Welds in Aluminum 3

[everestking]

How do you calculate the strength of fillet weld while welding two aluminum members? I need to weld an 4x4x1/2" angle to a rectangular base plate. Both the angle and rectangular base plate are Aluminum alloy 6061-T6 with ASTM Designation B209. I looked on AASHTO LRFD Section for aluminum but it does not say much about weld strength.

Thanks.

 

[Bagman2524]

You'll need a copy of the Aluminum Design Manual. Aluminum typically loses about 2/3 of it's strength when welded.

http://www.aluminum.org/

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[gtaw]

AWS D1.2 Structural Welding Code/Aluminum may prove to be useful in your application. It lists the "as welded" ultimate tensile strength for the different aluminum alloys typical used for structural applications. The code does not list the minimum UTS for combinations of dissimilar aluminum alloys.

As noted in another response, there is usually a degradation of the mechanical properties in the "as welded" condition when compared to the "as wrought" condition. In some cases it may be as little as 10%, but in other cases it can be 40%. The designer must consider the properties in the "as welded" condition in their design assumptions.




Best regards - Al

 

[dik]

Many aluminum products are heat treated alloys and a welded assembly may require heat treatment...

Dik

 

[everestking]

About the reduction in strength of the member. The angle described above act as a cantilever with load applying at the top. Do I have to consider the reduction in the flexural capacity of the angle itself because it will be welded to the plate at one end? That will change the whole design scenario. I was thinking of using no reduction for flexural capacity of the member but the weld being the governing factor for the amount of load I can apply at the top.

Thanks

 

[gtaw]

Al the mechanical properties suffer some extent depending on the particular alloy.

Best regards - Al

 

[Ron]

The Aluminum Design Manual gives reduced allowable stresses for various alloys when at or within one inch of a weld. The one inch criterion is in any contiguous direction

 

[hokie66]

Agree with using the Aluminum Design Manual. And yes, when you weld the angle to the plate, the strength of the angle at its most critical point is reduced in accordance with that standard. Aluminum is a beautiful material, but this is probably its most significant shortfall.

 

[gtaw]

Aluminum: "Almost a metal"

Best regards - Al

 

[a2mfk]

It sounds like you may be designing a handrail or similar post? Then you will see as others have stated that this reduction in bending stress within one inch of the weld will make your design difficult because of the cantilever producing the end moment. You will often need to upsize your vertical member because of this reduction. We have also done smaller diameter steel pipes welded to steel bases, then wrapped in neoprene or other barrier (for galvanic action protection), and then slid the aluminum post on top and attached with fasteners.

My solution to this whole issue is to talk architects out of specifying aluminum handrails/guardrails when painted or galvanized steel will suffice at a much lower cost with higher strength and durability.