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# Ultimate shear Question

## Ultimate shear Question

(OP)
Hi,

I am trying to determine the load at which a weld will shear. Basically a solid metal disk is pressed into a tube and then they are laser welded together through the tube (weld penetrates into disk). My question is, can you use T = F/A where T = 0.75 UTS to ball park a load? is the equation valid in both the elastic and plastic regions with the only difference being significant changes in the CSA?

### RE: Ultimate shear Question

You could always suck it and see by doing a tensile test on the welded assembly (after substituting a long solid bar for the disk).

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

### RE: Ultimate shear Question

With an autogenous laser weld how will you estimate the strength of the weld metal?
Testing is the easiest and fastest way to do this. Test 10-12 pieces and get a feel for the load and the scatter.
There will be a lot of scatter because of hte very narrow laser weld every slight dimensional variation will impact the size of the weld.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

### RE: Ultimate shear Question

Just to be sure, does ultimate modify shear or does it modify question? Big difference!

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

### RE: Ultimate shear Question

T isn't 0.75, but ~60% (1/sqrt(3) IIRC). Goes for both yield and ultimate.
But as said, laser welding (without filler) isn't known for it's strength...

### RE: Ultimate shear Question

"they are laser welded together through the tube".
This begs a sketch or drawing.

If joint strength is important, and the loading is pushing the disk deeper into the tube, I'd put a shoulder on the tube ID or the disk OD with appropriate chamfers an radiuses and press the pieces well home before welding and keep them clamped while welding.

### RE: Ultimate shear Question

Quote: Tmoose (Mechanical)11 Apr 21 12:55
"they are laser welded together through the tube".
This begs a sketch or drawing.

If joint strength is important, and the loading is pushing the disk deeper into the tube, I'd put a shoulder on the tube ID or the disk OD with appropriate chamfers an radiuses and press the pieces well home before welding and keep them clamped while welding." unquote

and it helps locate for the weld, In addition with a couple of tacks

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