The design of lifting blade shapes is a key engineering application, especially in domains such as those of marine propellers, hydrofoils, and tidal energy converters. In particular, the excitation frequency must be different from that of the structure to avoid resonance. The natural frequency in the cases where the fluid–structure interaction (FSI) is considerably different if considering the coupling added mass (AM) of the water. In this study, vibration experiments were performed using a real propeller in air and water. The modal parameters, natural frequencies, and mode shapes were determined. Validations were performed using 3D solid and acoustic elements in a direct coupling finite element format. The modal results and AM ratios were in agreement with the experimental results. Convenient application and high efficiency are basic requirements for an engineering application. Therefore, an empirical formula was established for the first-order FSI natural frequency to enable rapid estimation, thereby satisfying this requirement.

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The assessment of the finite element analysis results on stiffened plating structures is not straightforward because of the stress singularities that are inherent in the overall geometry. Some guidance is available but it is generally founded on limited comparisons with experiments rather than on an overall analysis of the problem, and the guidance is almost certainly not generally applicable. Fracture mechanics finite element methods are very useful but generally provide little understanding of the behaviour and a very limited basis for checking the quality of the results. This paper reports some work carried out recently to try to provide an understanding of the nature of the singularities in these details and some simple ‘rules of thumb’. This provides a direct calculation method for fracture mechanics stress intensity factors and stress concentration factors for fatigue analysis based on the S–N approach (where S is the stress and N is the number of cycles to failure). By providing a better understanding of the nature of the stress fields, it also provides a good foundation for a finite element analysis of these details. This paper concentrates on the analysis of a simple planar right-angled cruciform corner with no bending, overlapping plates or weld reinforcement geometry. Also the effects of the mean stress and the residual stress are ignored. Some initial insights into the stress field are studied when the detail is not planar; this gives some further understanding of the behaviour of real structure details

Stress intensity factors (SIFs) are important parameters in brittle fracture assessment of marine notched components; in respecting of previous researches, it has found that there are several ways for SIF solutions. Following outline of LEFM based fatigue analysis; the paper has proposed a closed-form SIF solution as an alternative way for ship structural details prediction. It has shown that the stress intensity factors (SIFs) can be solved revealing the effect of the geometric parameters. Numerical tool has offered an evaluation as convergence behavior of relative SIF results between CCT (central crack) and DENT (double edge notch). Then the proposed methodology is applied onto the construction similar to HHI #1 and #2 specimens. It has be concluded in results that the SIFs and fatigue lives by the proposed method have good agreement with those by FEA calculations, furthermore, these key parameters can be expressed in formula format. For real engineering application, the main advantage of the proposed method will be useful for fatigue prediction rapidly and conveniently.

Stress concentrations typically exist around the perimeter of an opening and on attached structures, thereby resulting in a potential risk of crack initiation. Experimental and numerical methods on stress concentration distribution analysis can be applied in this study. This study reveals the differences in stress concentration distributions around various types of slots. Typical slots have been selected to discuss the influence on stress concentration distribution when the connections of flat bar and connection plate are considered. This concept is novel given the experiments conducted and finite element method (FEM) results found under complex loads. The FEM is used to compare calculated results with experimental data, and continuous plotting of numerical results can verify the outcomes. The results show the stress concentration distribution around the selected slot edge, where peak stress appears around the openings of different types of slots.