The Spherical Acrylic Pressure Hull for Hydrospace Application: Part IV. Cyclic Fatigue of NEMO Capsule Number 3
Abstract
The 66-inch outside diameter 2.5-inch thick NEMO Model 600 spherical hull 63 was hydrostatically pressure cycled till fatigue cracks appeared in the acrylic plastic and the top hatch plastically buckled. The plastic buckling of the hatch, fabricated from annealed 4130 alloy steel, took place during simulated repeated dives in the 2080 to 2250 foot depth range. The cracks in the acrylic plastic hull were located in the beveled surface in contact with the metallic polar closures. The cyclic tests conclusively prove that (1) an adequate cyclic fatigue safety factor exists for NEMO hulls performing, routinely, extended manned dives to 600-foot depth, and that (2) manned proof dives of 1 hour duration to 1200-foot depth can be performed providing the total number of proof test dives does not exceed 100. To prevent plastic buckling of the polar steel closures prior to general implosion of the capsule it is necessary to specify heat treated 4130 steel alloy for the polar penetration closures.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1970
- Accession Number
- AD0715345
Entities
People
- J. D. Stachiw
Organizations
- Naval Facilities Engineering Service Center