Deep-sea pressure hulls are at risk of implosion when subjected to extreme hydrostatic pressures that exceed their ultimate bearing capacities. Therefore, it is essential to investigate the failure mechanisms and shock response characteristics of titanium alloy cylindrical shells under implosion conditions.

First, an independent deep-sea implosion experimental platform was developed, and underwater experiments were conducted on the titanium alloy cylindrical shell in a deep-sea high-pressure environment. A compressible multiphase flow module was then developed to simulate the high-speed motion of the flow field during the underwater implosion. The explicit nonlinear finite element method was employed to analyze the dynamic response associated with the collapse and failure of the titanium alloy cylindrical shell. Finally, the characteristics of the titanium alloy cylindrical shell implosion were investigated, focusing on the fluid-structure interaction mechanism, the evolution of asymmetric shock waves in the multiphase medium, the nonlinear dynamic response of the structure, and the energy balance relationships.

The results showed that the titanium alloy cylindrical shell, with a length-to-diameter ratio of 2, collapsed in the first-order instability mode, and the implosion center formed twice successively. As hydrostatic pressure increased, a pronounced migration effect of the first implosion center was observed. Meanwhile, the failure mechanism of the shell transitioned progressively from inward extrusion to inward curling, and the rupture morphology evolved from an arcuate shape to an M-shaped configuration.

This study reveals the failure mechanism and shock response characteristics of the titanium alloy cylindrical shell implosion, providing valuable insights for the implosion assessment and protection of deep-sea pressure hulls.

This study aims to investigate the shock load characteristics during implosion and the thermodynamic response mechanisms of a ceramic pressure hull in the extreme deep-sea environment. A numerical simulation method for the implosion of a deep-sea ceramic pressure hull is proposed using a compressible multiphase flow model that ensures pressure-velocity-temperature equilibrium and adaptive mesh refinement (AMR).

The proposed method enables accurate prediction of shock waves and precise capture of the flow field. Then, underwater implosion experiments of the ceramic pressure hull are conducted to verify the effectiveness of the numerical method. Finally, a numerical study on the implosion of a ceramic pressure hull at a depth of 10 000 m reveals the characteristics of the shock load and thermal effects during implosion. The implosion of a deep-sea ceramic pressure hull at different water depths and temperatures is studied numerically, and the effects of these factors are analyzed.

The implosion of a deep-sea ceramic pressure hull releases shock waves outward and produces a significant thermal effect when the gas is highly compressed. As the ambient pressure increases, the peak overpressure of the implosion shock wave decreases, and the shock wave attenuation rate increases. However, the ambient water temperature has little effect on the implosion characteristics of the ceramic pressure hull.

This study provides insights into the implosion characteristics of deep-sea ceramic pressure hull, offering valuable theoretical insights and engineering implications for the assessment and mitigation of underwater implosion effects.

This paper aims to study the influence of the approximation model, consistency constraints, and boundary update strategy of the BLISS-2000 multidisciplinary design optimization method on its convergence performance and optimization efficiency based on OpenMDAO.

First, the optimization process and boundary update strategy of BLISS-2000 are given. A BLISS-2000 model is then established based on OpenMDAO, and its accuracy is verified by mathematical and engineering examples. Finally, the effects of the approximation model's accuracy, consistency equality constraints, constraint relaxation, and boundary update strategy on the convergence performance and optimization efficiency of the model are studied.

The results show that improving the accuracy of the approximation model and selecting the appropriate constraint relaxation factors and boundary update factors can greatly improve the convergence performance and optimization efficiency of the BLISS-2000 model. At the same time, the recommended values of the relevant parameters based on constraint relaxation are obtained.

The results of this study can provide useful references for the improvement of the BLISS-2000 method and its application in the conceptual design stage of ships and marine equipment.