Loading Cycles on Submarine

[amateur mariner]

Hi everybody!

I want to ask that what is loading cycles on a submarine?Can anybody refer me some documents?

Regards,

Thanx

[Kay9]

Dock the Sub, walk to the dock, pick up your package, walk back to the sub, load package.

K9

[Olav]

The load cycles of (military) submarines are actually quite low: 10^4...4*10^4

Admittedly I have only very few documents or literature about submarines. I guess you are familiar with "Submarine Design" (http://www.amazon.com/Submarine-Konstruktion-Unterseebooten-Englische-Ausgabe/dp/3763762027/ref=sr_1_10?ie=UTF8&s=books&qid=1234437952&sr=8-10) by Ulrich Gabler (published by Bernard U. Graefe, ISBN 3-7637-6202-7)? Quite a good paper is "Some Aspects of Submarine Design" by Prof. P. N. Joubert of Australia's Defence Science and Technology Organisation (DSTO), consisting of Part 1: Hydrodynamics (http://dspace.dsto.defence.gov.au/dspace/bitstream/1947/3919/1/DSTO-TR-1622%20PR.pdf) and Part 2: Shape of a Submarine 2026 (http://dspace.dsto.defence.gov.au/dspace/bitstream/1947/8027/1/DSTO-TR-1920.PR.pdf). The DSTO publications (http://www.dsto.defence.gov.au/publications) are generally an excellent source.

Additionally, I have a well-written university hand-out which however is in German. If you can read German (since you are located "anywhere" there is a good chance that you can ;) ) just PM me your e-mail address and I'll send it to you.

[dskira]

"Theory of Submarine Design" by Professor Yuri N. Kormilitsin and Professor Oleg A. Khalizev from the Saint-Petesburg State Maritime Technical University.
Published in English and printed in England in 2001.
328 pages of highly technical work by two leading designer in submarine.
Yuri Kormilitsin use to work at Rubin as a General Designer.

[amateur mariner]

Sir, unfortunately I cant understand German otherwise it would have been quite beneficial.Can somebody provide me in English or is there anyway I can get a translated version of this and/or the other mentioned handouts??

[Olav]

Sorry, but the hand-out was written by a prof of mine and so there's only the German version available. The paper is 85 pages so a translation of the entire text unfortunately would be too time-consuming for me at the moment.

However, if there's a certain topic you're interested in I could do a quick translation of the relevant part/chapter.

Edit: Contents of the hand-out

1. Introduction
1.1. Scope of this lecture
1.2. Characteristics of submarines
1.3. Development of military submarines
1.4. Development of civilian submarines

2. Hydrostatics of submarines
2.1. Weight situation
2.2. Weight and trim adjustment
2.3. Stability

3. Hydrodynamics of submarines
3.1. Hullform
3.2. Resistance and propulsion
3.3. Manoeuvring characteristics
3.4. Model tests and trials

4. Hull
4.1. Loads on the hull
4.2. Pressure hull: Strength, stability
4.3. Non-pressure resistant areas of the hull
4.4. Materials, welding

5. Propulsion plants, energy generation
5.1. Introduction
5.2. Battery operation
5.3. Diesel-electric operation
5.4. Fuel cell propulsion (AIP)
5.5. Closed-circle diesel engine (AIP)
5.6. Stirling engine (AIP)
5.7. Closed-circle gas turbine (AIP)
5.8. Steam turbine (AIP)
5.9. Nuclear reactor (AIP)
5.10. Other propulsion systems

6. Safety and rescue facilities
6.1. Safety philosophies
6.2. Safety facilities
6.3. Rescue facilities

7. Equipment and accomodation
7.1. Breathable air management
7.2. Equipment
7.3. Facilities for the crew
7.4. Control facilities

8. Sensors / signatures of submarines
8.1. Signatures
8.2. Sensors

9. Construction, quality management and sea trials
9.1. Construction of submarines
9.2. Quality management measures
9.3. Documentation
9.4. Sea trials

[amateur mariner]

I want to know the basic concept about loading cycles? is there any procedure to predict loading cycles?

[Guillermo]

You can buy an article on the matter here:
http://cat.inist.fr/?aModele=afficheN&cpsidt=1305070

An article on fatigue cracks, cycles and the Paris equation here:
http://steel.keytometals.com/Articles/Art49.htm

Basics about fatigue:
http://en.wikipedia.org/wiki/Fatigue_(material)

Fatigue crack initiation:
http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Structure/fatigue.htm

Cheers.

