Weld

[ben3929]

What is the best practice of fillet welding for steel undergo vibration? Someone informed me that it is preferable the weld perpendicular to the vibration plane? Is this true. It is a 12" long 1/4" fillet weld size.

 

[BAretired]

Never heard that one before. I don't think it is true.

BA

 

[BridgeSmith]

All that I know to add is that the allowable fatigue stress is higher for a weld parallel to the applied stress than for a weld perpendicular to the applied stress. (Also higher for groove welded connections of either configuration).

 

[TehMightyEngineer]

I could see that being true. Vibrating the weld puddle, if you're moving the weld puddle perpendicular to the long. axis of the weld you're going to just be squishing or stretching the puddle as it solidifies. However, if you're vibrating it along the long. axis of the weld you're now shearing the weld puddle as it solidifies; I can imagine the low-strength weld metal possibly building up some interesting built-in stresses from this.

Ideally though, I'd just consider junk any welds put down while it's vibrating. I'd either over design the welds like crazy or special-inspect the welds visually and radiographically. Alternatively, perhaps you could construct a mock-up of the weld setup, attach it to the vibrating steel, perform the weld, and then bend test the weld to ensure proper bond and ductility.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[BridgeSmith]

I didn't realize the OP was asking about vibration during welding...seems like a bad idea regardless of the direction...

 

[BAretired]

I interpreted it the same as HotRod10.

BA

 

[WARose]

If we are talking about welding steel while it is vibrating.....that is unacceptable. Not good practice.

If we are talking about exposing welded steel to vibration......see the steel manual or Sect. 2.9 of Blodgett's 'Design of Welded Structures'.

 

[dhengr]

Ben3929:
Actually, I believe that the Vibratory Stress Relieving people recommend some slight/small, properly oriented vibration, with their equipment, during some welding procedures to condition the welds. That is, supposedly to reduce the residual stresses due to welding and to reduce the distortion caused by the welding. And, once in a while, there seems to be some proof that this is actually happening and is beneficial. Just as many times there seems to be little benefit and much work to set it up and try to make it work for you. Years ago, I did considerable study on this process for some work we were doing. There does seem to be some logic, rationale and science involved in what they are doing and selling, but there seems to be about the same amount of ‘black box,’ ‘witchcraftery’ and ‘voodoo’ associated with the process and results. One of the biggest issues is that on a complex weldment you do not know how to place the equipment to get a dependable and properly oriented vibration pattern to accomplish anything constructive. Whereas, on a simple beam, a vibrating mass does produce a fairly dependable and predictable vibration mode pattern, so you can relate this to the welding results.

I’m not sure I understand what the OP’er. wants. He’s provided little detail and info. which explains his real problem. As HotRod10 suggests, the strength parallel to the fillet weld is a bit stronger, while stresses perpendicular to the weld length are a bit more problematic. But. this has much to do with tensile stresses across the root of the fillet weld, which is always a potential weak point in the weld due to lack of fusion, lack of penetration, etc., and then the potential of fatigue and fracture at this location on the weld. And, vibration, assuming you can orient it in the right direction probably won’t improve this condition.