Loading Cycles on Submarine

is it is the only method of predicting the dive cycles and wave cycles.There is no deep theory related to it?How to understand these values as applied load means convert these 10^3 and 10^6 values of load cycles in load?

 

You don't "convert load cycles into load", but you read the remaining strength after n load cycles of a certain material from a so-called S-N curve, also known as Wöhler curve (named after August WÖHLER, 1819-1914). This is the strength your scantlings have to base upon.

The translation of chapter 4 of the hand-out is in progress, but unfortunately not finished yet.

 

Olav pretty much answered your question. Lets say for some strange reason we wanted to build a hull out of the Al plate shown in the wiki entry. At maximum test depth, if we assign a life of 5,000 dive cycles, the maximum stress anywhere in the hull (including load bending and dynamics, not just static pressure) can only be ~160 MPa. Realistically, this value is reduced even further for fabrication imperfections and errors, circularity problems, stress risers, plate wastage, std dev of the S-N curve, etc.

Similiarly, we also need to check the hull on or near the surface when maximum bending moment occurs (including load, dynamics and some shallow submergence static pressure) for 67M flex cycles. In this case the maximum stress can only be ~90MPa.

FWIW, this is not a trivial problem or mental exercise. Most military submarines are retired based on dive cycle life, not obselence. The proper selection of material and safety factors for strength at depth allowed the vast majority of the crew of the USS San Francisco to come home.

 

EEK, building a sub is as complicated as an airplane. Both can get you crushed, splatter and very dead...

 

Hi,I am loooking forward for your translation.

Cheers

 

Aren't we all Amateur Mariner, aren't we all...