Cyclical deep-sea pressure loading of cylindrical submersibles: Analytical solution with damage-scaling factors and application to the Titan submersible failure

This study applies fundamental stress tensor analysis to quantify cyclic deep-sea pressure loading on cylindrical submersibles with end-caps. It examines differential stress distributions along the hull, highlighting how longitudinal stress shifts from tensile at mid-span to compressive near end-caps, while hoop stress varies due to superposition effects. The methodology is applied to the Titan submersible failure, incorporating strain gage data and adhesive bond degradation between its carbon-fiber hull and titanium end-rings. A damage-scaling factor is introduced to assess the impact of bonding failure on stress modifications. The analysis also considers stress accumulation leading to implosion once pressure-sealing breaches. Failure analysis suggests that repeated compression and decompression cycles contributed to progressive delamination and ultimate structural failure. While prior studies examined material damage, this research uniquely quantifies dynamic stress variations and their role in the submersible's collapse. The findings offer insights into differential stress concentrations in cylindrical pressure chambers, relevant to both passive submersibles and active submarines. The closed-form stress model may aid future investigations and inform submersible design improvements.