• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.14-21
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• 2021

Inner shell material of LNG storage tanks that store ultra-low temperature LNG at -162℃ requires structural integrity assessment of a crack-like defect. From the viewpoint of conventional fracture mechanics, the assessment has mainly performed by single parameter using stress intensity factor K, J-integral and CTOD. However, the stresses in a material of crack tip are not unique caused by constraint loss due to size and geometry of the structure. Various attempts have been made to complement a single parameter fracture mechanics, typically with Q-stress. In this paper, we have performed a two-parameter approach by deriving the Q-stress coupling with J-integral suitable for the evaluation of the crack tip stress field in the non-linear elastic region. A quantitative evaluation of the constraint effect has performed by using the J-Q approach. It was evaluated that the SENB type specimen had a crack ratio of 0.1 to 0.7 and the wide type specimen had a crack ratio of 0.2 to 0.6.

• Journal of the Korean Society of Safety
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• v.31 no.4
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• pp.9-14
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• 2016

STS304L of membrane structure has been used for a LNG storage tank and has exposed long time under the cryogenic temperature. The purposes of this study are to evaluate the mechanical properties of base and used materials for STS304L of membrane. The tensile and high cycle fatigue tests were investigated for STS304L of membrane used over 20 years at room temperature and $-162^{\circ}C$. In addition, the test of base STS304L was performed in order to compare with used material properties. The chemical composition and phase change were investigated from EDS and XRD. From results of tensile test, yield and ultimate tensile strengths of used STS304L are smaller than those of base STS304L. S-N curves were obtained from fatigue tests at both temperatures. Also, P-S-N curves were presented with statistical method recommend by JSME-S002. Fractography was conducted for analysis of fracture mechanisms.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.918-922
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• 2015

As international environmental regulations for pollutant and greenhouse gas emissions discharged from ships are being reinforced, it is drawing attention to use LNG as ship fuel. This paper compares the explosion risk potential in the LNG fuel gas supply systems of two types used in marine LNG fuelled vessels. By selecting 8500 TEU class container ships as target, LNG storage tank was designed and pressure conditions were assumed for the use of each fuel supply type. The leak hole sizes were divided into three categories, and the leak frequencies for each category were estimated. The sizes of the representative leak holes and release rates were estimated. The release rate and the leak frequency showed an inverse relationship. The pump type fuel gas supply system showed high leak frequency, and the pressure type fuel gas supply system showed high release rate. Computational fluid dynamics simulation was applied to perform a comparative analysis of the explosion risk potential of each fuel supply system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.333-340
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• 2019

Tests using a middle velocity propulsion impact machine (MVPIM) were performed to verify the impact resistance capability of sandwich concrete panels (SCP) in a modular liquefied natural gas (LNG) outer tank, and numerical models were constructed and analyzed. $2{\times}2m$ specimens with plain sectional characteristics and specimens including a joint section were used. A 51 kg missile was accelerated above 45 m/s and impacted to have the design code kinetic energy. Impact tests were performed twice according to the design code and once for the doubled impact speed. The numerical models for simulating impact behaviors were created by LS-DYNA. The external steel plate and filled concrete of the panel were modeled as solid elements, the studs as beam elements, and the steel plates as elasto-plastic material with fractures; the CSCM material model was used for concrete. The front plate deformations demonstrated good agreement with those of other tests. However the rear plate deformations were less. In the doubled speed test for the plain section specimen, the missile punctured both plates; however, the front plate was only fractured in the numerical analysis. The impact energy of the missile was transferred to the filled concrete in the numerical analysis.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.51-54
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• 2001

지진 등과 같은 외부 진동하중에 의해 발생되는 구조물의 진동은 구조물의 독립적 거동뿐만 아니라 지반과 구조물 기초의 접촉면을 통해 상호 영향을 미치게 된다. 특히 LNG 저장탱크나 원자력발전소 등과 같이 대현 상부구조물의 경우 상호작용력은 크게 작용하게 된다. 본 연구에서는 상부 구조계의 단순화된 형태인 기초계의 동적거동을 파악하기 위해 주파수영역 경계요소법을 사용하여 수치적으로 연구하였다. 반무한체 상에 존재하는 무질량 강체 표면기초에 대해 반무한 기본해를 이용하여 동적거동이 고찰되었으며 기존의 해석결과와 비교, 검토하여 본 연구방법의 타당함을 입증하였다.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.2
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• pp.98-107
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• 1985

In this thesis, the Sol-Air temperature distribution for the side-wall of a cylindrical cryogenic storage tank made of nonhomogenious composite layer was studied, in order to calculate the thermal load by Newton's cooling law, when the solar radiation was applied upon the side wall. In the analysis, the atmospheric slab was assumed to be horizontal and infinitely large, and the Sol -Air temperature, which was found by the Net- Radiation method considering the longwave radiation wi th surroundings, was used for boundary condition. Energy equation and boundary conditions were normalized by the defined reference- temperature, and solved. The solutions were developed by the Fourier cosine series. Then, the Sol-Air temperature distribution for the side-wall of LNG storage tank was calculated.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.307-313
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• 2016

