• Journal of the Korean Wood Science and Technology
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• v.42 no.5
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• pp.571-578
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• 2014

As a way of developing wooden joint development, a glass fiber reinforced wood plate was manufactured to replace a steel plate. Also, the fracture toughness was evaluated. Through application to a cantilever-type specimen made of a column and a beam, the moment resistance performance was evaluated. For the fracture toughness specimen of the wood plate, 12 types were manufactured by varying the combination of a main member (veneer and plywood) and reinforcement (glass fiber sheet and glass fiber cloth). The results of the fracture toughness test indicated that the 5% yield load of the specimen using plywood was 18% higher than that of the specimen using veneer, and that the specimen reinforced by inserting glass fiber sheets between testing materials (Type-3-PS) had the highest average 5% yield load 4841 N. Thus, a moment resistance strength test was performed by applying Type-3-PS to a column-beam joint. The results of the test indicated that compared to the specimen using a steel plate and a drift pin (Type-A), the maximum moment ratio of the specimen using a glass fiber reinforced wood plate (Type-3-PS) and a drift pin (Type-B) was 0.79; and that a rupture occurred in the wood plate due to high stiffness of the drift pin. The maximum moment ratio of the specimen using a glass fiber reinforced wood plate (Type-3-PS) and a glass fiber reinforced wooden laminated pin (Type-C) was 0.67, which showed low performance. However, unlike Type-A, a ductile fracture occurred on Type-C, and the load gradually decreased even after the maximum moment.

• Corrosion Science and Technology
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• v.3 no.1
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• pp.14-19
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• 2004

Crack growth rate and threshold stress intensity factor for stress corrosion cracking(SCC), $K_{ISCC}$ were measured for type 403 stainless steel in 3,5% NaCl solution at room temperature and SCC was monitored by electrochemical noise technique during $K_{ISCC}$ testing. In rising load test, pits were formed at the tip of pre-crack for the pre-cracked compact tension specimen unlike in smooth round specimen in which only unstable pits were observed and hence immune to SCC. Micro-cracks were found to initiate from the pits in the former specimen, and initiation of micro-crack as well as macro-crack was detected by electrochemical noise technique in rising load $K_{ISCC}$ tests. Crack growth rate increased with increasing either displacement rate or stress intensity factor at crack initiation and was higher in rising load $K_{ISCC}$ test compared to constant load $K_{ISCC}$ test at given stress intensities.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.216-221
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• 2001

In this study, the effects of nitriding methods and times on the fatigue strength of SACM 645 steel were investigated. The rotary bending tests were carried out to obtain and compare the fatigue strengths of plasma ion nitrided specimens and gas nitride specimen. The 70 hr. gas nitrided specimen had the highest fatigue strength of 1.05$\times$$10^3$ MPa over the 40 hr., 70 hr. and 90 hr. plasma ion nitrided specimens, which had the fatigue strength of 3.48$\times$$10^2$, 4.57$\times$$10^2$ and 4.64$\times$$10^2$ respectively. Also, the microhardness tests were conducted to measure the effective case depths. The plasma ion nitrided specimens showed much higher surface hardness values than the gas nitrided specimen overall.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1990-2001
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• 1991

The fatigue life and crack penetration behavior of high strength steel have been studied in detail both experimentally and analytically. The fatigue crack shape of a smooth specimen is almost semicircular, while a specimen with stress concentration becomes semielliptical according to stress concentration shape. The aspect ratio of smooth specimens calculated using the Newman-Raju's formular is smaller than the value obtained from the experiment. On the other hand, the aspect ratio of the stress concentration specimen shows a good agreement with experimental results. It is found that the crack growth behavior on the back surface after the penetration is unique and can be divided into three stages ; rapid growth region, constant growth region and acceleration growth region. By using the K value suggested in this study, the particular crack growth behavior and crack shape can be estimated quantitatively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.921-924
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• 1995

Case hardening behavior of carbon tool steel(SK5) was investigated after pulsed YAG laser irradiation. In the case od beam passes,martensite formed in the melt zone and in former pearlite regions of the austenitization zone exhibits vary high Vickers hardness values. The molten depth and width decrease as the beam power density increase. The influence of depth and width of color painted specimen was also investigated. The molten zone of the black painted specimen was the largest. The were loss of the black painted specimen was smaller than any other painted or raw material.

• Journal of Industrial Technology
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• v.2
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• pp.69-75
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• 1982

The fracture of a hot rolled SM 45C steel plate was investigated for various crack ratio, thickness and loading point using the method of J-integral. It was found that the stable crack growth increased as the thickness and crack ratio of the specimen. The results are summerized as follows. 1. The more crack ratio increase, the less fracture toughness tend to. 2. Considering fracture toughness, a thin specimen is stronger a thick one. 3. Considering only the bending of specimen without thickings of the axial direction, we can get $J_{1c}$ value decreased about 10 percentage within the scope of experimental crack ratio.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.78-83
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• 2010

This study was carried out to investigate the effect of microstructure on the damping capacity of 12Cr martensite heat-resisting steels, in case of the specimen with martensite phase contained the volume faction of ferrite phases, under 5%. The damping capacity was decreased with the increase of solution treatment temperature and time. While it was increased with the increase of tempering temperature and time. The damping capacity was higher in case of specimen with martensite single phase structure than the specimen with martensite phase contained of ferrite phases.

• Design & Manufacturing
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• v.1 no.1
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• pp.23-26
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• 2007

This paper has comparatively analyzed the characteristics of the machined surface of a specimen made by machining Die Steel STD11 and a specimen obtained by W-EDM steel. If a press die is manufactured through W-EDM, products of shapes that cannot easily be made through machining can be manufactured easily. However, the life of the press die is significantly reduced compared with the press die made through machining. This is believed to be caused by the deformed layer that has occurred on the surface of the press die that was made through W-EDM. The roughness of the 2 specimens was measured, and it was learned that the distribution of the roughness of the specimen made through the 1st W-EDM was rough.

• Journal of Welding and Joining
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• v.19 no.6
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• pp.608-613
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• 2001

In this study, the rotary bending fatigue test was carried out with two kinds of base metal, martensite stainless steel STR3 and austenite stainless steel STR35 and the dissimilar friction welded material with them. To compare the fatigue fifes according to the notch positions, the small circular defect was worked on the bonded line, 1.0mm and 0.5mm distance form the bonded line. The fatigue limits of the STR3 and STR35 base metal were 429.0MPa and 409.4MPa respectably. In comparison with fatigue life at the same notch positions, the STR35 specimens showed about 190% for base metal, 82% for 1.0mm distance notched specimens higher than that of the STR3. But the fatigue life of the 0.5mm distance notched STR35 specimen showed about 35% lower than that of the STR3 specimen. And the bonded line notched specimen was much lower fatigue life than the other specimens because of separation of the bonded line.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.4
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• pp.67-72
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• 2003

In this study, to investigate the effects of 2-step shot peening at the surface of spring steel, crack growth tests are conducted on spring steel and shot peened specimens. And then the residual stresses and fractographs are examined. The crack growth equation that can describe the whole crack growth behavior is used to evaluate the experiment results. The results show that fatigue crack glows slowly in the shot peened specimen than in the unpeened. And in the case of the 2-step shot peened specimen the initial stress intensity factor range and the fracture toughness is higher than the unpeened specimen due to the compressive residual stress. Fractographs show that the compressive residual stress of the surface suppress the fatigue crack opening and consequently slow crack growth rates.