Lightweight Vessels Research Articles

Compartment level progressive collapse analysis of lightweight ship structures

The continued development of large high speed ships, often constructed from aluminium alloy, has raised important issues regarding the response of lightweight hull girders under primary hull girder bending. In particular, the response of lightly framed panels in compression may be influenced by overall panel buckling over several frame spaces. Therefore, to provide improved ultimate strength prediction for lightweight vessels, an extended progressive collapse methodology is proposed. The method has capabilities to predict the strength of a lightweight aluminium midship section including compartment level buckling modes. Nonlinear finite element analysis is used to validate the extended progressive collapse methodology.

Fatigue Life Assessment and Lifetime Management of Aluminum Ships Using Life-Cycle Optimization

The development of aluminum ship structures has been promoted in the context of the rapid evolution of high-speed and light-weight vessels. Under the repeated and/or fluctuating application of stresses during voyages, fatigue damage of structural ship members is accumulated. For this reason, fatigue reliability analysis has to be conducted for assessing and predicting lifetime performance of aluminum ships. This assessment offers the opportunity to optimally perform the lifetime ship structural management planning. To allocate limited financial resources required to balance the lifetime reliability of ship structural details and the life-cycle cost, single-or multi-objective optimization can be used. The multi-objective optimization problem has several competing objectives such as:(minimizing the life-cycle maintenance cost,maximizing the fatigue reliability of details with welded attachments, andminimizing the fatigue damage. The S-N (stress vs. number of cycles) approach and available sea loading information are used to evaluate the time-dependent fatigue reliability. In this paper, the estimated fatigue reliability is incorporated into a life-cycle cost optimization problem to find the optimal inspection and repair interventions. The proposed approach is illustrated on an aluminum ship detail.

Strength and Modal Analysis of Thin-Shell-Structured Vessel with Rib Reinforcement

The Thin-shell-structured vessel with rib reinforcement is a key structure in petrochemical industry. For large scale and lightweight vessels design, it is essential to optimize the design based on the strength and modal analysis. In this paper a FEM model of Thin-shell-structured vessel with rib reinforcement was set up using Ansys software. It uses finite element programming to calculate its strength and modal numerically. The results indicate that the structure’s strength distribution, displacement distribution and situations about the first-six orders frequency of the vessel structure. Analysis of the calculation provides the numerical and theoretical supports of liquid vessels design under real working conditions.

Slamming Response of a Large High-Speed Wave-Piercer Catamaran

Commercial and military requirements for high-speed sea transportation has led to the evolution of large, fast, lightweight vessels. Knowledge of the effect of sea loads on the structure of such vessels is required in order to carry out structural design optimization. Wet deck slam events, which occur when the vessel's motion causes an impact between the cross-deck structure and the water surface when operating in large waves, are of particular importance for high-speed catamarans. Extensive full-scale hull stress, motion, and wave measurements have been conducted on an 86-m Incat high-speed catamaran ferry during a delivery voyage. A definition of a slam event, for this vessel, is proposed and used to identify slam events from the data records. The character and effects of these slamming events are investigated with respect to a number of factors, including structural loading, wave height and length, vessel speed and heading angle, relative vertical velocity, and frequency of occurrence. The results of the full-scale data analysis are presented. Particular attention is paid to the whipping response of the structure, with the principal structural response frequencies being identified through spectral analysis.

The Threshold Conditions and Characteristic Analysis of the Marine Fire Spread Phenomena

In the event of a spontaneous outbreak of fire in a ship, it is necessary to secure sufficient time for the safe evacuation of the personnel on board and for the crew to engage in fire extinguishing activities. Fire spread prevention designs are to be developed to sufficiently take care of the requirements of an ever increasing number of light weight vessels, such as high speed crafts made by aluminum alloys, which are highly prone to develop ruptures when exposed to the high temperature of a marine cell fire. The performance assessment of such designs should be settled down immediately, with special emphasis on the faultless design of fire preventive partitions, bulkheads and ceilings.This paper makes an investigation of the threshold conditions and characteristics of the problem of the spread phenomena of cell fires enhanced by ruptures and holes broke open on the partitions and structural members on light weight vessels by using a mathematical model which gives the combustion characteristics. The relationships between the critical fire spread conditions and the governing factors which are, the point of rupture of structural member, the thickness of the fire preventive insulation and the fire load, are clarifired through the results of the numerical calculations.

Gas permeation of fibre reinforced plastics

Propulsion with liquid hydrogen or methane is under development. Storage and transportation of these fuels is part of these activities. Lightweight vessels out of fibre composites are promising candidates. Their disadvantage might be gas permeation, especially when exposed to mechanical and thermal cycling. For several applications of superconducting magnets (pulsed magnets, SQUID detectors), non-metallic and non-magnetic cryostats are required. Fibre glass composites are promising candidate materials, but again a sufficient low helium gas permeation is required. The permeation of helium, hydrogen and methane gas has been investigated. The principal arrangement for measuring gas permeation through polymers, fibre glass and carbon reinforced epoxy resins will be shown. The behaviour of coating materials or organic and metallic liners is a further topic of these measurements. Special emphasis has been put on the influence of thermal and mechanical cycling on the permeation rate.