• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.11
• /
• pp.6440-6445
• /
• 2014

In steel structures, including ships and offshore structures, defects induced during construction or in use causes cracks and damages. Calculation of the stress intensity factor (SIF) K is one method for crack analysis by fracture mechanics approach. In this paper, an evaluation of K was carried out using the J integral. In particular, in this study, a CT specimen was used to calculate the J integral. In the evaluation, 859 nodes and 1618 elements were used for the J integral calculation of the CT specimen by the in-house FEM program. A comparison of the result with the ASTM formula showed that the results from the current research of the J integral was in the 99% coincidence interval. Overall, cracks in this study can be studied satisfactorily by the J integral from the above mesh size.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2016.10a
• /
• pp.230-233
• /
• 2016

In this paper, we developed the ice machine conditions monitoring system that confirms conditions of the ice machine. The developed system is composed of Communication Board, Server Program, and Web-based User Application. Communication Board which is connected to the ice machine periodically sends various data, such as current, voltage, the refrigerant pressure and temperature, the external temperature and humidity. Server Program stores the data received from Communication Board into database. The manager or the ice machine operator can see the state of the own machine through User Application based on Web. When a symptom is detected on the ice machine, the manager and the operator can checks the current condition of the ice machine by using the data obtained in real time and also prevents the machine troubles by taking proper actions.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.4
• /
• pp.363-371
• /
• 2023

To construct a ship, blocks of various sizes must be moved and erected . In this process, lugs are used such that they match the block fastening method and various functions suitable for the characteristics of each shipyard facility. The sizes and shapes of the lugs vary depending on the weight and shape of the block structures. The structure is reinforced by welding the doubling pads to compensate for insufficient rigidity around the holes where the shackle is fastened. As for the method of designing lugs according to lifting loading conditions, a simple calculation based on the beam theory and structural analysis using numerical modeling are performed. In the case of the analytical method, a standardized evaluation method must be established because results may differ depending on the type of element and modeling method. The application of this ambiguous methodology may cause serious safety problems during the process of moving and turning-over blocks. In this study , the effects of various parameters are compared and analyzed through numerical structural analysis to determine the modeling conditions and evaluation method that can evaluate the actual structural response of the lug. The modeling technique that represents the plate part and weld bead around the lug hole provides the most realistic behavior results. The modeling results with the same conditions as those of the actual lug where only the weld bead is connected to the main body of the lug, showed a lower ulimated strength compared with the results obtained by applying the MPC load. The two-dimensional shell element is applied to reduce the modeling and analysis time, and a safety working load was verified to be predicted by reducing the thickness of the doubling pad by 85%. The results of the effects of various parameters reviewed in the study are expected to be used as good reference data for the lug design and safe working load prediction.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.2
• /
• pp.197-205
• /
• 2015

Offshore structures for the gas production are exposed to the risk of gas leaks, and gas explosions can result in fatal damages to the primary structures as well as secondary structures. To minimize the damage from the critical accidents, the study of the dynamic response of structural members subjected to blast loads must be conducted. Furthermore, structural dynamic analysis has to be performed considering relationships between the natural frequency of structural members and time duration of the explosion loading because the explosion pressure tends to increase and dissipate within an extremely short time. In this paper, the numerical model based on time history data were proposed considering the negative phase pressure in which considerable negative phase pressures were observed in CFD analyses of gas explosions. The undamped single degree of freedom(SDOF) model was used to characterize the dynamic response under the blast loading. A blast wall of FPSO topside was considered as an essential structure in which the wall prevents explosion pressures from the process area to utility and working areas. From linear/nonlinear transient analyses using LS-DYNA, it was observed that dynamic responses of structures were influenced by significantly the negative time duration.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.6
• /
• pp.704-709
• /
• 2014

Plate heat exchanger is being applied in the field of marine plants and chemical industry, such as OTEC and SWAC equipment. The study aims to interpret the heat transfer and pressure drop characteristics of plate heat exchangers to determine the geometric design parameters such as the channel space. In this study, heat transfer performance was numerically studied with respect to the variation of channel spaces. The results from numerical analysis indicated that the j factor was linearly decreased with the flowrate of seawater over every cases. As the flowrate of water increased with respect to channel spaces, the j factor decreased linearly. And the f factor decreased linearly with the increase of flowrate. When the channel space is 2.8~3.2 mm and 3.2~3.2 mm, respectively, the area goodness factor of plate heat exchanger showed the highest performance.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.2
• /
• pp.187-195
• /
• 2015

The gas explosions in offshore installations are known to be very severe according to its geometry and environmental conditions such as leak locations and wind directions, and a dynamic response of structures due to blast loads depends on the load profile. Therefore, a parametric study has to be conducted to investigate the effects of the dynamic response of structural members subjected to various types of load shapes. To do so, a series of CFD analyses was performed using a full-scale FPSO topside model including detail parts of pipes and equipments, and the time history data of the blast loads at monitor points and panels were obtained by the analyses. In this paper, we focus on a structural dynamic response subjected to blast loads changing the magnitude of positive/negative phase pressure and time duration. From the results of linear/nonlinear transient analyses using single degree of freedom(SDOF) and multi-degree-of freedom(MDOF) systems, it was observed that dynamic responses of structures were significantly influenced by the magnitude of positive and negative phase pressures and negative time duration.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.9
• /
• pp.150-155
• /
• 2019

Cavitation refers to a phenomenon in which empty spaces occur in a fluid due to changes in pressure and a velocity. When a liquid moves at a high speed, the pressure drops below the vapor pressure, and vapor bubbles are generated in the liquid. This study used CFD to analyze the flow of fluid machinery used in marine and offshore plants. The goals are to ensure the validity of the analysis method for marine propellers in an open water test, to increase the forward ratio, and to use FLUENT to understand the flow pattern due to cavitation. A three-dimensional analysis was performed and compared with experimental data from MOERI. The efficiency was highest at advance ratios of 0.7 - 0.8. Thrust was generated due to the difference between the pressure surface and the suction surface, and it was estimated that bubbles would be generated in the vicinity of the back side surface rather than the face side of the propeller, resulting in more cavitation. The cavitation decreased sharply as the advance ratio increased. The thrust and torque coefficients were comparable to those of the MOERI experimental data except at the advance ratio of 1, which showed a difference of less than 5%. Therefore, it was confirmed that CFD can evaluate an open water propeller test.