Bending stress on circular disc

[htngwilliam]

Guys

I borrowed the attachment from the web but I have a similar problem. I am trying to cal the bending stress of a circular disc but it is sort of different from the generic beam formula we use.

I wonder whether we can still apply

Bending stress = MY/I

Thanks for all the help

 

[israelkk]

Roark, formulas for stress and strain

 

[rb1957]

give us a few more clues ...

"I borrowed the attachment from the web but I have a similar problem." ... wtf ??

"I am trying to cal the bending stress of a circular disc ..." ... you have a flat plate (ok, a round plate = disc) loaded transversely ?? My/I works for thick plates. thin plates are very different (membrane reactions).

Roark, mentioned above, is a good place to start.

 

[htngwilliam]

Guys

Sorry for the confusion. I have a circular plate welded to a tube. I wanted to calculate the bending and shear stress so that I can see whether the weld is strong enough for my application.

I have attached a pic of my problem and it will be great if someone can point me to the formula

 

[HandsOnEngineer]

Ok,

If you really need a solution/help I suggest you give the following info:

Pipe OD:
Pipe ID:
Flange OD:
Flange ID:
Flange Thickness: Given (Thanks)
The 20kg load, is it a Uniformly Distributed Load (UDL) around the Flange or Several (How many?) 20kg Point loads equidistant around the flange?

 

[rb1957]

if you're not going to use Roark, then i'd start with a free body diagram, to work tout the reactions at the side of the tube then estimate what is a reason length of weld to react the tension load (due to bending)

 

[corus]

For the weld you have the shear stress from the 20kg(/mm circumference?) over the weld throat area. In addition you have a bending stress which can be simply calculated as the two equal and opposite forces in the upper and lower welds required to balance the applied moment. The stress in the disc isn't needed if you're simply looking at the weld strength.

Tata

 

[trainguy]

Agree with corus.

tg

 

[Cockroach]

Your move to circular disk stress and deformation is really overkill noting a 20kg load! Give a strong weld, probably 1/4 inch fillet above and below the disk can take the load, she looks good.

On the other hand, if you need to abuse yourself for no reason, then as mentioned, Roarks has the closed form solution set for this exact geometry.

You must have a million miles of pipe as added weight to be bummed out about a 20 kg load, brother. Otherwise there are better solutions than circular plate deflection.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[JStephen]

Roark's includes formulas for deflection and stress in circular plates with holes and for cylinders of varying lengths and end conditions. If the load shown is a distributed load about the disk at that radius, then you can combine the two for a solution in your case. It can get tedious. If that is two point loads on a disk, it's not covered in Roark's loads, and some sort of approximate solution is in order.

 

[htngwilliam]

Thanks everyone. I have re-looked at the problem again. Well, I guess my boss passed me the wrong information.

After looking at this problem and studying at the cad-models again, I realized that the stresses is all acting on the ring of the cylinder and not the ring flange.

Therefore the ring is just subjected to a small bolt tightening force of a few kgf. Even if the whole assembly were to be subjected to a drop test, the ring of the cylinder will take all the stresses.

Even if I were to compare the strength of the 4 bolts to a full weld at the top and bottom, based on my calculation, the weld is still stronger than the 4 bolts.

Any comments from anyone?