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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.

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.

[Objectives] To explore the influence of core materials on the vibration of composite grid sandwich panels,[Methods] taking the panels as the research object, the vibration response of rubber-core grid sandwich panels and buoyancy-core grid sandwich panels under different conditions is compared by means of experiment, with emphasis given to the analysis of vibration suppression effect of core material on the two composite panels.[Results] The results show that the mid-frequency and low-frequency(0-1 000 Hz) vibration response of the buoyancy-core grid sandwich panels in air is low, while the high-frequency(1 000-3 000 Hz) vibration response of the rubber-core grid sandwich panels is low. The influence of the factors such as the mass of the sandwich panel and the damping of the core on the vibration response of the panel is weakened due to the added mass effect and the added damping effect and the integral of the sandwich structure and the local bending stiffness of the panel are the main factors. The vibration response of the buoyancy-core grid sandwich panel within full-frequency band (0-3 000 Hz) is lower than that of the rubber-core grid sandwich panel.[Conclusions] To reduce the vibration response of the panel, the core stiffness of the grid sandwich panel shall be close to the grid stiffness. In addition, the smaller the density and damping of the core, the greater the difference between the vibration response in air and water.

Taking certain CNC camshaft grinder as the subject its motion error analysis and modeling were studied. The movement forms and types of errors between the moving parts were analysed, the movement between coordinate systems of the adjacent bodies was used to express the movement between the two adjacent bodies, and the ideal motion equation and actual motion equation in case of errors between the adjacent bodies were set up. Actual motion equation between adjacent bodies was made and further extended to analyse arbitrary low-order body arrays, which provides a theoretical basis for studying the multi-branch CNC camshaft grinding machine error modeling. Complex multi-branch chain CNC camshaft grinder simplified was made as a simple multibody system, and corresponding body coordinate systems and motion reference coordinate systems for moving parts were established to calculate the corresponding transformation matrix between adjacent bodies. Moving parts of the machine were divided into “workpieces-bed” and “wheel-bed” two kinematic chains. The precision constraint equation of the machine is Pt = Pw in case of using errors influence, and the constraint equation was solved. It provides necessary conditions for study of CNC camshaft grinder error compensation. Results show that the machine precision is significantly improved after error compensation.