• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.62-66
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• 2004

A study for investigating the effects of the cutting conditions(feed rate, radial depth of cut, cutting speed) and the tool diameter on the circumferential geometry of the cyl indrically end-mi1led workpiece is described. In this work, the circumferential geometry is characterized by the roundness error. Experimental results show that the circumferential geometry is directly affected by the material removal per tooth,which is defined as a function of the cutting speed, the feed rate and the radial depth of cut. And, the radial depth of cut is revealed to be the most critical condition among them. It is also found that the roundness error decreases when the tool diameter is larger under the same cutting conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.154-162
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• 1991

In this study, the simulation program is developed where the tooth profile error in internal gear shaping is calculated considering several factors which affect it. This factors are the circular feed of the pinion cutter, the interference by the geometric conditions of the cutter and the internal gear, the deviation from the theoretical involute profile of the cutter and the eccentricity of the cutter and the internal gear. With this program, the effects are investigated which the geometric conditions and the cutting conditions in internal gear shaping have on the tooth profile error of the internal gear. The condition for the minimization of it is derived and then the results of simulation are adequately verified by measurements of internal gears cut by a pinion cutter.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.58-66
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• 2012

The work roll surface temperature rises and falls repetitively during hot slab rolling because the work roll surface is cooled continuously by water. This study focused on Std. No. 7 to determine a cooling method which significantly reduces the tangential tensile stresses on the work roll surface of the hot slab mill at Hyundai Steel Co. in Korea. A series of finite element analyses were performed to compute the temperature distribution and the tensile stresses in the circumferential direction of the work roll. The virtual slab model was used to reduce the run time considerably by assigning a high temperature to the virtual slab. Except for the heat generated by plastic deformation, this is equivalent to the hot rolling condition that a high temperature slab (material) would experience when in contact with the work rolls. Results showed that when the virtual slab model was coupled with FE analysis, the run time was found to be reduced from 2000 hours to 70 hours. When the work roll surface cooled with a certain on-off patter of water spray, the magnitude of the tangential stresses on the work rolls were decreased by 54.1%, in comparison with those cooled by continuous water spraying. Savings of up to 83.3% in water usage are possible if the proposed water cooling method is adopted.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.170-176
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• 1987

This study is concerned with dynamic characteristics of a circular ring with a concentrated mass attached. The equations of motion are set up and are solved by using Laplace transformation. The ratio of a concentrated mass to the mass of circular ring is used as a parameter. Experiment was performed by employing impulse test and the results show good agreement with those of analysis. The results of this study can be utilized in vibrational analysis of axisymmetric shells with slight asymmetries.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.1
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• pp.34-39
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• 2013

In the advanced research deducted infrared thermography (IRT) test using 4 inch pipe with artificial wall-thinning defect to measure on the wall-thinned nuclear pipe components. This study conducted for defect detection condition of nuclear small-bore pipe research using deducted condition in the advanced research. Defect process is processed by change for defect length, circumferential direction angle, wall-thinning depth. In the used equipment IR camera and two halogen lamps, whose full power capacitany is 1 kW, halogen lamps and Target pipe experiment performed to the distance of the changed 1 m, 1.5 m, 2 m. To analysis of the experimental results ensure for the temperature distribution data, by this data measure for defect length. artificial defect of 4 inch pipe is high reliability in the 2 m, but small-bore pipe is in the 1.5 m from the defect clearly was detected.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.439-442
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• 2009

In this study, the residual strength of CFRP filament winding pressure vessel after low velocity impact was evaluated quantitatively. After impact test, the pressure vessel was sectioned to produce 25 mm-wide ring specimen and the bursting pressure of this specimen was measured. A finite element model was also fabricated to investigate the deformation and stress distribution characteristics of the impacted CFRP vessel. The degradation of the residual strength along with the increase of impact energy was successfully measured and reviewed.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.1
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• pp.1-9
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• 2000

This study shows the defect detection and sizing capability of ultrasonic guided waves in the nondestructive inspection of heat exchanger and steam generator tubing. Phase and group velocity dispersion curves for the longitudinal and flexural modes of a sample Inconel tube were presented for the theoretical analysis. EDM(Electric Discharge Machining) wears in tubing under a tube support plate and circumferential laser notches in tubing were detected by an axisymmetric and a non-axisymmetric transducer set up, respectively. EDM wears were detected with L(0, 2), L(0, 3) and L(0, 4) modes and among them L(0, 4) mode was found to be the most sensitive. It was also found that the flexural modes around L(0, 1) mode could be used for the detection and sizing of laser notches in the tubing.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.4
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• pp.323-329
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• 2013

This perform research of angle rated defect detection conditions and nuclear power plant piping defect detection by lock-In infrared thermography technique. Defects were processed according to change for wall-thinning length, Circumference orientation angle and wall-thinning depth. In the used equipment IR camera and two halogen lamps, whose full power capacitany is 1 kW, halogen lamps and target pipe's distance fixed 2 m. To analysis of the experimental results ensure for the temperature distribution data, by this data measure for defect length. Reliability of lock-In infrared thermography data is higher than Infrared thermography data. This through research, Shape of angle rated defect is identified industry place. It help various angles defect detection in the nuclear power plant in operation.

• Transactions of Materials Processing
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• v.17 no.5
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• pp.364-372
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• 2008

In this study, the circumferential creep behaviors ofpilgered advanced Zirconium alloy tubes such as Zr-Nb-O and Zr-Nb-Sn-Fe were investigated in the temperature range of $400\sim500^{\circ}C$ and in the stress range of 80$\sim$150MPa. The test results indicate that the stress exponent for the steady-state creep rate of the Zr-Nb-Sn-Fe alloy decreases with the increase of stress(from 6$\sim$7 to 4), while that of the Zr-Nb-O alloy is nearly independent of stress(5$\sim$6). The activation energy of creep deformation is found to be nearly the same as the activation energy for Zr self diffusion. This indicates that the creep deformation may be controlled by dislocation climb mechanism in Zr-Nb-O. On the other hand, the transition of stress exponent(from 6-7 to 4) in Zr-Nb Sn-Fe strongly suggests the transition of the rate controlling mechanism at high stresses. The lower stress exponent at high stresses in Zr-Nb-Sn-Fe can be explained by the dynamic deformation aging effect caused by interaction of dislocations with Sn substitutional atoms.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1227-1234
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• 2012

In this study, fatigue tests were carried out using real-scale pipe bend specimens with wall-thinning defects under a cyclic bending load together with a constant internal pressure of 10 MPa. The wall-thinning defect was located at the extrados and the intrados of the pipe bend specimens. A fully reversed cyclic in-plane bending displacement was applied to the specimens. For the pipe bends with wall thinning at the extrados, an axial crack occurred at the crown of the pipe bend rather than at the extrados where the defect was located. In addition, the fatigue life was longer than that of a sound pipe bend predicted from the design fatigue curve in ASME Sec.III, and it was less dependent on the axial length of the wall-thinning defect. For the pipe bends with wall thinning at the intrados, a circumferential crack occurred at the intrados. In this case, the fatigue life was much shorter than that of a sound pipe bend predicted from the design fatigue curve, and it clearly decreased with decreasing axial length of the wall-thinning defect.