Partial Penetration Weld Analysis 2

[engpes]

I have a 1 1/2" thick lift lug that I am trying to analyze a 3/8" partial penetration weld all the way around the lug (see attached sketch).

Is there an effective throat calculation for partial pens like fillets (t=.707y)?

Thank you for your help.

Regards,

 

[desertfox]

Hi engpes

Have a look at this site:-

http://www.roymech.co.uk/Useful_Tables/Form/Weld_strength.html#Table_Weld

desertfox

 

[dvd]

That weld looks more like a bevel-groove weld. Why not use a fillet weld?

 

[Ron]

Since your weld is in tension, not shear, the "effective throat" is 3/8" on each side as that is the tension interface width. So your stress would be P/(2(3/8)(weld length)). I usually discount the last 1/2" of each end of the weld length due to termination defects.

 

[corus]

For this lifting lug the weld stress is a shear stress, composed of a direct shear plus bending, depending on the load direction. The weld detail is as a fillet, if you consider the fillet weld mirrored about the vertical. As such you'd take 0.707t as you say.

ex-corus (semi-detached)

 

[Ron]

corus...I see you point; however, the weld is in tension on the bottom and in shear along the plane of the bevel, only if there is no fusion between the weld and the lug. If fusion and solutioning occur, the shear component goes away, but the tension at the bottom does not. The load is straight up. The weld on the bottom leg is directly in tension to whatever the lug is welded to.

 

[Compositepro]

I would say that the weld itself is mostly under pure tension, but having the square transition from the lug to the base puts high shear stresses in the base material in the heat affected zone. This is where failures will start and does not seem to be the best design. You will also have stress concentration at the weld tip at the center of the lug. If there is no gap between the lug and the base it will behave almost like a crack.

 

[engpes]

Thank you. This has been very helpful.

 

[Ron]

engpes..for what it's worth, when I was designing tanks a hundred years ago, we welded lifting lugs with fillet welds all around. Weld was always in shear. Our lugs were permanent and used for loading/unloading tanks up to 12 feet in diameter and 50 feet long, so they had reasonably high loads....don't recall ever having one fail.