• Journal of the Korean Society of Safety
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• v.16 no.3
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• pp.7-11
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• 2001

In this study, specimens were classified four welded specimens and a base metal to investigate fatigue life and crack growth rate of pure titanium welding materials, and Ti was used in turbine equipment of nuclear power generation, etc. The summarized results are as follows; 1) Specimen-2 was bigger 712% than base metal, when it was compared with other welding materials, 2) As the result of specimens data, specimen-2 crack behavior rate res lower 30 times than base metal, and so total fracture life was very influenced by it, 3) Notch tip of Specimen-2 was offsetted 6.7mm from boundary H.A.Z, and if formed 25% in total fracture length, 4) As the considering of da/dN and $\Delta$K, Paris' law is incongruous in this study, because fro inclines nsf on one date.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.68-73
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• 1991

Results of an experimental investigation of low-rise reinforced concrete shear walls with barbell cross section under cyclic loads are discussed and evaluated. Four halr scale models of test specimens with height to length ratio of 0.75 were experimented. The dimension of all walls is 1500mm wide $\times$ 950 mm high $\times$ 100 mm thick and the section of all boundary column at both ends is 200 mm $\times$ 200mm. Main variables are : design concept, vertical flexural reinflrcement ratios and reinforcement details(including crossed diagonal shear reinforcement in SW7 specimen). In SW7 specimen, maximum strength and consequently dissipating energy index were 1.45 and 1.28 times greater than those of SW6 specimen, respectively.

• Korean Journal of Metals and Materials
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• v.50 no.6
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• pp.433-438
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• 2012

Strength change in ultra low carbon steel carburized at $880^{\circ}C$ and $930^{\circ}C$ for 10, 30, 60 and 120 minutes was investigated. The results were analyzed by a tensile test, chemical composition analysis, optical microscopy and scanning electron microscopy. Stress in the 0.5% strain specimen in the tensile test increased as the time treated at $880^{\circ}C$ and $930^{\circ}C$ increased, because the carbon diffusion layer and the martensite of the specimen increased with increasing treatment time. Martensite was found in the ferrite region in the specimen treated at $880^{\circ}C$, which is attributed to grain boundary diffusion.

• Magazine of the Korea Concrete Institute
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• v.5 no.2
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• pp.140-140
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• 1993

• Korean Journal of Materials Research
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• v.4 no.3
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• pp.334-338
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• 1994

This report details the microscopic aspects of grain boundary cracking in Pb-Sn eutecticduring displacement-controlled mechanical tests performed over a range of low frequency ($10^{-3}-10^{-5}$/s)and moderate strain range (0.2 - 1 %) where is the most technologically relevant to solder jointssubjected to thermal cycling. It is shown that intergranular cracking begins with the appearance ofcrack-like features (CLF's), which can be seen due in part because they are associated with grainboundary sliding, and is able to be described by certain stages of isolated crack growth. In the initialstages CLF's are not ture cracks but instead what I shall call "proto-cracks" where grain boundarysliding begins to damage the gram boundary at the surface. At some point during the initiation stagesonce proto-cracks become ture cracks, they develop into isolated cracks and the growth of isolatedcracks is eventually accomplished by coalescence, resulting in 5 stages of cracking.ing in 5 stages of cracking.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.251-254
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• 1998

The ($0.8BaTiO_3-0.1SrTiO_3-0.1MgTiO_3$)+$0.006Nb_2O_5$ ceramics were fabricated by conventional ceramic process. The dielectric property of specimen was investigated that the specimen was sintering temperature at 1,300C for 3hours and then annealed at $1,100^{\circ}C$ for 3hours in a atmosphere (air) to be painted on the surface with CuO paste. The results of the temperature and frequency are varied, the dielectric constant and loss tangent are unsuitable for BL capacitor. The dielectric constants were varied to be negative temperature coefficient(2.000-3,000) in the temperature range between -10 and $140^{\circ}C$, the dissipation factors (tan $\delta$) were some high(0.1-0.3). It was not grain insulation, in cause of the some difficult to be annealed temperature with CuO paste and fired atmosphere. But, we have some different annealing temperature and fired atmosphere, it will be suitable BL(Boundary Layer)capacitor.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.697-699
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• 2002

In this paper, the characteristics analysis of the eddy current sensor by using boundary element method package is presented. For the boundary element analysis. Faraday, which is the commercial package of the integrated engineering software, is used. To observe the impedance characteristic of the eddy current senor with the sensor position and lift-off, the eddy current testing analysis is performed on the ferromagnetic plate with defect. Considering the skin depth of the ferromagnetic specimen, the 800(Hz) driving source is chosen. The result shows that electro motive force is reduced as the probe moves to near the defect and the lift-off of the probe increases.

• Journal of Welding and Joining
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• v.3 no.1
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• pp.32-39
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• 1985

Fatigue lives of C.T. specimens containing the holes or the holes filled with other materials are investiated by experimental and analytical methods. The results of the study are as follows; 1) The fatigue lives are in the order of E'/E > 1, E'/E = 1, and E'/E < 1, where E' is the Young's modulus of other materials filling holes and E is that of matrix. 2) The fatigue life of E'/E = 0 is shortest than thost of E'/E > 1, E'/E = 1 and E'/E < 1. 3) The fatigue life of C.T. specimen containing the holes filled with other materials is shorter than that of matrix without holes. 4) Because of the stress concentration around the bonding boundary, crack initiates from the lower left on the boundary and propagates toward the upper right along the boundary.

• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.1029-1038
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• 1993

The microstructures of aluminas, included of dissolved CaO as $\alpha$-alumina seeded pseudo-boehmite hydrosol was gelled in plaster mold and doped of MgO as dipping of calcines(120$0^{\circ}C$-2h) into Mg-nitrate solution, were compared to the one of which additives are excluded during the gellation. It was formed the boundary layer of 300~350${\mu}{\textrm}{m}$ distance from surface to the inside, containing of approximately 500ppm CaO by dissolved Ca from plaster mold. As the MgO addition to the boundary layer with dissolved CaO, the microstructure of the layer was uniformed and inhibited the grian growth, compared to one of that additives be excluded specimen and of MgO doped-inside region. This result was considered as abnormal grain growth and effect of flat boundary formation be appeared by effects of dissolved CaO, were decreased by MgO co-doping.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2475-2482
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• 1993

The effects of the hole size(2R) and the specimen width(W) on the fatigue strength and the fatigue life in plain woven glass/epoxy composite plates are experimentally investigated under constant amplitude tensile fatigue loading. It is shown in this study that the notch sensitivity under fatigue loading is lower than that under static loading. It can be explained by the fact that the stress concentration is relaxed by the damage developed at the boundary of circular hole. To predict the fatigue strength at a specific cycle, the modified point stress criterion represented as a function of the geometry of the specimen(2R and W) is applied. It is found that the model used in the prediction of the notched tensile strength predicts the fatigue strength with reasonable accuracy. A model for predicting the fatigue life in the notched specimen, based on the S-$N_f$, curve in the smooth specimen, is suggested.