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At present, the cylindrical shell was regarded as the dominating structure in underwater vehicles, which raised the crucial significance to research underwater vehicles’ vibration and acoustic radiation features. In this study, the analytical expression of vibration–acoustic theory had been given according to the derivation with the vibration–acoustic theory of ribless cylindrical shell structure. Meanwhile, the effects of key parameters on vibration–acoustic characteristics are investigated including modulus, density, thickness, loss factor, etc. The research shows that the stiffness and damping of the shell directly affected the vibration of the structure. Furthermore, the performance of vibration attenuation and noise reduction of the shell had been enhanced by increasing the modulus, thickness, and loss factor in materials.

To investigate the influence of residual stress on the fracture performance of T-joint welded joints in 6063 aluminum alloy, ABAQUS simulation was utilized to obtain the post-weld residual stress fields for different welding methods. A finite element model for toughness fracture of T-joints was established using the Johnson-Cook constitutive and damage models, aiming to analyze the impact of welding residual stress on fracture performance. The results indicate that under the same tensile rate, residual stress can lead to earlier fracture occurrence in the welded joints, thereby reducing the overall fracture performance. Among the different welding methods, the double-sided corner weld exhibits the best fracture performance, while the butt joint with a backing plate can effectively mitigate the influence of post-weld residual stress on fracture performance. Through the comparison of experiments and simulations, the material constitutive and damage parameters of each welding zone are verified, and the hardness test is carried out. The results indicate that the average hardness in the weld zone is approximately 63.8 HV, which is higher than the average hardness of 60.2 HV in the heat-affected zone. However, both the weld zone and the heat-affected zone have lower hardness values compared to the average hardness value of 81.5 HV in the base metal zone. Furthermore, it is observed that residual tensile stresses are predominantly distributed in the weld zone, which is one of the reasons contributing to the lower hardness at the center of the weld. [ABSTRACT FROM AUTHOR]

A simple analytical model to estimate the longitudinal strength of ship hulls in composite materials under buckling, material failure and ultimate collapse is presented in this paper. Ship hulls are regarded as assemblies of stiffened panels which idealized as group of plate-stiffener combinations. Ultimate strain of the plate-stiffener combination is predicted under buckling or material failure with composite beam-column theory. The effects of initial imperfection of ship hull and eccentricity of load are included. Corresponding longitudinal strengths of ship hull are derived in a straightforward method. A longitudinally framed ship hull made of symmetrically stacked unidirectional plies under sagging is analyzed. The results indicate that present analytical results have a good agreement with FEM method. The initial deflection of ship hull and eccentricity of load can dramatically reduce the bending capacity of ship hull. The proposed formulations provide a simple but useful tool for the longitudinal strength estimation in practical design.