When liquefied natural gas (LNG) is stored in a tank, it is necessary to maintain low temperature. It is very important that insulation techniques are applied to the LNG cargo because of this extreme environment. Hence, laminated wood, especially plywood, is widely used as the structural member and insulation material in LNG cargo containment systems (CCS). However, fracture of plywood has been reported recently, owing to sloshing effect. Therefore, it is necessary to increase the strength of the structural member for solving the problem. In this study, compressed wood, which is used as a support in LNG independent type B tanks, was considered as a substitute for plywood. Compression and bending tests were performed on compressed wood under ambient and cryogenic temperatures to estimate the mechanical behaviors and fracture characteristics. In addition, the direction normal to the laminates surface was considered as an experimental variable. Finally, the feasibility of using compressed wood for an LNG CCS was evaluated from the test results.

• Journal of the Korean Institute of Gas
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• v.6 no.4 s.18
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• pp.23-32
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• 2002

The purpose of the present study is to analyze the response of Gas Utility subjected to Earthquake and to discuss the failure prediction of Kogas Storage Tank. Initially here, characteristics of Earthquake are reviewed and then earthquake-resistance Design is investigated based on previous earthquake hazard cases. Next, considering the distribution of the transverse permanent ground displacement and equivalent spring constant effect, formulae obtained by a beam theory are established to analyze PeungTak Center Control Room. This analysis was performed without consideration of axial effects. So the finite element analysis was used in order to consider the axial stiffness of Structure.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.49-49
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• 2009

마찰교반접합법은 특정한 회전수로 회전하는 용접 툴을 이용하여 접합하고자 하는 피접합재의 맞댄면에 삽입시킨 후 툴을 이동시키거나 혹은 시편을 견고하게 고정시킨 장치(backing plate)가 움직여 고상 상태에서 접합이 이루어진다. 알루미늄, 마그네슘 등 비교적 융점이 낮은 저융점 재료의 재료에 처음 적용이 되어 많은 연구가 활발히 진행되었고 타 용접방법에 비해 우수한 접합특성을 나타내었다. 최근 이러한 마찰교반접합은 이러한 저융점 재료를 넘어서 스틸, 타이타늄, 니켈 등과 같은 고융점 재료 등에 대한 적용이 늘어나고 있다. 마찰교반접합을 이용하여 이러한 고융점 재료의 접합 경우 내마모성 및 내열성 등의 내구성이 갖추어진 툴과 이러한 툴을 냉각시킬 수 있는 냉각 장치 등이 필요로 하나 경제적 측면이나 접합부의 우수한 특성 등을 고려 할 때 그 적용 및 발전 가능성이 매우 높다고 볼 수 있다. 최근 무공해 연료로 각광받고 있는 액화천연가스 (LNG)의 수요가 급증함에 따라 LNG 저장탱크 소재로 널리 사용되고 있는 9% Ni강의 수요 또한 증가하고 있는 상황이다. 하지만 9% Ni 강은 극저온용 소재로 용접부의 저온인성 ($-196^{\circ}C$)이 가장 중요하기 때문에 저온인성을 확보하고자 Inconel 계나 Hastelloy계 등의 니켈 기 합금을 용접재료로 사용하고 있으나 이러한 용접재료는 가격이 매우 고가이며 또한 용접 후 용접부의 강도가 낮다는 문제가 제기되고 있다. 또한 LNG 탱크 제작시 사용되는 용접법은 GTAW, SAW 및 SMAW 이지만 국내에서는 주로 SMAW에 의존하고 있는 실정인 관계로 보다 더 경제적인 용접 프로세스의 적용 가능성이 검토되고 있는 상황이다. 본 연구에서는 마찰교반용접을 이용하여 두께 4mm의 9% Ni 강에 대해 맞대기 마찰교반접합을 실시하였다. 툴 회전 속도 및 접합 속도를 고정한 상태에서 접합을 실시 하였으며 접합 시 툴은 $Si_3N_4$로 제작된 툴을 사용하였다. 접합 후 외관상태 점검, 미세조직 관찰, 경도, 인장 강도 및 저은 충격 측정 등의 실험을 실시하였고, 이러한 결과를 이용하여 미세조직과 기계적 특성과의 관련성을 조사하였다.

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.86-93
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• 2018

Recently, the use of composite steel plate concrete structural modules filled with concrete between steel plates of complex internal structure, in which a large amount of studs are installed, is increasing in order to reduce the weight and to increase workability of structures such as LNG storage tanks. However, in Korea, there is no systematic criterion for evaluating the construction performance of composite steel plate concrete structural modules. Therefore, in this study, we propose a filling guideline of concrete for composite steel plate structural module. For this purpose, high filling performance concrete with general strength range was formulated and tested for filling ability and permeability for each formulation. Rheology analysis was performed to quantitatively evaluate the flow characteristics of concrete. The reliability of $T_{500}$ and plastic viscosity was evaluated to reflect the results of each test, and a guideline for high filling concrete satisfying the reliability of 0.9 or more was derived by reflecting the results of the study on the relationship between the $T_{500}$ and plastic viscosity. Through final fill-box test, filling performance was verified and guidelines were suggested.