• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.442-448
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• 2007

The ultrasonic inspection system for the expansion/transition area of steam generator tube was successfully developed. Variety of artificial flaw and real track specimen was tested using the UT system to verify the performance of the system. All artificial flaws of which through-wall depth larger than 10% was clearly detected by UT system. Measurement results of through-wall depth of flaws larger than 20% had good linearity and reproducibility with 3.27 of standard deviation. Results of real crack specimen test suggested that the detection limit of real crack strongly depends on the track morphology. A potential for measurement of PRL(percentage of remaining ligament) was recognized by the real crack specimen test.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.6
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• pp.320-328
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• 2003

A specimen of Cu-35%Sn alloy has been subjected to the unidirectional heat treatment in an attempt to examine the evolution of microstructures under varying thermal conditions. The specimen was cast in the form of a cylinder 10 mm in diameter and 200 mm in length, which was then installed in the temperature gradient field established inside a vertical tube furnace. The furnace temperature was adjusted to make the upper part at $750^{\circ}C$ and bottom end part at $300^{\circ}C$ of the specimen. The experiment was terminated by dropping it into water after the 30 minutes holding at given temperature. By the rapid cooling, the high temperature phases, ${\gamma}$ and ${\zeta}$, were retained at ambient temperature with some of ${\gamma}$ phase transformed to ${\varepsilon}$ phase, especially at the grain boundaries of ${\gamma}$ phase. The presence of ${\varepsilon}$ phase was found to determine the nature of phase transformations of the ${\zeta}$ phase undergoes upon cooling. In the close area of the ${\varepsilon}$ phase, ${\varepsilon}$ phase grew separately out of ${\zeta}$, and adds to the preexisting ${\varepsilon}$ whereas in areas away from ${\varepsilon}$, both ${\delta}$ and ${\varepsilon}$ grew simultaneously out of ${\zeta}$, and formed a lamella eutectoid structure. The transformation to ${\delta}$ was found to occur only in slow cooling. The hardness on each phase showed that the retained phases, ${\gamma}$ and ${\zeta}$, could be plastically deformed without brittle fracture while the phases, ${\varepsilon}$ and ${\delta}$, were too brittle to be deformed.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.249-267
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• 1994

The purpose of this study was to compare the fatigue, physical properties, flexibility and surface roughness of titanium used in removable partial dentures with those of a type IV and alloy and a cobalt- chromium alloy. Fatigue testing subjected the test specimen to rapid cycling at a given stress until failure occurred by using a small-sized, electrodynamic type bending fatigue testing machine. The S-N curves for the framework materials were generated. For tensile testing, a tensile bar as described in the ADA Specification No.14 was subjected to tensile loading until failure occurred. Load-displacement curves were generated for 18 gauge round specimen and tapered half round specimen. Then the flexibilities were calculated. The surface roughnesses were compared by analyzer. Through analyses of the data, the following conclusions were obtained. 1. The fatigue property of titanium was higher than that of a type IV gold alloy$(p\leq0.05)$, but there was no significant difference between titanium and a cobalt-chromium alloy $(p\geq0.05)$. 2. The yield strength, the ultimate tensile strength and Victors hardness of titanium were higher than those of a type IV gold alloy but lower than those of a coalt-chromium alloy$(p\leq0.05)$. 3. The percentage of elongation and reduction of area of titanium were the highest $(p\leq0.05)$. 4. The surface roughness of titanium was the greatest$(p\leq0.05)$. 5. The flexibility of titanium was lower than that of a type IV gold alloy but higher than that of a cobalt-chromium alloy$(p\leq0.05)$.

• Composites Research
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• v.17 no.4
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• pp.53-60
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• 2004

This paper describes a method for a falling weight impact test to estimate the impact energy absorbing characteristics and impact strength of CFRP laminate plates based on considerations of stress wave propagation theory. The absorbed energy of T300 orthotropic composites is higher than that of quasi-isotropic specimen over impact energy 6.8J, but in case of using T700 fiber, much difference does not show. Also, absorbed energy of T300 orthotropic composites, which are composed of the same stacking number and orientation became more than that of T700 fiber specimen; however there was no big difference in case of quasi-isotropic specimens. The delamination areas of the impacted specimen were measured with the ultrasonic C-scanner to find correlation between impact energy and delamination area. The fracture surfaces were observed by using the SEM (scanning electron microscope) through a low-velocity impact test in order to confirm the fracture mechanism.

• Korean Journal of Agricultural Science
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• v.17 no.2
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• pp.95-101
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• 1990

In order to investigate the influence of unconfined compression strength on undisturbed cohesive soil, the unconfined compression test were carried out on the basis of various size of specimen and compression rate. The result of these experiments were summarized as follows. 1. As the section area of specimen increased. the unconfined compression strength was decreased. 2. As the ratio of height and diameter of specimen increased, the unconfined compression strength was decreased. 3. The unconfined compression strength was increased by 3%, but in values over the 3% was decrease. 4. As the compression rate increased. the modulus of deformation was increased.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.531-536
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• 1999

Experiments on micro-leak of water were carried out with the water injecting simulator in liquid sodium atmosphere. The leak path was plugged by the sodium-water reaction products in the 2.25Cr-1Mo steel specimen. However, leak paths re-opened in most cases. The self-wastage patterns were not affected by the sodium temperature in the re-opened specimen. The diameter of the defected area, including the re-opened part, was about 5 min. It took 143, 40.7 and 34.7 minutes to re-open the leak path at 450, 475, and $510^{\circ}C$, respectively. It was concluded that the reopening time decreased with the increasing temperature.

