• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.880-886
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• 1991

본 연구에서는 이미 크랙전파의 제단계에 있는 평골재의 정유 크랙을 대상으 로, COD를 고정밀도로 측정하는 것을 주된 수단으로하여, 피로한도의 존재유무를 지배 하는 미소크랙의 정유구조를 상세히 밝히고자 한다. 또한 변형시교에 근거한 현상으 로만 알려져온 과소응력효과, coaxing효과를 크랙폐구현상의 관점에서 검토하여, 크랙 정유현상의 본질적인 이해를 얻고자 한다.

• Journal of Welding and Joining
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• v.15 no.3
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• pp.1-11
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• 1997

용접이음부에서는 피로크랙 전파거동이 모재와 다르다는 것은 이미 알려져 있으며 그 원인으로서는 용접부에 있어서의 금속조직의 변화와 잔류응력 등이 일컬어 진다. 금속조직의 변화에 따른 영향에 대하여서는 비교적 그 영향이 작으며 또한 피로 크랙 전파속도에 대해서 안전한 쪽으로 역할을 한다고 보고되어져 있다. 따라서 용접 이음부에 있어서의 피로크랙 전파에 대하여서는 주로 잔류 응력의 영향에 주목하여, 잔류응력이 피로크랙의 전파속도에 어떻게 영향을 미치는가를 파악하여야 한다. 이러 한 관점에서 지금까지 용접잔류응력장을 전파하는 피로크랙을 대상으로 하여 잔류응력 이 피로크랙 전파에 미치는 영향을 정량적으로 평가하고자 하느 시도가 많은 연구진에 의해 수행되어 왔다. 표1에 이러한 연구의 흐름을 평가방법과 평가에 고려된 사항을 중심으로 나타내었다. 이러한 배경으로부터, 본고에서는 피로크랙 전파거동에 미치는 잔류응력의 영향에 대해서 지금까지 수행된 연구의 내용을 연구 발전형태에 주목하여 검토하였다.

• Elastomers and Composites
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• v.33 no.5
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• pp.335-344
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• 1998

In this study, the tearing energy and the rate of crack propagation of natural rubber (NR) compounds were evaluated to improve the crack resistance of tank-track pads. Although the factors affecting the crack resistance properties of NR compounds are various in this experiment, the effects of filler(carbon black) and the crosslinking system were evaluated. When the amount of accelerator is equal to that of sulfur( eg. efficient vulcanization), the compound shows the most excellent in the aged mechanical properties and the crack resistance properties. The ISAF carbon black(CB) having a good reinforcing characteristics was better than any other CB grades in physical properties and processablity. The optimum content was 50phr.

• Korean Journal of Construction Engineering and Management
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• v.8 no.5
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• pp.80-91
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• 2007

Crack in Pavements have been continually increased a by water penetration Therefore, the cracks can result in deterioration of the pavements that could be extremely dangerous fro road users. Creak sealing work performed in outdoor is very dangerous, costly and labor intensive. To slove these problems, automated crack sealing systems have been developed. it Would be needed that work information related to crack sealing must be gathered in an effort to used for existing or future crack sealing work. Furthermore, work information related to crack sealing could be utilized in analyzing work productivity and condition. The primary objective of this study is to propose a PDA and Web-based system for work information management of crack sealing which enables to effectively interchange work information between head office and fields, and to accurately collect work information. Finally, it is anticipated that the effective use of the developed PDA and web-based system would be able to effectively share work Information, measure productivity, estimate costs as well as plan future work schedule.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1493-1502
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• 1992

The purpose of this study is to identify the effects of loading variables on fatigue crack opening behavior, using structural steel SS41. To use various stress ratios, three kinds of the methods varying stress ratio were used; .DELTA.P const., P$_{max}$ const., and P$_{min}$ const.. To measure the opening load, the direct measuring method which measures the distance between two micro indentations 20 .mu.m behind crack tip and the elastic compliance method were used. As the results of present study, the following conclusions are obtained. First, using the direct measuring method, it was possible to measure the COD at any location behind crack tip. Second, as measuring point becomes farther from crack tip, opening load becomes smaller. Third, the acceleration of da/dN near notch is due to crack opening behavior. Finally, opening ratio is a function of not only R, but .DELTA.K.K.K.

• Journal of the KSME
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• v.28 no.2
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• pp.177-180
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• 1988

파괴안전설계를 하기 위하여 파괴역학원칙을 성공적으로 적용시키기 위해서는 주로 믿을 수 있는 크랙성장을 예측하는데 달려있다. 일정크기의 피로하중을 받는 구조물 구성요소의 경우 안전계수로 빈도수와 환경의 영향을 설명할 수 있다면 경험적인 데이터를 바탕으로 하여 그 피로거동은 상당히 쉽게 예상될 수 있다. 그러나 구조물 구성요소가 변화크기의 피로하중을 받는다면, 크랙성장예측을 위한 데이터를 마련하는데는 무엇보다도 그러한 변화크기의 피로하 중상태의 적용모델이 확실히 필요하며, 일어날 수 있는 여러 가지 상황들을 통합할 수 있는 모 델에 입각하여야 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.709-711
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• 2003

위성기술의 발달로 대규모의 고해상도 지형정보 생성이 가속화되고, 사실적 지형묘사 요구는 더욱 높아지고 있으므로 대규모 지형자료를 효율적으로 처리하여 실제감(realism)을 주는 실시간 렌더링 기법이 필수적이다. 본 연구에서는 지형 셀의 쿼드트리 구조를 기반으로 시각 거슬림 현상을 최소화하기 위한 연속적인 다단계 상세도 기법 및 기하모핑 기법을 적용할 때 발생할 수 있는 기하모핑 크랙을 제거하기 위한 확장된 기법을 제안한다.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.76-82
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• 2002

In this study, the rotary bending fatigue test was carried out with low carbon steel(SM25C). The specimens were heat-treated in order to change the grain size, and investigated items are fatigue limit, small crack initiation, fatigue crack propagation behavior and possibility of fatigue life prediction according to the different grain size. The summarized result are as follows ; Fatigue limit of the smooth specimen was dependent upon the grain size. The fatigue crack initiation of the small grain size specimen was delayed more than that of the large grain size specimen. And the small cracks of small grain size specimen were distributed in the narrow region of the main crack circumference contrary to the large grain size specimen. The main crack was grown along the grain boundary having co-alliance with small cracks. The experiment material has quantitatively disclosed the possibility of fatigue life prediction because the fatigue crack propagation behavior is dependent upon the grain size.

• Korean Journal of Food Science and Technology
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• v.20 no.4
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• pp.553-557
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• 1988

To investigate the effect of storage humidity on the textural characteristics of crackers, their crispness and tenderness were measured by sensory and instrumental methods. Domestic cracker samples stored for 1 and 3 weeks at 4 different relative humidities of 23, 31, 51 and 79% showed the decrease in crispness intensity as the humidity increased while storage period did not affect their textural characteristics. When domestic and imported cracker samples were stored for 1 and 3 weeks at relative humidities of 31% and 79%, there was no significant difference in their textural characteristics.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.328-336
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• 2004

This paper describes the effect of loading rate, specimen geometries and material properties for ModeⅠ and Mode Ⅱ interlaminar fracture toughness of hybrid composite by using double cantilever beam (DCB) and end notched flexure (ENF) specimen. In the range of loading rate 0.2~20mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate (Gc).The value of Gc for variation of initial crack length are nearly similar values when material properties are CF/CF and GF/GF, however, the value of Gc are highest with the increasing intial crack length at CF/GF. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF.