Determining point of permanent deformation in aluminum pieces
Determining point of permanent deformation in aluminum pieces
(OP)
I have some unique aluminum shapes that I need to determine at which point they will have been stressed beyond their yield point. I can't just test one as we're designing this part and don't really want to get a die made just to do some testing.
When doing calculations like that, can I use the full yield strength, or do I need to use .6Fy or something like that? The shapes are quite non-symmetrical with some areas that are thin enough that they could buckle prematurely I suspect. Any thoughts?
Thanks.
When doing calculations like that, can I use the full yield strength, or do I need to use .6Fy or something like that? The shapes are quite non-symmetrical with some areas that are thin enough that they could buckle prematurely I suspect. Any thoughts?
Thanks.






RE: Determining point of permanent deformation in aluminum pieces
RE: Determining point of permanent deformation in aluminum pieces
RE: Determining point of permanent deformation in aluminum pieces
RE: Determining point of permanent deformation in aluminum pieces
Agree with civilperson on the parameters to check, but include torsional considerations since your section is assymmetric.
RE: Determining point of permanent deformation in aluminum pieces
I'm probably in over my head on this as I don't have the Aluminum Design Manual nor the money to spend on just this one problem. I've calculated my moment of inertia and section modulus of this, but the local buckling is what's throwing me.
To over-simplify, I have a double U-shaped piece that will be used as a beam (sliding door vertical). The legs of one of the U-shapes are going to be pinned at 24" o.c. to framing members but the other U-shaped piece is pretty much free to buckle. Obviously, it really helps my moment of inertia to get that material away from my centroid, but I fear that it's too slender and would yield far too quick.
I'm wondering if it would be too simplistic and conservative to just leave off that extended piece so that I don't need to concern myself with the LTB or local buckling. Unless somebody would like to see a picture of what I'm trying to accomplish and offer further thoughts, I'll probably just go that route.
Do extruders generally have people on staff to solve these sorts of problems?
Thanks.
RE: Determining point of permanent deformation in aluminum pieces
Post a photo so we can see what the section looks like, and the loading parameters.
RE: Determining point of permanent deformation in aluminum pieces
This piece is actually a vertical sliding door rail, where extruded "girts" will frame into that 2.5" area. This piece will have wind load applied to it bending it about the X-axis. I feel that the bottom portion of this piece (which will actually just be a trim to cover the end of the exterior cladding) though it adds significantly to the section properties, in reality will not behave very well due to local buckling concerns.
Any thoughts would be appreciated.