• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.173-177
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• 1995

Thermal cracks ard occured when thermal stress due to the hydration of cement exceeds the tensile strength of concrete. Since cracking causes poor durability of concrete, the effect of thermal cracking should be included for the desing and construction of massive concrete structures. In this study, an experiments are performed for the investigation of time dependent temperature and thermal stress of massive concrete structure at early ages. In order to measure temperatures and thermal stresses, concrete stress meter, embedded strain meter, non-stress meter, and thermocouples are used. Based on the analyses of measured thermal stress data, measured values by concrete stress meter are more reliable than those by embedded strain meter and non-stress meter, And measured values by concrete stress meter are compared with the calculated values by FEM program developed by DICT (DWTS2D). Calculated values by DWTS2D show good agreement with measured values.

• Corrosion Science and Technology
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• 제6권1호
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• pp.33-35
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• 2007

Welding technology plays an important role in the fabrication of structure, and this has led to an increasing attention in the use of high quality advanced welding technology such as power beam welding, friction stir welding, and laser-arc hybrid welding, etc. At the same time, welding can influence various factors in the performance of plant and equipment, and corrosion behaviour of weldment has been one of the major issues for both welding and corrosion research engineers. The aim of this paper is to give a short survey of the recent technical trends of welding and corrosion behaviours including the electrochemical corrosion, stress corrosion cracking, and corrosion fatigue in connection with the welding materials, welding process, and welding fabrication.

• 비파괴검사학회지
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• 제10권1호
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• pp.38-46
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• 1990

It is difficult to detect such flaws as stress - corrosion cracking or corrosion wastage(loss of bolt diameter) in the threads. In many cases the critical size of a flaw is very small(1-2 mm order). This paper describes how it is possible to discriminate small flaw indications in threads using the time difference or thread signals(TDTS) by a signal-conditioning technique.

• 대한기계학회논문집
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• 제17권8호
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• pp.2033-2042
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• 1993

In conventional SCC susceptibility test, there are constant strain test, constant load test, slow strain rate test(SSRT) and K$_{ISCC}$ test. Among them, the SSRT method is much more aggressive in producing SCC than the other tests, so that the test time of it is considerably reduced. But this SSRT method has mostly been worked using the uniaxial tensile specimen untill now. Therefore, the SSRT method using the tensile specimen(Ten-SSRT) has much difficulty in SCC susceptibility evaluation of a localized region like weldment and the advantage material of high order. Recentely, the small punch(SP) test method using miniaturized small specimen is the very effective test method for fracture strength evaluation of a localized region like weldment and fusion reactor wall irradiated in the nuclear power plant. This paper investigated the possibility of SCC susceptibility evaluation by the SP-SSRT method using the miniaturized small specimen. Therefore, we obtained the result that the SP-SSRT had the possibility for the evaluations of SCC susceptibility for shorter time to corrosive environment compare to Ten-SSRT which was conventional method.

• 대한토목학회논문집
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• 제14권1호
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• pp.1-12
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• 1994

본 논문은 철근콘크리트와 프리스트레스트 콘크리트 보의 시간의존적 거동해석에 관한 내용으로 재령-보정 유효 탄생계수법에 토대를 두고 단면 내 힘의 평형관계와 변형의 Compatibility 조건을 사용한 반복해석을 통해 부재의 거동을 파악하였다. 콘크리트의 전 단면이 유효하고 부재가 선형 탄생체로 거동하며 강재의 효과는 단지 환산단면적 개념에 따라 해석시 강성만으로 보정되는 기존의 해석방법과는 달리 모든 재료가 고유의 성질을 유지할 수 있도록 함께 고려하며 균열의 영향도 동시에 고려함으로써 모든 하중조건에서 보다 정확한 결과를 얻을 수 있도록 하였다. 특히 예제해석을 통해 시간에 따른 각 재료의 응력 재분배, 장기처짐의 발생 등 시간의존적 거동에 영향을 미치는 여러 인자의 비교 검토와 균열의 영향분석을 하였으며 설계시 보다 정확하고 합리적으로 이들의 효과를 고려할 수 있도록 하였다.

• Journal of Welding and Joining
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• 제14권6호
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• pp.48-57
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• 1996

The weldability of high purity aluminum-lithium binary alloys has been investigated using the Varestraint test. Autogenous GTAW (gas-tungsten-arc-welds) were run along specimens of different lithium concentration using three sets of welding parameters. Welding voltage was held constant at 10 volts. Welding current (70∼100 amps) and travel speed (23∼33 cm/min) were the parameter varied. Hot-tearing susceptibility varied with lithium content and exhibited a steep peak at 2.6 weight percent lithium. Depth of penetration increased with increasing heat input and lithium concentration. The susceptibility is influenced by the wettability of dendrites by the interdendritic eutectic liquid as well as the time available for back-Siting by eutectic liquid. The welding condition of welding current 70A and travel speed 23 cm/min was showed good resistance to cracking in aluminum-lithium alloys. Suggestions for improving weld cracking resistance are also provided.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.77-82
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• 2004

노후선박의 구조적 안전성을 확보하기 위해서는 부식이나 피로균열 및 기계적인 손상에 의하여 선체 구조 강도가 어떠한 영향을 받는지 충분히 검토하여 적절한 수리 보수 등 이에 대한 대책을 강구할 필요가 있다. 본 연구에서는 이러한 관점에서 부식, 피로균열, 기계적인 손상과 같은 노후 선박에 발생할 수 있는 여러 가지 손상이 선체강도에 미치는 영향을 이론적, 수치적, 실험적인 방법을 통하여 조사하고, 이를 통하여 선각거더의 소성붕괴강도 저하를 고려한 신뢰성 평가법 및 보수, 수리를 통한 인정수준 이상의 선각강도를 유지하게 하는 지침도 연구하였다.

• Corrosion Science and Technology
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• 제2권3호
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• pp.135-140
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• 2003

The effect of temperature on stress corrosion cracking o f Al-brass used in vessel heat exchanger tube was studied in 3.5% NaCI + 0.1% $NH_4OH$ solution. The SCC test using a CDT(constant displacement test) and the specimens using a SEN(single edge notched) specimens. For setting the environment similar to working environment of a heat exchanger, the specimens was immersed in solution and solution flow onto the specimens were performed. The results are as follows : The latent time of stress corrosion crack occurrence gets shorter, as the temperature gets higher. Dezincification phase showed around the crack occupy wider range, as the temperature gets higher. Zn composition falls under 4% at the dezincifiction area.

• Advances in concrete construction
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• 제3권1호
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• pp.39-54
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• 2015

Relative humidity and strains within a massive concrete cylinder (${\varphi}450mm{\times}900mm$) in the drying and the re-saturating process were measured for elucidating the process of ASR surface cracking in concrete. The expansion behavior of mortars in dry atmospheres with various R.H. values and the resaturating process was revealed. Non- or less-expansive layers were formed in near-surface regions in the concrete cylinder in the drying process, but ASR expansions actively progressed in inner portions. After resaturating, R.H. values of near-surface regions rapidly increased with time, but expansions in the regions were found to be very small. However, in the middle portions, of which R.H. values were kept 80% ~ 90% R.H. in the drying process, expansion actively progressed, resulting in further development of surface cracks in the re-saturating process.

• 콘크리트학회논문집
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• 제11권4호
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• pp.3-11
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• 1999

The creep characteristics of concrete under tensile stress has been usually assumed to have the same characteristics as that under compressive stress in the time-dependent analysis of concrete structures. However, it appears from the recent experimental studies that tensile creep behavior is much different from compressive one. In particular, high sustaining tensile stress may cause time-dependent cracking and thus lead to tensile failure. It is, therefore, necessary to model the tensile creep behavior accurately for realistic time-dependent analysis of concrete structures. The present paper to have been focused to suggested more realistic model for the tensile creep behavior of concrete. The models are compared with tensile creep test data available in the literature. The proposed model may allow more refined analysis of concrete structures under time-dependent loading.