• Journal of Ship and Ocean Technology
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• 제3권4호
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• pp.35-51
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• 1999

Fatigue strength assessment procedures have been implemented in the ship design rules by many classification societies. However, a large variation tin the details of the different approaches exists in practically all aspects influding load history assessment, stress evaluation and fatigue strength assessment. In order to assess the influences of thesd variations on the prediction of fatigue lives. a comparative study is organized by the ISSC Committee III.2 Fatigue and Fracture. A pad detail on the top of longitudinal hatch coaming of a panamax container vessel is selected for fatigue calculation. The work described in this paper is one set of results of this comparative study in which the ABS dynamics approach is applied. Through this analysis the following conclusions can be drawn. (1) With the original ABS approach, the fatigue life of this pad detail is very low, only 2.398 years. (2) The treatment of the stillwater bending moment in the ABS approach might be a source of conservatism. If the influence of stillwater bending moment is ignored, then the fatigue life for this pad detail is 7.036 years. (3) The difference between the nominal stress approach and the hot spot stress approach for this pad detail is about 26%.

• 한국공작기계학회논문집
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• 제15권3호
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• pp.120-126
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• 2006

In this paper, we investigated the characteristics of fatigue fracture on TB(Tailored Blank) weldment by comparing the fatigue crack propagation characteristics of base metal with those of TB welded sheet used for vehicle body panels. We also investigated the influence of center crack on the fatigue characteristic of laser weld sheet of same thickness. We conducted an experiment on fatigue crack propagation on the base metal specimen of 1.2mm thickness of cold-rolled metal sheet(SPCSD) and 2.0mm thickness of hot-rolled metal sheet(SAPH440) and 1.2+2.0mm TB specimen. We also made an experiment on fatigue crack propagation on 2.0+2.0mm and 1.2+1.2mm thickness TB specimen which had center crack. The characteristics of fatigue crack growth on the base metal were different from those on 1.2+2.0mm thickness TB specimen. The fatigue crack growth rate of the TB welded specimens is slower in low stress intensity factor range$({\Delta}K)$ region and faster in high ${\Delta}K$ region than that of the base metal specimens.

• 한국해양공학회지
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• 제15권3호
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• pp.100-106
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• 2001

In this study, CT specimens were prepared from Pressure Vessel Steel which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$, -3$0^{\circ}C$, -6$0^{\circ}C$, -10$0^{\circ}C$ and -12$0^{\circ}C$ and in the range of stress ratio of 0.05 and 0.3 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ${\Delta}K_{th}$ in the early stage of fatigue crack growth (Region I) and stress intensity factor range ${\Delta}K$ in the stable of fatigue crack growth (Region II) was increased in proportion to descent temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da/dN $-{\Delta}K$ in Region II, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It was assumed that the fatigue crack growth rate da/dN in proportion to descending temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.320-325
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• 2001

In this study, CT specimen were prepared from Pressure Vessel Steel which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$, -3$0^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, -10$0^{\circ}C$ and -12$0^{\circ}C$ and in the range of stress ratio of 0.05 and 0.3 by means of opening mode displacement. At the constant street ratio, the threshold stress intensity factor range ΔK$_{th}$ in the early stage of fatigue crack growth(Region I) and stress intensity factor range ΔK in the stable of fatigue crack growth(Region II) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm do/dN -ΔK in RegionII, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It was assumed that the fatigue crack growth rate do/dN is rapid in proportion to descending temperature in Region IIand the cryogenic-brittleness greatly affect a material with decreasing temperature.e.greatly affect a material with decreasing temperature.

• 한국생산제조학회지
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• 제21권2호
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• pp.290-296
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• 2012

Cold-rolled carbon steel sheets are commonly used in railroad car or commercial vehicles such as the automobile. These are mainly fabricated by spot welding which is a kind of electric resistance welding. But fatigue strength of spot welding joint is lower than that of base metal due to high stress concentration at nugget edge of the spot welded part. And fatigue strength of them is especially influenced by not only geometrical and mechanical factors but also welding conditions of the spot welded joint. So for fatigue design of gas welded joints such as TS-type joints, it is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of spot welded joints. And also, the influence of the geometrical parameters of spot welded joints on stress distribution and fatigue strength must be evaluated. And analysis approach for fatigue test using design of experiment are evaluated optimum factor in TS-type welded joint and geometrical parameters of materials. Using these results, that factors applied to fundamental information for automation of fatigue design.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.231-237
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• 2000

A15052/AFRP laminates were developed principally to obtain a material with good fatigue strength, in which possible cracks would grow very slowly. Weight savings of more than 30% should be attainable in practice. Also, the crack bridging fibers could still was carry a significant part of the load over the crack, thus the COD and stress intensity factor was reduced at the crack tip. A15052/ AFRP laminates consists of three thin sheets of 5052-H34 aluminum alloy and two layers of [0] unidirectional aramid fiber prepreg. The cyclic-bending moment test was investigated based on applying the five kinds of bending moments. The size of the delamination zone produced between 5052-H34 aluminum alloy sheets and fiber-adhesive layers was measured from ultrasonic C-scan pictures taken around the fatigue crack. In addition, the relationship between the cyclic-bending moment and the delamination zone size was studied and the effect of fiber bridging mechanism was also considered.