• Polymer(Korea)
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• v.25 no.1
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• pp.56-62
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• 2001

When polyethylene terephthalate(PET) film specimen were stepwise elongated under tension with various speeds of about 0.5~500 mm/min, the necking area, consisted of transparent and opaque bands, was formed during plastic deformation. Stress oscillation was apparently obtained in the stress-strain curve of above specimen. However, stress oscillation was not obtained in the stress-strain curve of annealing specimen. Microstructure was examined dynamically using an optical microscopy and thermal analysis was carried out in a differential scanning calorimeter at a heating rate of 10${\circ}$/min. Also, orientation and crystallization were examined using monochromatic-pinhole technique and elastic modulus was measured by a dynamic mechanical analyzer in the temperature range of -150~70 ${\circ}$ with the frequency of 1 Hz. Transparent PET products were fabricated by use of the PET pellets annealed at 83${\circ}$ for 30 min in an electric furnace.

• Korean Journal of Materials Research
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• v.25 no.4
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• pp.202-208
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• 2015

Alumina dispersion strengthening copper(ADSC) alloy has great potential for use in many industrial applications such as contact supports, frictional break parts, electrode materials for lead wires, and spot welding with relatively high strength and good conductivity. In this study, we investigated the oxidation behavior of ADSC alloys. These alloys were fabricated in forms of plate and round type samples by surface oxidation reaction using Cu-0.8Al, Cu-0.4Al-0.4Ti, and Cu-0.6Al-0.4Ti(wt%) alloys. The alloys were oxidized at $980^{\circ}C$ for 1 h, 2 h, and 4 h in ambient atmosphere. The microstructure was observed with an optical microscope(OM) and a scanning electron microscope(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS). Characterization of alumina was carried out using a 200 kV field-emission transmission electron microscope(TEM). As a result, various oxides including Ti were formed in the oxidation layer, in addition to ${\gamma}$-alumina. The thickness of the oxidation layer increased with Ti addition to the Cu-Al alloy and with the oxidation time. The corrected diffusion equation for the plate and round type samples showed different oxidation layer thickness under the same conditions. Diffusion length of the round type specimen had a value higher than that of its plate counterpart because the oxygen concentration per unit area of the round type specimen was higher than that of the plate type specimen at the same diffusion depth.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.192-196
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• 2005

Key part of main equipment in a gas turbine may be likely to be damaged due to operation under high temperature, high pressure, high-speed rotation, etc. Accordingly, the cost for maintenance increases and the damaged parts may cause generation to stop. The number of parts for maintenance also increases, but diagnostics technology fur the maintenance actually does not catch up with the demand. Blades are made of precipitation hardening Ni superalloy IN738 and the like for keeping hot strength. The surface of a blade is thermal-sprayed, using powder with main compositions such as Ni, Cr, Al, etc. in order to inhibit hot oxidation. Conventional regular maintenance of the coating layer of a blade is made by FPI (Fluorescent Penetrant Inspection) and MTP (Magnetic Particle Testing). Such methods, however, are complicated and take long time and also require much cost. In this study, defect diagnostics were tested for the coating layer of an industrial gas turbine blade, using an infraredthermography camera. Since the infrared thermography method can check a temperature distribution on a wide range of area by means of non-contact, it can advantageously save expenses and time as compared to conventional test methods. For the infrared thermography method, however, thermo-load must be applied onto a tested specimen and it is difficult to quantify the measured data. To solve the problems, this essay includes description about producing a specimen of a gas turbine blade (bucket), applying thermo-load onto the produced specimen, photographing thermography images by an infrared thermography camera, analyzing the thermography images, and pre-testing for analyzing defects on the coating layer of the gas turbine blade.

• Journal of The Korea Institute of Healthcare Architecture
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• v.25 no.1
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• pp.17-27
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• 2019

Purpose: Clinical laboratory in hospital has taken a great role in protection of chronic disease. as well as diagnosis and treatment, And laboratory layout has been considered by the management and laboratory section more than the function and workflow. Methods: So this study figures out the workflows of laboratory sections in the recently upgraded Laboratory Medicine, and searches the functional relationships and spatial block diagram between each disciplines as follows. Literature review and expert adviser has been conducted. Results: 1) Laboratory type of Laboratory Medicine is divided into routine and specialized laboratory according to the workflow by automated or specialized test. 2) The general workflow consists of specimen collection, specimen classification, test by discipline, test report, and specimen disposal. 3) Though the function of each laboratory section is very complicated and specific, the characteristics and the workflow can be shown in detail by each lab through [Figure 4], [Figure 5], [Figure 6], [Figure 7], and [Figure 8]. 4) Functional relationship diagram can be displayed to the adjacency and relation between each laboratory and support spaces. 5) The spatial block diagram could be presented as shown in [Figure 10], in which the emergency lab lay in front side, routine lab in the central open area, and specialized lab in the behind side. Implications: This study can be used as a useful data in planning and designing a Laboratory Medicine Department.