Peeling Force Calculation

[SSergey]

Hi There,

I need some guidance/help with weld calculation.
Imagine that you have a C-channel converted to a rectangular tube by welding additional flat plate to it, "CI", with fillet weld. Internal dimensions of a channel are 2"by 3". Now we fixed one end of this welded rectangular tube (c-channel + flat plate) and insert a smaller rectangular member (1.9"X2.9") inside of it (so, we have a cantilever telescopic boom). We apply some force at the tip of a small rectangular tube. Due to some dimensional clearances, small rectangular tube slightly pivots around the edge of the welded rectangular tube until the top edge (from the inserted side) of a smaller tube touches the top internal surface of welded rectangular tube.
Question: how can we estimate the peeling force acting on the fillet weld? C channel is on top of the flat piece.

https://files.engineering.com/getfi...-8e97-4946-b8f7-6ce6d5cb7f65&file=bending.PNG

Thank you,
Sergey

 

[SSergey]

@ Kingnero
"Should have posted such a diagram yourself, and don't have us guessing."

I apologize for not being clear in the beginning. Will be much better next time. Please, see the attached image. I am interested in the strength of a fillet weld of a larger welded tube.

@ Tmoose, I hope the the attached image answers your question as well.

Thanks to both of you!

https://files.engineering.com/getfi...68-d272-4c99-9bd6-f6577c575e4a&file=state.PNG

 

[kingnero]

See attached file, this is how I'd start. Your codes might be different though.
I'd neglect torsion and bending depending on thicknesses of the parts and magnitude of forces. instead of taking half of the force on each side, you can take 2/3F in order to compensate for the bending.

 

[dhengr]

SSergey:
You have asked the right question for your particular cross sectional detail, but your detail is really a poor detail for your particular application. Put dimensions, thicknesses, member lengths, min. backspan length on outer member, loads and other pertinent engineering detail info on you latest sketch, so we have some idea of proportions, loads, etc. We shouldn’t have to guess at these or dig through many post to find little tid-bits, because you are too lazy to do a good engineering drawing and presentation of your problem. You would be surprised at how important that type of info is for an experienced engineer in making his/her first judgements about the approach to a problem. Yes, a 16” masonry corbel, a 20’ long horiz. cantilevered C section, and a flag pole are all canti’s., as is your problem, but they are treated and analyzed quite differently. So, get with it…, and give us enough info to really help you.

The tight fit of your two boom members within each other is not very practical in the real fabricating world. Formed and welded members never fit the way you wish they would, or stay straight after welding, so you end up having to machine everything. You would like a well defined bearing surface, replaceable wear surface, on the innermost left end top surface of the right boom member. Likewise, you want a well defined bearing surface, replaceable wear surface, on the inside, of the bottom flange of the left (outer) boom member, right out at its right tip. Now, you have well defined bearing points as you analyze the boom and their wear can be managed. These bearing pls. may be steel bars, there are some plastics which work well, or these bearing points could be four cam rollers on wear pls.

Next, you want to get those reaction forces as directly and cleanly as possible into the webs of the of the two main members. And, you are certainly not doing that by applying them to the flanges, and then through an inferior fillet weld end (termination) and finally into the webs. Those weld terminations are really likely to just unzip since you are applying the max. loads/stresses at the worst locations on those welds. This is an awful weld condition for that loading, and it must be corrected, or eliminated. Consider the flg. pl. flexing and bending and how this pries on the weld roots. Uniform bearing doesn’t exist on the flg. pls., they well bend and all the bearing reaction is concentrated out near the webs. So, try to put the loads directly into the webs and eliminate those stress raisers. Look at most booms and you will see some sort of reinforcement around the tip of the outer boom section, or special detailing to manage these large ripping reactions.

 

[Tmoose]

//If// the loads are low enough, and not repetitive none of this matters.

By inspection your welded channel design loads the outer beam's fillet weld as cantilever. The cantilever length is 1 to 2X the member thickness depending on the fusion/penetration at the root of the weld.
The maximum stress is right at the root of the weld, and that area is at a big disadvantage in 3 dimensions.
Similar to a bend test on a fillet weld in the difficult direction.
Depending on the condition of fusion / "penetration" there, and the skill of the welder "terminating" the weld at the end of the outer tube will be a mighty sharp corner or for all practical matters a "crack" will be formed there when the weld is brand new.

https://weldinganswers.com/wp-content/uploads/2018/03/004-Macroetch-1024x771.png

The suspected use of rolled materials might even add the exciting prospect of lamellar tearing type failure.
h

https://www.twi-global.com/technical-knowledge/job-knowledge/defects-lamellar-tearing-047