Journal of Marine Science, Engineering & Technology

EFFECT OF DYSPROSIUM ADDITION ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Al5083

Chee Loon Siow — Thu, 09 Dec 2021 00:00:00 +0000

Aluminium has been widely used in engineering industry because of their excellent properties. Aluminum 5083 alloys are Al-mg alloys that have major applications in marine industry due to their excellent corrosion resistant and high strength. Various research has been carried out to increase its properties and in this research micro-alloying method by adding dysprosium, in Al5083 is employed. The melting was performed using crucible in induction furnace for different concentration of Dy 0wt%, 0.25wt%, 0.50wt% and 0.75wt%. The cast is cut and grinded using SiC from grids of 320 to 1200 followed by polishing in Silica Struer solution to achieved mirror surface finished before examined by optical microscope and scanning electron microscope. Additions of Dy promote the formation of Al structure and fine grain size. Mechanical properties of Al5083 have been determined by three different testing which are compression test, hardness test and impact test. Results show that addition of Dy increase the strength, impact properties and hardness of Al5083 alloy through the improved microstructures.

VORTEX INDUCED VIBRATION (VIV) SUPPRESSION DEVICE

Chee Loon Siow — Thu, 09 Dec 2021 00:00:00 +0000

The study of Vortex-induced vibration (VIV) is one of the main concern in designing marine riser system to untapped the oil and gas reserve from the seabed. The VIV phenomenon will cause severe fatigue as well as total damage to the structure. In this paper, the simulation was carried out in two-dimensional involving bare cylinder and cylinder with parallel plates in different lengths and gaps by using ANSYS CFX 16. A circular cylinder of 114mm in diameter with different plate lengths and gaps dimension were used in these simulations. Simulation with a bare cylinder in the Reynolds number range from 5x10^4 to 1x10^5 has been performed to serve as reference. The validation by using the Strouhal number is the common practice for the stationary circular cylinder simulation. The Strouhal frequency obtained from this research was St ≈ 0.2. By having the idea parallel plates attached to the cylinder, it will help the flow separation become streamline as well as reduce the VIV on the marine riser. In addition, the Reynolds numbers are believed will give some significant effect on the behavior of VIV. Results from this paper can be very helpful to design riser system and future endeavor to perform similar kind of simulation.

NUMERICAL SIMULATION ON MOTION OF SEVEN CYLINDRICAL FPSO IN DIFFERENT LOADING CONDITIONS

Chee Loon Siow — Thu, 09 Dec 2021 00:00:00 +0000

This paper is proposed to present the difference of motion response in wave of SEVEN’s Cylindrical FPSO when the structure is in full loaded and when it is in ballast condition. Based on the theory, the motion of the floating structure will be influenced on the weight of FPSO. Where, when the weight of the FPSO changed, the natural frequency of the motion will be changed. This will lead to shift of the peak response frequency and amplitude of the motion. To analyse the motion of the FPSO in different loading condition, the study was conducted by simulate the motion of FPSO in wave by using commercial software. The heave and pitch of the FPSO are focused. The added mass, damping coefficient, wave loading and Response amplitude operator of the FPSO in different loading condition are presented in the paper. From the simulation results, it is observed that the peak heave response of the FPSO in full loaded condition happened at lower frequency as compared to ballast condition. However, the peak pitch response of the FPSO in full loaded condition happened at higher frequency as compared to ballast condition. This result obtained is due to the displacement of the FPSO at full loaded condition is higher than ballast condition but the GM value is smaller at full load condition.