[amateur mariner]

I am interested in Chapter 4 which is related to hull part of your document.It will be quite nice if you can send me the english version of it.

[jehardiman]

Ama,
Tell us the question you are looking to have answered, and we will be better able to point you in the correct direction. There is very little out there available to the amateur on hull design. Try to get copies of Manned Submersibles (1976 ed) by Busby; and Submersible Vehicle Systems Design (1990 ed), PNA (the 1967 single volume ed), SD&C (the 1969 ed) all by SNAME.

From a pressure loading cycle point of view, there are two seperate and distinct considerations over the life of a submarine/submersible. High load-low cycle loads and Low load-high cycle loads.

The first, as Olav mentioned, is based upon dive cycles and is measured in the low thousands for submarines and the hunderds for submersibles. It mainly effects material and fabrication requirements. The second is based upon the seaway, and is measured in the 10's of millions for submarines and low millions for submersibles, and is a concern of the fatigue life of the hull material. No material is best suited for these two different criteria given the other operational criteria (i.e. depth, shock, size, etc.)

[jehardiman]

I want to know the basic concept about loading cycles? is there any procedure to predict loading cycles?

Rule of thumb is 1 to 2 dive cycles per operational day. Suppose you have a submarine with a 20 year life undergoing 2 60 day deployments a year with a tech refresh docking every 5 years. So (20-4)*(2*60*2 ) = 3840 dive cycles.

Wave cycles are a little different, they are based upon a significant wave period (i.e a wave which causes flexture stress to excede a certian threshold) over the entire life of the vessel as long as it is afloat. Using the above 20 year life example with a 10 second significant wave. (20)*(365.25*24*60*6)=63 million

[amateur mariner]

I am looking to learn the basics about the loading cycles.how to use them to predict the life of different materials?how to use these loading cycles in numerical simulations in order to predict and understand their effects.

[jehardiman]

I am looking to learn the basics about the loading cycles.how to use them to predict the life of different materials?how to use these loading cycles in numerical simulations in order to predict and understand their effects.

That is metalurgy, not Naval Architucture. Go read Chapter IV of Submersible Vehicle Systems Design.

PS, That sounded a little harsh, so I apologize. What I mean is that while Naval Architecture can give you the loads and cycles a particular structure will see, the actual data of material strength, flexture-limits, crack growth propensity, etc are handled in the materials lab and are not directly addressable by hydrodynamic/hydrostatic simulations.

You chose a material based upon your desired properties and tune the structure to the materials limits, not the other way around becuase it is too difficult to tune a material to get the desired properties. CF structures are a prime example, as little as 2 degrees off axis fiber orientation can cause a 20% reduction in material strength so you must accept lower loads than you could calculate.

[amateur mariner]

Bu How to predict the loads?What all things need to be taken care of?

[jehardiman]

Bu How to predict the loads?What all things need to be taken care of?

All the normal ship strength stuff; primary, secondary, and tertiary loads. Nothing really changes except shell plate normal loads become the dominate factor instead of girder bending (but don't ignore it just like you shouldn't ignore wave slap when calculating surface ship bending loads). Get the referenced editions of PNA or SD&C, they both have fairly good design outlines for pressure hull strength in them.

The design of hull fittings is a whole other matter though, but can be handled seperatly from the actual pressure hull.

[amateur mariner]

Rule of thumb is 1 to 2 dive cycles per operational day. Suppose you have a submarine with a 20 year life undergoing 2 60 day deployments a year with a tech refresh docking every 5 years. So (20-4)*(2*60*2 ) = 3840 dive cycles.

Wave cycles are a little different, they are based upon a significant wave period (i.e a wave which causes flexture stress to excede a certian threshold) over the entire life of the vessel as long as it is afloat. Using the above 20 year life example with a 10 second significant wave. (20)*(365.25*24*60*6)=63 million
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?

[Olav]

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 (http://en.wikipedia.org/wiki/Fatigue_(material)#The_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.

[jehardiman]

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 (http://en.wikipedia.org/wiki/Fatigue_(material)#The_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.

[mydauphin]

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

[amateur mariner]

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 (http://en.wikipedia.org/wiki/Fatigue_(material)#The_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.

Hi,I am loooking forward for your translation.

Cheers

[Submarine Tom]

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