymer electrolyte membrane according to the temperature were studied. The test specimens of polymer electrolyte membrane were heat treated at 40℃, 60℃, 80℃, 100℃, and 120℃, and then the tensile tests were performed. As results of this study, the residual stress of the polymer electrolyte membrane was removes by the heat treatment and the elastic modulus decreased due to the decrease in internal energy. In addition, in the plastic region, the mechanical properties and crystallization rate of the polymer electrolyte membrane increased in proportion according to increase of the heat treatment temperature.

• Journal of the Korean Society for Heat Treatment
• /
• v.15 no.1
• /
• pp.3-8
• /
• 2002

The effect of ADI heat treatment conditions on the core microstructures and mechanical properties of GCD 45 has been investigated. In the case of $25{\ss}{\AE}$ in diameter, it has been found that pearlite structure is not obtained, and the matrix is consisted of graphite, bainite and retained austenite. Upon cooling isothermally from $900^{\circ}C$, the core structure of 35 mm in diameter is converted to pearlite. However, the structure is transformed to bainite after slow cooling from $900^{\circ}C$ to $800^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
• /
• v.31 no.3
• /
• pp.97-103
• /
• 2018

The objective of this study is to develop the mechanical properties of AlSiCu aluminum alloy by the two-step solution heat treatment. The microstructure of gravity casting specimen represents a typical dendrite structure having a secondary dendrite arm spacing (SDAS) of 40 mm. In addition to the Al matrix, a large amount of coarsen eutectic Si phase, $Al_2Cu$ intermetallic phase, and Fe-rich phases are generated. The eutectic Si phases are fragmented and globularized with solution heat treatment. Also, the $Al_2Cu$ intermetallic phase is resolutionized into the Al matrix. The $2^{nd}$ solution temperature at $525^{\circ}C$ might be a optimum condition for enhancement of mechanical properties of AlSiCu aluminum alloy.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.48 no.2
• /
• pp.68-74
• /
• 2016

Nanofibrillated cellulose (NFC) was prepared from cotton linter after electron beam irradiation to investigate its effects on the manufacturing efficiency of the NFC preparation and the property changes by the treatment. Mechanical device (Super Masscolloider) was used to prepare the NFC and its passing frequency for each NFC preparation was recorded. More electron beam irradiation resulted in less passing frequency. Alpha cellulose content, molecular weight, crystallinity index, and thermal decomposition behavior of each treatment were lowered by electron beam treatment (10 and 100 kGy) and grinding process. NFC films were prepared to investigate their mechanical properties. There were little changes in tensile properties of the NFC films.

• Journal of Mechanical Science and Technology
• /
• v.16 no.5
• /
• pp.647-654
• /
• 2002

This study deals with the characteristic of quenching refrigerant for heat treatment deformation control of SM45C steel. Heat-treatment deformation must be controlled for the progress of production parts for landing gear. Most of deformation is occurred on inconsistent cooling. The inconsistent cooling is caused by a property of quenching refrigerant. When a heated metal is deposited in the quenching refrigerant, the cooling speed is so slow in early period of cooling because of a steam-curtain. After additional cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for landing gear by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on thermal deformation and fatigue strength are also investigated.