• 한국해양공학회지
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• 제7권2호
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• pp.173-181
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• 1993

This work has been investigated the ralationship between single surface crack length and crack depth have influence on the fatigue life. The simulation based on experimental results of 2.25 Cr-1Mo steel at various crack configuration ratios has enabled successful prediction of fatigue life at room temperature. The effect of crack depth should be considered for predicting fatigue crack growth rates as well as that of surface crack length. It is also shwn that the crack growth mechanisms are in good agreement with expreimental data according to the interaction of crack length and crack depth.

• 경영과정보연구
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• 제32권2호
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• pp.83-106
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• 2013

본 연구는 컨버전스 제품의 대표격인 스마트폰을 대상으로 해당 스마트폰에서 광고의 양, 하드웨어 다양성, 소프트웨어의 다양성 등이 스마트폰에 대한 유용성 지각과 복잡성 지각에 동시에 영향을 줄 수 있고 복잡성은 기능적 피로에 영향을 미칠 수 있다는 것을 검증하려고 하였다. 먼저, 소비자가 모바일 광고를 과다하다고 느낄수록 스마트폰의 유용성을 낮추고 복잡성을 높인다는 것은 검증되지 못하였지만 하드웨어의 다양성은 유용성을 높이고 복잡성을 높게 지각하게 만들 것이라는 가설은 강하게 지지되었다. 몇번 논의되었듯이 컨버전스의 가장 기본은 상당히 많은 하드웨어의 통합이다. 결국, 많은 하드웨어는 스마트폰의 효용가치를 높이는 중요한 원인이 되기도 하지만 동시에 복잡성을 높여 소비자에게 스마트폰을 이용하는데서 피로를 유발하는 원인으로 작용할 수도 있다는 결론이다. 소프트웨어의 다양성은 유용성을 높게 지각하게 만드는 요소이기는 하나 복잡성에는 별다른 영향을 미치지 못하는 것으로 나타났다. 유용한 모바일 앱을 많이 제공하는 것은 역시 하나의 매력적인 요소로 작용할 수 있다고 결론지었다. 마지막으로 복잡성은 기능적 피로를 높게 지각하는데 영향을 미치는 중요한 요인으로 밝혀졌으며 결국, 이는 무조건 많다고 좋은 것이 아니라 최적의 컨버전스 조합을 찾는 것이 바람직하다는 시사점을 제시할 수 있다.

• 한국컴퓨터정보학회논문지
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• 제27권9호
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• pp.235-242
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• 2022

지난 10여 년간 프라이버시 문헌에서 중요한 연구흐름들 중의 하나는 자기노출과 관련한 의사결정 과정인 비용-혜택 분석에 영향을 미치는 요인들을 발견하는 것이었다. 그러나 인간의 행동은 인지적 요인뿐만 아니라 정서적 요인에 의해서도 크게 영향을 받음에도 불구하고, 기존 연구에서 발견된 요인들 대부분은 인지적 속성을 갖는 요인들이었다. 본 연구는 이러한 불균형적 상황에 대한 인식을 토대로 자기노출 의사결정에 영향을 미치는 정서적 요인으로서 SNS 즐거움과 SNS 피로감의 역할을 검토한다. 데이터 분석결과, 자기노출 의사결정에 대한 이러한 정서적 요인들의 영향이 적지 않고, 또한 SNS 피로감 보다 SNS 즐거움의 영향 정도가 크다는 사실을 발견하였다. 정서적 요인들과 의사결정 요인들 사이의 관련성은 일치효과 메커니즘에 의해서 긍정적 정서는 긍정적 평가요인에만(혜택요인), 부정적 정서는 부정적 평가요인에만(비용요인) 차별적으로 영향을 미치는 것으로 나타났다. 본 연구는 이러한 분석결과를 토대로 향후 연구를 위한 의미있는 시사점들을 논의한다.

• 한국해양공학회지
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• 제9권2호
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• pp.141-148
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• 1995

Fatigue tests were carried out by a rotary bending testing machine of cantilever type. M.E.F.(ferrite encapsulated islands of martensite) materials were made by a series of heat treatment from a low carbon steel(SM 20 C). The fatigue tests were conducted at stress levels of 302 MPa and with frequencies of 25Hz, 2.5 Hz and 0.5 Hz in 3% NaCl solution. The fatigue strength increased with frequency got higher. The microcracks and corrosion pits were generated at the boundary between the matrix and the 2nd phase. The cracks generated by the corrosion pits were coalesced with the pits around the notch and became the initial crack. The $N_i/N_f$ ratio increased as the frequency and stress level decreased. The interference phenomenon increased with stress level and frequency gots higher. The crack propagation rate was delayed as the stress level lowers and the frequency gets higher, however, the range of the stress intensity factor depended only on a stress level.