CTRIA3 Elements
CTRIA3 Elements
(OP)
I’m trying to de-idealise results from a very large existing aircraft FE Model. The model contains a number of TRIA3 elements in the fuselage side skins and I can’t quite workout how these elements are working. If you de-idealise them using the grid point forces as you would a QUAD4 it would suggest that these elements to a large extent simply carry end load along the edges, as the end loads are equal and opposite along each edge and therefore there doesn’t appear to be any shear forces involved. So instead of representing the shear capability of the skin they appear to have the effect of introducing additional end load carrying stiffeners. In certain instances, were there is a gap between existing stiffeners these elements seem to bridge this gap and in effective change the load path from what would be expected. Looking at various web sites what comes through is that these elements are ‘over stiff’, I could reduce the thickness down to virtually zero to remove the end load capability, but then in effect I would be introducing a hole.
Has any body come across a similar problem and found a solution to using these elements to effectively transfer shear but not end load.
Has any body come across a similar problem and found a solution to using these elements to effectively transfer shear but not end load.





RE: CTRIA3 Elements
it sounds like you've noticed "issues" with the internal loads, not only of the triangles, but also on their neighbours. perhaps, if you wanted to make them shear stiff (and endload soft) you could trick the material matrix. i'd try this out of a test panel to see how it works before committing to this approach.
i expect that most of these are in areas of mesh transition. i'd investigate remeshing quads and tris to remove the tris, this'll produce kites, but i think they're better than tris.
good luck
RE: CTRIA3 Elements
RE: CTRIA3 Elements
The area I’m looking at is the side skin below the canopy on a fighter, so it’s not your standard stringer/frames configuration where every thing tends to be at right angles to each other. On the actual structure, stingers/ stiffeners are not all horizontal and they do actually come together at certain positions to produce a ‘point’. Also the canopy posts are not vertical (looking inb’d/out’bd) so again when in attaches to the frame you do actually have a triangular piece of skin.
The stingers are modelled using rods for the stringers and shear elements for the skin. I suppose if you just consider a triangular piece of skin on it’s own it can’t be balanced by pure shear on it’s edges alone. So would it be safe to say I’m never going to be able to get any ‘reasonable’ results using this combination of element types.
RE: CTRIA3 Elements
you might look at a 6 noded triangle, these behave much better.
RE: CTRIA3 Elements
RE: CTRIA3 Elements
RE: CTRIA3 Elements
Paul
RE: CTRIA3 Elements
RE: CTRIA3 Elements
NE/Nastran may be different...I have never used it...
RE: CTRIA3 Elements