Cracked weld, follow-up

[Watermelon]

Hello all.

For background please see weld puzzler thread.

Much has been written on the effects of dynamic loads on various welded configurations. It seems the configuration for my problem is the worst type when it comes to fatigue capacity. (A fillet weld across a bending member.)

Also, intermittent fillet welds are prohibited for most applications where stress reversal is involved. THere are situations where intermittent is okay, but if there's no real good reason to use intermittent welds, then why not weld solid?

Initially the finger was pointed at the welds because that's where the cracks were. We cut out a piece of the crack and found the surface to be smooth as glass. This is a classic indicator for a fatigue failure. Once the smooth crack has propagated too far, the material snaps leaving the remainder of the crack with a rough face.

So I recommended the weld be made larger, continuous with a minimum preheat of 225 F. And then they decided to fix it their way.

Life....

All the best.

 

[arto]

There's 3 ways to do things:
1. the right way
2. the wrong way
& 3. the bosses' way

;-)

 

[evelrod]

With any luck they will consult with someone else when it breaks the next time. Makes one feel invaluable does it not?


Rod

 

[diamondjim]

Thanks for giving the update. Often
the quickest answer wins. Sorry that
you were overruled and did not have time
to evaluate all possibilities. Rest assured
that they will be back.

 

[CivlEng]

Some reasons continuous welds are not used
1. Heat Affection
2. Time
3. Locations

Some times too much heat is just as bad as too little. Additional renforcing may be a better alternative that welding continous

 

[Watermelon]

Hi CivlEng:

Yup, I agree with you. "If there's no real reason to use intermittent welds, why not weld solid?" So if heat is going to cause warpage, or the cost of continuous welds is too high or fabrication time is too long, then you might want to take a look at intermittent welds. But, on a dynamically loaded structure, be careful.