Welding Strength?

[aith]

I am trying to find the failure load for a 6061-T6 Aluminum forklift pocket weld with 4043 filler. Can I simply multiply the cumulative throat area by the ultimate yield strength of the filler for this value? I never had any formal education on welds, wasn't sure if I'm missing something here.

This is a dual fillet weld failing in the transverse direction similar to the middle picture shown below. This data is pretty available for steel but I can't find any charts on aluminum.

http://www.roymech.co.uk/images/weld_dir.gif

I ask because if i have a 6 inch weld (along the length of the pocket, connecting the bottom to the right side) with a throat of 0.25, I have a throat area of 1.5 in^2. This means using the above method, if the yield strength of 4043 is 20 ksi or whatever that I'm looking at 30,000 lbs to fail a single weld? That can't be right. The forklift doesn't even weigh over 10,000 and isn't going fast enough to impart a force that high.

Help :-X

[ironmangq]

Shock loads can hit that pretty easily, bringing a load down and stopping it suddenly. I am more inclined to think that you are dealing with metal fatigue caused by a cyclic load (driving a load over bumps) and the fact that the heat affected zone around the weld will be weaker than either the filler metal or the base metal. Once you weld the aluminum any heat treatment it had in the welded area will be gone.

[Landing]

Ironmangq is right about the HAZ. The Aluminum Association in the U.S. publishes welded strengths for various alloys including 6061. Don't know if this can be downloaded. ABS publishes similar information but it's not as conservative as the Aluminum Association. See http://www.eagle.org/eagleExternalPortalWEB/ShowProperty/BEA%20Repository/Rules&Guides/LinkedGeneralGuideTitles/Current/Part2RulesMatWeldingFiberFRP . Look at Table 2 on (hard copy) page 49.

[Qwest]

The suggested allowable stresses from the old Alcoa handbook for 6061T6 are 11,000 psi tensile stress and 7000 psi shear stress after welding and within one inch of the weld. Before welding, those allowable stresses are 19,000 psi and 12,000 psi. You have to know from the type of loading what type of stress governs in your application.

I was promoted to journeyman welder 59 years ago from helper but haven't welded in many years. Doing engineering now and follow Welding Web regularly. I really enjoy the a vicarious association with real welders.

[satanzhand]

As far as I know you loose about 40-60% of the original strength around the weld, unless you re-temper the part. This is why a lot of motorcycle performance parts are made from one billet piece at greater expense than just welding a chuck/s on, like you can with steel. From experience with small parts I've found the 6061 after welding behaves similar to an annealed 3000 series piece around the weld.

[aahuraa]

our Charpy test result are so low, 8 &10 @ 0C( Submerged Arc Welding-thickness 14.27)
Whats the cause of these results ?

also other specimen with these properties with the results of 14,115,126,10 ????

[dumb as a stump]

I was promoted to journeyman welder 59 years ago from helper but haven't welded in many years. Doing engineering now and follow Welding Web regularly. I really enjoy the a vicarious association with real welders.

Well you joined in 09 and that was your first post??? You been hiding in the background and watchin the children havn't ya? <G> welcome

[sn0border88]

You're right, in a perfect world. Realistically you have to take into account the damaging effects of the heat from welding on the heat treatment of the 6061. Also you need to account for defects like porosity, crater cracks, undercut and any other kind of stress riser that is going to essentially make the joint "weaker" as these increase the K factor when doing stress calculations and will dramatically decrease the force a weld can hold.

[andrew15]

So true, i also have same thoughts.


As far as I know you loose about 40-60% of the original strength around the weld, unless you re-temper the part. This is why a lot of motorcycle performance parts are made from one billet piece at greater expense than just welding a chuck/s on, like you can with steel. From experience with small parts I've found the 6061 after welding behaves similar to an annealed 3000 series piece around the weld.

[Awelderiam]

our Charpy test result are so low, 8 &10 @ 0C( Submerged Arc Welding-thickness 14.27)
Whats the cause of these results ?

also other specimen with these properties with the results of 14,115,126,10 ????

What does the effects of an impact test have to do with the SMYS of his weldment? At what temp was your impact test performed? At what temp will his weldment be subjected to? :dizzy: