• Structural Engineering and Mechanics
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• 제81권6호
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• pp.691-703
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• 2022

To obtain the seismic response of lead-cored rubber, shape memory alloy (SMA)-rubber isolation Plate-shell Integrated Concrete Liquid-Storage Structure (PSICLSS), based on a PSICLSS in a water treatment plant, built a scale experimental model, and a shaking table test was conducted. Discussed the seismic responses of rubber isolation, SMA-rubber isolation PSICLSS. Combined with numerical model analysis, the vibration characteristics of rubber isolation PSICLSS are studied. The results showed that the acceleration, liquid sloshing height, hydrodynamic pressure of rubber and SMA-rubber isolation PSICLSS are amplified when the frequency of seismic excitation is close to the main frequency of the isolation PSICLSS. The earthquake causes a significant leakage of liquid, at the same time, the external liquid sloshing height is significantly higher than internal liquid sloshing height. Numerical analysis showed that the low-frequency acceleration excitation causes a more significant dynamic response of PSICLSS. The sinusoidal excitation with first-order sloshing frequency of internal liquid causes a more significant sloshing height of the internal liquid, but has little effect on the structural principal stresses. The sinusoidal excitation with first-order sloshing frequency of external liquid causes the most enormous structural principal stress, and a more significant external liquid sloshing height. In particular, the principal stress of PSICLSSS with long isolation period will be significantly enlarged. Therefore, the stiffness of the isolation layer should be properly adjusted in the design of rubber and SMA-rubber isolation PSICLSS.

• 한국압력기기공학회 논문집
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• 제15권1호
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• pp.28-32
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• 2019

In nuclear power plant operation and spent fuel canisters, it is necessary to provide a sound technical basis for the safety and security of long-term operation and storage respectively. Recently, the peening technology is being discussed and the technology will be adopted to ASME Section III, Division 1, Subsection NX (2019 Edition). The peening is prohibited in current edition, but it will be approved in 2019 Edition and adopted. However, Surface stress improvement techniques such as the peening is used to mitigate SCC susceptible in operating nuclear plants. Although the peening will be approved to ASME CODE, there are no performance criteria listed in the 2019 edition. The Korean International Working Group (KIWG) formed a new Task Group named "Advanced Surface Stress Improved Technology". The task group will develop a CODE CASE to address PWSCC(Primary Water Stress Corrosion Cracking) and CISCC(Chloride Induced Stress Corrosion Cracking) for new ASME Section III components. TG-ASSIT was started to make peening performance criteria for ASME Section III (new fabrication) applications. The objective of TG-ASSIT is to gain consensus among the relevant Code groups that requirements/mitigation have been met.

• Earthquakes and Structures
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• 제5권2호
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• pp.207-223
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• 2013

Practical seismic assessment and design of retrofit for the multitude of small ecclesiastical monuments that abound in the Balkans is the subject of this work. Application of the proposed procedures and methodologies are illustrated in an example case study, a small byzantine church located in Western Greece, which is the region with the highest seismicity in Europe. The church, known as the Fragavilla Monastery, had remained almost undamaged for 800 years, until 1993 when the Pyrgos earthquake caused critical damage mainly in the vaults. Linear elastic analysis to the recorded ground motion, capped by a biaxial failure criterion reproduced the developed damage. The same modelling and analysis procedure was subsequently used for assessment of the intended retrofitting measures. Proposed retrofitting measures included mitigation of the undesirable implications of past interventions along with a combination of strengthening schemes with externally bonded AFRPs strategically placed in the structure. The effectiveness of the proposed solutions is gauged by successful reduction of stress intensity in the critical regions and mitigation of stress localization throughout the structure.

• Journal of Welding and Joining
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• 제31권3호
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• pp.17-21
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• 2013

Sn whiskers are one of the serious causes of the failure of electronics. Sn whiskers grow spontaneously from Sn-based, lead-free finished surfaces, even at room temperature. A primary factor of these Sn whiskers growth is compressive stress, which enhances the diffusion of Sn or other elements. The sources of compressive stress are the growth of non-uniform large intermetallic compounds along the interface between the Sn grain boundary and Cu substrate. Recent studies revealed the methods for reducing Sn whisker growth. This paper gives an overview about recent researches for mitigation methods of Sn whisker growth during nearly room temperature storage.

• 한국방재학회 논문집
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• 제8권2호
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• pp.39-43
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• 2008

Determination of strain associated with shear modulus and damping ratio during torsional test is complicated. This is due to nonuniform stress-strain variation occurring linearly with radius in a soil specimen in torsion. A conventional equivalent radius approach proposed by Chen and Stokoe appears to be adequate for evaluating strain associated with shear modulus at low to intermediate strain levels. This approach is less accurate for damping measurement, particularly at high strain. Modified equivalent radius approach was used to account for the nonuniform stress-strain effect more precisely. The modified equivalent radius approach was applied for hyperbolic, modified hyperbolic, and Ramberg-Osgood models. The results illustrate the usefulness of the modified equivalent radius approach and suggest that using a single value of equivalent radius ratio to calculate strains is not appropriate.

• 한국항공운항학회지
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• 제26권3호
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• pp.77-86
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• 2018

Stress is the main source of a human error or can potentially contribute to it. Recently, the rate of accidents which is associated with human factors among the total aircraft accidents is showing a tendency of gradual increase. In order to prevent the accidents related to human factors, stress mitigation of the mission personnel is highly required. In this study, a 'stress cognitive alteration' technique, which is one of the stress relief methods, is applied to the Air Force pilots to verify if the technique is effective in reducing stress. The 'stress cognitive alteration' technique is comprised of two parts: a positive function of stress and a process to positively alter the physical, psychological response to stress. As a result of the application, it is found that this technique has an effect of reducing stress of the pilots under a relatively high level of stress.

• 한국군사과학기술학회지
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• 제20권5호
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• pp.608-619
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• 2017

In this paper, the effects of parameters related to the residual stress induced due to laser shock peening process to determine mitigation of the initial tensile residual stresses are discussed, such as the maximum pressure, pressure pulse duration, laser spot size and number of laser shots. In order to estimate the influence of the initial tensile residual stresses, which is generated by welding in 35CD4 50HRC steel alloy, the initial condition option was employed in the finite element code. It is found that $2{\times}HEL$ maximum pressure and a certain range of the pressure pulse duration time can produce maximum mitigation effects near the surface and depth, regardless of the magnitudes of tensile residual stess. But plastically affected depth increase with increasing maximum pressure and pressure pulse duration time. For the laser spot size, maximum compressive residual stresses have almost constant values. But LSP is more effective with increasing the magnitudes of tensile residual stress. For the multiple LSP, magnitudes of compressive residual stresses and plastically affected depths are found to increase with increasing number of laser shots, but the effect is less pronounced for more laser shots. And to conclude, even though the initial tensile residual stresses such as weld residual stress field are existed, LSP is enough to make the surface and depth reinforcement effects.

• 디지털융복합연구
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• 제16권1호
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• pp.371-379
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• 2018

이 연구는 청소년 운동선수들의 부적응적 완벽주의와 스트레스 대처가 만성적 피로에 미치는 상대적인 영향을 분석하는데 그 목적이 있었으며, 청소년 운동선수들 총 254명을 대상으로 부적응적 완벽주의와 스트레스 대처가 만성적 피로에 미치는 영향을 분석한 결과, 부적응적 완벽주의 수준이 높을수록 스트레스 대처의 소극적 대처 요인인 정서 완화적 대처 수준과 소망적 사고 추구 수준, 그리고 만성적 피로 수준이 높은 것으로 나타났다. 부적응적 완벽주의와 스트레스 대처 및 만성적 피로 하위요인들 간에는 유의한 관련성이 있는 것으로 나타났으며, 만성적 피로에 가장 많은 영향을 미치는 요인은 실수에 대한 염려요인이었고 다음으로 수행에 대한 의심과 소망적 사고 추구 및 정서 완화적 대처의 순으로 영향력이 있는 것으로 나타났다. 이 연구의 결과들은 만성적 피로의 대처에서 부적응적 완벽주의와 스트레스 대처에 대해 다루는 것의 중요성을 시사한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.90-95
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• 2004

In this study, we proposed new method to mitigate tensile welding residual stress for preventing PWSCC in CRDM nozzle. Residual stress analysis using finite element method is performed to confirm benefit of the new method. In case of applying existing method, tensile axial residual stress decrease by about 28% and tensile hoop residual stress decrease by about 33%. In case of applying the new method, tensile axial residual stress decrease by about 32% and tensile hoop residual stress decrease by about 43%. Therefore, we conclude the new proposed method is more effective to prevent PWSCC than existing method.

• 한국방재학회 논문집
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• 제7권5호
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• pp.11-18
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• 2007

고인성 섬유보강 시멘트 모르터의 휨피로 거동을 규명하고자 실내실험을 실시하였다. 정적 휨실험과 휨피로 실험을 위해 섬유혼입율에 따라 5개의 시험체와 14개의 시험체를 각각 제작하였다. 휨피로 시험에 앞서서 정적 파괴하중과 응력수준을 결정하기 위하여 정적 휨시험이 실시되었다. 피로응력수준과 섬유혼입율에 따른 휨피로 거동을 분석하였으며 휨피로응력수준과 파괴시 하중반복회수와의 상관관계식을 제안하였다.