Crack propagation mechanism and simulation analysis of unmanned underwater vehicle pressure shell structures

This study examines surface crack propagation in the shell structure of an Unmanned Underwater Vehicle (UUV) operating in complex deep-sea loading environments, with a focus on titanium alloy components. The investigation elucidates the surface crack initiation mechanism and develops a simulation framework for crack growth based on the Paris formula. A surface crack propagation model is formulated, incorporating calculations of the stress intensity factor, and an equivalent initial flaw size is introduced to address the stochastic nature of small crack propagation. This equivalent defect is used as the starting point for the crack growth analysis. A three-dimensional model of the cylindrical shell containing a surface crack is subsequently developed through coupled simulation using Abaqus and Franc3D, enabling evaluation of the crack propagation behavior at a water depth of 1000 meters. The findings offer a theoretical basis for the selection of crack monitoring sensors in deep-sea unmanned systems and provide substantial engineering insights for structural safety evaluation and service life prediction.