Ship hull bending analysis

[LNGuy]

thread727-317253

Hell people,
I am newby to Abaqus, never used it before, and have taken up a project to do bending moment analysis for a ship hull, focusing primarily on mid-ship position. I will first do it for ship's self weight and then place weights at different locations along the length. I was reading the thread referenced above to start with.

1. I am wondering where do I apply the boundary condition so that I don't get free body movement? Is mid ship a good location?
2. The ship hull is symmetrical, so is it a good idea to work on only half the hull or will the results change if I work on the whole hull.

Any other suggestions to start with? I have attached a sample picture of my hull (I will remove other parts other than the hull while working)
Thank you.

 

[Onda]

- 1 Usually you should apply equilibrated loads the ship. then you can use an inertia relief system to analyze your ship.
Another system is to use the 3-2-1 system:

http://www.roshaz.com/images/FEA_best_and_worst_practice.pdf

you shall be very sure that your loads are equilibrated.

-2If the hull is symetrica and your loads too, you can model half a ship. in my experience this never happen and you end up by model the full ship.
regards
Onda

 

[rb1957]

this seems like an involved project for your first model ... I'd start with simpler models, to understand the FEA better.

1) if you're interested in a section of your model, don't place the rigid body constraints there ! 3-2-1 is a good approach ... this defines a plane that will remain plane after the model runs ... choose your plane carefully and you'll get results that look sensible. The precise set of three nodes used should have little impact on the internal stresses but will affect the datum for displacements ... try some different sets to see.

2) if your ship is symmetric, use the plane of symmetry as this plane. I agree with the comment above, you'll need to consider unsymmetric loads soon enough !

another day in paradise, or is paradise one day closer ?