On Nov 2, 2009, Cliff Redus <cliffordredus@sbcglobal.net> wrote:
Sean
I did not know you were working on this. Excellent!
A synopsis of the project:
Entering a hull design and having the software calculate the failure
modes and corresponding depths is one possible mode of operation, although it
is not the real strength of this software.
Similarly to some other online tools, the maximum allowable operating depths
in my software model are derived from the American Bureau of Shipping "Rules
for Building and Classing Underwater Vehicles, Systems and Hyperbaric
Facilities" publication. This is done not because the ABS rules represent a
definitive restriction on hull design, but rather because the Rules are freely
available, (relatively) easy to understand, and have been used to guide the
design of a large number of commercially successful hulls, making them a good
basis for design comparison without examining finer points of engineering. It
is assumed that anyone with sufficient knowledge to deviate from the prescribed
rules will be able to understand the limitations and abilities of particular
design tools, and act accordingly.
Unlike other available tools, the real strength of my software, when it is
completed, will be the ability to optimize a design for a given desired
operating depth and internal hull envelope. The optimization algorithm works
to find a hull design which meets the size and depth criteria, but which
simultaneously minimizes water displacement, hull steel volume, and weld
deposition volume. In addition, it optimizes stiffener design and spacing, so
that, for example, in a conical hull section, the stiffeners are not spaced
equidistant from each other, but rather so that each bay is of equivalent
strength.
I don't view this as an exhaustive design tool; however, it will dramatically
simplify concept evaluation for new subs, and in the case of pre-existing or
modified hulls, provide a quick means of checking the expected performance.
Without posting too much detail, I have pasted below the results from a simple
semi-elliptical head check - operating in the former (trivial) mode.
(Incidentally, these results are the simple text output from a sub-module of
the application. The finished product will be highly graphical and intuitive).
Try to envision the latter optimization mode, where instead of the inputs
indicated below, one would enter only the desired diameter and maximum
operating depth, and the most appropriate hull will be indicated.
Clear as mud?
-Sean
> INPUTS
>
> Head mean diameter: 1.3716m
> Shell Thickness: 0.028575m
> Length of Flange: 0.05715 (ABS requirement is that flange length >=
> 2*shell thickness)
> Steel Density: 7865 kg/m^3
> Acceleration due to gravity: 9.80665 m/s^2
> Fresh Water Density: 1000 kg/m^3
> Salt Water Density: 1025 kg/m^3
> Material: ASTM A516 Grade 70
> Material Yield Strength: 262 MPa
> Poisson's Ratio: 0.285
> Modulus of Elasticity: 200 GPa
>
> OUTPUTS:
>
> Displacement volume: 0.455 m^3
> Internal volume: 0.391 m^3
> Material volume: 0.063 m^3
> Material mass: 498.201 kg
> Displacement (fresh): 454.654 kg
> Displacement (salt): 466.021 kg
> Net mass (fresh): 43.547 kg
> Net mass (salt): 32.181 kg
> Material weight: 4885.685 N
> Buoyant force (fresh): 4458.635 N
> Buoyant force (salt): 4570.100 N
> Net weight (fresh): 427 N
> Net weight (salt): 316 N
> Maximum allowable working pressure: 4.87193 MPa
> Maximum allowable working depth (fresh): 496.80 m
> Maximum allowable working depth (salt): 484.68 m
> Gross register tons (GRT) - this section only: 0.13819
> Gross tonnage (GT) - this section only: 0.075
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