Safety assessment of the acrylic conical frustum viewport structure for a deep-sea manned submersible

For new manned submersibles to dive deep sea, the conical frustum windows need to be designed under external uniform pressure, not only based on the rule design method but also verified by numerical or experimental methods. In this paper, the contact finite element (FE) model is provided for the conical window and validated accordingly. Based on the presented FE model, the stress and deformation characteristics have been accomplished for the thick conical window and then the failure reasons and design criterion of acrylic plastics viewports are thoroughly investigated by comparing with the experiment data and those from some existed windows. Meanwhile, the structural characteristics especially for stress concentration have been exposed by numerical calculation. Finally, the failure of conical frustum viewport has been discussed totally referring to the existing design criteria and some principles for its optimal design have been proposed.