• Proceedings of the KSR Conference
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• 2007.05a
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• pp.798-803
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• 2007

The brake system of railway plays an important role to enhance the speed of train, and the brake disc is one of major components relating to frictional braking. The performance enhancement of brake disc directly affects the braking performance of train. It is required to understand and investigate the factors need to be considered for the development of new brake disc with improved materials and performance. In this study, through the literature reviews of previous study, several factors including thermal crack phenomena, friction coefficient, materials and durability of disc, temperature characteristics, etc., were introduced for the design of improved brake disc. Moreover, based on the review results, the design direction of new brake disc was suggested. Eventually, a new brake disc with improved performance would be developed based on this investigation.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.650-655
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• 2010

The ground vibration which is induced by train leads defect and crack of neighborhood structure. Consequently, in order to reduce the train vibration, it is need to appropriate countermeasure. Wave-guide typed roadbed induce the train vibration to a channel wave forms using the difference of the track layer's stiffness. Therefore train vibration is restrictively attenuated along the longitudinal direction of the track. 5 kind of wave-guide typed roadbed structure is selected in this paper. A finite element, time history, linear spectrum, transfer function and damping ratio analysis are performed to evaluate the vibration reduction efficiency as the wave-guide roadbed.

• Nuclear Engineering and Technology
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• v.33 no.5
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• pp.498-513
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• 2001

Performed here is a comparative assessment study for the generation of the pressure- temperature (P/T) limit curve of the reactor vessel. Using the cooling or heating rate and vessel material properties, the stress distribution is obtained to calculate stress intensity factors, which are compared with the material fracture toughness to determine the relations between operating pressure and temperature during cool-down and heat-up. P/T limit curves are generated with respect to crack direction, clad thickness, toughness curve, cooling or heating rate and neutron fluence, and their results are compared.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.88-93
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• 2008

Weld overlay is one of the residual stress mitigation method which arrest crack. An overlay weld sued in this manner is termed a preemptive weld overlay(PWOL). PWOL was good for distribution of residual stress of dissimilar metal weld(DMW) by previous research. Because range of overlay welding is wide relatively, residual stress distribution on PWR is affected by welding sequence. In order to examine the effect of welding sequence, PWOL was applied to a specific DMW of KORI nuclear power plant by finite element analysis method. As a result, the welding direction that from nozzle to pipe is better good for residual stress distribution on PWR.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.357-362
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• 2001

The pipe fracture tests were performed on 102mm-Sch.80 carbon steel pipe with various local wall thinning shapes, in order to understand failure behavior of thinned pipe. Pipe specimens were subjected to monotonic bending moment, using 4-points loading system, under internally pressurized condition. From the results of experiment, the failure mode, load carrying capacity, and deformability of local wall thinning pipe were investigated. Failure mode of thinned pipe depended on magnitude of internal pressure and thinning length as well as loading direction and thinning depth and angle. The variation in load carrying capacity and deformability of thinned pipe with length of thinned area was determined by stress type appled to thinning region and circumferential thinning angle. Also, the effect of internal pressure on failure behavior was dependent on failure mode of thinned pipe, and it promoted crack occurrence and mitigated local buckling at thinned area.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.173-182
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• 1995

The purpose of this study was to evaluate the adaptability of light-cured glass ionomer cement to cavity walls. Class V cavities were prepared on the labial surfaces of extracted bovine incisor teeth. The cavities were restored with Fuji II as self-cured glass ionomer cement and Fuji II LC, Vitremer as light-cured glass ionomer cement. Fluorescent markers (fluoreceine and rhodamin B) were incorperated into liquid and primer for a better image of microscopic observation. Restored teeth were sectioned by longitudinal and labiolingual direction. The adaptability at the tooth-restoration interface was assessed incisally, axially and cervically by confocal scanning laser microscope. Following results were obtained : 1. Chemical-cured glass iomomer cement restoration showed close adaptation on the all of the cavity walls, but, cracks formed within the cement. 2. Light-cured glass ionomer cement restoration was well adapted to the cavity walls, but showed crack in the cement adjacent to axial dentinal wall. 3. There' was no significant difference in adaptability between two light-cured glass ionomer cement restorations.

• Journal of the Korean Wood Science and Technology
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• v.17 no.4
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• pp.83-88
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• 1989

목재의 섬유방향에 경사진 균열의 모-드I과 모-드II의 혼합모-드파괴시의 파괴거동을 조사하기 위하여 라왕(Shorea Spp.)의 LA시스템에 있어서 서로 다른 경사각도를 가진 SEN시험편(Single edge notch specimen)에 대하여 휨 시험을 행하였다. 얻이진 결과는 혼합모-드파괴시, 모-드I응력확대계수$K_I$과 모-드II응력확대계수$K_II$간에 일정한 상호작용이 존재한다는 것을 나타내었다. 또한, 모-드I과 모-드II의 임계응력확대계수(Critical stress intensity factor) $K_{IC}$와 $K_{IIC}$ 이용하여 혼합모-드파괴시의 $K_I$과 $K_II$간의 상호관계를 규정할 수 있었으며, 이미 보고된 여러 실험식과 본 실험결과를 비교하여 가장 적합한 관계로서 아래와 같은 관계를 얻을 수 있었다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.88-95
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• 2001

Silicon nitride based ceramics reinforced with 3wt% Si$_{3}$N$_{4}$ whisker was prepared by tape casting to investigate the effect of microstructure on erosion behaviors. Hardness and fracture toughness were measured with prepared specimens. A gas blast type erosion tester was used to examine the erosion behavior of the specimens with different impact directions and angles. The erosion rate increases with increasing impact angle. Erosion rate of the silicon nitride ceramics also depends on the grain orientations, The erosion rate was lowered when impaction direction was parallel to the grain orientation This result was explained by the crack deflection and bridging due to the grain orientation.

• Proceedings of the Korean Reliability Society Conference
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• 2004.07a
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• pp.335-342
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• 2004

The failures such as flaking, wear, crack and seizing caused by the high contact pressure accompanied with sliding motion between inner or outer ring and ball are potential failures of ball bearing. In this research, we have qualitatively selected the efficient test items through the analysis of the life and potential failures of ball bearing. The bearing's failures are related closely to the whole system in using the bearing. So, the bearing itself requires an estimation of life in order to opreate the system safely. We have tested ten ball bearings. Our research has applied both radial and axial direction force of maximum torque conditions simultaneously for the accelerated life testing. The result is established by employing the weibull plot and compared the predicted life of ball bearing to the experimental result.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.49-55
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• 1996

The aim of this study is to investigate the change of bending strength and fatigue strength in the unpoled and poled Pb(Zr, Ti)O3 ferroelectrics of tetragonal morphotropic phase boundary (MPM) and rhombohedral com-position in terms of internal stress which is measured by XRD method. Before poling treatment the highest bending strength was found in rhombohedral composition. After poling treatment the bending strength decreas-ed in all compositions but it decreased most remarkably in tetragonal composition. The most prominent de-crease of bending strength after poling treatment in tetragonal was attributed to the occurrence of microcracks due to highanisotropic internal stress around grain boundary which was induced of bending strength after poling in MPB and rhombohedral composition was not due to the occurrence of microcracks but to the increase in tensile internal stress perpendicular to the direction of crack propagation by domain alignment. Fatigue strength was higher before poling treatment than after poling treatment for various compositions.