fatigue in aluminum jig plate weldment

[Tatonka]

what methods/design intent can be used to minimized fatigue with aluminum weldments? i'm working on a weldment with several jig plate gussets that are essentially cantilevered to a vertical plate. the gussets have moderate static loading, but have rather high dynamic loads (they're supporting about 3000 lb per gusset and each gusset is about 120" long). they need to undergo dynamic loads in all 3 orthogonal directions up to 10g's. I'm not even close to a materials/metallurgy guy and this stuff gives me a headache. anyone got some advice and an advil?

 

[TVP]

Several questions for you before providing any feedback:

1. What is the alloy and temper designation of the plate and the gussets?
2. Is any post-weld heat treatment performed?
3. Is there any other post-weld process performed, e.g. machining, shot peening, coating, etc.?
4. What weld method is used (GTAW, GMAW, laser, etc.)?
5. If filler wire is used, what is the alloy?

 

[Tatonka]

1. The material is 6061-T6.
2. There can be post weld HT, we're still in the design stages, so this is entirely possible...we may need to do post weld HT to normalize the mat'l properties back to the -T6 condition, right?
3. Same deal...there can be other post weld operations performed as long as it's possible to do them to a weldment that may be 15' Long x 10' Wide. It will be painted/powder coated and then painted for sure...
4. Weld process is up in the air...what would work to reduce stress concentration/loss of heat treatment/increase in life cycle, etc.
5. Not sure about this yet...I'm sure there will be filler wire used, but I'm not very familiar with aluminum weldments...do they come in grades like arc welding rods?