• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.68-78
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• 1993

Fatigue crack shape variation by a residual stress during crack growth and life predition are studied. An analytical method is presented to predict the influence of a residual stress due to heattreatment on crack shape variations. Computer simulation results using this me thod are graphically shown that crack growth rate to surface direction are decreased due to compressive residual stress exisiting in surface area. These results are commpared with experimental results. The fatigue life is also predicted by computer simulation of crack aspect ratio variation which is based on the surface crack length increment per unit cycle calculated from a-N diagram. Predited life is about 12 percent lower than experimental life.

• Korean Journal of Environmental Agriculture
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• v.14 no.3
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• pp.272-281
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• 1995

The residual Polychlorinated biphenyls(PCBs) in the sediment of the Kumho River basin were measured because the Nakdong River was considered to be affected by the environmental quality of Kumho River. PCBs in the sediment were chlorinated and converted into Decachlorinated biphenyl(DCB) which showed the single peak in the GC-ECD chromatogram. The detectable concentrations of PCBs was 0.5ng/g in the sediment. PCBs in the 21 sediment samples was of Kumho River located at 7.5km from conjunction of Nakdong River were not detected from 100 samples. 49% of samples was showed lower than 50ng/g, and 9% did more than 400ng/g. The mean of PCBs concentrations was 131ng/g. The means of COD and organic carbon were 14.5mg/g and 3.41%, respectively. The relationship between PCBs were concentration and the distance from conjunction with Nakdong River was not significant. The concentration of PCBs were varied with the depth of the sediment down to the 250cm depth. The concentrations of PCBs in the depth 0-20cm and 50-90cm were higher than the mean concentration of PCBs. Along the cross of the stream, the concentrations of PCBs were 142ng/g at the center and 126 and 131ng/g at the river sides.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1479-1485
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• 2010

In recent times, due to wire drawing of high carbon steel at a high speed to ensure a high productivity and high strength, axial residual stress are generated because of rapid increase in surface temperature. In the process, the temperatures of the wires increased because of the deformation of the wires and the friction between the die and wire. In particular, in the case of the wire drawing at a high speed, friction leads to a large temperature gradient so that considerable axial residual stress is generated on the surface. In this study, the relationship between axial residual stress and increase in the surface temperature was investigated, and a prediction model of uniform temperature was proposed. Then, a prediction model for residual stress was developed. The proposed model was verified by measuring the residual stress by X-ray diffraction on drawn wires.

• Tunnel and Underground Space
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• v.17 no.3 s.68
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• pp.186-196
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• 2007

In this study, direct shear tests were carried out on the 30 rock joint samples in order to investigate the influence of roughness and normal stress on the shear behaviour. Joint roughness profiles were measured by use of 3D laser profiler, and then the samples were equally classified into three individual groups according to the roughness index of rock joints. Peak shear strength, residual shear strength, shear stiffness, dilation angle of rock joints were investigated in condition of five different constant normal load. Peak shear strength was increased as roughness index was increased, and the influence of roughness on strength was found to be more considerable in case of lower normal stress condition. Residual shear strength and shear stiffness were increased as roughness index and normal stress were increased. Finally dilation angle was decreased as normal stress was increased, but it was increased as roughness index was increased in the same normal stress condition.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.121.1-121.1
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• 2005

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1989.11a
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• pp.69-72
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• 1989

구형의 압자를 유리평판 위에 올려 놓고 미끄럼 시험을 할 때 하중이 임계치보다 크면 유리평판 표면에 소위 "semi-circular cone-crack(SCCC)"들이 형성된다. 그리고 이 SCCC형성에 필요한 임계하중은 유리의 강도에 의하여 결정된다. 한편 소석회 유리에서 크기가 작은 이온인 $Na^+$를 큰 이온인 $K^+$로 대치시켜주는 경우 시편표면에 잔류압축응력이 생성되어 강도가 크게 증가한다. 따라서 유리의 내마모성도 이온교환을 하면 크게 향상될 것임을 예측할 수 있다. 본 연구의 목적은 이 예측을 실험적으로 확인하는 것이다. 확인하는 것이다.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.1
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• pp.65-69
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• 1990

Gas침탄질화처리 후 20Cr-2Ni-4A, 25Mn-Ti-B-Re, 20Cr-Mn-Ti 3가지 다성분강에서의 Ms온도를 계산하는 방법이 개발되어 왔으며, 결과적으로 각각의 gas 침탄질화층에 있는 잔류 austenite의 양이 계산될 수 있다. 이렇게 계산된 결과는 전형적인 실험 결과와 좋은 일치를 보이며, 그 예로서 En 354 강에서 침탄층을 통한 Ms 온도 분포가 계산되어진다.

• Bulletin of the Korean Institute for Industrial Safety
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• v.2 no.1
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• pp.34-40
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• 2002

화학설비나 산업설비 또는 국가 기간 설비에서 파이프(pipe)는 중요한 위치를 차지하고 있으며 파이프의 파열은 그대로 대형 사고나 설비 가동의 중단으로 연결되는 경우가 많다. 따라서 파이프의 구조건전성을 유지하는 것은 안전의 확보와 생산 설비의 효율적 운용을 위하여 긴요하다. 파이프 재료 내부에는 재료 제작 시, 또는 파이프 제작 시 발생된 결함이나 사용 중 부식이나 피로 등의 영향으로 생성된 결함이 존재한다. 이러한 결함은 파이프의 강도를 낮추게 되고, 파이프의 잔류강도가 사용압력보다 낮아지게 되면 파이프가 파열하게 된다. 따라서 본 글에서는 파이프에 균열이 존재하거나 손상된 경우의 구조안전성 평가를 위하여 필요한 해석방법에 대하여 살펴본다.(중략)

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05b
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• pp.675-680
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• 1995

원자로 압력용기 재료인 SA508-3 강의 인장소성변형에 따른 자기적 성질변화를 연구하였다. 소성변형에 따른 보자력, 잔류자화, 자기이력손실 및 Barkhausen Noise의 변화를 측정하였으며, 변형에 따른 자기적성질의 변화를 자구와 전위와의 상호작용으로 설명하였다. 강자성체의 자기적 성질과 기계적 성질 사이는 밀접한 관련이 있으며, 이를 이용하면 압력용기강의 조사효과 평가에 적용 할 수 있을 것으로 보인다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.81-92
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• 2013

The ultimate flexural strength of HSB I-girders, considering the effect of local bucking, was investigated through a series of nonlinear finite element analysis. The girders were selected such that the inelastic local flange buckling or the plastic yielding of compression flanges governs the flexural strength. Both homogeneous sections fabricated from HSB600 or HSB800 steel and hybrid sections with HSB800 flanges and SM570-TMC web were considered. In the FE analysis, the flanges and web were modeled using thin shell elements and initial imperfections and residual stresses were imposed on the FE model. An elasto-plastic strain hardening material was used for steels. After establishing the validity of present FE analysis by comparing FE results with test results published in the literature, the effects of initial imperfection and residual stress on the inelastic flange local buckling behavior were assessed. The ultimate flexural strengths of 60 I-girders with various compression flange slenderness were obtained by FE analysis and compared with those calculated from the KHBDC, AASHTO LRFD and Eurocode 3 provisions. Based on the comparison, the applicability of design equations in these specifications for the flexural strength of I-girder considering flange local buckling was evaluated.