Select a steel for use in high-pressure cylindrical containment vessels for the next generation of nuclear submarines. Two steels are being considered for this application, HY-130 and HY-180, which are both martensitic steels. The material properties for these two steels are shown in the table below.
PROPERTIES HY-130 HY-180
Yield strength, ksi. 130 180
Tensile strength, ksi 150 190
K~c, ksiX/~n. 280 300
K~c in seawater, ksiX/~n. 260 180
Hypothetical cost $/lb 0.50 1.00
Design parameters for the containment vessels are as follows:
(a) Internal pressure = 5000 psi
(b) Internal diameter of cylindrical portion -- 30 in.
(c) Overall length of each vessel is 20 ft. Ends are to be hemispherical.
(d) Welded fabrication will be used. Assume that weld metal properties are the same as base metal properties.
(e) The vessel must have a factor of safety of at least 2.0 against both yielding and fracture of a 0.5-in-deep surface flaw. Assume that a/2c is 0.4.
(f) The vessels will be cycled from 0 to full design pressure (5000 psi).
(g) Inspection is such that all flaws greater than 0.05 in. can be found during fabrication. In service, the vessels will be in the forward-flooding zone of the submarine and cannot be Inspected, although they can be protected by painting.