Quote:
Originally Posted by Kapitan
As for the HY ratings i understand the pressure ratings but in terms of thickness relation to strength thats where i get lost, given the state of technology today i would assume that HY 120 steel is some what cheaper today than back in the 70's and 80's when the 688's were coming online, i do know the hull cost for seawolf was extremely expensive again that was a cost forecast taken from 1997 so again thats taken from the time.
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So in terms of pressure vessels, which submarines are, there are two factors at play: geometry and material properties. Thickness is a property of the geometry and Strength is a property of the material. Beam of the submarine and thickness of the hull play into the stress the pressure hull experiences from a geometrical standpoint (in addition to bulkheads). It's different analyzing internal pressure vessels (like spray paint cans or beer cans) versus external pressure vessels (like submarines), but for internal pressure vessels, a larger beam results in more stress and a thicker wall results in less stress in the design.
So now that you know the stress the submarine will experience, you have to pick a material with a sufficient Strength to handle that stress, but stress in a design doesn't depend on the material. In terms of material properties, a stronger material can take more stress. For HY120 vs HY80, it's fair to say that HY120 is 50% stronger than HY80.
So, HY120 has a strength of 120,000 psi. Say, for example, that a submarine at a certain depth is experiencing 60,000 psi in its hull. The HY120 has sufficient strength to not fail because of that stress level.