Challenge

[Lunner]

You have two metal shapes, cut from 5mm steel sheet, you need to think of the strongest possible way of attaching the two thinner ends together, hooks will be put through the holes at the end and the joint will eb tensile tested.

It only needs to be strong enough so that the structure itself fails before the join, also needs to be 20mm (about how they are positioned) from the larger section, and as light as possible.



Ideas so far are glue, and welding, but no specifics

[arj256]

Could bolt it consistnantly along the thin bit and if you want it really strong, put some sealing compound in as well. If your going really strong lol.
Or could use rivets as well. And even spot weld, but do you want to minimise distortion?
If its for a tensile test then id say a few bolts would be allright as decent bolts can hold a few tonne, just get em small enough not to risk fracturing the thin bit.

[edde]

If costs no problem then stir friction weld the parts together the joints are stronger than a solid block of material. However its costs and difficult to do. We use it at work and it is strong.

The section doesn't look to thick but rivetting it with sealing compount well done will be very strong depending how the material is the material can be weeker. However its a thin secon so you'll probably pull the material first. Round where the joint is your supposed to have about 2.5 times the thickness of the rivet on both sides which is probably impossibly.

I take it junction plates are out the question ie sandwhich it together?

[richy]

gaffer tape ???? pmsl

[BenR]

if they are spaced that far apart, then are you allowed to use a material to bridge the gap, or must the actual joining method/compound be the bridging material?

[Lunner]

No i just spaced them like it to illistruate the point.

Basically its a uni project, the area of the thin bits to be joined are rectangular sections 5x8mm, and the join can be 80mm long.

You can do literally ANYTHING, but the emphasisis on strength and lightness.

For example you could cut half the material away and create almost a lap joint, so one half fits into the other half, and resembles a section 5x8mm rather then 10x8mm or 5x16mm as you would get if you over lapped them

[stan]

Rivets will be the best bet.

wot tensile force does it have to take? if you know that you can work out the required ammount for a given pin diameter to give a maximum shear....

[Lunner]

Need to work that out, can't remember the tensile strength of steel off the top of my head, but its the structure that has to fil before the joint does, so 40mm^2 of steel.

Thing i was worred about wiht riveting it, the rivets will take the stress easy anough, but if you use say a 3mm rivet that leaves you wiht 2.5mm of steel each side, will this just not fail instead?

[stan]

got u, so its a failure test...and the test piece has to fail before the joint?

if you bond and rivet it (or if the clamping force is great enough), the lap joint effectively becomes one solid section (up to a point). so, so long as the total cross-sectional area at the rivet (i.e twice one side) is greater then the cross-sectional area of the neck, then the neck will fail first. if your smart you can work in stress concentration factors that are applied at the neck.

[Fred]

arc weld the ****er together, job done