• 동력기계공학회지
• /
• 제15권2호
• /
• pp.49-54
• /
• 2011

Effect of tempering treatment on the mechanical properties of 12Cr heat resistant steel with ferrite phase was investigate in this study. As time and temperature of tempering treatment were increase, C and Cr contents in matrix structure were decreased. Due to increase of the amount of Cr26C6 type carbides. It was confirmed in mechanical properties experimental that tensile strength and hardness were decreased, while elongation and impact value were, increased with increasing the time and temperature.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
• /
• pp.172-179
• /
• 1999

As the martensite structure cause fracture failure during drawing from 5.5mm rod to 3.05mm dia. wire without additional heat treatment, the optium cooling condition to inhibit the occurrence of martensite was investigated. In order to get SAE9254+V quality, the effects of alloying element, vanadium on the mechanical properties were investigated. Based upon CCT and TTT curves and the results form cooling test in mill, optimun cooling was found in the condition of the laying head temp of 780$^{\circ}C$ and of the conveyor speed at 0.15m/sec with the whole cover closed. The wire rods produced under the condition showed the best mechanical properties of 120kg/$\textrm{mm}^2$ in TS and 50% in RA, having an excellent drawability. In vanadium added steels, tensile strength was improved without degrading elongation and charpy impact value. That means the strengthening by vanadium is mainly due to the grain refinement by the fine precipitates during tempering process.

• 한국공작기계학회논문집
• /
• 제11권3호
• /
• pp.51-56
• /
• 2002

In order to achieve high precision machine tools, Performance enhancement of feed drive systems is required. One of the important technical issues is how to decrease thermal expansion of ball screw in proportion to the increase of machining speed. When measuring force of stretch of ball screw, since not only actual expansion and the value of bending have to be considered, it is impossible to define the exact value of expansion. In addition, support bearings of ball screw gain considerable force in axial direction. It also generates thermal expansion on the ball screw, and deteriorates the performances of the hearings. In conclusion, it is impossible to give the pretension enough to absorb all the elongation due to thermal expansion generated during machine is running. If given bed column and saddle are all bent to chance machine accuracy, and the support bearings of ball screw is damaged.

• Macromolecular Research
• /
• 제13권3호
• /
• pp.194-205
• /
• 2005

The network structure of Ni-coated carbon black (NCB) composites filled with phenolic resin was investigated by means of using scanning electron microscopy, viscosity, interfacial tension, shrinkability, Flory-Huggins interaction parameters, and swelling index. The electrical properties of the composites have been characterized by measurement of the specific conductivity as a function of temperature. Additionally, the variation of conductivity with temperature for the composites has been reported and analyzed in terms of the dilution volume fraction, relative volume expansion, and barrier heights energy. The thermal stability of phenolic-NCB composites has been also studied by means of the voltage cycle processes. The experimental data of EMI wave shielding were analyzed and compared with theoretical calculations. The mechanical properties such as tensile strength, tensile modulus, hardness and elongation at break (EB) of NCB-phenolic resin composites were also investigated.

• 한국정밀공학회지
• /
• 제23권2호
• /
• pp.51-56
• /
• 2006

This paper shows the development of flexible force sensor using the fiber Bragg grating. This force sensor consists of a Bragg grating fiber and flexible silicone rubber (DC184, Dow corning co. Ltd). This sensor does not have special structure to maximize the deflection or elongation, but have good sensitivity and very flexible characteristics. In addition, this sensor has the immunity to the electro magnetic field and can be multiplexed easily, which is inherited from the characteristics of fiber Bragg grating sensor. In the future, this sensor can be utilized the tactile sensor system minimizing the sensor size and developing the fabrication method.

• 대한물리의학회지
• /
• 제2권2호
• /
• pp.219-228
• /
• 2007

Objective : The purpose of this study was conducted to find treatment of forward head posture and shoulder instability with proprioceptive neuromuscular facilitation concept. Methods : This is literature study with books, seminar note and international course. Results : Forward head posture and shoulder instability has related each other. Forward head posture will make muscle instability, weakness and stiffness on neck and shoulder girdle. It will make pain also. Important muscle are suboccipital muscle, omohyoid muscle, sternoclaidomastoid muscle, scaleni, pectoralis minor, levator scapular and digastric. Conclusion : Treatment of the forward head posture and shoulder instability is provided. It is that treatment of stiff muscle with eccentric muscle work, muscle elongation, muscle strengthening at the structure level and at the functional level for daily activities.

• Korea-Australia Rheology Journal
• /
• 제19권3호
• /
• pp.133-139
• /
• 2007

Low density polyethylene nanocomposites were prepared by melt intercalating maleic anhydride grafted polyethylene and montmorillonite clay. It has been found that maleic anhydride has promoted strong interactions between polyethylene and montmorillonite, leading to the homogeneous dispersion of clay layers. Rheological experiments revealed that prepared nanocomposites exhibited shear thinning behaviour. Polyethylene nanocomposites exhibited an increase in steady shear viscosities compared to virgin polyethylene owing to strong polymer clay interactions. The tensile strength of nanocomposites was improved but elongation at break decreased considerably. Also, barrier properties improved significantly with montmorillonite content.

• 열처리공학회지
• /
• 제15권4호
• /
• pp.166-171
• /
• 2002

The effects of Ni and N addition to 304 stainless steel on mechanical properties and microstructure were investigated within temperature ranged from $-196^{\circ}C$ to $25^{\circ}C$. The addition of nickel and nitrogen induced the stability against the formation of provide significantly enhanced ductility at $-196^{\circ}C$ and reduce the Md temperature. Fe-18Cr-10Ni-0.2N alloy showed the ${\gamma}$ phase in deformed structure which it was beneficial to enhance the tensile strength and elongation at $25^{\circ}C$ and $-196^{\circ}C$.

• Macromolecular Research
• /
• 제8권6호
• /
• pp.292-297
• /
• 2000

The theoretical synthesis of the isotactic and syndiotactic poly(methyl methacrylate) were carried out as a model for real polymerization reactions following the normal chain reaction processes by repeating the uniform localization of wave functions with inclusion of the interaction between the end group of the cluster and an attaching molecule by the elongation method, and then, the calculated value was compared with the usual PM$_3$ calculation. The results revealed that a reaction of cluster with monomer molecules has made it possible to calculate the electronic structure and total energy of polymer with nearly infinite length and a matrix of constant dimension. The isotactic poly(methyl methacrylate) is more stable than syndiotactic one. The same tendency have been found between the experimentally measured properties and a calculated total energy to explain the chain motion in isotatic and syndiotactic poly(methyl methacrylate).

• PNF and Movement
• /
• 제5권2호
• /
• pp.1-10
• /
• 2007

Purpose : The purpose of this study was conducted to find treatment of forward head posture and shoulder instability with proprioceptive neuromuscular facilitation concept. Methods : This is literature study with books, seminar note and international course. Results : Forward head posture and shoulder instability has related each other. Forward head posture will make muscle instability, weakness and stiffness on neck and shoulder girdle. It will make pain also. Important muscle are suboccipital muscles, omohyoid muscle, sternoclaidomastoid muscle, scaleni, pectoralis minor, levator scapular and digastric. Conclusion : Treatment of the forward head posture and shoulder instability is provided. It is that treatment of stiff muscle with eccentric muscle work, muscle elongation, muscle strengthening at the structure level and at the functional level for daily activities.