UNDERSEA TECHNOLOGY 



47 



increase in crack-growth rate well below the proportional limit in sea 

 water as compared to air. 



STRUCTURES AND MATERIALS FOR 

 UNDERSEA INSTALLATIONS 



The design of an undersea installation requires analysis of the struc- 

 tural and environmental behavior of materials in the deep ocean. Mate- 

 rials such as steel, aluminum, concrete, ceramic, plastic, and wire rope 

 are presently available for building undersea installations. The behavior 

 of materials in the deep ocean when exposed for long periods of time 

 must be determined. 



Engineering experiments are underway to determine the effects of the 

 deep ocean environment and bottom sediments on the corrosion of con- 

 struction materials. Submersible Test Units (STU's) carrying specimens 

 of metal, plastic, ceramic, wood, wire, rope, and fiberglass have been 

 placed on and retrieved from the ocean floor. The Navy under this pro- 

 gram has exposed 11,000 samples of 800 materials at depths of 2500 



Submersible test unit 1-4 being brought aboard after 13 months exposure at 

 6780 ft. This unit contains approximately 1800 specimens of metal, plastic, ceramic, 

 wood, wire rope, and fiberglass. 



