5059 aluminum alloy has become the preferred choice for the ship structure due to its excellent mechanical properties and corrosion resistance. However, the current code lacks the S-N fatigue curve of the 5059 aluminum alloy, imposing difficulties on the fatigue evaluation of the 5059 aluminum alloy ship structure. The 5059 aluminum alloy and a typical marine welded joint are designed to carry out the fatigue tests at the room temperature and the low temperature (-35℃). The corresponding fatigue S-N curve is fitted by the least square method based on the test data. A finite element model of the specimen for fatigue test is established, and the stress obtained by the finite element analysis is extrapolated to obtain the hot spot stress. The fatigue life of the fatigue specimen is predicted by using the fitted S-N curve and compared with the result from the fatigue test. The results show that the proposed S-N curve of the 5059 aluminum alloy material and the welded joint can be used to predict the fatigue life of the ship structure under the low temperature environment.

A software for rapid estimation of the natural frequency of the stern frame vibration has been developed in order to quickly estimate the important parameter of the natural frequency of the stern frame vibration. This software uses QT and MATLAB for interface design and core solver compilation based on the empirical formula for the calculation of the natural frequency of stern frame vibration given in the “Method for Structural Design and Strength Calculation of Naval Surface Ships”. The influence of different hull parameters on the vibration of the stern frame is summarized based on the developed software system. It is found that the factors affecting the natural frequency of the single-arm stern frame are mainly the length of the shaft frame arm and the average inertia moment of the shaft frame section, and the factors affecting the natural frequency of the double-arm stern frame are the length of the shaft frame arm, the cross-sectional area of the shaft frame arm, and the angle between the shaft centerline and the plane of the shaft frame. The results can provide references for the selection of parameters during the design of the stern frame. The practical value of this software is demonstrated in the rapid estimation of the natural frequency of the stern frame vibration.

Owing to the complex geometric curved surface of the propeller, general software for the rapid prediction of the vibration characteristics of the propeller with trailing edge cutting is developed for the geometric modelling and vibration analysis of the trailing edge cutting. The development of the software for the vibration analysis of the propeller with trailing edge cutting is completed by using the finite element method together with the MATLAB programming language and the ANSYS module based on the QT platform. This software is used to calculate and analyze the first five-order natural frequency values of the 4384 propeller. It is found that the relative errors are within 5% combined with the published data in order to prove the accuracy of the software program and the calculation results. The software is characterized of easy usage, fast calculation and great engineering application value. It provides a new analysis method for the matching of ship-machine-propeller after the trailing edge cutting.

The influence of the side wall effect on the ship motion should be taken into account to predict the motion of the ship in the restricted waters, such as a narrow channel or a canal. The side wall effect has been considered by introducing the green function of channel free surface. The green function of the side wall with free surface is then approached by Chebyshev polynomial to perform the efficient and high accurate calculations. The results calculated in the current study are compared with which is calculated by the commercial software. The artificial numerical damping is adopted for the free surface in order to address the numerical resonance phenomenon of the free surface during the numerical calculation, ensuring that the motion of the floating body and the calculated elevation of the free surface are more accordant with the actual conditions.

A virtual experimental study of the resistance characteristics of the suction pipe structure of a full-scale trailing suction dredger with the underwater pump has been carried out by using the numerical tank technology. It analyzes and studies the resistance characteristics of the bare and fully appended suction pipe that are varied with different inclined angles and speeds. It also analyzes the resistance components of each structure of the fully appended suction pipe. It can provide reference for the resistance prediction, evaluation of the ship propulsion power and the design optimization of the suction pipe structure.