In Part I of this paper, six liquid nitrogen (LN₂) pool boiling tests were carried out to locally cool down six different EH36 steel plates to cryogenic temperatures. Leindenfrost and Critical Heat Flux (CHF) points of LN₂ boiling curve were estimated. These estimations together with the recorded temperature histories are used in this part for the development of a heat flux curve for EH36 steel-LN₂ pool boiling through Finite Element Thermal Analysis (FETA) of the problem investigated experimentally in Part I. Thermal conductivity and heat capacity of EH36 are defined by two unprecedented temperature functions based upon experimental studies in cryogenic temperatures. A user subroutine written in FORTRAN defines the air convection coefficient as a function of surface-air temperature difference, which changes with time and location. Results of this study contribute to the Accidental Limit State (ALS) design of marine and offshore structures for liquified gas spill scenarios.

Subsea power cables are subjected to various external loads induced by environmental and mechanical factors during manufacturing, shipping, and installation. Therefore, the prediction of the structural strength is essential. In this study, experimental and theoretical analyses were performed to investigate the axial stiffness of subsea power cables. A uniaxial tensile test of a 6.5 m three-core AC inter-array subsea power cable was carried out using a 10 MN hydraulic actuator. In addition, the resultant force was measured as a function of displacement. The theoretical model proposed by Witz and Tan (1992) was used to numerically predict the axial stiffness of the specimen. The Newton–Raphson method was employed to solve the governing equation in the theoretical analysis. A comparison of the experimental and theoretical results for axial stiffness revealed satisfactory agreement. In addition, the predicted axial stiffness was linear notwithstanding the nonlinear geometry of the subsea power cable or the nonlinearity of the governing equation. The feasibility of both experimental and theoretical framework for predicting the axial stiffness of subsea power cables was validated. Nevertheless, the need for further numerical study using the finite element method to validate the framework is acknowledged.

An accurate prediction of the ultimate strength of lashing devices and deck structures is important to ensure the safety of the crews and carrying ships. In this study, finite element analysis using ABAQUS/implicit was performed to investigate the ultimate strength of D-ring devices subjected to various external loads. The resistance of deck plates to which the D-ring devices were clamped was also analyzed numerically, considering the effects of the plate thickness and corrosion wastage. The resultant force-displacement relationship of the devices and the deck plate was investigated from the simulations and the threshold was determined by means of the tangent interaction method. The numerical results were compared with the Cargo Stowage and Securing Code proposed by the International Marine Organization and the results showed that the code predicts conservative ultimate strength of the D-ring devices in most cases. The deck plate with a thickness of 6 mm should have a local stiffener to increase structural strength whereas corrosion wastage has negligible effect on the deck strength. The numerical analysis verified the feasibility of predicting the ultimate strength of D-ring devices and deck structures. Nevertheless, the need for further experimental study is acknowledged to validate the feasibility of the numerical results.

The effectiveness of a ductile fracture model in accurately predicting fracture initiation has been demonstrated. In this study, we concentrate on applying the ductile fracture model to pre-cracked structures constructed from SUS304L stainless steel with experimental and numerical analyses. The Swift hardening law was employed to extend the plastic behavior beyond the onset of necking. Additionally, the Hosford–Coulomb model, integrated with a damaged framework, was utilized to predict ductile fracture behavior, particularly under non-proportional loading conditions. Tension tests were conducted on various specimens designed to illustrate various fracture modes resulting from geometric effects. Numerical analyses were conducted to explore the loading histories, utilizing an optimization process to calibrate fracture model parameters. The proposed fracture model is validated against pre-cracked structures detailed in a reference paper. The results convincingly demonstrate that the fracture model effectively predicts both fracture initiation and propagation in pre-cracked structures.

서 론 지난 수십 년 동안 지구 온난화는 북극항로(Northern sea route, NSR)에서의 선박 운송 및 석유, 가스와 같은 에너지 자원 의 추출 등 북극 활동의 상당한 증가를 야기했다. 북극 지역을 덮고 있는 빙(Ice)의 감소로 수에즈 운하 대신 북극항로를 이용 하면서 상당한 경제적 이점을 얻을 수 있다. 하지만 북극항로를 이용하는 선박 및 해양 구조물은 극한 환경 조건, 특히 영하의 기온과 빙 충돌의 위험에 노출된다. 일반적으로 북극해의 평균 온도는 여름철 10℃, 겨울철-40℃, 기록된 가장 낮은 온도는-68℃로 알려져 있다