No abstract

No abstract

No abstract

Abstract-This paper analyzed the reliability of the mechanical system of a new conceptual Autonomous Underwater Vehicle (AUV) using FMECA and FTA method. In the FMECA procedure, the failure modes were studied by analyzing their effects and criticalities. Then, the fault tree was built. The research was carried out in both qualitative and quantitative analysis of FTA. Using aforementioned methods, the probability of the top event, the structural and critical importance coefficients of the bottom events were performed. Finally, the failure modes of this AUV mechanical system were sequenced according to the severity and the criticality and list of the critical components was presented as well. The reliability-improving suggestions provided in the paper can be used in further reliability design and structural improvement of AUV or other similar UUV mechanism.

a b s t r a c tThe computational efficiency of CFD on maneuverability simulation poses a great difficulty resulting in its restricted applications. A hybrid reference frames method is established that combines the rotating reference frame method and an added momentum source method. The computational domain is separated into two parts under the rotating reference frame and the inertial frame respectively. A single mesh is needed for all conditions of a testing model such as different rotating arm radius, pitch angles and drift angles. The validation is carried out based on the numerical simulations on the flow fields around the SUBOFF models including sterns and full appended models. Results show that the stability derivatives of the yawing moment and yawing force agree well with the experimental data. Using a dimensional analysis method, the influences of the rotating arm radius and linear velocity are investigated. The similarity is maintained when the radius is constant, and the rotating effect performs strongly when the radius is small. The effects of pitch angle and drift angle are also discussed when the linear velocity is fixed with the fully appended SUBOFF model.

The max collision force of ship-bridge collision is one of the most important references for bridge design. By means of nonlinear digital simulation method, the collision forces of the collisions between ngld bridge pier and ship bow were calculated out for four different ships, whose tonnages are 5 000,10 000,50 000 and 60 000 DWT respectively. Curves sorbed energy-penetration are obtained, and the data of the max loads are then summarized. On set of curves describing the relationships between max collision forces and tonnages of the ships the max collision forces of the ships-bridge with different tonnages and in different velocihes can be estimated easily and reliably.

No abstract

No abstract