Stress on a chain link

[bimasu]

Hi,

This is my first post here. I have read a lot of the threads and learned so much. I have problem calculating shear stress on a chain link i hope someone can help me.

The chain link is consisting with 5 links that is 10mm in diameter. I found the normal stress and compared it with my FEM results and it is fine. But shear stress giving me problems. I calculated using tau=F/A, but my shear stress is too large compared to the one i get from my FEM analysis. I cannot understand why. Eventhough I know the shear stress distribute through the whole chain.

Can anyone explain me a way to find the proper shear stress?

Thank you in advance.

 

[bimasu]

Can someone help me please?

 

[racookpe1978]

Sketch your problem. What you are using as a "shear stress" issue is not clear from your words.

Also: the geometry is unclear. You have only 5 links, but what shape are each of the five links?
What dimension is the 10 mm? What is the diameter of the cross-section of each link?

At that small a chain, why don't you just test it, rather than run a approximation as a FEA problem?

If your links are circular, they will not fail in shear but in "ovaling" as they straighten out into a series of tiny ovals.

What size are your FEA blocks inside each link- if you do insist on using FEA?

How are your links fastened back to themselves in each link?

 

[btrueblood]

...and further, how do you handle the contact problem of the round link section bearing on the next link, in either FEA or a hand calc? There is probably something in Roarke's that lets you calculate those stresses...or you could probably model it in a suitably advanced FEA solver...but why?

 

[dhengr]

Shvima:
Take a look at some good Theory of Elasticity and Advanced Strength of Materials texts, that problem has been tackled, with some rigor, before. It is a curved beam, a ring shape in bending or a chain link. Why do you think shear stress is the controlling stress in the chain link? For the most part, the shear stress should be related to the bending normal stresses, as in other bending problems. As Btrueblood mentioned, you will have the Hertz contact /bearing stresses issues to deal with and several locations of localized yielding and redistribution of stresses, at the max. chain load.

 

[KENAT]

Might be able to find something applicable researching lugs - as this could be considered a chain of double ended lugs.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[bimasu]

Thank you everyone for the help.

racookpe1978 : The 5 links are oval shaped. I have attached the sketch below. The FEM analysis working fine. I used 1mm elements with tie contacts. But the hand calculations are confusing comparing to the FEM results. Normal stress is correct in FEM and in hand calculations. Only the shear isn't working.
btrueblood : Im using abaqus to model it. I need the hand calc to match my result in FEM. I checked the Roarke's but couldnt find anything much related to this.
dhengr : If you look at my attached imagine you will see the danger is in the shear area. Im trying to solve it using hertzian, cylinder to cylinder in grove.
KENAT : I will try using lugs too.

 

[bimasu]

Can someone check the image and let me know your opinion? Thank you!

 

[racookpe1978]

126,000 newtons?

 

[bimasu]

Yes..

 

[prex]

Concerning the shear stress, how did you calculate it? Did you account for the fact that it is distributed over two cross sections at the right and the left of the contact point?
And what about bending stresses,as pointed out by someone else above?
Difficult (impossible?) to believe that this chain can sustain 126000 N, also considering the safety factor required by codes.

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[bimasu]

I just used the average shear force. But I only considered one cross section area, because one of the links makes the force there.
I have found the bending stresses, but I still don't get the matching answer I need.
The 12600N is the ultimate load. So when using the chain it is not suitable to use that load. But it is important to check just for the analysis.

 

[bimasu]

Any ideas?

 

[prex]

Consider a supported beam with a point load: the shear load is not the point load, but half of it. Either you count the area twice or half the load. This problem is very basic and you can find a treatment of chain links in many textbooks.

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[bimasu]

Thank you everyone for the suggestions