A deep-submersible diving bell has a cylindrical pressure hull expected to experience an external pressure of 50 MPa. What should be considered in the hull design?

In the design of a deep-submersible diving bell's pressure hull, which is expected to withstand an external pressure of 50 MPa, it is crucial to treat the pressure vessel as a thick-walled pressure vessel. This is due to the high external pressures involved, which significantly influence the stress distribution across the wall thickness.

Thick-walled pressure vessels are defined by their wall thickness relative to their radius; in this case, the high pressure necessitates that shear and radial stresses be considered throughout the thickness of the wall rather than just on the inner or outer surfaces. This is important as the radial stress is not negligible in thick-walled vessels. The thick-walled assumption allows for more accurate calculations of the stress distribution and ensures that the design can withstand the extreme conditions without yielding or failure.

Using the appropriate formulae for thick-walled cylindrical vessels, such as Lamé’s equations, provides insight into how stresses are distributed through the thickness of the hull, allowing designers to account for varying stress states effectively.

While a factor of safety is an important consideration, the specific structural response to intense external pressure is the primary reason for classifying the pressure hull as a thick-walled vessel. The nature of material behavior under high pressures also emphasizes the need